Multiple sclerosis is an inflammatory demyelinat- ing disorder that may clinically mimic stroke. In the acute phase, patients may present with sudden-onset aphasia, dysarthria, hemiplegia, or hem- isensory deficits. Diagnosis is easy when the typical MRI findings of multiple periventricular, deep, and juxtacortical hyperintensities are seen on T2-weighted or FLAIR images. Many of these patients can be accurately diagnosed by considering the patient history, clinical findings, associated MRI findings, and CSF examination for oligoclonal bands. However, acute demyelinating lesions may show prominent restricted diffusion that could be confused with acute ischemia/lacunar infarction35 (? Fig. 6.19). In such cases, a combination of clinical features and short-term follow-up imaging allows accurate diagnosis.
Transient Global Amnesia
Transient global amnesia (TGA) is a clinical syndrome characterized by the sudden onset of profound memory impairment resulting in both retrograde and anterograde amnesia, without other neurological deficits.3637 The symptoms typically resolve in 3 to 4 hours. Clinically, TGA needs to be differentiated from stroke or TIA. The majority of these patients are negative on imaging. However, numbers of studies have reported punctate or diffuse lesions with decreased diffusion in the medial hippocampus, the parahippocampal gyrus, and the splenium of the corpus callosum that resolved on follow-up imaging.36,37 Lesions measure 1 to 3 mm in size and are most often unilateral. It is currently unclear whether the TGA patients with DWI abnormalities have a different prognosis or a different etiologic mechanism, or whether they should be managed differently compared to TGA patients without DWI abnormalities.