You are asked to see a 75 year old man who is presenting with reduced mobility. Examination reveals an apraxic gait. Through discussion with the family they tell you he had recently had a long term catheter in for incontinence and that concerns regarding his safeguarding had been made due to forgetfulness and change in personality.
An MRI scan was performed:
Below shows a T1 weighted axial image
This shows significant dilation of the lateral ventricles without significant cerebral atrophy.
Diagnosis is made by exclusion of other causes of hydrocephalus for example in this case, we don’t have all the slices of the axial MRI scans or CT scan therefore we can’t comment that this is truly a NPH.
NPH: can be idiopathic or due to secondary preceeding causes such as a SAH, Meningitis
However presuming this is the case Hakin’s triad is often mentioned:
- Dementia/Cognitive Impairment (suggested due to pressure on frontal lobes)
- Gait Apraxia- ‘Marche A Petit Pas’ (suggested pressure on the motor fibres passing from the internal capsule to the pre-central gyrus)
- Incontinence (Due to the pressure on the paracentral lobule and cortical centres governing urinary continence and voiding)
Diagnosis and Assessment is made via a Multi-Disciplinary Approach:
Physiotherapists: Assessent of Gait
Neuropsychologists: Assessment of cognitive status i.e MMSE or AMT
Neurosurgical Doctors: Perform an LP, and draining 40mls of CSF.
If there is an improvement in the symptoms the patient can be listed for a Ventriculo-Peritonel Shunt
Type of Shunt
For further information please see section on Shunt Problems, however the main problem is that over-drainage of CSF can lead to sub-dural collections and haematomas.
Simply over-drainage of CSF, lower the ICP, causing cerebral atrophy, stretching of the bridging veins and hence sub-dural collections.
To prevent this a variable pressure valve shunt is used such that CSF can be drained at alternative pressures. In patients with NPH you would ideally want to drain the CSF at a low pressure but doing so may incur a sub-dural collection therefore the valve is initially set at high pressure than gradually lowering it allowing expansion of the brain and preventing sub-dural collections.