|Anteroposterior and lateral radiographs of cervical spine showing ossification of the stylohyoid ligament on both sides|
Eagle syndrome (also termed stylohyoid syndrome styloid syndrome, styloid-stylohyoid syndrome, or styloid–carotid artery syndrome) is a rare condition commonly characterized but not limited to - sudden, sharp nerve-like pain in the jaw bone and joint, back of the throat, and base of the tongue, triggered by swallowing, moving the jaw, or turning the neck. Since the brain to body's nerve connections pass through the neck; many seemingly random symptoms can be triggered by impingement or entanglement. First described by American otorhinolaryngologist Watt Weems Eagle in 1937, the condition is caused by an elongated or misshapen styloid process (the slender, pointed piece of bone just below the ear) and/or calcification of the stylohyoid ligament, either of which interferes with the functioning of neighboring regions in the body, giving rise to pain.
Signs and symptoms
Possible symptoms include:
Classic eagle syndrome is present on only one side, however, rarely, it may be present on both sides.
In vascular Eagle syndrome, the elongated styloid process comes in contact with the internal carotid artery below the skull. In these cases, turning the head can cause compression of the artery or a tear inside the blood vessel, which restricts blood flow and can potentially lead to a transient ischemic attack (TIA) or stroke. Sometimes, compression of the internal jugular vein can also occur and might lead to increased intracranial pressure. 
Eagle syndrome occurs due to elongation of the styloid process or calcification of the stylohyoid ligament. However, the cause of the elongation hasn’t been known clearly. It could occur spontaneously or could arise since birth. Usually normal stylohyoid process is 2.5–3 cm in length, if the length is longer than 3 cm, it is classified as an elongated stylohyoid process.
Diagnosis is suspected when a patient presents with the symptoms of the classic form of "Eagle syndrome" e.g. unilateral neck pain, sore throat or tinnitus. Sometimes the tip of the styloid process is palpable in the back of the throat. The diagnosis of the vascular type is more difficult and requires an expert opinion. One should have a high level of suspicion when neurological symptoms occur upon head rotation. Symptoms tend to be worsened on bimanual palpation of the styloid through the tonsillar bed. They may be relieved by infiltration of lidocaine into the tonsillar bed. Because of the proximity of several large vascular structures in this area this procedure should not be considered to be risk free.
Imaging is important and is diagnostic. Visualizing the styloid process on a CT scan with 3D reconstruction is the suggested imaging technique. The enlarged styloid may be visible on an orthopantogram or a lateral soft tissue X ray of the neck.
In both the classic and vascular form, the treatment is surgical. A partial styloidectomy is the preferred approach. Repair of a damaged carotid artery is essential in order to prevent further neurological complications. Regrowth of the stylohyoid process and relapse being a common occurrence is debatable. Medical management may include the use of pain and anti-inflammatory medications, antidepressants, and/or corticosteroids. The overall success rate for treatment (medical or surgical) is about 80%.
Approximately 4% of the general population have an elongated styloid process, and of these about 4% give rise to the symptoms of Eagle syndrome. Therefore, the incidence of stylohyoid syndrome may be about 0.16%.
Patients with this syndrome tend to be between 30 and 50 years of age but it has been recorded in teenagers and in patients > 75 years old. It is more common in women, with a male:female ratio ~ 1:2.
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