Tumefactive Multiple Sclerosis presenting as Acute Ischemic Stroke.

BACKGROUND AND PURPOSE Multiple sclerosis (MS) plaques appear as well-demarcated, homogenous small ovoid lesions on magnetic resonance imaging (MRI). Atypical radiographic features of MS lesions include size greater than 2 cm, mass effect, and edema. Tumefactive MS lesions can radiographically mimic intra-cranial neoplasms, infarction, as well as infections. In atypical cases of tumefactive demyelinating lesions, brain biopsy may be required for the diagnosis. METHODS The authors describe the case of a 43 year old woman who presented with worsening right-gaze preference and left side weakness and was initially diagnosed with acute ischemic stroke. The patient underwent laboratory investigation and brain contrast-enhanced MRI before undergoing brain biopsy. RESULTS Fluid attenuation inversion recovery (FLAIR) MRI showed an increase in signal intensity in the right frontal lobe sub-cortical region. Diffusion-weighted imaging showed an area of restricted diffusion involving the white matter of the right-frontal lobe. Cerebrospinal fluid studies were normal except for the presence of oligo-clonal bands. Magnetic resonance spectroscopy (MRS) demonstrated an elevated choline (Cho)/creatine ratio, increase lactate, and normal N-acetylaspartate (NAA)/creatine ratio, findings suggestive of an inflammatory or a demyelinating disease. A brain biopsy of the right frontal lesion was performed and revealed well-demarcated foci of demyelination with axonal preservation. Peri-vascular and parenchymal CD3(+) T-cells were also identified within the demyelinated foci, findings that further supported the diagnosis of active multiple sclerosis. CONCLUSION Tumefactive MS can be radiographically misdiagnosed as one of several conditions, among which are infarction, infections, and tumors. Brain biopsy may be needed for diagnosing challenging cases of tumefactive MS.