Changes in cerebral physiology following cranioplasty: a ¹⁵oxygen positron emission tomography study

Introduction

Patients with skull defects report symptoms, which improve with cranioplasty (CP). We used ¹⁵O positron emission tomography (PET) to examine whether this resulted from improvements in cerebral physiology.

Methods

Seven patients were imaged 6–12 months post craniectomy with PET to derive maps of cerebral blood flow (CBF), oxygen metabolism (CMRO₂), and oxygen extraction fraction (OEF) before and after CP. PET maps were coregistered with magnetic resonance images and segmented into grey matter (GM) and white matter (WM). Physiology was quantified in mixed GM + WM, GM and WM regions of interest (ROIs) underlying the craniectomy and in whole-brain GM, WM and GM + WM ROIs.

Results

See Figure 1. There were no significant changes in CBF, CMRO₂ or OEF following CP, even within ROIs underlying skull defects. Individual patients showed increases in CBF and CMRO₂ and decreases in OEF, but all values were above ischemic thresholds [1].

Figure 1

Abstract

Conclusion

Although individual subjects demonstrate improvements in physiology following CP, there were no systematic changes. Future studies will assess changes in individuals and relate these to metabolic changes within specific brain regions.