The Challenges of Normal Pressure Hydrocephalus: A Case-Based Review

Idiopathic normal pressure hydrocephalus (iNPH) is one of the few reversible causes of dementia. Unfortunately, the symptoms of iNPH—cognitive impairment, gait change, and urinary incontinence—develop slowly and are often mistaken for those of other conditions or for normal aging. This article explains when to suspect iNPH and the steps you need to take when iNPH is in the differential.

Ten years ago, a 74-year-old semi-retired cardiologist self-referred to neurology for evaluation of forgetfulness that had increased in the previous two years. He remained functionally independent in all daily activities. Mental status screening with the Mini-Mental State Exam was within normal limits. He underwent comprehensive neuropsychologic testing, which revealed an estimated verbal IQ of 130, a word list recall in the low average range, and normal results for all other tests; the report also noted mild depression. He was seen one year later for follow-up and reported continued memory difficulties. A brain MRI showed ventricular dilatation with cerebral and cerebellar atrophy “consistent with age.” He was placed on an off-label trial of donepezil and vitamin E.

Two years later, he began to experience slowing of his gait and was noted to have “mild Parkinsonism” on neurologic examination. He was started on carbidopa/levodopa, with no improvement. Another MRI showed no progression from two years prior, but the “possibility of normal pressure hydrocephalus” (NPH) was noted in the radiology report. He underwent a lumbar drain procedure, after which he had slow improvement in gait over the next two months.

Four to 12 months following the lumbar drain procedure, he experienced worsening gait, balance problems, and urinary urgency, and he reported increasing memory difficulty. Neurologic examination was noteworthy for soft voice with hoarse quality, slightly increased tone in the upper extremities (right greater than left), and wide-based and unsteady gait with dragging of feet. Another brain MRI was done, with the report noting “ventriculomegaly out of proportion to volume loss … NPH cannot be excluded.” After review of the results for a second opinion, an MRI with cerebrospinal fluid (CSF) flow study was performed; based on the results, the patient was determined to be a good candidate for ventriculoperitoneal shunt placement. He underwent shunt placement without incident and had sustained improvement in gait and cognition over the next six years.

Idiopathic normal pressure hydrocephalus (iNPH) is an uncommon but important differential to consider in any older individual with cognitive decline. NPH was first discussed in the medical literature in 1965, when Adams and Hakim described the characteristic features of iNPH: the triad of walking impairment, “dementia,” and urinary incontinence in the presence of enlarged ventricles but normal intracranial pressure.¹

With the continued aging of the population, an increasing number of individuals can be expected to experience cognitive decline, gait and balance difficulties, and urinary incontinence. Clinicians caring for patients who present with one or more of these symptoms must keep iNPH in mind for the differential diagnosis. iNPH is a treatable condition, and appropriate intervention can significantly improve affected patients’ lives, as well as reduce health care expenditures.^2,3

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