Because of an absence of thrombus on MRA and the patient's poor neurologic status, angiography and thrombolysis were not indicated. Both MRI and MRA were repeated within 24 hours and showed progression of ischemia with extensive edema throughout the midbrain, pons, brachium pontis, medulla, right thalamus, right internal capsule, and medial aspect of the right temporal lobe (Figure). An intraventricular catheter was inserted for management of intracranial pressure due to development of noncommunicating hydrocephalus on MRI. Intracranial pressure was normal at all times. The patient received 1 g of intravenous methylprednisolone acetate for 5 days for the possibility of an inflammatory process, with no improvement. Cerebrospinal fluid analysis on day 1 postinjection yielded slightly bloody fluid with 8 white blood cells per cubic millimeter (97% polymorphonuclear cells), 5235 red blood cells per cubic millimeter, protein level of 23 mg/dL (normal, 15-45 mg/dL), and a glucose level of 100 mg/dL (5.6 mmol/L) (normal, 50-75 mg/dL [2.8-4.2 mmol/L]). Myelin basic protein was 77.3 μg/L (normal, 0.0-4.0 μg/L). Test results were normal for the following: prothrombin time, partial thromboplastin time, international normalized ratio, C3, C4, vitamin B12, liver function, electrolytes, and hematology panel. Westergren erythrocyte sedimentation rate was 46 mm/h. Anti–hepatitis B surface and hepatitis C virus antibody screens were positive. Screens were negative for hepatitis B surface antigen. Transcranial Doppler examination of the posterior circulation on day 1 postinjection showed normal cerebral blood flow velocities in the basilar artery and both vertebral arteries. Transthoracic echocardiogram showed normal left ventricular systolic function and no cardiac source of embolus. Brainstem auditory evoked response study showed absence of waves IV and V on the left and waves III through V on the right. Median nerve somatosensory evoked potential study revealed absent cortical responses bilaterally (N20 and P23). Repeated MRI and MRA on day 7 showed transtentorial herniation and hemorrhagic transformation of infarcts in the thalamus, midbrain, and pons. Because of the patient's progressive clinical and radiological deterioration, comfort care measures were instituted on day 7 after injection.