Transcranial Doppler for Eagle Syndrome: Rare Presentation of Unilateral Internal Carotid Artery Compression by the Stylohyoid Ligament With Provocative Maneuvers

Eagle syndrome is a rare condition caused by compression of the internal carotid artery (ICA) or cranial nerves by an elongated styloid process or calcified stylohyoid ligament. This patient is a 56 year-old woman who presented with episodes of positional syncope for 8 years. Transcranial Doppler (TCD) demonstrated abnormally decreased flow in the left middle cerebral artery (MCA) during the syncopal episodes. The patient was evaluated by TCD, transcranial imaging (TCI), and carotid duplex (CD). First, a baseline CD and TCI were performed with the patient in a neutral position. TCD was then used during symptomatic provocative maneuvers to monitor the bilateral MCAs. Intraoperative TCD monitoring was also done during bilateral stylohyoid ligament resection, and postoperatively during the same provocative maneuvers.

The baseline CD examination revealed normal extracranial carotid anatomy; TCD and TCI showed normal mean velocities and a normal anatomic variant of fetal origin of the left posterior cerebral artery. During provocative maneuvers, TCD showed abnormally dampened to absent flow in the left MCA, consistent with compression of the left extracranial ICA. CT scan confirmed elongated stylohyoid ligaments bilaterally. The MCA mean velocities were monitored intraoperatively and postoperatively by TCD and showed no changes with head positioning immediately following resection of the stylohyoid ligaments. The patient reported no syncopal episodes at follow-up 6 days after surgery. Although rare, Eagle syndrome should be considered as a cause of positional syncope. TCD can serve as a diagnostic test, an intraoperative monitoring tool, and a method for documenting the surgical outcome.