From the Research
Normal pressure hydrocephalus (NPH) is primarily caused by impaired cerebrospinal fluid (CSF) absorption, though the exact mechanism often remains unclear, as stated in the most recent study 1. In most cases (about 50%), NPH is idiopathic, meaning there is no identifiable cause. Secondary causes include conditions that disrupt normal CSF flow or absorption, such as:
- subarachnoid hemorrhage
- meningitis
- traumatic brain injury
- previous brain surgeries
- tumors The pathophysiology involves CSF accumulating in the brain's ventricles, causing them to enlarge while maintaining normal CSF pressure. This ventricular enlargement compresses surrounding brain tissue, particularly affecting areas controlling:
- gait
- bladder function
- cognition The compression of periventricular white matter tracts disrupts neural pathways, leading to the classic triad of symptoms:
- gait disturbance
- urinary incontinence
- cognitive decline As noted in 2, treatment typically involves surgical placement of a ventriculoperitoneal shunt to divert excess CSF from the brain to the peritoneal cavity, which can improve symptoms in 60-80% of properly selected patients. It is essential to carefully select patients for treatment, as the symptoms are potentially reversible, and the tap test has a high positive predictive value as a predictor of therapeutic response, but a negative test does not exclude the possibility of treatment, as mentioned in 1.