Lumbar puncture (spinal tap)

[exinilu]

Lumbar puncture is used to do the following:

Evaluate intracranial pressure and CSF composition (see table Cerebrospinal Fluid Abnormalities in Various Disorders)
Therapeutically reduce intracranial pressure (eg, idiopathic intracranial hypertension)
Administer intrathecal drugs or a radiopaque contrast agent for myelography

Relative contraindications include

Infection at the puncture site
Bleeding diathesis
Increased intracranial pressure due to an intracranial mass lesion, obstructed CSF outflow (eg, due to aqueductal stenosis or Chiari I malformation), or spinal cord CSF blockage (eg, due to tumor cord compression)

If papilledema or focal neurologic deficits are present, CT or MRI should be done before lumbar puncture to rule out presence of a mass that could precipitate transtentorial or cerebellar herniation.