I think that Normal Pressure Hydrocephalus (NPH) is one of the most challenging diseases in Neurology.
The condition is certainly frequent, especially in people over 80’. The first time, the term Normal Pressure Hydrocephalus was adopted in 1964 in a thesis of the Colombian neurosurgeon Salomon Hakim. In the following years, the Hakim-Adam’s clinical triad indicated the main clinical features of the disease (urinary incontinence, gait difficulties or magnetic gait or apraxic gait with astasia/abasia and frontal subcortical dementia). Often, patients with NPH, before than neurologists, are evaluated by colleagues of other specialties (psychiatrists, urologists, geriatrics, specialist in internal medicine) who added alternative or supplemental diagnosis and comorbidities.
For diagnosis, it is important to have clinical and radiological MRI concordance and to have excluded other causes. However, clinical criteria have some weakness, as the whole triad might be absent. The same NPH clinical findings are also identified in a very large number of other dementia diseases (actually more than 30). In my experience, certainly 90% of patients, and probably more, with suspicion of Normal Pressure Hydrocephalus, had alternative diagnosis.
Furthermore, clinical criteria are not corroborated by unequivocal neuropathological findings and the etiology of NPH remains unknown.
The spinal tap test (removal of 30-50 ml of CSF) could be helpful for diagnosis and to establish the indication for a shunt procedure. However, sensibility and specificity of this test are low. Clinical scales to evaluate the improvement after spinal tap are not always adequate. Clinical improvement after the spinal tap should be evident in the first 24 hours but it could be delayed too.
A 3-day inpatient lumbar drainage trial (with removal of 300 ml of CSF) or the infusion test with a lumbar catheter are probably more sensitive and specific tests. These tests are often impracticable in demented and elderly patients and I am not sure that they could be done with accurate clinical evaluation in all neurosurgical units. Actually, for some authors, the VP shunt procedure should be considered the true final test for NPH.
VP shunt, which should treat the disease, might have severe complications either in the acute phase or in the successive years. There are several controversies on the choice of the best valve for the VP shunt.
Normal Pressure Hydrocephalus is probably very frequent in the elderly population, however, it is really a challenging neurological disease! Isn’t it?
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