Alexander disease: Diagnosis with MR imaging

BACKGROUND AND PURPOSE: To date, the demonstration of Rosenthal fibers on b rain biopsy or autopsy specimens is considered a prerequisite for a definit ive diagnosis of Alexander disease. We initiated a multiinstitutional surve y of MR abnormalities in both presumed and confirmed cases of Alexander dis ease to assess the possibility of an MR-based diagnosis. METHODS: MR imaging studies in three patients with;an autopsy-based diagnos is of Alexander disease were analyzed to define MR criteria For the diagnos is. These criteria were then applied to 217 children with leukoencephalopat hy of unknown origin. RESULTS: Five MR imaging criteria were defined: extensive cerebral white ma tter changes with frontal predominance, a periventricular rim with high sig nal on T1-weighted images and low signal on T2-weighted images, abnormaliti es of basal ganglia and thalami, brain stem abnormalities, and contrast enh ancement of particular gray and white matter structures. Four of the five c riteria had to be met for an MR imaging-based diagnosis. In a retrospective analysis of the MR studies of the 217 patients, 19 were found who fulfille d these criteria. No other essentially new MR abnormalities were found in t hese patients. In four of the 19 patients, subsequent histologic confirmati on was obtained. The clinical symptomatology was the same in the patients w ith and without histologic confirmation and correlated well with the MR abn ormalities. MR abnormalities were in close agreement with the known histopa thologic findings of Alexander disease. CONCLUSION: The defined criteria are sufficient for an in vivo MR imaging d iagnosis of Alexander disease; only in atypical cases is a brain biopsy sti ll necessary for a definitive diagnosis.