# Cerebrospinal Fluid Density Measured Using Hounsfield Units on a Head CT Scan May Be Utilized as a Radiologic Indicator of Shunt Malfunction: A Pilot Study

## TL;DR

This pilot study suggests that measuring cerebrospinal fluid density on CT scans may help detect shunt malfunctions in hydrocephalus patients.

## Contribution

The study introduces cerebrospinal fluid Hounsfield unit measurements on CT scans as a potential radiologic indicator for shunt malfunction.

## Key findings

- Lower pre-operative cerebrospinal fluid Hounsfield unit values correlated with shunt malfunction.
- Postoperative Hounsfield unit values increased significantly after shunt revision.
- The correlation was statistically significant (p-value = 0.045).

## Abstract

Objective: For patients of all ages, symptoms of headache, nausea, vomiting, or altered mental status due to shunt malfunction are frequent causes of visits to the emergency department. However, in shunted patients, those symptoms can also be attributed to other conditions. In this study, we evaluated the use of cerebrospinal fluid density measurements on the head CT scans as a potential radiologic indicator of shunt malfunction. The study aimed to evaluate whether lower ventricular cerebrospinal fluid Hounsfield unit values on pre-operative CT scans correlate with shunt malfunction, as reflected by an increase in Hounsfield unit following revision.

Methods: The University of Puerto Rico Neurosurgery Database was scrutinized to identify patients diagnosed with hydrocephalus who underwent a ventricular shunt revision from August 2021 to August 2024. For each patient, we measured the mean ventricular cerebrospinal fluid Hounsfield unit value within the atrium of the lateral ventricles on the CT scan axial view before and after the shunt revision. The correlation between the preoperative group and the postoperative group was assessed using the non-parametric Spearman’s rank correlation coefficient.

Results: The cohort consisted of 34 patients, aged one to 71 years, with a median age of 35.5 years (interquartile range, 26-45 years). Eighteen percent of the cohort was under 18 years of age. There were 17 females and 17 males. The mean ventricular cerebrospinal fluid pre-operative Hounsfield unit value was 5.2 (range: -1 to 12), and the postoperative mean Hounsfield unit value was 6.0 (range: -2 to 13). The difference in Hounsfield unit values between the preoperative and postoperative patients with shunt malfunction who underwent shunt revision was significant (p-value = 0.045).

Conclusion: Our study findings suggest that lower ventricular cerebrospinal fluid Hounsfield unit values may correlate with shunt malfunction. When a prior head CT scan is available, Hounsfield unit comparison can serve as an adjunctive diagnostic tool to guide clinical decision-making.