Delayed appearance of bilateral cerebral peduncle lesions in autoimmune glial fibrillary acidic protein astrocytopathy: A serial MRI case series.

Autoimmune glial fibrillary acidic protein astrocytopathy (GFAP-A) is an immune-mediated inflammatory disorder of the central nervous system. Although delayed magnetic resonance imaging (MRI) abnormalities have been reported in patients with GFAP-A, the anatomical distribution of brain lesions that become apparent on follow-up MRI remains unclear. We retrospectively reviewed three patients with cerebrospinal fluid anti-GFAPα immunoglobulin G-positive GFAP-A who underwent serial brain MRI. The patients ranged in age from 40 to 80 years and were clinically heterogeneous: patients 1 and 2 required ventilatory support, whereas patient 3 had a milder course and improved without immunotherapy. Initial brain MRI performed 10-21 days after symptom onset showed leptomeningeal or periventricular radial linear enhancement and/or T2-weighted imaging (T2WI)/fluid-attenuated inversion recovery (FLAIR) hyperintensities in the supratentorial white matter, deep gray matter, or brainstem. Definite bilateral cerebral peduncle involvement was not evident in the corresponding initial axial midbrain images. Follow-up brain MRI performed on days 31-59 revealed bilateral cerebral peduncle T2WI/FLAIR hyperintensities in all three patients. Pathological plantar reflexes were documented during the subacute phase in two patients, although coexisting spinal cord lesions detected during follow-up may also have contributed to these signs. Previous reports have described delayed non-enhancing T2WI/FLAIR abnormalities and brainstem involvement in GFAP-A. However, whether the cerebral peduncles are involved as part of these delayed MRI abnormalities remains unclear. Thus, bilateral cerebral peduncle lesions may represent a delayed non-enhancing MRI manifestation of GFAP-A. Careful assessment of the cerebral peduncles on follow-up MRI may help characterize the evolving lesion distribution.