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ArticlePDF AvailableDetermining C5, C6 and C7 myotomes through comparative analyses of clinical, MRI and EMG findings in cervical radiculopathy

• February 2021
• Clinical Neurophysiology Practice 6(3)

DOI:10.1016/j.cnp.2021.02.002

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• CC BY-NC-ND 4.0

Authors: Yuichi FurukawaYuichi Furukawa

• This person is not on ResearchGate, or hasn't claimed this research yet.

Yosuke Miyaji

• Yokohama City University

Akiko KadoyaAkiko Kadoya

• This person is not on ResearchGate, or hasn't claimed this research yet.

Hisao Kamiya

• Teikyo University

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Abstract

Objective There are many myotome charts in the literature, but few studies have presented actual data to support their identification. We aimed to determine C5/C6/C7 myotomes based on clinical and EMG data of patients with cervical spondylotic radiculopathy (CSR) having a single-root lesion confirmed by MRI. Methods Medical Research Council (MRC) scores and EMG findings were retrospectively reviewed for patients enrolled from our EMG database. Results Enrolled were 25 patients (10 C5, 6 C6, and 9 C7 CSR). In C5 CSR, weakness or denervation potentials in EMG, or both, were observed in the deltoid (Del) and infraspinatus (Isp) muscles for all patients, and in the biceps brachii (BB) and brachioradialis (BR) muscles for 9/10 and 8/9 patients, respectively. In C6 CSR, weakness of the wrist extensor and/or denervation of the extensor carpi radialis longus (ECRL)/extensor carpi radialis brevis (ECRB), and those of the pronator teres (PT) were observed for all patients. Weakness was not observed for any other muscle in C6 CSR. Denervation potentials of ECRL were found in 5/8 and 3/5 patients with C5 and C6 CSR, respectively, whereas those of ECRB were found in 1/5, 6/6, and 2/5 patients with C5, C6 and C7 CSR, respectively. In C7 CSR, weakness/denervation of the triceps brachii (TB) and denervation potentials of the flexor carpi radialis (FCR) were observed for all patients. Denervation potentials in PT and weakness/denervation of the extensor digitorum (ED) were observed in 2/9 and 4/9 patients, respectively. Conclusion Suggested dominant myotomes are: C5 for the Del, Isp, BB, and BR, C5/6 for the ECRL, C6>C7 for the ECRB and PT, and C7 for the TB and FCR. Significance The current study identified dominant myotomes that differ from the existing literature

