Lumbar Puncture: Background, Indications, Contraindications

Lumbar puncture is a procedure that is often performed in the emergency department to obtain information about the cerebrospinal fluid (CSF). [1, 2, 3, 4] Although usually used for diagnostic purposes to rule out potential life-threatening conditions (eg, bacterial meningitis or subarachnoid hemorrhage), it is also sometimes used for therapeutic purposes (eg, treatment of pseudotumor cerebri). CSF fluid analysis can also aid in the diagnosis of various other conditions (eg, demyelinating diseases and carcinomatous meningitis).

Lumbar puncture should be performed only after a neurologic examination but should never delay potentially life-saving interventions, such as the administration of antibiotics and steroids to patients with suspected bacterial meningitis. [5]

Relevant anatomy

The lumbar spine consists of five moveable vertebrae numbered L1–-L5.The lumbar vertebrae have a vertical height that is less than their horizontal diameter. They are composed of the following three functional parts:

• The vertebral body, designed to bear weight

• The vertebral (neural) arch, designed to protect the neural elements

• The bony processes (spinous and transverse), which function to increase the efficiency of muscle action

The lumbar vertebral bodies are distinguished from the thoracic bodies by the absence of rib facets. The lumbar vertebral bodies (vertebrae) are the heaviest components, connected together by the intervertebral discs. The size of the vertebral body increases from L1 to L5, indicative of the increasing loads that each lower lumbar vertebra absorbs. Of note, the L5 vertebra has the heaviest body, smallest spinous process, and thickest transverse process.

For more information about the relevant anatomy, see Lumbar Spine Anatomy.

A meta-analysis of randomized controlled trials suggests that ultrasound guidance may improve first puncture success rate in infants but not in older children. [6]