What is Normal Pressure Hydrocephalus?
Normal pressure hydrocephalus (NPH) is a chronic form of the hydrocephalus, where there is an increase in the intracranial pressure (ICP). This happens due to the accumulation of the cerebrospinal fluid (CSF).
The ICP gradually stabilizes and the formation of the CSF also equilibrates with absorption. Slowly, the ICP falls but remains towards the elevated side, while the CSF pressure reaches a normal, but still high, level of 150 to 200 mmH2O.
This equilibrium results in the patients not feeling any of the usual symptoms of the high intracranial pressure, the like of which are headache, nausea, vomiting or altered consciousness. However, this does not mean that there is simply no affect on the patients.
Some people are reported to exhibit some symptoms like gait difficulties, urinary incontinence, mental decline etc. due to the lack of symptoms, the disease at times gets misdiagnosed as the Parkinson’s disease, Alzheimer’s disease or senility due to the other symptoms that it some times exhibits.
Although how the disease exactly occurs or the mechanism of the disease is unknown, it is assumed that the normal pressure hydrocephalus is a form of communicating hydrocephalus which has impaired CSF reabsorption at the arachnoid villi.
Causes of Normal Pressure Hydrocephalus
An abnormal accumulation of the cerebrospinal fluid (CSF) in the ventricles of the brain is known to be the chief cause of the Normal Pressure Hydrocephalus or NPH. In most of the cases, the exact cause for this to happen is unknown; while a head injury, subarachnoid hemorrhage or an infection such as meningitis
NPH is an abnormal accumulation of cerebrospinal fluid (CSF) in the ventricles of the brain, with little or no increase in pressure.
In most people, the cause is unknown; in others it can be secondary to head injury, subarachnoid hemorrhage or an infection like meningitis etc might also result in the manifestation of the NPH in some people.
Symptoms of Normal Pressure Hydrocephalus
Symptoms like urinary incontinence, wide-based ataxic gait, and dementia might be exhibited by some of the people suffering from NPH. Gait and ataxia are amongst the first of the symptoms to show up and are usually seen as being progressive in nature. This progression is due to the expansion of the ventricular system, especially at the level of lateral ventricles, resulting in the traction on the lumbosacral motor fibers running in the region.
This shows up in the person in the form of unsteadiness in motion and impaired balance, especially when the person is climbing the stairs or around the curbs. Tiredness and weakness are also reported in few cases, though these are extremely rare in the people suffering from the NPH. In the problem of gait which appears, the feet appear to be stuck on the ground until a lot of effort is put to wrest them free and move forward.
This has also led to people calling this form of gait as the “magnetic gait”. Dementia usually affects the frontal lobe only in this case, with apathy, dullness in thought and inattention following up. Loss of memory or inability to recall things fast is one of the chief factors which occur in this disease.
Diagnosis of Normal Pressure Hydrocephalus
NPH is diagnosed by first lumber puncturing, which is then followed by the evaluation of the clinical response by the patients on the removal of CSF. This can further be followed up by a CT scan, MRI or continuous external lumbar CSF drainage. Any improvement shown by the patient on removal of the CSF confirms the diagnosis of the disease. Enlarged ventricles without convolutional atrophy when seen in the CT scan also confirm the diagnosis.
Normal Pressure Hydrocephalus Treatment
Using a surgery to implant the ventriculoperitoneal shunt, so as to drain the excess cerebrospinal fluid to the abdomen so that it gets absorbed there, can be performed. This helps in reducing the size of ventricles, while visible reduction in the ventricular swelling also happens, leading to a remarkable improvement in the symptoms. In majority of the cases, this method is used and is proven to be quite a success too.