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Join for freePublic Full-text 1Available via license: CC BY-NC-ND 4.0Content may be subject to copyright. Journal Pre-proofsResearch paperDetermining C5, C6 and C7 myotomes through comparative analyses of clini‐cal, MRI and EMG findings in cervical radiculopathyYuichi Furukawa, Yosuke Miyaji, Akiko Kadoya, Hisao Kamiya, TakashiChiba, Kei-ichi Hokkoku, Yuki Hatanaka, Ichiro Imafuku, Kota Miyoshi,Masahiro SonooPII: S2467-981X(21)00006-8DOI: https://doi.org/10.1016/j.cnp.2021.02.002Reference:CNP 173To appear in:Clinical Neurophysiology PracticeReceived Date:24 May 2020Revised Date:2 January 2021Accepted Date:8 February 2021Please cite this article as: Y. Furukawa, Y. Miyaji, A. Kadoya, H. Kamiya, T. Chiba, K-i. Hokkoku, Y. Hatanaka,I. Imafuku, K. Miyoshi, M. Sonoo, Determining C5, C6 and C7 myotomes through comparative analyses ofclinical, MRI and EMG findings in cervical radiculopathy, Clinical Neurophysiology Practice (2021), doi:https://doi.org/10.1016/j.cnp.2021.02.002This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a coverpage and metadata, and formatting for readability, but it is not yet the definitive version of record. This versionwill undergo additional copyediting, typesetting and review before it is published in its final form, but we areproviding this version to give early visibility of the article. Please note that, during the production process, errorsmay be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.© 2021 Published by Elsevier B.V. on behalf of International Federation of Clinical Neurophysiology. 1Determining C5, C6 and C7 myotomes through comparative analyses of clinical, MRI and EMG findings in cervical radiculopathyYuichi Furukawa a, Yosuke Miyaji a,b, Akiko Kadoya c, Hisao Kamiya a, Takashi Chiba a, Kei-ichi Hokkoku a, Yuki Hatanaka a, Ichiro Imafuku d, Kota Miyoshi e, and Masahiro Sonoo a,*a Department of Neurology, Teikyo University School of Medicine, Kaga 2-11-1, Itabashi-ku, Tokyo, Japanb Department of Neurology and Stroke Medicine, Yokohama City University Graduate School of Medicine, Fukuura 3-9, Kanazawa-ku, Yokohama-shi, Kanagawa, Japan c Department of Neurology, Anti-aging and Vascular Medicine, National Defense Medical College, Namiki 3-2, Tokorozawa-shi, Saitama, Japand Department of Neurology and e Department of Orthopedics, Yokohama Rosai Hospital, Kozukue 3211, Kohoku-ku, Yokohaya-shi, Kanagawa, Japan*Corresponding author: M. SonooDepartment of Neurology, Teikyo University School of Medicine, 2-11-1 Kaga, Itabashi-ku, Tokyo 173-8605, JapanTel: +81 3 3964 1211Fax: +81 3 3964 1707E-mail: [email protected] 2E-mail addresses of co-authors:Yuichi Furukawa: [email protected] Miyaji: [email protected] Kadoya: [email protected] Kamiya: [email protected] Chiba: [email protected] Hokkoku: [email protected] Hatanaka: [email protected] Imafuku: [email protected] Miyoshi: [email protected]: There are many myotome charts in the literature, but few studies have presented actual data to support their identification. We aimed to determine C5/C6/C7 myotomes based on clinical and EMG data of patients with cervical spondylotic radiculopathy (CSR) having a single-root lesion confirmed by MRI.Methods: Medical Research Council (MRC) scores and EMG findings were retrospectively reviewed for patients enrolled from our EMG database.Results: Enrolled were 25 patients (10 C5, 6 C6, and 9 C7 CSR). In C5 CSR, weakness or denervation potentials in EMG, or both, were observed in the deltoid (Del) and infraspinatus (Isp) muscles for all patients, and in the biceps brachii (BB) and brachioradialis (BR) muscles for 9/10 and 8/9 patients, respectively. In C6 CSR, weakness of the wrist extensor and/or denervation of the extensor carpi radialis longus (ECRL)/extensor carpi radialis brevis (ECRB), and those of the pronator teres (PT) were observed for all patients. Weakness was not observed for any other muscle in C6 CSR. Denervation potentials of ECRL were found in 5/8 and 3/5 patients with C5 and C6 3CSR, respectively, whereas those of ECRB were found in 1/5, 6/6, and 2/5 patients with C5, C6 and C7 CSR, respectively. In C7 CSR, weakness/denervation of the triceps brachii (TB) and denervation potentials of the flexor carpi radialis (FCR) were observed for all patients. Denervation potentials in PT and weakness/denervation of the extensor digitorum (ED) were observed in 2/9 and 4/9 patients, respectively. Conclusion: Suggested dominant myotomes are: C5 for the Del, Isp, BB, and BR, C5/6 for the ECRL, C6>C7 for the ECRB and PT, and C7 for the TB and FCR. Significance: The current study identified dominant myotomes that differ from the existing literatureKeywords: Myotome; Cervical spondylotic radiculopathy; Brachioradialis; Pronator teres; Extensor carpi radialis longus; Extensor carpi radialis brevis. 41. IntroductionMyotome charts play an important role in the clinical and electrodiagnosis of neuromuscular disorders. There are many charts in the literature, all differing from one another. However, the source of the identification of myotomes is not clear in most charts (Brendler, 1968). Few studies have presented actual data supporting their identification (Yoss et al., 1957; Brendler, 1968; Levin et al., 1996; Chiba et al., 2015). Levin et al. (1996) provided strong evidence by investigating electromyography (EMG) findings in patients with surgically confirmed single-root lesions. However, C6-innervated muscles were less well defined in their study.In our previous study, we clarified C8 and T1 innervations of the forearm muscles (Chiba et al., 2015).In this study, we investigated the C5, C6 and C7 myotomes by reviewing clinical (manual muscle testing; MMT) and EMG findings of patients with cervical spondylotic radiculopathy (CSR) and evidence of a single-root lesion confirmed by magnetic resonance imaging (MRI).2. Methods2.1. Inclusion criteria and subjectsSubjects were retrospectively enrolled from our EMG database from 2009 to 2018. Inclusion criteria were: 1) Symptoms and signs that are typical for CSR, such as radicular pain, back pain, segmental weakness, segmental sensory disturbance, reflex changes, and Spurling’s sign, 2) One month or more from the symptom onset (this restriction was set because an acute lesion may not cause denervation in the affected muscles), 3) Needle EMG showing abnormality in at least one muscle, 4) Needle EMG localizing the lesion at the root level, e.g. denervation at the cervical paraspinal muscles (PSM) or involvement of two muscles innervated by different peripheral nerves and different plexus components, 5) Cervical MRI documenting an isolated unilateral C5, C6, or C7 root lesion that may well cause radiculopathy, and the affected root coinciding with the symptoms and signs of the patient such as segmental sensory disturbance, reflex changes, or the site of shoulder or back pain (Mizutamari et al., 2010). Patients with polyradiculopathy, myelopathy 5evident from clinical or MRI findings, or both, previous neck surgery, or other disorders that might affect clinical signs or EMG results were excluded. Medical Research Council (MRC) scores and needle EMG findings of the upper-limb muscles were retrospectively reviewed. The study design was approved by the ethics committee of Teikyo University (approval number: 17-147)2.2. MRC scoreThe MRC scores during routine neurological examinations of the patient were used as parameters in this study. The evaluated muscles were the deltoid (Del), infraspinatus (Isp), biceps brachii (BB), brachioradialis (BR), pronator teres (PT), triceps brachii (TB), and extensor digitorum (ED). The wrist extensor (WE) was evaluated as a muscle group (extensor carpi radialis longus (ECRL) / extensor carpi radialis brevis (ECRB) and extensor carpi ulnaris). Similarly, the wrist flexor (WF) was evaluated as a muscle group (flexor carpi radialis (FCR) and flexor carpi ulnaris (FCU)). All MRC scores were evaluated by a single skilled examiner (MS; Sonoo, 2018). The MRC score was graded by the standard method except that a modified scale was adopted for muscles that are free from the effect of gravity (Brandsma et al., 1995; Sonoo, 2018).2.3. Needle EMGNeedle EMG was conducted as a routine diagnostic evaluation for CSR patients in our laboratory as recommended by existing guidelines (American Association of Electrodiagnostic Medicine, 1999). We reviewed the EMG findings for the Del, BB, BR, ECRL, ECRB, PT, TB, FCR, ED, FCU, and PSM. EMG findings were scored as previously described (Chiba et al., 2015). Fibrillation potentials and positive sharp waves (fib/psw) were graded from 0 (none) to 3 (profuse). Voluntary activities were graded based on the qualitative assessment of the recruitment pattern (Nomenclature Committee of American Association of Electromyography and Electrodiagnosis, 1987; Chiba et al., 2015) from 0 (normal) to 3. In the PSM, only fib/psw were evaluated. All EMG 6examinations were conducted by MS or under his close supervision. Positive fib/psw were considered definite abnormalities, whereas abnormal voluntary activities were considered supplementary findings. 3. Results3.1. Enrolled subjectsIn all, 25 subjects were enrolled. They consisted of 10 patients with C5 CSR (9 men and 1 woman, age 65.6 ± 16.8 years, range 29–86), 6 patients with C6 CSR (4 men and 2 women, age 48.2 ± 5.9 years, range 43–56), and 9 patients with C7 CSR (7 men and 2 women, age 50.7 ± 6.5 years, range 38–59). Duration of illness was 2 to 24 months (6.9 ± 5.2, median 5 months). The symptoms and signs were unilateral in all patients. Weakness was present in 24/25 patients. Pain was present in 21/25 patients, neck pain in 2/10, 4/6 and 1/9 and back pain in 2/10, 0/6 and 9/9 patients with C5, C6, and C7 CSR, respectively. Subjective tingling was noted in 18/21, and objective sensory disturbance was observed in 14/22 patients. Spurling’s sign was positive in 21/25 patients. 3.2. MRI findingsCervical MRI documented a lesion that likely caused unilateral root compression at a single level of either C4/5, C5/6 or C6/7, which coincided with the symptomatic side and the corresponding level inferred from the symptoms and signs. An evident protrusion into the spinal canal or intervertebral foramen was observed for all cases. The nature of the protrusion was likely either disc or bony spur (hard disc), but the precise differentiation between the two could not be determined as computed tomography (CT) was not performed. The location of the protrusion was lateral in 9 patients and foraminal in 16 patients (Yamano, 1985; Hamasaki et al., 2005). No patients showed lesions at the central or paracentral region. 73.3. MRC scoresMRC scores of evaluated muscles for individual subjects are shown in Figure 1. For C5 CSR, weakness was found in all 10 patients in the Del and Isp muscles, and in 9/10 and 8/9 patients in theBB and BR muscles. For C6 CSR, weakness of the WE and PT muscles was observed in 5/6 and 3/3 patients, respectively. For C7 CSR, weakness of the TB, WF and ED muscles was observed in 9/9, 4/9 and 2/9 patients, respectively. These relations were specific for each muscle or segment as follows. Weakness of the Del, Isp, BB and BR muscles was observed only in C5 CSR but in no patients with C6 or C7 CSR. Similarly, weakness of the WE and PT was observed only in C6 CSR, and weakness of the TB, WF and ED was observed only in C7 CSR. 3.4. EMG findingsEMG grades of evaluated muscles for individual patients are also shown in Figure 1. For C5 CSR, the Del, BB, BR and ECRL were abnormal (positive fib/psw) in 8/9, 2/2, 3/3 and 5/8 patients, respectively, whereas the ECRB and PT was abnormal only in 1/5 and 1/9 patients, respectively. For C6 CSR, the ECRB and PT most frequently showed abnormalities (7/7 and 6/7 patients, respectively), followed by the ECRL (3/5 patients). For C7 CSR, the TB and FCR were abnormal in all patients examined, but the ED, ECRB and PT showed denervation in limited cases (3/7, 2/5 and 2/9 patients, respectively). The FCU showed profuse denervation in a patient examined. The PSM showed denervation in 18/19 patients examined. 