What Is NPH?
Normal pressure hydrocephalus (NPH) is a neurological condition where there is accumulation of fluid (CSF – cerebrospinal fluid) within the ventricular system of the brain, which can cause issues with thinking, concentrating, memory, movement, urination and more. Usually the disease of old age, the symptoms are common after 60 years and it can easily be confused with common yet progressive degenerative brain disorders like Parkinsonism or Alzheimer’s disease or simply “normal ageing” phenomena. The distinction is important as even though the symptoms are those of dementia, NPH is treatable and reversible if diagnosed and managed in time.
What Is CSF and What Is the Mechanism Behind NPH?
CSF aka cerebrospinal fluid is a clear, colourless liquid produced within the nervous system. It surrounds and protects the brain and spinal cord from injuries, like a cushion. It fills the ventricles of the brain and flows through the cisterns of the brain and plays a role in delivering nutrients into and removing waste products out of the brain.
Every day, our body produces 500 mL of CSF. The nervous system contains 150 mL of CSF and the extra CSF is resorbed by the body. But in NPH, the excess CSF is not resorbed and gets accumulated instead. This accumulation leads to the enlargement of the brain ventricles. While the brain can adjust to this increased volume, beyond a point, the pressure on the brain structures leads to the symptoms of NPH. Those afflicted with NPH experience changes in CSF pressure at any given time frame and this increases progressively.
Who Can Develop Normal Pressure Hydrocephalus (NPH)?
NPH is most commonly seen in adults over 60 years of age, and with age the risk increases. Incidence and prevalence of this disease are not clear and it is not dependent on race, ethnicity or sex. The number of people in a community suffering from NPH may be high, as many dismiss its symptoms to be part of the normal ageing process. It is often misdiagnosed as Alzheimer’s disease, post-stroke, vascular dementia or Parkinson’s disease. Many times, these co-exist with NPH. However, NPH is one of the treatable forms of dementia. Hence, the importance of this condition.
Types of NPH
Primary or the idiopathic variety is where the exact cause for developing NPH is not known. It is suspected that idiopathic NPH can involve degenerative processes which may be age-related as to CSF production, circulation and resorption. Most of the NPH cases are idiopathic, meaning there is no nervous condition predisposing to NPH.
On the contrary, a secondary NPH usually develops secondary to an underlying disease process of the nervous system.
Head injury, tumours of the brain, infections and inflammations of the brain, bleeding like subarachnoid or intraventricular bleed or previous surgeries on the brain can all cause NPH as a complication.
What Are the Symptoms of Normal Pressure Hydrocephalus?
The symptoms are mainly three and it is called Hakim’s triad. The symptoms are:
- Gait disturbances, ranging from not being able to walk freely to severe restriction of movement.
Many times, patients have difficulty lifting their leg off the ground. The steps become shorter with a tendency to be unsteady. Turning while walking is extremely challenging. Patients often say they feel that a magnet is bound to their legs and their feet feel stuck to the ground as they walk. The gait issue is the most common symptom. - Urinary urgency, incontinence and bed wetting are also symptoms. Patients suffering from NPH tend to lose control over urination. Over time, they will feel less embarrassed about not being able to control and will not be bothered by it.
- Cognitive dysfunction in the form of mental slowness, memory disturbances, mood changes, denial, lethargy and apathy with no interest in surroundings and a tendency to lie down.
More than 70% of people with NPH show all three symptoms, but almost all will have at least one or more in varying degrees. However, not having these symptoms at the same time does not rule out NPH.
How to Diagnose NPH?
Symptoms of NPH are often confused with other neuro-degenerative conditions and it is important to differentiate before embarking on a treatment plan.
A patient’s history is the important first step, which often gives us a clue as to what the patient is suffering from. Often, patients’ relatives account of symptomatology will clear many doubts.
Next is a neurological assessment, where we check the cognition, posture and gait of the patient. This is very important to clinically understand the disease spectrum. Many times, differentiation between Parkinson’s and NPH or even Alzheimer’s dementia can be diagnosed by careful clinical examination of the patient.
An MRI scan is a very useful and important imaging study to diagnose NPH where we can visualise the dilated ventricles. It will also help to rule out other conditions like tumours, cysts, infections and inflammatory and degenerative conditions. The Single Shot Fast Spin Echo sequence is a fast procedure which helps evaluate ventricle size.
CT scan is another imaging tool which can help us identify NPH very quickly. However, it lacks the spatial and temporal resolution of MRI and it also has a radiation risk.
A spinal tap is often used to let out CSF and also to perform analysis. The patient is assessed for gait before and after the tap. If the patient improves after the spinal tap, it is a sure indication that he will benefit from the CSF diversion procedure. CSF analysis also helps us to rule out any neoplastic, infective or inflammatory condition.
What Is the Treatment for NPH? Is It Reversible?
NPH usually responds to treatment and is reversible, too. The type of NPH determines the treatment. However, medications are rarely used as NPH is not affected by medications.
Primary/Idiopathic NPH Treatment
Primary/idiopathic NPH is a treatable condition. Proper neurological assessment and patient selection are important to obtain the best results. The most recommended treatment is a CSF diversion procedure. This is done by inserting a shunt into the ventricular system and then inserting the other end into the peritoneal cavity, or very rarely, the pleural cavity. Usually, there will be a valve or reservoir between these two ends, which will allow one way flow of CSF only from outside the ventricles of the brain to the peritoneal cavity.
There are various kinds of shunt systems, both Indian and imported. Indian ones are cheaper but less sophisticated as they come with a fixed pressure gradient. Imported ones are programmable, wherein they allow the manipulation of CSF pressure as required according to the clinical scenario without further surgery. However, these are expensive.
Secondary NPH Treatment
Secondary NPH can be cured if it is caused by a curable condition. Therefore, management is dependent on the underlying condition. The treating doctor is the best person to decide on the treatment modality.
In short, NPH is an eminently curable condition of old age, which can be easily confused with other forms of dementia or degenerative neurological conditions. Early identification and prompt management will add much-needed quality of life to these individuals who are often overlooked by bracketing them into old age and its maladies. Awareness about this condition can help in early assessment and treatment, which can add golden years to our elderly population.
Dr Rajesh Menon Moothedath
Consultant Neurosurgeon,
Kauvery Hospital, Chennai
