Normal pressure hydrocephalus (NPH) is a condition in which an impairment of mental acumen and motor proficiency occurs as a result of communicating hydrocephalus, with normal intracranial pressure. NPH is considered communicating because there is no impediment in the normal pathway of CSF, but rather an impairment of the absorption of CSF. However, due to the non-compliance of the brain, the excess fluid will result in enlarged ventricles or progressive ventriculomegaly without the corresponding increase in intraventricular pressure.

Because NPH generally occurs in people over the age of 65, and the symptoms closely parallel the symptoms of other prevalent geriatric diseases, such as Alzheimer’s and Binswanger’s disease (vascular dementia), it is often difficult to diagnose and can easily be misdiagnosed. However, evidence suggests that once diagnosed, the earlier a patient is treated the better the prognosis. The clinical symptoms of NPH include: dementia, gait disturbance, and urinary incontinence. Many patients will experience signs of mental and/or motor slowing, apathy, emotional indifference, anosognosia (unawareness or denial of a neurological disorder), and memory and attention deficit. Other deficits such as dyslexia, dysgraphia (difficulty in writing), acalculia (inability to do simple math) and apraxia (inability to perform familiar functions) may also occur.16

Shunting is the primary treatment for NPH patients, and research suggests the significance of early diagnosis and shunting of these patients. Tallaksen, et al., demonstrated the importance of diagnosing patients early, as a delay in treatment would worsen the prognosis after shunting.20 Although the type of valve to be used for NPH patients is commonly debated, evidence suggests that low-pressure valves seem to have better results than medium pressure valves. Boon in 1998, determined that low-pressure valves resulted in a better outcome for the treatment of NPH.4 And McQuarrie, et al., demonstrated a 60% improvement in patients treated with a low-pressure valve versus a 23% improvement in patients treated with a medium pressure valve. Their conclusion was that a low-pressure valve is more effective for the treatment of NPH.15 However both studies indicated that there was a significant higher risk of subdural hematomas with the LPV. Subdural hematomas, produced by the rupture of the menengial blood vessels at tight junctions, are primarily caused by rapid pressure changes in relatively non-compliant brains, as occurs in older patients. These changes can be caused by overdrainage, which has been reported to occur with standard differential pressure (DP) valves as well as programmable valves.10