This 30 year old hypertensive female smoker presented with acute onset of right hemiparesis. Her history also included OCP use and dyslipidemia. MRI demonstrated an acute infarct in the posterior limb of the left internal capsule. ADC maps showed corresponding low ADC values. MR angiography, echocardiography, and lower extremity venous ultrasound were all normal.

Seven months later the patient re-presented to the ED with persistent waxing and waning hemiparesis, peripheral loss of sensation, and worsening ataxia. MRI at this admission demonstrated resolution of diffusion abnormalities in the left internal capsule but new right hemispheric lesions. The more inferior lesion was associated with restrained diffusion. The bright signal on DWI in the more superior lesion was due to “T2 shine-through”.

FLAIR imaging at the second presentation demonstrated multiple white matter lesions.

There was prominent “ring” enhancement on of the uppermost right hemispheric white matter lesion.

Subsequent clinical evaluation supported a diagnosis of multiple sclerosis.

Discussion:

Lesions of multiple sclerosis may demonstrate diffusion restraint. This does not reliably correlate with acute inflammation and blood brain barrier breakdown, as illustrated by the enhancing lesion with increased ADC in this case. The presenting lesion location and clinical background in this patient led (unsurprisingly) to a diagnosis of lacunar infarction. Her young age (30) might have been a clue to suggest an alternate diagnosis.

References:

1. Karaarslan E, Arslan A. Diffusion weighted MR imaging in non-infarct lesions of the brain. EJR 2007;65:402-16

2. Stadnik TW, Demaerel P, Luypaert RR, et al. Imaging tutorial: Differential diagnosis of bright lesions on diffusion-weighted MR images. Radiographics 2003;23:e7