4. DiscussionExisting literature on the typical myotome charts of the muscles described in the current study are summarized in Figure 2. Only a few presented raw data of anatomical, clinical, electromyographical, or intraoperative findings (Herringham, 1887; Yoss et al., 1957; Brendler, 1968; Levin et al., 1996). In contrast to the most recent study by Levin et al. (1996) which referred to surgically confirmed cases, we used MRI to determine the affected root. There may be criticisms 8in adopting this approach due to the non-specific nature of MRI findings (Nardin et al., 1999), but we believe that the findings from our study is reliable since we strictly selected patients whose symptoms and signs coincided with the single root lesion documented by MRI. Katirji et al. (1988) also correlated EMG findings with imaging studies (metrizamide CT), without intending to revise the myotome chart. MRI with its better resolution should be used more extensively to update the myotome charts. This study suggested that the Del, Isp, BB, and BR are mainly innervated by C5, the ECRL by both C5 and C6, the ECRB and PT mainly by C6, and the TB and FCR mainly by C7. C7 contribution to ED and FCU has also been suggested, but it has been established that the main innervation to these two muscles is C8 (Chiba et al., 2015). Therefore, these two muscles probably receive C7 to a lesser extent than C8 innervation. The present results largely coincided with existing charts for several muscles (Del, Isp, BB, TB, and FCR), but were different from most conventional charts for other muscles (Figure 2). The BR has usually been attributed to C6 or C5/C6. However, this study suggested C5-dominant innervation, which coincided with two old studies based on raw data (Yoss et al., 1957; Brendler, 1968). Levin et al. (1996) stated that C6 may not have definite innervation. However, we identified at least two muscles that were dominantly innervated by C6, which were PT and ECRB. Regarding PT, most authors have suggested double innervation by C6 and C7, sometimes dominant in C7. Only two authors concurred with our findings, C6 greater than C7 innervation (Brendler, 1968; Ellenberg et al., 1994). Our study also suggested dissociation between the ECRL and ECRB. Similar dissociation, ECRL rostral and ECRB caudal, has been reported by a few authors (Eisen, 1985; Campbell, 2013; Kimura, 2013), although they attributed the ECRL to C6 or C6/7 and the ECRB to C7 or C7/8. Our conclusion is more rostral, ECRL by C5/C6 and ECRB by C6 greater than C7. The previously published myotome charts listed in Figure 2 that were not based on the raw data were established in several ways. Several authors stated that their chart was based on their own experiences, which were not explicitly presented (Chu-Andrews and Johnson, 1986; Wilbourn and 9Aminoff, 1988; Ellenberg et al., 1994; Geiringer, 1999). Two authors stated that they referred to other specific charts (Kendall et al., 1971; Dumitru and Zwarts, 2002). The reasons were less clear in others (Eisen, 1985; Perotto, 1994; Members of the Mayo Clinic Department of Neurology, 1998; Guarantors of Brain, 2010; Preston and Shapiro, 2012; Kimura, 2013; Hislop et al., 2014). As Brendler (1968) discussed, the basis of the conventional myotome charts might be animal studies or very old anatomical study of human dissection (Herringham, 1887), which could not accurately trace the nerve fiber course (Sharrard, 1964). Figure 2 indicates that our identifications are generally in good agreement with studies providing raw data (red boxes), typically in the BR, PT, or ED. There are several limitations in this study. First, the examiner was not blinded to other information. The MRI findings were sometimes known prior to the examination. More importantly, if the examiner came to believe that the patient had, e.g., a C6 lesion during the MMT and other neurological examinations, then the overall findings may have been biased. However, EMG abnormalities, especially fib/psw, are objective findings and not subject to bias. The EMG results overall agreed well with MRC scores, which supports the reliability of our MRC scores. Second, MRC scores of certain movements cannot separate the actions of individual muscles. MMTs of the BB and BR are such examples. It has been proposed that the BB and BR can be separately evaluated by changing the forearm position for pronation/supination (Hislop et al., 2014), but we feel that it is difficult to definitely separate the actions of the BB and BR. In this regard, normal BB may have masked the BR dysfunction in C6 lesion. Normal EMG in the BR in C6 CSR was confirmed in only one patient. However, we often observed that the BR was extremely atrophic in patients with C5 lesion, which supports the C5-dominant innervation of the BR. Lastly, normal strength of a muscle does not exclude minor innervation from the affected root. EMG is sensitive to detecting subclinical abnormalities (Wilbourn and Aminoff, 1988), but in order to not cause further discomfort, we performed limited EMG in muscles of normal strength. Therefore, we could not evaluate minor contributions from a specific root when EMG was not done. These include C6 contribution to the Del, Isp, BR and TB. In such situations, this study just revealed major 10innervations to relevant muscles. AcknowledgementsWe thank Dr. Takahiro Nakayama (Department of Neurology, Yokohama Rosai Hospital), Dr. Hiromasa Matsuno (Department of Neurology, Jikei University School of Medicine), and Drs. Fumiaki Katada, Yoko Tomoda, Yoshito Arakaki and Toshio Fukutake (Department of Neurology, Kameda Medical Center) for cooperating with this study. This study was partly supported by Grants-in-Aid for Scientific Research (19K07966) from the Ministry of Education, Science, Sports and Culture of Japan, and by AMED under Grant Number 19ek0109252h0003.Conflict of interestNone of the authors have conflicts of interest to be disclosed. 11ReferencesAmerican Association of Electrodiagnostic Medicine. Guidelines in electrodiagnostic medicine. Practice parameter for needle electromyographic evaluation of patients with suspected cervical radiculopathy. Muscle Nerve Suppl 1999;8:S209-S221.Brandsma JW, Schreuders TA, Birke JA, Piefer A, Oostendorp R. Manual muscle strength testing: intraobserver and interobserver reliabilities for the intrinsic muscles of the hand. J Hand Ther 1995;8:185-190.Brendler SJ. The human cervical myotomes: functional anatomy studied at operation. J Neurosurg 1968;28:105-111.Campbell WW. Dejong's the neurologic examination. 7th ed. Philadelphia: Wolters Kluwer, 2013.Chiba T, Konoeda F, Higashihara M, Kamiya H, Oishi C, Hatanaka Y, et al. C8 and T1 innervation of forearm muscles. Clin Neurophysiol 2015;126:637-642.Chu-Andrews J, Johnson RJ. Electrodiagnosis: an anatomical and clinical approach. Philadelphia: J. B. Lippincott Company, 1986.Dumitru D, Zwarts MJ. Radiculopathies. In: Dumitru D, Amato AA, Zwarts MJ, editors. Electrodiagnostic Medicine. 2nd ed. Philadelphia: Hanley & Belfus Inc, 2002:713-776.Eisen A. Electrodiagnosis of radiculopathies. Neurol Clin 1985;3:495-510.Ellenberg MR, Honet JC, Treanor WJ. Cervical radiculopathy. Arch Phys Med Rehabil 1994;75:342-352.Geiringer SR. Anatomic localization for needle electromyography. 2nd ed. Philadelphia: Hanley & Belfus Inc, 1999.Guarantors of Brain. Aids to the examination of the peripheral nervous system 5th edition. Edinburgh: Saunders Elsevier, 2010.Hamasaki T, Baba I, Tanaka S, Sumida T, Manabe H, Tanaka N, et al. Clinical characterizations and radiologic findings of pure foraminal-type cervical disc herniation: CT discography as a useful adjuvant in its precise diagnosis. Spine 2005; 30: E591-E596. 12Herringham WP. The minute anatomy of the brachial plexus. Proc R Soc 1887; 41: 423-441. Hislop HJ, Avers D, Brown M. Daniels and Worthingham's Muscle testing: techniques of manual examination and performance testing. 9th ed. Philadelphia: W. B. Saunders, 2014.Katirji MB, Agrawal R, Kantra TA. The human cervical myotomes: an anatomical correlation between electromyography and CT/myelography. Muscle Nerve 1988;11:1070-1073.Kendall HO, Kendall FP, Wadsworth GE. Muscles: testing and function. 2nd ed. Baltimore: The Williams and Wilkins Company, 1971.Kimura. Electrodiagnosis in Diseases of Nerve and Muscle: Principles and Practice, 4th ed. New York: Oxford University Press, 2013.Levin KH, Maggiano HJ, Wilbourn AJ. Cervical radiculopathies: comparison of surgical and EMG localization of single-root lesions. Neurology 1996;46:1022-1025.Members of the Mayo Clinic Department of Neurology. Mayo Clinic Examinations in Neurology. St. Louis: Mosby, 1998.Mizutamari M, Sei A, Tokiyoshi A, Fujimoto T, Taniwaki T, Togami W, et al. Corresponding scapular pain with the nerve root involved in cervical radiculopathy. J Orthop Surg (Hong Kong) 2010; 18: 356-360.Nardin RA, Patel MR, Gudas TF, Rutkove SB, Raynor EM. Electromyography and magnetic resonance imaging in the evaluation of radiculopathy. Muscle Nerve 1999;22:151-155.Nomenclature Committee of American Association of Electromyography and Electrodiagnosis. AAEE glossary of terms in clinical electromyography. Muscle Nerve 1987;10:G1-G60.Perotto AO. Anatomical guide for the electromyographer. The limbs and trunk, 3rd edition (translated by Kayamori R). Springfield: Charles C. Thomas, 1994.Preston DC, Shapiro BE. Electromyography and Neuromuscular Disorders: Clinical-Electrophysiologic Correlations. 3rd ed. London: Elsevier Saunders, 2012.Sharrard WJW. The segmental innervation of the lower limb muscles in man. Ann R Coll Surg 1964; 35: 106-122. 13Sonoo M. Guidebook for MMT and needle EMG. Tokyo: Chugai Igakusya, 2018.Wilbourn AJ, Aminoff MJ. The electrophysiologic examination in patients with radiculopathies. Muscle Nerve 1988;11:1099-1114.Yamano Y. Soft disc herniation of the cervical spine. Int Orthop 1985; 9: 19-27.Yoss RE, Corbin KB, MacCarty CS, Love JG. Significance of symptoms and signs in localization of involved root in cervical disk protrusion. Neurology 1957;7:673-683. 14Figure Legends Figure 1. MRC scores and EMG grades for evaluated muscles of individual patients.MRC score: 5; 4; ≤ 3; no data.Grades for spontaneous activities (S): 0, none; 1, few; 2 moderate (observed following about half of insertions) and 3 (observed following almost every insertion); no data.Grades for voluntary activities (V): 0, normal; 1, reduced; 2 discrete and 3 single oscillation; no data. Del, deltoid; Isp, infraspinatus; BB, biceps brachii; BR, brachioradialis; WE, wrist extensors; ECRL, extensor carpi radialis longus; ECRB, extensor carpi radialis brevis; PT, pronator teres; TB, triceps brachii; WF, wrist flexors; FCR, flexor carpi radialis; FCU, flexor carpi ulnaris; ED, extensor digitorum; PSM, paraspinal muscles; S, spontaneous activities; V, voluntary activities; MRC, Medical Research Council; CSR, cervical spondylotic radiculopathy. Figure 2. Typical myotome charts from the literature, together with our identification.Authors presenting raw data as the basis for their identification are written in bold letters, together with the number of patients included in each study (n). Note that this is the total number of patients and the number of patients having lesion of a specific root or receiving stimulation of a specific root is smaller. dominant innervation; lesser contributions (studies with raw data). dominant innervation; lesser contributions (studies without raw data). *For the present authors, results of Chiba et al. (2015) and this study were combined, and were graded semi-quantitatively as follows according to the percentage of patients showing abnormal results, except when we had too few data. In the latter situation, the grade was sometimes modified by other experiences of the authors or with reference to past studies. 60% or more; between 20 and 60%; 20% or lessECRL, extensor carpi radialis longus; ECRB, extensor carpi radialis brevis. 15 16HIGHLIGHTS• We determined C5/C6/C7 myotomes from patients with MRI-confirmed single-root radiculopathy.• The brachioradialis was mainly innervated by C5.• C6 muscles were the pronator teres and extensor carpi radialis brevis. 17

