Pathophysiology
Clinical meaning
Hydrocephalus is the abnormal accumulation of cerebrospinal fluid (CSF) within the ventricular system of the brain, causing ventricular dilation and increased intracranial pressure. CSF is produced primarily by the choroid plexus within the lateral ventricles at approximately 500 mL per day. The total CSF volume at any given time is 125-150 mL. CSF flows from the lateral ventricles through the foramen of Monro into the third ventricle, through the cerebral aqueduct into the fourth ventricle, and exits through the foramina of Luschka and Magendie into the subarachnoid space, where it is absorbed by arachnoid granulations into the venous sinuses. Hydrocephalus develops when there is an imbalance between CSF production and absorption. Non-communicating (obstructive) hydrocephalus occurs when CSF flow is blocked within the ventricular system, commonly at the narrow cerebral aqueduct. Communicating hydrocephalus occurs when absorption by arachnoid granulations is impaired. Normal pressure hydrocephalus (NPH) in elderly patients presents with the classic triad of gait disturbance, urinary incontinence, and dementia — one of the few reversible causes of dementia. Treatment involves VP shunt placement (diverts CSF from lateral ventricle to peritoneal...