- Normal Pressure Hydrocephalus (NPH) is a relatively but treatable syndrome causing a clinical triad of abnormal gait (ataxic or apractic), dementia (usually mild to moderate, with an emphasis on executive impairment), and urinary urgency or incontinence.
- Neuroimaging reveals enlarged lateral ventricles (hydrocephalus) with little or no cortical atrophy. A characteristic “magnetic” gait with external hip rotation, low foot clearance and short strides, along with prominent truncal sway or instability, favours NPH.
- Lumbar puncture opening pressure falls in the high normal range, and the CSF protein, glucose and cell counts are normal.
- The precise underlying pathophysiology remains unclear.
- In contrast to Alzheimer’s disease, the patient with NPH complains of an early and prominent gait disturbance without cortical atrophy on CT or MRI.
- A transient improvement in gait or cognition may follow lumbar puncture (or serial punctures) with removal of 30-50 mL of CSF. If CSF drainage causes improvement, a curative ventricular shunt surgery will probably be considered.
- Thirty to fifty percent of patients identified by careful diagnosis as having NPH will improve with ventricular shunting.
- Gait may improve more than cognition, but many reported failures to improve cognitively may have resulted from co-morbid Alzheimer’s. Short-lasting improvement is common.
- Patients should be carefully selected for shunting, because subdural hematoma, infection, and shunt failure are known complications.
Adapted from Harrison’s.