Cerebrospinal fluid tap test in normal pressure hydrocephalus.

Normal pressure hydrocephalus (NPH) is a common cause of gait apraxia, cognitive impairment and urinary incontinence in older adults and can respond to cerebrospinal fluid (CSF) shunting. It can be challenging to select optimal candidates for CSF shunting given that communicating hydrocephalus is common in the normal ageing population as are the clinical symptoms of NPH. Large-volume lumbar puncture or CSF tap test can identify good candidates for CSF shunting. While neurologists are familiar with and have access to routine lumbar punctures, there are nuances about the CSF tap test for NPH to consider in clinical practice. In this article, we describe our practice for CSF tap tests with reference to the current evidence and common pitfalls while accepting the limitation of the test itself.