A procedure performed under local anaesthetic in which cerebrospinal fluid is withdrawn by means of a hollow needle inserted into the subarachnoid space in the region of the lower back (usually between the third and fourth lumbar vertebrae). The fluid obtained is examined for diagnosis of meningitis, multiple sclerosis, and various other disorders of the brain and spinal cord. Lumbar puncture may also be perfomed to inject agents into the subarachnoid space. The procedure is usually without risk to the patient, but in patients with raised intracranial pressure it may be hazardous. CT and MRI scanning prior to lumbar puncture have greatly reduced the risk of performing the test in patients with unsuspected raised intracranial pressure. The commonest side-effect of the procedure is a headache that is worse on standing and reduces on lying down (intracranial hypotension headache). See also Queckenstedt test.
Subjects: Medicine and Health.