Objective: MRI parameters of iron concentration (R2*, transverse relaxation rate), microstructural integrity (mean diffusivity and fractional anisotropy), as well as gray and white matter volumes were analyzed in patients with subarachnoid hemorrhage (SAH) and uncomplicated clinical course to detect the evolution of brain tissue changes 3 weeks and 12 months after ictus.
Methods: MRI scans of 14 SAH patients (aneurysm of the anterior communicating artery, n = 5; no aneurysm n = 9) were compared with 14 age-matched healthy control subjects. Statistical parametric mapping (SPM) was applied to objectively identify focal changes of MRI parameters throughout the entire brain and to correlate image parameters with neuropsychological measures.
Results: SPM localized significant bilateral increases in R2* signal within the white matter compartment of the temporal and parietal lobe and the cingulate gyrus (P < 0.001) which did not change significantly at 12 months. Significant gray matter volume reduction of the left insula and superior temporal gyrus (P < 0.001), as well as decreases in fractional anisotropy of the cingulate gyrus (P < 0.01) were also evident at 12 months. Significant correlations were found between fractional anisotropy signal alterations adjacent to the left middle and superior frontal gyrus and cognitive parameters of executive dysfunction (P < 0.001).
Interpretation: The study indicates that iron is trapped predominantly throughout large portions of the white matter compartment in SAH patients at 12 months postbleeding. Increased disintegration of fiber tracts colocalizing with iron overload and correlating with lower executive function performance suggests that the white matter compartment is primarily susceptible toward long-term damage in patients with good clinical grade SAH.