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Normal Pressure Hydrocephalus

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Overview

Normal pressure hydrocephalus (NPH) is a type of communicating hydrocephalus characterised by the dilation of the ventricles in the brain with an absence of raised cerebrospinal fluid (CSF) pressure on a lumbar puncture. It classically presents with a triad of dementia, urinary incontinence, and gait abnormalities.

It is a reversible cause of dementia, hence why its diagnosis is essential. It should be considered in patients that have apraxia unresponsive to levodopa.

There are two forms of NPH:

  • Idiopathic (primary) NPH – aetiology unknown (50%)
  • Symptomatic (secondary) NPH, which may be secondary to:

Communicating and non-communicating hydrocephalus

Communicating hydrocephalus is the blockage of the flow of CSF when it exits the ventricles. The “communicating” part means that the CSF can still flow between ventricles. 

Non-communicating hydrocephalus is also known as obstructive hydrocephalus. This is where the flow of CSF is blocked along the passages between the ventricles.

Epidemiology

  • Average age of onset is around 70 years
  • Men and women are affected in equal numbers
  • Idiopathic NPH accounts for around 6% of all cases of dementia

Risk Factors

  • Aged >65 years
  • Cardiovascular disease
  • Cerebrovascular disease
  • Hypertension
  • Diabetes mellitus

Presentation

The classic triad of symptoms is:

  • Gait disturbance
    • Gait usually slow and cautious – may be a magnetic gait
    • Patients often shuffle
    • Patients are unsteady
    • Patients take small steps
  • Urinary incontinence, sometimes bowel incontinence as well
  • Dementia

Differential Diagnoses

Parkinson’s disease

  • Symptoms such as tremors are usually asymmetrical

Multisystem atrophy

Parkinsonism

  • Dementias
  • Cognitive impairment usually precedes gait impairment

Investigations

  • CT head without contrast or MRI head which may show:
    • Ventricular enlargement
    • Damage to tissues surrounding the ventricles
    • May be normal
  • Lumbar puncture:
    • Opening pressure usually normal
  • Large-volume CSF tap
    • Usually improves gait symptoms

Management

  • If suitable for surgery:
    • 1st-line: ventriculoperitoneal shunting
  • If unsuitable for surgery:
    • Repeated large-volume CSF taps

Complications

  • Cognitive impairment
  • Complications with shunting:
  • Shunt infection
  • Subdural haematoma
  • Stroke

Prognosis

  • Early treatment improves outcomes

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