Answer and Discussion of Quiz Set: N-001

3.    A 72 year-old retired engineer was brought to the hospital by his family because of unstable gait and urinary incontinence. On physical examination, the patient was well developed, well developed, and with not sign of distress. On neurologic examination, there were no focal signs. You also confirmed the family members' impression of forgetfulness and inability to do simple calculation. The patient, however, was mentally clear but apathic, well oriented, and free of hallucination. Fundic examination was within normal limits. Physical examination does not reveal any constitutional symptoms such as fever. What is the most likely diagnosis?

A.  Infarction in the territory supplied by the left middle cerebral artery

B.  Herpes simplex encephalitis

C.  Aqueductal stenosis

D.  Normal pressure hydrocephalus

E.  The patient's symptoms resulted from normal aging and has no ongoing pathologic process.

Answer and Discussion: The answer is (D). The patient was an engineering before he retired and should be able to do simple calculation. This suggest some kind of dementia. Together with gait disturbance and incontinence, the presentation of this patient fit best with the Adams triad or Hakin's triad associated with normal pressure hydrocephalus. Normal pressure hydrocephallus is due to abnormal increase in intracranial pressure secondary to abnormal accumulation of cerebral spinal fluid (CSF). Since there is no real increase in intracranial pressure, patient do not usually have signs of increased intracranial pressure such as headache, nausea, vomiting, or altered consciousness.

There is no focal sign pointing to infarction of his motor areas (middle cerebral artery territory). Patient with herpes simplex encephalitis are usually rather sick and have constitutional symptoms. Aqueductal stenosis is resulted from obstruction of the aqueduct which leads to obstructive hydrocephalus. Patients with this condition will have typical clinical manifestations of increased intracranial pressure due to any other causes and include headache, nausea and/or vomiting, deterioration of the level of consciousness. Severe and untreated cases may lead to coma or death. Aqueductal stenosis is the most common cause of congenital hydrocephalus. It can also be acquired later in life. Since the aqueduct is immediately adjacent to the mesencephalic tectum, pathologic changes in this area may lead to motor dysfunction of the eye in a mechanism similar to Parinaud syndrome. For this reason, conjugate down gaze in the primary position ("sun-setting" sign) is a classic feature in congenital hydrocephalus.

Alzheimer disease cannot be entirely ruled out based on the above description but unstable gait, urinary incontinence, are more likely to be seen in later stages of the disease with significant dementia. The unstable gait also raise a suspicion of Parkinson's disease. In fact, due to the protracted course of normal pressure hydrocephalus, these patients may be easily misdiagnosed as Alzheimer's disease or Parkinson's disease.