Pathogenesis of normal-pressure hydrocephalus--preliminary observations

Area of Science:

• Neurology
• Neurosurgery
• Radiology

Background:

• Normal-pressure hydrocephalus (NPH) is a neurological condition characterized by enlarged ventricles, gait disturbance, urinary incontinence, and cognitive decline.
• Accurate diagnosis and prediction of treatment response are crucial for managing NPH patients.

Purpose of the Study:

• To prospectively evaluate changes in local cerebral blood flow (LCBF) and xenon solubility (partition coefficients) in NPH patients before and after cerebrospinal fluid (CSF) shunting.
• To determine if these physiological measurements can predict shunt responsiveness and identify patients who will benefit from surgical intervention.

Main Methods:

• Eight NPH patients underwent a 6-month prospective study including clinical assessments, Mini-Mental Status tests, and xenon-contrast computed tomography (CT) for LCBF and partition coefficient measurements.
• CSF shunting procedures were performed in seven patients, with follow-up measurements to assess treatment effects.

Main Results:

• Pre-shunting, NPH patients exhibited reduced LCBF and partition coefficients in frontal and temporal lobes, basal ganglia, and thalamus.
• Post-shunting, LCBF and partition coefficients increased significantly, particularly in frontal white matter, frontotemporal cortex, and basal ganglia.
• Improved cognitive function and reduced ventricular size were observed post-shunting, correlating with physiological changes.

Conclusions:

• Reduced LCBF and partition coefficients in NPH reflect increased tissue water and CSF diffusion into white matter, which is reversible with shunting.
• Xenon-contrast CT measurements of LCBF and partition coefficients are valuable tools for diagnosing NPH and predicting shunt responsiveness.
• These findings aid in identifying NPH patients likely to benefit from CSF shunting, including those with shunt failures.