Review Question - QID 107132

This man has the classic triad of normal-pressure hydrocephalus (NPH), which is confirmed by his normal opening pressure and enlarged ventricles on MRI. NPH is a form of communicating hydrocephalus that is the result of scarring of arachnoid granulations.

Hydrocephalus refers to abnormal accumulation of CSF fluid in the ventricles, which can lead to dilation of the ventricles. Hydrocephalus can be classified as communicating, in which the flow of CSF between ventricles remains unimpeded, or non-communicating, in which CSF flow has become obstructed. NPH is a form of communicating hydrocephalus that is due to decreased reabsorption of CSF. NPH occurs slowly over time, and chronic dilation of the ventricles is eventually seen, but with normal CSF opening pressure on lumbar puncture.

Verrees et al. discuss the symptoms and diagnosis of NPH. NPH presents with the classic triad of gait disturbances, urinary incontinence, and dementia (“wacky, wobbly, and wet”). This symptomatic triad has a high predictive value in diagnosing NPH. Gait disturbance is usually the first presenting sign, followed by urinary incontinence. Dementia is often the last recognized symptom and is the least specific in the diagnosis of NPH.

Jaraj conducted a study to determine the presence of NPH on imaging in the elderly. The authors correlated clinical exam findings with CT imaging findings in over 1,200 elderly patients. They found an NPH prevalence of 5.9% in patients over the age of 80, which was substantially higher than the diagnosed prevalence. Accordingly, the authors concluded that NPH is likely underdiagnosed in their patient population.

Figure A shows an axial brain MRI slice from a patient with NPH. Note the enlarged ventricles.

Incorrect Answers:
Answer 1: Bacterial infection of the meninges would be unlikely to have a slow course. Moreover, the normal CSF WBC count effectively rules this out. Urinary tract bacterial infection can cause altered mental status in the elderly but again would not have such a slow course and is not consistent with the urinalysis findings. Meningitis could scar the arachnoid granulations leading to hydrocephalus; however, this is less likely given the patient's age, chronic picture, and lack of a history of infection.
Answer 2: Viral infection of the meninges would have increased lymphocytes in the CSF.
Answer 3: Beta-amyloid deposition is seen in Alzheimer's disease.
Answer 5: Ventricular stenosis causes non-communicating hydrocephalus. NPH, with it's classic triad of "wacky, wobbly, and wet", is a form of communicating hydrocephalus.