(See also Overview of Delirium and Dementia and Dementia.)
Dementia is chronic, global, usually irreversible deterioration of cognition.
Normal-pressure hydrocephalus is thought to result from a defect in cerebrospinal fluid (CSF) resorption in arachnoid granulations. This disorder accounts for up to 6% of dementias.
Dementia should not be confused with delirium, although cognition is disordered in both. The following helps distinguish them:
Other specific characteristics also help distinguish dementia and delirium (see table Differences Between Delirium and Dementia).
Symptoms and Signs
The gait disturbance in normal-pressure hydrocephalus is usually nonspecific unsteadiness and impaired balance, although a magnetic gait (the feet appear to stick to the floor) is considered the characteristic gait disturbance.
Dementia may not occur until late in the disorder. The most common early symptoms of dementia are disturbances of executive function and attention; memory tends to become impaired later.
Urinary incontinence is common.
Diagnosis
The classic symptoms (gait disturbance, urinary incontinence, and dementia), even combined, are nonspecific for normal-pressure hydrocephalus, particularly in older people. For example, some forms of vascular dementia can cause dementia, gait disturbance, and, less commonly, urinary incontinence.
A general diagnosis of dementia requires all of the following:
Evaluation of cognitive function involves taking a history from the patient and from someone who knows the patient plus doing a bedside mental status examination or, if bedside testing is inconclusive, formal neuropsychologic testing.
Brain imaging may show ventricular enlargement disproportionate to cortical atrophy; this finding is nonspecific but may support the diagnosis of normal-pressure hydrocephalus. Sulci high on the cortical convexity are often compressed, and the Sylvian fissures are disproportionately atrophic.
Lumbar puncture with removal of 30 to 50 mL of CSF can be done as a diagnostic trial. Improvement in gait, continence, and cognition after removal helps confirm the diagnosis, but improvement may not be evident until several hours after removal. Additional CSF may leak out after lumbar puncture, sometimes contributing to neurologic improvement.
Treatment
Ventriculoperitoneal shunting is useful for patients with acceptable surgical risks. Improvements after lumbar puncture to remove CSF, done during diagnosis, may predict the response to shunting. In several case series (but in no randomized trials), patients improved substantially, typically in gait, continence, and daily functioning, after shunting; improvement in cognition was less common.
Key Points
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Suspect normal-pressure hydrocephalus based on classic symptoms (gait disturbance, urinary incontinence, dementia), but consider lumbar puncture to remove excess CSF as a diagnostic trial to help confirm the diagnosis.
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If surgical risks are acceptable, insert a ventriculoperitoneal shunt, which may significantly improve gait, continence, and daily functioning; improvement in mental function are less.
