New neuro deficits in patient with history of right basal ganglia and thalamic hyperintense signals, status post brain biopsy, now with new unequal pupils and diplopia (partial Parinaud syndrome). There are postoperative findings related to prior right transfrontal biopsy. There is decreased T2 hyperintensity in the right basal ganglia, cerebral peduncle, and pon. However, there is a new, mildly expansile, infiltrative, T2 hyperintense lesion involving the left posterior limb of the internal capsule and midbrain with patchy enhancement, which resembles the previous lesion in this region. There is no evidence of acute intracranial hemorrhage or acute infarct. The ventricles and basal cisterns are normal in size and configuration. There is no midline shift or herniation. The major cerebral flow voids are intact. The orbits are grossly unremarkable. There is mild scattered paranasal sinus mucosal thickening.
Interval decrease in size of the lesion involving the right basal ganglia, cerebral peduncle, and pons, but new left internal capsule and midbrain lesion with patchy enhancement. The constellation of findings may represent an inflammatory process or perhaps an atypical infectious encephalitis. Although potentially nonspecific, MR spectroscopy may provide additional insights.