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... Surgical level selection did not rely on typical "Netter diagram" or characteristic symptoms of each nerve root compression, as research has shown that these typical clinical pictures are often flawed [8]. Considering previous studies based on myotomes and electrophysiological studies, levels that could potentially contribute to patient's symptoms were included in the operation level [14,15]. However, levels with FS that were unlikely to be the cause of patient symptoms were not operated. ...... Notably, severe motor weakness (grade <3) is more likely caused by the expected level based on the typical cervical radiculopathy symptom description [25]. Electromyog- raphy-based studies have established connections between nerve roots and upper extremity muscles [15,[27][28][29]. The electromyography-based myotome mapping by Furukawa et al. [15] summarizes previous research, enabling surgeons to identify levels unlikely to contribute to patient symptoms by referencing these studies and mappings [14,15]. ...... Electromyog- raphy-based studies have established connections between nerve roots and upper extremity muscles [15,[27][28][29]. The electromyography-based myotome mapping by Furukawa et al. [15] summarizes previous research, enabling surgeons to identify levels unlikely to contribute to patient symptoms by referencing these studies and mappings [14,15]. In the present study, we included all levels with FS likely to contribute to patient symptoms, considering possible variations in cervical nerve root course, and excluded levels very unlikely to cause symptoms. ...Does residual foraminal stenosis at levels not covered by anterior cervical discectomy and fusion aggravate postoperative outcomes in cervical radiculopathy?Article

