Acueductal stenosis leads to which type of hydrocephalus?

• A. Communicating hydrocephalus
• B. Normal pressure hydrocephalus
• C. Hydrocephalus ex-vacuo
• D. Obstructive hydrocephalus

Answer: (D)

The main idea is that this condition creates a blockage within the ventricular system, stopping CSF from flowing past a point. Aqueductal stenosis blocks CSF movement from the third to the fourth ventricle, so CSF backs up upstream and the lateral and third ventricles enlarge while CSF in the fourth ventricle can stay normal or be reduced. This pattern is characteristic of obstructive (non-communicating) hydrocephalus. In contrast, communicating hydrocephalus involves CSF flow continuing but being poorly absorbed, leading to overall enlargement of all ventricles without a fixed blockage. Hydrocephalus ex-vacuo results from brain tissue loss rather than CSF flow obstruction, and normal pressure hydrocephalus is a communicating form seen in older adults with triad symptoms but not due to an obstructive blockage.