Objective: To describe the imaging and clinical features in type II (late-onset) Alexander disease (AxD).
Methods: We retrospectively identified all cases of type II AxD evaluated at Mayo Clinic, Rochester from January 1996 to February 2012. Clinical and neuroimaging data abstracted from the record included age at onset of symptoms, age at diagnosis, first symptom, neurologic symptoms, physical/neurologic findings on examination, genetic testing and/or biopsy (if performed), and MRI findings.
Results: Thirteen patients with type II AxD were identified. Median age at onset was 38 years (range: 12-63). Five patients were female. Eleven of 13 patients had atrophy of the medulla while all 13 had medullary T2 hyperintensity. In 7 patients, these brainstem regions showed patchy enhancement. Five subjects had T2 signal change in the middle cerebellar peduncle, with associated contrast enhancement in 4 subjects. Eleven of 12 patients with T2 fluid-attenuated inversion recovery (FLAIR) imaging had pial FLAIR signal change in the medulla. Nine of 12 patients with spinal cord imaging had cord atrophy, and 3 of 9 of these evaluated with contrast had cervical cord enhancement.
Conclusions: Our study confirms prior reports of atrophy and signal change of the medulla and spinal cord in late-onset AxD. We expand on previous imaging studies by identifying middle cerebellar peduncle and pial FLAIR signal changes as important diagnostic clues. Variable patchy enhancement may occur in regions of T2 hyperintensity, leading to diagnostic uncertainty. In addition, we demonstrate that previously emphasized clinical features such as palatal tremor may not be common. We affirm that age at onset predicts clinical phenotype and imaging findings.