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• San Kim
• Jae Hwan Cho

Study design: Retrospective cohort study. Purpose: To evaluate whether untreated foraminal stenosis (FS) at levels not included in anterior cervical discectomy and fusion (ACDF) impacts postoperative outcomes in patients with cervical radiculopathy and assess if residual FS increases the risk of adjacent segment disease (ASD). Overview of literature: Level selection for ACDF for cervical radiculopathy is complex, considering variable patient anatomy and symptoms. It is unclear whether treating only potentially symptomatic levels could provide equivalent results to managing all pathologic levels. Methods: This was a retrospective cohort study of 188 patients undergoing ACDF for degenerative cervical radiculopathy between 2014 and 2020. Patients were divided into two groups: those with all symptomatic levels decompressed (No-FS group, n=162) and those with untreated FS at levels not targeted in surgery (FS group, n=26). Postoperative outcomes, including neck pain, arm pain, and Neck Disability Index (NDI), were evaluated at 3 months and 2 years. Radiographic parameters and ASD incidence were also compared between groups. Results: Both groups showed significant improvement in neck pain, arm pain, and NDI postoperatively, with no significant intergroup differences at 3 months and 2 years. C2-C7 lordosis and sagittal vertical axis showed similar improvement in both groups postoperatively. Rates of ASD and revision surgery did not differ significantly between No-FS and FS groups (5.6% vs. 7.7%, respectively; p=0.652). Logistic regression revealed no significant predictors of NDI improvement >50% among preoperative demographic or radiographic factors. Conclusions: Untreated FS at levels outside the surgical target area did not adversely affect ACDF outcomes or increase ASD risk over a 2-year follow-up. These findings suggest that ACDF can be safely limited to levels directly associated with patient symptoms without compromising clinical outcomes, potentially reducing the surgical extent and associated risks.ViewShow abstract... Electromyography (EMG) signs can be utilized for clinical/biomedical applications, Evolvable Equipment Chip (EHW) impro-vement, and present day human PC connection. EMG signals gained from muscles require progressed techniques for identification, deterioration, handling, and order [6]. The reason for this paper is to delineate the different techniques and calculations for EMG signal investigation to give productive and viable approaches to figuring out the sign and its tendency. ...... This paper provides specialists with a solid understanding of EMG signals and their analysis methods. This information will assist them with growing all the more impressive, adaptable, and effective applications [6]. When performing neuromuscular activities, the EMG signal is a biological signal that gauges the electrical fluxes produced in muscles during contraction. ...Comparison of dynamic neuromusuclar stabilisation and Maitland’s mobilisation on nerve conductivity in subjects with cervical radiculopathyArticleFull-text available

• Oct 2024

• Pavithralochani .V
• Jibi Paul
• Jagatheesan Alagesan
• Hema Lakshmi .V

Aim. To compare the effect of Dynamic Neuromuscular Stabilisation and Maitland mobilisation in improving nerve conductivity and muscle activity in patients with cervical radiculopathy Methodology. A pilot study done on 34 subjects with unilateral cervical radiculopathy was conducted based on selection criteria. Subjects were divided into 2 groups. Group DNS received Dynamic neuromuscular stabilisation exercise. Group MM received Maitland mobilisation. Pre-test was done using NCV for median nerve conductivity and EMG for pronator teres muscle activity. Following the intervention’s termination, a post-test was conducted using the same measurements. The gathered data was put to use in statistics. Result. The statistics revealed that there is no significant difference between two groups. But group DNS who were treated with Dynamic neuromuscular stabilisation showed a better improvement in nerve conductivity and muscle activity than the subjects treated with Maitland mobilisation in cervical radiculopathy.ViewShow abstract... Some authors have made reliable diagnoses by correlating appropriate symptoms, MRI or CT findings of foraminal stenosis, and positive response to isolated C4 nerve root block [9]. Although electromyography is routinely employed for lower cervical roots, it often fails to detect abnormalities specific to C4 radiculopathy, which does not include the presence of motor symptoms, as evidenced by the occasional denervation of periscapular muscles [19,20]. ...The resisted levator scapulae test: a clinical test for C4 radiculopathyArticleFull-text available

