Dynamic Nature of Arachnoid Granulations During Acute Changes in Intracranial Pressure: A Pilot Study.

BACKGROUND AND PURPOSE: Arachnoid granulations (AGs) are cerebrospinal fluid drainage structures whose number and size may vary with intracranial pressure (ICP). Although changes in AG size following lumbar puncture have been reported, longitudinal changes in patients with and without acute ICP alterations have not been studied. This study evaluated AG number and volume over time in patients with and without acute ICP changes.

METHODS

We retrospectively reviewed head and neck computed tomography angiography scans over a 10-year period. Subjects had two consecutive scans with visible AGs. Controls had no acute intracranial pathology, whereas cases had acute hydrocephalus with decompression and ICP monitoring via extraventricular drains. AG volume was measured in both groups; AG number was assessed in controls only. Wilcoxon signed rank tests and paired t-tests were used to assess within-group differences. Welch's t-test and Type III analysis of variance were used for between-group differences and interaction effects.

RESULTS

In 88 controls, AG volumes had a statistically significant change over time (p = 0.010). In four hydrocephalus cases, AG volume decreased by 29.9 mm3 (p = 0.030) after ICP reduction. Between-group analysis showed a significant point estimate difference (p = 0.020) and interaction (p < 0.0001), indicating differing AG responses to acute ICP changes.

CONCLUSION

AGs are dynamic structures exhibiting measurable changes in number and volume over time. AG volume appears responsive to acute ICP alterations, supporting their function in ICP regulation and suggesting a potential role as an imaging biomarker for ICP dynamics in acute hydrocephalus.