Normal Pressure Hydrocephalus Flashcards
Normal Pressure Hydrocephalus
Normal pressure hydrocephalus is a reversible cause of dementia seen in elderly patients. It is thought to be secondary to reduced CSF absorption at the arachnoid villi. These changes may be secondary to head injury, subarachnoid haemorrhage or meningitis
A classical triad of features is seen
urinary incontinence
dementia and bradyphrenia
gait abnormality (may be similar to Parkinson’s disease)
Imaging
hydrocephalus with an enlarged fourth ventricle
Management
ventriculoperitoneal shunting
Normal Pressure Hydrocephalus - Difficult Diagnosis: Example Question
A 78-year-old male with a background of atrial fibrillation, ischaemic heart disease, hypertension is brought to hospital by his wife who is concerned about a recent deterioration in his health. For the last few weeks his wife has noticed that the patient has been more unsteady on his feet which has resulted in falls around the house. His wife also informs you that the patient has been more forgetful and less interested in his hobbies than usual. When you ask the patient about his symptoms, his main concern is that he has recently developed problems with urinary incontinence which he finds embarrassing.
As part of the investigation into this patient’s condition, a CT scan of the patient’s head is requested. What is the most likely finding?
Diffuse cerebral atrophy with enlargement of cortical sulci and ventricles A hyper-dense bi-convex extra-axial collection beneath the squamous part of the temporal bone Small areas of low density in the distribution of the middle cerebral artery, suggestive of old lacunar infarcts A concave-shaped extra-axial collection with increased attenuation > Enlarged third and lateral ventricles, disproportionate to the enlargement of the cortical sulci
The patient’s history of atrial fibrillation places him at increased risk of stroke and so it may be tempting to attribute his deterioration to cerebrovascular disease. Another pitfall with this question is the report of falls at home, which may lead to a suspicion that the patient has developed a subdural haematoma (SDH). However, it is important to appreciate that his symptom of ataxia pre-dates his tendency to fall. The critical part of this question is that this patient’s presenting complaints of ataxia, dementia and urinary incontinence are the classical triad of clinical findings associated with normal pressure hydrocephalus. As such, a CT scan of his head would be expected to show ventricles which are dilated out of proportion to the enlargement of his sulci.
Normal Pressure Hydrocephalus TRIAD
DEMENTIA and BRADYPHRENIA (Slowness of thought) + URINARY INCONTINENCE + GAIT ABNORMALITY
Reversible cause of dementia seen in the elderly
2dry to reduced CSF absorption at arachnoid villi
May be 2dry to Head injury, SAH, Meningitis
Imaging - Hydrocephalus with an enlarged 4th ventricle
Mx = Ventriculoperitoneal shunting
NB NORMAL CSF opening pressure (10-20)
Despite the normal pressure, removal of a relatively significant amount of CSF and repeat of the patients walking time is a useful clinical predictor of whether the patient will improve after surgery.
Normal Pressure Hydrocephalus Diagnosis: Example Question
A 78 year old male presents with a one year history of progressive unsteadiness on walking. He had previously been extremely fit and healthy, walking around 2 miles to the shops every day and only retired as a publicist 3 years ago. He underwent radiotherapy for localised squamous cell carcinoma of his vocal cords 18 months ago but otherwise had no other past medical history. He admits to having drunk ‘more than he should have’ while working in the city but says he has since cut down to moderate levels. He stopped smoking 5 years ago, with a 30 pack year history. Over the past 3 months, he has become incontinent of urine and has to rely on pads, which he is greatly embarrassed by.
On examination, he has a shuffling gait in his lower limbs with good arm swing. He is markedly slowed and takes 120 seconds to walk 20 metres. He turns around 180 degrees in 6 steps with no resting tremor, rigidity or bradykinesia. Examination of his tone, power, sensation, coordination and reflexes are all unremarkable. His voice is quiet and whispering. His cranial nerves are normal with full range of eye movements. An abbreviated mental test scores 9/10, a Montreal cognitive assessment (MOCA) scored 29/30. His initial blood tests are as follows:
Hb 9.4 g’/dl
MCV 103.3 fl
Platelets 232 * 109/l
WBC 6.3 * 109/l
Na+ 139 mmol/l K+ 4.9 mmol/l Urea 7.5 mmol/l Creatinine 98 µmol/l CRP 2 mg/l Vitamin B12 327ng/l Folate 5.2 nmol/l
An MRI head is performed, demonstrating diffuse mild microangiopathic changes with prominently dilated lateral and third ventricles. No intracranial masses are noted. You perform a lumbar puncture, with the patient lying in the left lateral position using a 22G spinal needle and obtain cerebrospinal fluid with the first pass. His opening pressure is 16.6 cmH2O. What should you do?
> Remove 30mls cerebrospinal fluid and refer to neurosurgeons Prescribe urgent intravenous pabrinex Urgent urological referral for urodynamic studies +/- flexible cystoscopy Prescribe Sinemet 250 with anti-emetic and re-measure walking time Urgent CT angiography and prescribe aspirin 300mg
There are two of three features of the classic triad of gait disturbance, urinary incontinence and cognitive impairment, suggestive of normal pressure hydrocephalus (NPH). The normal opening pressure and dilated prominent ventricles lend further support to this diagnosis. Mild microangiopathic disease is not uncommon in this age group and potentially could cause gait disturbances; there is no indication of an acute ischaemic stroke secondary to embolic events however, urgent vascular imaging and aspirin loading would thus be inappropriate. Despite the previous alcohol history, the patients vitamin B12 and folate are within normal range with no neuroimaging features of degeneration, intravenous pabrinex is unlikely to resolve these symptoms. Although there may be a primary urological cause for the patients urological symptoms, his gait features are not easily explained. The patient does not display any ‘hard signs’ of Parkinsonism to warrant a Sinemet trial.
The definitive treatment for normal pressure hydrocephalus is neurosurgical implantation of a ventricular shunt, most commonly into the peritoneum. Of the three main features of NPH, gait apraxia is the most commonly improved feature with shunting, while dementia and cognitive impairment rarely improve after surgery. Despite the normal pressure, removal of a relatively significant amount of CSF and repeat of the patients walking time is a useful clinical predictor of whether the patient will improve after surgery.
CT imaging of Normal Pressure Hydrocephalus
CT scan would be expected to show ventricles which are dilated out of proportion to the enlargement of his sulci.