• May 2025
• EUR SPINE J

• William Peters
• James Thomas Ernest Smith
• Mario Zotti

Purpose Cervical radiculopathy results from compression of a nerve root in the cervical spine creating upper limb or shoulder girdle sensorimotor dysfunction which commonly affects the C5-8 roots. Isolated C4 radiculopathy is rare and lacks typical clinical radiculopathy features and, as a result is underreported and poorly diagnosed. Nerve blocks can be used on the basis of pain distribution and clinical suspicion, however, no bedside tests exist to identify and test C4 radiculopathy in isolation. The objective of our study was to assess the clinical utility of using the Resisted Levator Scapulae test in identifying patients with C4 radiculopathy on physical exam. Methods Participants were recruited on the basis of clinical suspicion of C4 radiculopathy. Participants were separated into test and pragmatic control based on radiographic evidence of C3/4 foraminal stenosis. Test group patients received the reference standard CT guided nerve root injection, pragmatic control patients were classed based on imaging. The reference standard was performed after review with a spinal surgeon where the RLS test result was recorded. Data was collected with primary and expanded analyses providing data for for predictive values using a contingency table. Results Twenty-five participants (12 male, 13 female) with a median age of 69 completed the study in the test group, with 298 participants (192 male, 106 female) completing the study in the pragmatic control group. Nine test group participants (2.8%) showed isolated C4 radiculopathy with response to the diagnostic CT guided C4 nerve block, while 15 (4.6%) had multilevel involvement including C4. Primary analysis revealed sensitivity of 90% and specificity of 20% with an odds ratio of 2.25 (confidence interval: 0.2–25.4). Expanded analysis strengthened specificity (93%) and NPV (99.6%). Conclusion The resisted levator scapulae test is a novel bedside physical diagnostic test for C4 radiculopathy used to complement a neurological examination and raise suspicion when positive.ViewShow abstract... Es gibt deutliche Belege dafür, dass die paravertebrale Muskulatur Radikulopathien elektromyographisch sensitiver sichern hilft als die Extremitätenmuskulatur [32]. Als Kritik an der Untersuchung paravertebraler Muskeln wird angeführt, dass PSA der paravertebralen Muskulatur bei Menschen mit einem Diabetes mellitus sowie bei älteren gesunden Personen unspezifisch gehäuft anzutreffen wäre [30]. ...EMG phenomena of myogenic hyperexcitabilityArticleFull-text available

• Jan 2024
• NERVENARZT

• Andreas Posa
• Malte Kornhuber

Zusammenfassung Art, Verteilungsmuster und der zeitliche Verlauf muskulärer Spontanaktivität sind für die Diagnostik neuromuskulärer Krankheiten im klinischen Alltag bedeutsam. Bei neurogenen Läsionen mit motorisch axonaler Beteiligung ist pathologische Spontanaktivität (PSA) meist 2 bis 4 Wochen nach Läsionsbeginn mittels Nadelelektromyographie sicher fassbar. Das Verteilungsmuster korreliert dabei mit dem Läsionsort. Schwerpunkt der vorliegenden Arbeit liegt in der Darstellung der unterschiedlichen PSA-Verteilungsmuster bei myogenen Erkrankungen.ViewShow abstractSegmental PhysiologyChapter

• Jan 2026

• Jazmín Ariza-Tarazona
• Laura Pinilla

Knowledge of the embryological development of metamers is of great importance for the understanding of the concept of “segment.” The segment is composed, in turn, of embryological derivatives of these metamers, such as dermatomes, myotomes, sclerotomes, and viscerotomes. The different parts of the segment are in obvious connection and are the morphological support of the pathophysiological reflexes that arise from any part of each segment. When a viscera or organ is pathologically altered, its expression occurs through the other parts of the same segment of embryological origin. In the case of the skin, dermatomes, according to Henry Head, are areas that have a segmental distribution and that, when they converge, form zones that are in semiological relationship with certain organs. According to James Mackenzie, deep tissues such as muscles, bones, tendons, and joints can also have semiological changes in the cases of visceral disease. In this chapter, the dermatomic, myotomic, sclerotomic, and viscerotomic segmental relationships of each organ of the face, neck, trunk, and pelvis are shown, which are the foundation for the physical examination, diagnosis, and treatment of segmental disorders in neural therapy medicine.ViewShow abstractDisorders of the Nerve Roots, Plexuses, and Peripheral NervesChapter

• Jan 2026

• Steven McGee

ViewMagnetic Resonance Neurography of the Brachial PlexusArticle

• May 2025
• Magn Reson Imag Clin N Am

• Emily J. Davidson
• Sophie C. Queler
• Delaram Shakoor
• Darryl B. Sneag

ViewWhat is Neuralgic Amyotrophy?脊髄外科医が知っておくべき病気―Neuralgic amyotrophyとは？―Article

• Oct 2024

• Masahiro Sonoo

ViewThe Concept and Diagnosis of True Neurogenic Thoracic Outlet SyndromeTrue neurogenic TOSの概念と診断方法Article

• Jan 2023

• Masahiro Sonoo

ViewOptimization of Muscle Selection for Needle Electromyography in Isolated C6 Root Lesion: A Prospective Chart Review StudyArticle

• Nov 2023
• AM J PHYS MED REHAB

• Seyed Mansoor Rayegani
• Mohammad Hasan Bahrami
• Kianmehr Aalipour
• Sara Maleki Kahaki

Objectives To evaluate muscles with more prominent needle electromyographic findings to optimize needle EMG screening of isolated C6 radiculopathy in patients with C6 root lesions. Design This prospective clinical study was performed on 39 patients with isolated and unilateral cervical radiculopathy selected from all referrals of 1733 patients to the electrodiagnosis unit of the Physical Medicine and Rehabilitation department of a tertiary medical center (from April 2021 to December 2021). The presence of fibrillation potentials, positive sharp waves, and/or neurogenic motor action potentials that occurred in isolation or combination with selected muscles was considered an abnormal finding. Results Out of 1733 referrals, 39 patients (18 males (46.1%) and 21 females (53.8%)), with a mean age of 49.7 ± 9.6 years were found eligible. According to needle EMG findings, the most involved muscles in C6 root lesion were pronator teres (100%), followed by extensor carpi radialis longus (94.8%), flexor carpi radialis (89.7%), brachioradialis (82%), infraspinatus (82%), supraspinatus (79.4%), deltoid (74.3%), biceps brachii (64.1%), extensor digitorum communis (33.3%), and triceps brachii (15.3%) muscles. Conclusion The pronator teres is the most involved muscle of patients diagnosed with C6 radiculopathy. It might be considered the key muscle for screening and accurate diagnosis of C6 root involvement.ViewShow abstractShow moreManual muscle strength testing: intraobserver and interobserver reliabilities for the intrinsic muscles of the handArticleFull-text available

