Image of the Month

A 36-year-old man presented to the emergency department after the acute onset of right hemiparesis, which was primarily affecting the arm. The patient had a history of hypertension and also of polysubstance abuse. Additionally, his urine tested positive for cocaine, which was considered likely to have contributed to an infarct. To find out how imaging ultimately led his neurologists to the correct diagnosis, see Image of the Month, page 13.