Fisher test
Encyclopedia
The Miller Fisher test is a diagnostic procedure used to confirm suspected normal pressure hydrocephalus
(NPH). The Miller Fisher test confirms NPH if the removal of 30 mL of cerebrospinal fluid (CSF) results in clinical improvement of NPH symptoms.
Diagnosis of NPH is usually first led by a lumbar puncture
, followed by the evaluation of clinical response to removal of CSF. This can be followed by a CT, MRI
, and continuous external lumbar CSF drainage during 3 or 4 days.
Lumbar puncture
is usually the first step in diagnosis of NPH and the opening pressure measured carefully. In most cases, CSF pressure is usually above 155 mmH2O. Clinical improvement after removal of CSF (30 mL or more) has a high predictive value for subsequent success with shunting
. This is called the "lumbar tap test" or "Miller Fisher test". 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.
Normal pressure hydrocephalus
Normal pressure hydrocephalus , also termed symptomatic hydrocephalus, occurs when there is an increase in intracranial pressure due to an abnormal accumulation of cerebrospinal fluid in the ventricles of the brain, which can cause ventriculomegaly...
(NPH). The Miller Fisher test confirms NPH if the removal of 30 mL of cerebrospinal fluid (CSF) results in clinical improvement of NPH symptoms.
Diagnosis of NPH is usually first led by a lumbar puncture
Lumbar puncture
A lumbar puncture is a diagnostic and at times therapeutic procedure that is performed in order to collect a sample of cerebrospinal fluid for biochemical, microbiological, and cytological analysis, or very rarely as a treatment to relieve increased intracranial pressure.-Indications:The...
, followed by the evaluation of clinical response to removal of CSF. This can be followed by a CT, MRI
Magnetic resonance imaging
Magnetic resonance imaging , nuclear magnetic resonance imaging , or magnetic resonance tomography is a medical imaging technique used in radiology to visualize detailed internal structures...
, and continuous external lumbar CSF drainage during 3 or 4 days.
Lumbar puncture
Lumbar puncture
A lumbar puncture is a diagnostic and at times therapeutic procedure that is performed in order to collect a sample of cerebrospinal fluid for biochemical, microbiological, and cytological analysis, or very rarely as a treatment to relieve increased intracranial pressure.-Indications:The...
is usually the first step in diagnosis of NPH and the opening pressure measured carefully. In most cases, CSF pressure is usually above 155 mmH2O. Clinical improvement after removal of CSF (30 mL or more) has a high predictive value for subsequent success with shunting
Cerebral shunt
Cerebral shunts are commonly used to treat hydrocephalus, the swelling of the brain due to excess buildup of cerebrospinal fluid . If left unchecked, the cerebral spinal fluid can build up leading to an increase in intracranial pressure which can lead to intracranial hematoma, cerebral edema,...
. This is called the "lumbar tap test" or "Miller Fisher test". 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.