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Magnetic Resonance Imaging of Normal Pressure Hydrocephalus
1Department of Radiology, University of California San Diego, San Diego, CA.
Seminars in Ultrasound, CT, and MR
|April 12, 2016
Summary
Normal pressure hydrocephalus (NPH) is a treatable elderly syndrome. Enhanced MRI measures cerebrospinal fluid (CSF) flow, improving shunt response prediction for patients with NPH.
Area of Science:
- Neurology
- Radiology
- Geriatrics
Background:
- Normal pressure hydrocephalus (NPH) is a geriatric syndrome characterized by ventriculomegaly, deep white matter ischemia (DWMI), gait disturbance, dementia, and urinary incontinence.
- NPH accounts for up to 10% of dementia cases and is significant due to its treatability via ventriculoperitoneal shunting.
- Past patient selection for shunting was suboptimal, leading to varied outcomes, with better responses observed in cases with known causes of hydrocephalus compared to the idiopathic form.
Purpose of the Study:
- To investigate the role of cerebrospinal fluid (CSF) flow dynamics in predicting shunt responsiveness in Normal pressure hydrocephalus (NPH).
- To explore the potential etiology of idiopathic NPH as a "two-hit" disease involving benign external hydrocephalus (BEH) in infancy and DWMI in late adulthood.
Main Methods:
- Utilizing phase-contrast magnetic resonance imaging (MRI) to quantify aqueductal CSF stroke volume.
- Assessing the correlation between elevated aqueductal CSF stroke volume and shunt responsiveness in NPH patients.
- Reviewing the proposed pathophysiology of NPH, linking infantile BEH to adult DWMI and altered CSF resorption.
Main Results:
- Historically, large CSF flow voids on early MRI correlated with good shunt response (P < 0.003).
- Modern phase-contrast MRI demonstrates that elevated aqueductal CSF stroke volume has a 100% positive predictive value for shunt responsiveness in one study.
- Idiopathic NPH may result from permanent CSF resorption pathway changes initiated by infantile BEH, leading to hydrocephalus exacerbated by DWMI.
Conclusions:
- Phase-contrast MRI measurement of aqueductal CSF stroke volume is a highly effective tool for predicting shunt responsiveness in NPH.
- Understanding the "two-hit" hypothesis provides insights into the pathogenesis of idiopathic NPH.
- Improved patient selection based on CSF flow dynamics can optimize outcomes for NPH treated with ventriculoperitoneal shunting.