• Jul 1995

• Johannes Willem Brandsma
• Ton A R Schreuders
• James A. Birke
• Rob A B Oostendorp

ViewCorresponding Scapular Pain with the Nerve Root Involved in Cervical RadiculopathyArticleFull-text available

• Dec 2010
• J Orthop Surg

• Masaya Mizutamari
• Akira Sei
• Akinari Tokiyoshi
• Hiroshi Mizuta

To correspond scapular pain with the nerve root involved in cervical radiculopathy. In the anatomic study, 11 Japanese adult cadavers were dissected to examine the numbers and courses of the cutaneous nerves from C3 to C8 dorsal rami. In the clinical study, 14 men and 11 women aged 34 to 77 years who presented with scapular pain as well as pain, numbness or motor weakness in the upper limbs secondary to cervical radiculopathy were assessed. The involved nerve roots were identified based on the symptoms and signs in the arm and/ or fingers, the radiological diagnosis, and the pain response to cervical nerve root blocks. The sites and characteristics of radicular pain were assessed. In the anatomic study of 22 cutaneous nerves from medial branches of dorsal rami, 18 involved the C5 nerve root, 0 the C6 root, one the C7 root, and 8 the C8 root. In the clinical study, the radicular pain often occurred in the suprascapular region involving the C5 root, in the suprascapular to posterior deltoid region involving the C6 root, in the interscapular region involving the C7 root, and in the interscapular and scapular regions involving the C8 root. All patients with C5 or C8 radiculopathy had both superficial and deep pain, whereas almost all patients with C6 or C7 radiculopathy had deep pain only. No patient had superficial pain only. Cervical radiculopathy can cause scapular pain. Pain sites and characteristics are related to the affected nerve root.ViewShow abstractRadiculopathiesChapter

• Jan 2002

• Daniel Dumitru
• Machiel J Zwarts

ViewMuscles, Testing and FunctionArticle

• Jan 1974

• H O KENDALL
• F P KENDALL
• G.E. Wadsworth

The methods used in the preparation of the schedule of the muscles form part of those used for clinical diagnosis and constitute the essential element in the application of specific treatment adapted for the management of muscular and neuro muscular affections. This work comprises a detailed account of the methods of the schedule and the functional consequences of muscular deficiencies and retractions.ViewShow abstractElectromyography and Neuromuscular Disorders: Clinical-Electrophysiologic Correlations: Third EditionArticle

• Nov 2012

• D.C. Preston

Diagnose neuromuscular disorders more quickly and accurately with Electromyography and Neuromuscular Disorders: Clinical-Electrophysiologic Correlations, 3rd Edition! State-of-the-art guidance helps you correlate electromyographic and clinical findings and use the latest EMG techniques to their fullest potential.ViewShow abstractAnatomic Localization for Needle ElectromyographyArticle

• Mar 1994

• Donald G. Kikta

ViewC8 and T1 innervation of forearm musclesArticle

• Aug 2014
• CLIN NEUROPHYSIOL

• Takashi Chiba
• Fumie Konoeda
• Mana Higashihara
• Masahiro Sonoo

Objective C8-dominant innervation of ulnar-innervated and T1-dominant innervation of median-innervated intrinsic hand muscles have been suggested, although less is known regarding forearm muscles. We aimed to determine myotomal innervation of the forearm muscles based on the clinical and electromyographial findings of patients with C8 or T1 lesions. Methods Medical Research Council scale and EMG findings were retrospectively reviewed in 16 patients with C8 lesions (2 postmedian sternotomy C8 plexopathy and 14 C8 radiculopathy) and 9 patients with T1-dominant lesions (8 true neurogenic thoracic outlet syndrome and 1 T1 radiculopathy). Results Clinical and EMG findings revealed T1-dominant innervation of the flexor digitorum superficialis, flexor digitorum profundus of the index finger, abductor pollicis brevis, and flexor pollicis longus muscles, and C8-dominant innervation of the flexor carpi ulnaris, flexor digitorum profundus of the little finger, and digit extensors innervated by the posterior interosseous nerve. The first dorsal interosseous, and abductor digiti minimi muscles seem to be innervated by both C8 and T1 roots. Conclusions C8-dominant innervation of ulnar-innervated muscles and T1-dominant innervation of median-innervated muscles are also evident for forearm flexor muscles. Significance Such an additional evidence for myotomal innervation will improve localization in clinical as well as electrophysiological diagnoses.ViewShow abstractThe Minute Anatomy of the Brachial PlexusArticle

• Jan 1886
• Proc Roy Soc Lond

• W. P. Herringham

It has for some time appeared probable that the spinal nerves which form the brachial plexus do not become confounded one with another, but retain each its separate course and its separate functions. To the naked eye a nerve is a bundle of parallel threads bound together, and at the same time divided by a sheath of connective tissue. It seemed to me possible that the course of the spinal nerve roots could be traced by a dissection which should follow each through the plexus to the nerves which branch therefrom, and in these to its final destination.ViewShow abstractDaniels and Worthingham''s Muscle Testing: Techniques of Manual Examination 6th EdArticle

• H Hislop
• J Montgomery

ViewElectromyography and magnetic resonance imaging in the evaluation of radiculopathyArticle

• Feb 1999
• MUSCLE NERVE

• Rachel A. Nardin MD
• Mahesh R. Patel MD
• Thomas F. Gudas MD
• Elizabeth Raynor

Electromyography (EMG) and magnetic resonance imaging (MRI) are commonly used in the diagnosis of cervical and lumbosacral radiculopathy, but the agreement between the two studies is unknown. We retrospectively studied 47 patients with a clinical history compatible with either cervical or lumbosacral radiculopathy who were evaluated with both an EMG and a spine MRI within 2 months of each other. Among these patients, 55% had an EMG abnormality and 57% had an MRI abnormality that correlated with the clinically estimated level of radiculopathy. The two studies agreed in a majority (60%) of patients, with both normal in 11 and both abnormal in 17; however, only one study was abnormal in a significant minority (40%), suggesting that the two studies remain complementary diagnostic modalities. The agreement was higher in patients with abnormal findings on neurologic examination, underscoring the difficulty of confirming the diagnosis in mild radiculopathy. © 1999 John Wiley & Sons, Inc. Muscle Nerve 22: 151–155, 1999ViewShow abstractShow more

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P3-4-3. C5/C6/C7 myotome of upper limb muscles documented by MRI-confirmed cervical spondylotic radi...

