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:
- Subarachnoid haemorrhage
- Meningitis
- Central nervous system tumours
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
- This progresses more slowly than those with Alzheimer’s disease
Differential Diagnoses
Parkinson’s disease
- Symptoms such as tremors are usually asymmetrical
Multisystem atrophy
- Postural hypotension and impotence may be early features
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