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 as an outpatient, typically in the clinic, although sometimes fluoroscopic (X-ray) guidance may be helpful. Typically, about an ounce of fluid is drained and sent for routine lab tests. 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.