May 2018 · Clinical Neurophysiology

• Yuichi Furukawa
• Akiko Kadoya
• Masahiro Sonoo
• [...]
• Yosuke Miyaji

Many myotomal charts have been published, although there is considerable discordance among them. We aimed to determine C5, C6, and C7 myotomes of upper limb muscles. We retrospectively reviewed the patients with MRI-confirmed isolated C5, C6, or C7 cervical spondylotic radiculopathy (CSR). Twenty-four CSR patients (7 C5, 7 C6, and 10 C7 CSR) were enrolled. Muscle weaknesses were found in 7/7 ... [Show full abstract] deltoid, 7/7 infraspinatus, 6/7 biceps brachii (BB), and 5/6 brachioradialis among C5 CSR cases, in 4/4 pronator teres (PT) and 5/7 wrist extensor among C6 cases, and in 5/10 triceps brachii among C7 cases. Denervation potentials on needle EMG were found in 0/5 C5, 6/7 C6, and 1/4 C7 cases at PT, in 0/2 C5 and 4/7 C6 cases at extensor carpi radialis brevis (ECRB), in 2/4 C5 and 2/5 C6 cases at extensor carpi radialis longus (ECRL), and in 1/4 C6 and 5/8 C7 cases at flexor carpi radialis (FCR). Main innervation of deltoid, infraspinatus, and BB by C5, and that of triceps by C7 coincide with most previous literature. Among muscles in which controversy remains regarding myotome, brachioradialis is mainly innervated by C5 root, ECRL by C5/C6, ECRB and PT by C6, and FCR by C7.Read moreArticle

Recent advances in neuroanatomy: the myotome update

January 2023 · Journal of Neurology, Neurosurgery, and Psychiatry

• Masahiro Sonoo

The myotome of a muscle is the basis for diagnosing spinal and peripheral nerve disorders. Despite its critical importance in clinical neurology, myotome charts presented in many textbooks, surprisingly, show non-negligible discordances with each other. Many authors do not even clearly state the bases of their charts. Studies that have presented with raw data regarding myotome identification are ... [Show full abstract] rather rare. A classic study in the 19th century that pursued the nerve course in cadavers still has a substantial influence on existing charts, despite its definite limitations. Other scarce studies in humans include identification by root stimulation during surgery, clinical observations in root avulsion or spinal cord injury and clinical and electromyographical investigations in patients with single radiculopathies or certain plexopathies. A few recent studies have proposed new theories regarding the myotomes of some muscles. T1 innervation of the median intrinsic hand muscles is a typical example. We have added a number of new findings, such as T1 innervation of the forearm flexor muscles innervated by the median nerve except the pronator teres and flexor carpi radialis, C5 innervation of the brachioradialis, and two C6 indicator muscles, pronator teres and extensor carpi radialis brevis. Increased accuracy of the myotome charts will improve the localisation in neurology.Read moreArticle

O2-6-21. Comparison of muscle ultrasound findings between demyelinating neuropathy and axonopathy

September 2017 · Clinical Neurophysiology

• Masahiro Sonoo
• Keiichi Hokkoku
• Hiroshi Tsukamoto
• Yuki Hatanaka

Denervation causes increased echo intensity (EI) and decreased muscle thickness (MT) on muscle ultrasound (MUS). Chronic inflammatory demyelinating polyneuropathy (CIDP) does not present with denervation unless secondary axonal degeneration occurs. Hence, few MUS changes would occur compared to amyotrophic lateral sclerosis (ALS). The abductor pollicis brevis, abductor digiti minimi, and first ... [Show full abstract] dorsal interosseous muscles of 12 patients with CIDP and 13 patients with ALS were examined. There were no significant differences in Medical Research Council scales of each muscle between the CIDP and ALS group. EI and MT were measured quantitatively in every muscle. Raw values were converted into z-scores using the data from 40 normal controls (NCs). There were no significant differences between the CIDP and NC groups regarding EI and MT. The ALS group exhibited significantly higher EI and significantly lower MT than the other two groups (all P < 0.001). Our data suggested that patients with CIDP exhibit few changes on MUS. This finding may help to differentiate CIDP from ALS and predict whether the pathology is demyelination or axonal degeneration.Read moreArticle

C8 and T1 innervation of forearm muscles

August 2014 · Clinical Neurophysiology

• Takashi Chiba
• Fumie Konoeda
• Mana Higashihara
• [...]
• Masahiro Sonoo

Objective C8-dominant innervation of ulnar-innervated and T1-dominant innervation of median-innervated intrinsic hand muscles have been suggested, although less is known regarding forearm muscles. We aimed to determine myotomal innervation of the forearm muscles based on the clinical and electromyographial findings of patients with C8 or T1 lesions. Methods Medical Research Council scale and EMG ... [Show full abstract] findings were retrospectively reviewed in 16 patients with C8 lesions (2 postmedian sternotomy C8 plexopathy and 14 C8 radiculopathy) and 9 patients with T1-dominant lesions (8 true neurogenic thoracic outlet syndrome and 1 T1 radiculopathy). Results Clinical and EMG findings revealed T1-dominant innervation of the flexor digitorum superficialis, flexor digitorum profundus of the index finger, abductor pollicis brevis, and flexor pollicis longus muscles, and C8-dominant innervation of the flexor carpi ulnaris, flexor digitorum profundus of the little finger, and digit extensors innervated by the posterior interosseous nerve. The first dorsal interosseous, and abductor digiti minimi muscles seem to be innervated by both C8 and T1 roots. Conclusions C8-dominant innervation of ulnar-innervated muscles and T1-dominant innervation of median-innervated muscles are also evident for forearm flexor muscles. Significance Such an additional evidence for myotomal innervation will improve localization in clinical as well as electrophysiological diagnoses.Read moreLast Updated: 09 Jan 2026Interested in research on Radiculopathy?Join ResearchGate to discover and stay up-to-date with the latest research from leading experts in Radiculopathy and many other scientific topics.Join for free ResearchGate iOS AppGet it from the App Store now.InstallKeep up with your stats and moreAccess scientific knowledge from anywhere