Normal pressure hydrocephalus

Background

• Possible reversible cause of dementia
• CSF buildup in the ventricles leading to increased intracranial pressure with edema of the periventricular white matter and corona radiata
  • Sacral motor nerve fibers that produce gait instability; incontinence ensues when compressed

Clinical Features

• Gait disturbance is most common and earliest finding
  • "Glue-footed" gait: move slowly, take small steps, often wide base, with difficulty turning
• Memory loss and dementia symptoms may be mild, subtle
• Incontinence is usually later stage, though sensation of urinary urgency is usually present before incontinence
• Usually do not have symptoms of increased intracranial pressure, such as headache, nausea, vomiting, visual loss

Differential Diagnosis

• Alzheimer's
• Stroke
• Parkinson's disease
• Electrolyte abnormality
• Malignancy
• Uremic encephalopathy
• Hydrocephalus ex vacuo (diffuse cerebral atrophy on CT)

Evaluation

• Initial ED workup
  • CBC
  • Chem 7
  • CT brain non-con: Ventriculomegaly without signs of obstruction at the level of the third or fourth ventricles
• Additional workup (in coordination with neurology/neurosurgery), consider:
  • MRI (done as part of the general work-up, and should be done before LP)
  • LP (definitive diagnosis), with normal opening pressure and CSF studies
    • Symptom improvement supports diagnosis

Normal pressure hydrocephalus vs brain atrophy

	Normal pressure hydrocephalus	Brain atrophy
Preferable projection	Coronal plane at the level of the posterior commissure of the brain.
Modality in this example	CT	MRI
CSF spaces over the convexity near the vertex (red ellipse)	Narrowed convexity ("tight convexity") as well as medial cisterns	Widened vertex (red arrow) and medial cisterns (green arrow)
Callosal angle (blue V)	Acute angle	Obtuse angle
Most likely cause of leucoaraiosis (periventricular signal alterations, blue arrows)	Transependymal cerebrospinal fluid diapedesis	Vascular encephalopathy, in this case suggested by unilateral occurrence

Evan's index is the ratio of maximum width of the frontal horns to the maximum width of the inner table of the cranium. An Evan's index more than 0.31 indicates hydrocephalus.

Management

• Fall precautions
• Consult neurology and/or neurosurgery to decide if patient is candidate for inpatient vs outpatient MRI and LP.
• LP is rarely done in the ED as it requires MRI before LP, and workup is typically non-emergent and can often be done as outpatient.

Disposition

• Workup typically is extensive, but can often be done as outpatient, depending on your institution.
• Decide plan for workup with neurology and/or neurosurgery
• Consider admission if patient lives alone (fall risk), has no follow-up, or is significantly altered.

Also See

• Stroke (Main)
• Ataxia
• Parkinson's Disease