CSF tap test

CSF tap test
Lumbar puncture
Synonyms	Lumbar tap test
Purpose	test to decide shunting of cerebrospinal fluid

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 (CSF) would be helpful in a patient with suspected normal pressure hydrocephalus (NPH). The test involves removing 30–50 ml of CSF through a lumbar puncture, after which motor and cognitive function is clinically reassessed.^[1] The name "Fisher test" is after C. Miller Fisher, a Canadian neurologist working in Boston, Massachusetts, who described the test.^[2]

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.^[3]