The CSF tap test, sometimes lumbar tap test or Miller Fisher Test, is a medical test that is used to decide whether shunting of

cerebrospinal fluid Cerebrospinal fluid (CSF) is a clear, colorless body fluid found within the tissue that surrounds the brain and spinal cord of all vertebrates. CSF is produced by specialised ependymal cells in the choroid plexus of the ventricles of the bra ...

(CSF) would be helpful in a patient with suspected

normal pressure hydrocephalus Normal-pressure hydrocephalus (NPH), also called malresorptive hydrocephalus, is a form of communicating hydrocephalus in which excess cerebrospinal fluid (CSF) occurs in the ventricles, and with normal or slightly elevated cerebrospinal fluid p ...

(NPH). The test involves removing 30-50 ml of

(CSF) through a

lumbar puncture Lumbar puncture (LP), also known as a spinal tap, is a medical procedure in which a needle is inserted into the spinal canal, most commonly to collect cerebrospinal fluid (CSF) for diagnostic testing. The main reason for a lumbar puncture is to ...

, after which motor and cognitive function is clinically reassessed. The name "Fisher test" is after

C. Miller Fisher Charles Miller Fisher (December 5, 1913, Waterloo, Ontario – April 14, 2012, Albany, New York) was a Canadian neurologist whose notable contributions include the first detailed descriptions of lacunar strokes, the identification of transient ...

, a Canadian neurologist working in Boston, Massachusetts, who described the test. Clinical improvement showed a high predictive value for subsequent success with shunting. A "negative" test has a very low predictive accuracy, as many patients may improve after a shunt in spite of lack of improvement after CSF removal.

References

{{Central nervous system tests and procedures Medical tests Symptoms and signs: Nervous system