A 44-year-old woman with a progressive neurologic illness characterized by headache and seizure was admitted to the hospital with new dysarthria, left facial droop, and left hand weakness. Cerebrospinal fluid examination findings were unremarkable except for 5 oligoclonal bands. Magnetic resonance imaging demonstrated ring lesions on diffusion-weighted imaging (DWI) with corresponding changes on apparent diffusion coefficient mapping with associated gadolinium enhancement and increased signal on fluid-attenuated inversion recovery imaging (Figure 1). The patient's condition deteriorated and she died after a 3-week hospitalization. Autopsy showed pulmonary embolism as the cause of death. Neuropathologic examination of the brain demonstrated a cavitated lesion in the right centrum semiovale. Microscopy showed multiple lesions of active and recent demyelination in the periventricular white matter and left middle cerebellar peduncle with alternating bands of myelinated and demyelinated axons, characteristic of Baló concentric sclerosis, along with macrophages containing myelin breakdown products (Figure 2).
Finelli PF, Uphoff DF. Ring Sign on Diffusion-Weighted Imaging. Arch Neurol. 2011;68(11):1474. doi:10.1001/archneurol.2011.612