Eagle syndrome

The Eagle syndrome refers to symptomatic elongation of the styloid process or calcified stylohyoid ligament ^1-2. It is often bilateral. In most cases the cause is not known however the condition is sometimes associated with disorders causing heterotopic calcification such as abnormal Calcium-Phosphorus metabolism and chronic renal failure.

Clinical presentation

Clinical presentation is varied and establishing a causative relationship between the styloid process / stylohyoid ligament and symptoms can be challenging. Classically the pain develops following tonsillectomy, presumably due to distortion of the local anatomy following surgery, however it may be frequently found in patients who have not had regional surgery ^1-3.

The syndrome can be divided into two main sub types ^1,3:

1. due to compression of cranial nerves
2. due to compression of carotid artery

Cranial nerve impingement

Patients can have symptoms related to compression and irritation of cranial nerves in the region (cranial nerves V, VII, IX and X) such as ^1,3:

• facial pain while turning the head
• dysphagia
• foreign body sensation
• pain on extending tongue
• change in voice
• sensation of hypersalivation
• tinnitus or otalgia

On palpation of the styloid process tip, symptoms should ideally be exacerbated.

Arterial impingement

Additionally compression of the carotid artery may also produce vascular / ischaemic symptoms as well as pain along the artery to the supplied territory (thought to be mediated by the sympathetic plexus) including ^2-3:

• mechanical compression
  • visual symptoms
  • syncope
  • carotid dissection has also been described ⁵
• sympathetic plexus irritation (carotidynia)
  • eye pain
  • parietal pain

Radiographic features

The normal length of the adult styloid in an adult thought to be approximately 2.5 cm while an elongated styloid is considered > 3 cm. If this definition is used, approximately 4% of the population have an elongate process, however only a small proportion of them (4 - 10%) are symptomatic. Elongation can be unilateral or bilateral ^1-3. 

OPG and CT can both be used to assess the styloid process / stylohyoid ligament complex. 

It has also been proposed that in cases when mechanical vascular compression is potentially the cause of ischaemic symptoms that angiographic examination (CT angiography or catheter angiography) obtained with the patient's head positioned to reproduce symptoms may demonstrate mechanical stenosis of the carotid artery ³.

Treatment and prognosis

In many cases once the cause of pain has been attributed to the styloid process rather than a more sinister entity, no further treatment is required, perhaps supplemented with analgesics. 

Transpharyngeal injection of steroids / local anaesthetic agents have also been tried ⁶.

In severe cases surgical excision can be performed, either via a trans-oral approach or lateral approach. The trans-oral route has the disadvantage of increased infection rate, but does not have external scarring ^1,6. Persistent pain even after surgical excision may be as high as 20% ⁶.

Etymology

It was first described by Watt Eagle in 1937 ⁴

However there are reports that an Italian anatomist named Pietro Marchetti had described ossification of stylohyoid ligament in 17^th century.