Lumbar Puncture - Risks

Risks

Post spinal headache with nausea is the most common complication; it often responds to analgesics and infusion of fluids. It was long taught that this complication can often be prevented by strict maintenance of a supine posture for two hours after the successful puncture; this has not been borne out in modern studies involving large numbers of patients. Merritt's Neurology (10th edition), in the section on lumbar puncture, notes that intravenous caffeine injection is often quite effective in aborting these so-called "spinal headaches." Contact between the side of the lumbar puncture needle and a spinal nerve root can result in anomalous sensations (paresthesia) in a leg during the procedure; this is harmless and patients can be warned about it in advance to minimize their anxiety if it should occur. A headache that is persistent despite a long period of bedrest and occurs only when sitting up may be indicative of a CSF leak from the lumbar puncture site. It can be treated by more bedrest, or by an epidural blood patch, where the patient's own blood is injected back into the site of leakage to cause a clot to form and seal off the leak.

Serious complications of a properly performed lumbar puncture are extremely rare. They include spinal or epidural bleeding, adhesive arachnoiditis and trauma to the spinal cord or spinal nerve roots resulting in weakness or loss of sensation, or even paraplegia. The latter is exceedingly rare, since the level at which the spinal cord ends (normally the inferior border of L1, although it is slightly lower in infants) is several vertebral spaces above the proper location for a lumbar puncture (L3/L4). There are case reports of lumbar puncture resulting in perforation of abnormal dural arterio-venous malformations, resulting in catastrophic epidural hemorrhage; this is exceedingly rare.

The procedure is not recommended when epidural infection is present or suspected, when topical infections or dermatological conditions pose a risk of infection at the puncture site or in patients with severe psychosis or neurosis with back pain. Some authorities believe that withdrawal of fluid when initial pressures are abnormal could result in spinal cord compression or cerebral herniation; others believe that such events are merely coincidental in time, occurring independently as a result of the same pathology that the lumbar puncture was performed to diagnose. In any case, computed tomography of the brain is often performed prior to lumbar puncture if an intracranial mass is suspected.

Removal of cerebrospinal fluid resulting in reduced fluid pressure has been shown to correlate with greater reduction of cerebral blood flow among patients with Alzheimer's disease. Its clinical significance is uncertain.