Causes of moderate or severe narrowing by side
| Cause | Right Side (n = 108) | Left Side (n = 108) |
|---|---|---|
| Styloid process | 26/108 (24.1%) | 33/108 (30.6%) |
| Digastric muscle | 26/108 (24.1%) | 12/108 (11.1%) |
| Artery (ECA, ICA, or branches thereof) | 3/108 (2.8%) | 2/108 (1.8%) |
| Styloid process and digastric muscle | 5/108 (4.6%) | 0 |
| Other | 2/108 (1.9%) | 1/108 (0.9%) |
| None | 46/108 (42.6%) | 60/108 (55.6%) |
Note:—See Figure 1 for examples of narrowing by the styloid process and posterior belly of the digastric muscle. ECA indicates external carotid artery; ICA, internal carotid artery.