A hyperdense artery sign and middle cerebral artery dissection.

We describe a rare case of spontaneous middle cerebral artery (MCA) dissection that caused cerebral infarction and subarachnoid hemorrhage (SAH), which also presented with a hyperdense artery sign. A hyperdense artery sign of the MCA in acute cerebral infarction strongly indicates thromboembolic MCA occlusion, which is often treated with thrombolytic therapy. However, thrombolytic therapy for intracranial artery dissections has both risks and benefits, due to the association of artery dissections with SAH. Therefore, it is important to keep in mind that an MCA dissection can also cause cerebral infarction with a hyperdense artery sign, particularly in young patients presenting with headache.