High-volume Lumbar Puncture

To support a diagnosis of normal pressure hydrocephalus (NPH), in addition to the patient’s symptoms and imaging findings, one must perform a high-volume lumbar puncture.

This is performed to assess the cerebrospinal fluid (CSF) pressure as well as to determine if more permanent CSF procedures (such as a ventriculoperitoneal shunt) would be of benefit to the patient.

A lumbar puncture (also known as “Spinal Tap”) involves inserting a thin needle in the lower back to drain CSF from around the spinal nerves. This procedure is performed either in clinic or as an outpatient. Sometimes fluoroscopic (X-ray) guidance may be helpful. Typically, 30 ml (about an ounce) of fluid is drained and sent for routine lab tests, including tests for Alzheimer’s disease when applicable.  Patients are instructed to remain recumbent for about 1 hour before departing.

This procedure is well tolerated, but can have risks of infection, bleeding, over-drainage or nerve root injury. Patients should remain off blood thinners (including aspirin containing products) prior to the procedure.