Normal pressure hydrocephalus

What it is

Normal pressure hydrocephalus is a form of chronic communicating hydrocephalus that primarily affects adults over 60 years of age. It is characterized by a distinct clinical triad - gait apraxia, dementia and urinary incontinence - with normal or only mildly elevated ICP.

The etiology is idiopathic. The pathophysiology is reduced CSF absorption, then CSF accumulation, then enlargement of the ventricle.

How it presents

The classic triad is:

• Gait abnormalities: frequent falls, a broad-based gait with short shuffling steps - gait apraxia, also known as magnetic gait
• Dementia
• Urinary incontinence

What it does not do is as much part of the picture: normal pressure hydrocephalus does not manifest with signs of increased ICP, such as headache and papilledema.

The gait is the finding on neurological examination, and the gait table sets it beside the others:

• Normal: stand still, neutral gait, tandem gait
• Hemiplegic: decorticate upper arm and circumduction of the leg
• Diplegic, that is spastic: lower affected more than upper, scissoring gait, met in CP
• Neuropathic, that is high steppage: an LMN lesion, flex knee and hip, cannot dorsiflex the foot, foot drop
• Myopathic, that is waddling, where the contralateral hip is affected: cannot stabilize the hip, from proximal weakness
• Parkinsonian, that is shuffling: hypokinetic, lean forward, difficult initiating, small steps, resting tremor, hard tuning
• Ataxic: cerebellar, Post. Column, the drunken sailor gait
• Huntington

Normal pressure hydrocephalus often presents with a characteristic magnetic gait.