**Question:** The clinical feature of normal pressure hydrocephalus is

A. loss of balance and gait disturbance
B. cognitive impairment
C. urinary incontinence
D. constipation

**Core Concept:** Normal pressure hydrocephalus (NPH) is a neurological disorder characterized by the accumulation of cerebrospinal fluid (CSF) within the brain ventricles, leading to increased intracranial pressure without hypertension. It is often associated with aging and presents with a triad of symptoms:

**Why the Correct Answer is Right:** The correct answer, A. loss of balance and gait disturbance, is related to the compression of the brainstem and cerebellum, causing impaired coordination and balance. B. cognitive impairment is due to the compression of the brainstem, basal ganglia, and hippocampus, leading to memory loss and executive dysfunction. C. urinary incontinence is caused by the compression of the spinal cord and lower brainstem, leading to bladder dysfunction.

**Why Each Wrong Option is Incorrect:** B. D. constipation is incorrect because constipation is not a direct consequence of NPH; rather, it is a symptom related to the compression of the brainstem and spinal cord, which might indirectly affect gastrointestinal motility. D. constipation is not a direct consequence of NPH, as it results from the compression of the brainstem and spinal cord, which could indirectly affect gastrointestinal motility.

**Clinical Pearl:** Normal pressure hydrocephalus typically presents in elderly individuals and should be considered in the differential diagnosis of cognitive decline, gait disturbance, and urinary incontinence, especially in elderly patients with unexplained constipation. Early diagnosis and treatment can lead to significant improvement in patients' symptoms.