Anatomy of the styloid process

The styloid process is a thin, pointed spike of bone that projects down, forward and slightly inward from the temporal bone at the base of the skull, just below each ear. It lies behind the angle of the jaw and points toward the side of the throat. Three small muscles start from it: the styloglossus, which runs to the tongue, the stylohyoid, which runs to the hyoid bone, and the stylopharyngeus, which runs to the throat. Two ligaments attach to it as well: the stylohyoid and the stylomandibular ligament.

The stylohyoid chain

The styloid process, the stylohyoid ligament and the lesser horn of the hyoid bone together form the stylohyoid chain1. The ligament is normally flexible. When part or all of it turns to bone (ossification), the bony part of the chain becomes longer, and on a scan it can look like a single very long styloid process.

Imaging reports describe the ossified chain using a classification proposed in 19862:

The same classification describes four patterns of calcification: a calcified outline, partial calcification, a nodular pattern and complete calcification2. Some imaging studies add a fourth type, in which a separate calcified segment lies at a distance from the styloid3. Across published studies, the pseudo-articulated type is found on 4.4% of sides of the neck and the segmented type on 3.9%1.

Normal and elongated length

A styloid process under 30 mm long is considered typical, and 30 mm or more is called elongated. A 2025 meta-analysis of 104 studies, covering 136,010 sides of the neck, found a typical styloid on 75% of sides and an elongated one on 25%. The average length was 28.9 mm1.

Published rates vary widely, because studies use different imaging and different ways of measuring. CT studies report elongation more often than studies of dry skulls or dental X-rays, and rates differ between countries1. In one group of 407 dental patients, elongation was seen on 52.6% of cone-beam CT scans3.

The 30 mm figure is a convention for describing anatomy, not a threshold for disease. Most people with an elongated styloid process have no symptoms. Elongation is often present on both sides when symptoms affect only one4.

What lies around the styloid process

The styloid process sits in a narrow space at the top of the neck, often described as a corridor, that also contains the internal jugular vein, the carotid arteries and the lower cranial nerves5. Its main neighbors are:

• The external carotid artery and the parotid gland, on its outer side.
• The internal carotid artery, the main artery to the brain, which runs up toward the skull on the inner side of the styloid tip. The tip often sits between the external and internal carotid arteries.
• The internal jugular vein, the main vein draining the brain, which lies behind the styloid and passes between it and the first vertebra of the neck.
• Four cranial nerves: the glossopharyngeal nerve (IX), which winds around the stylopharyngeus muscle on its way to the throat and tongue; the vagus nerve (X), which runs between the carotid artery and the jugular vein; the accessory nerve (XI), which crosses the jugular vein near the first vertebra; and the hypoglossal nerve (XII), which runs to the tongue.
• The sympathetic nerve fibers that run along the carotid artery to the face and eye.
• The tonsil, on the inner side, where the tip of a long styloid can sometimes be felt through the throat.
• The facial nerve, which leaves the skull through a small opening, the stylomastoid foramen, just behind the base of the styloid.

These neighbors explain the symptoms of Eagle syndrome. Pressure on the glossopharyngeal nerve and the throat causes classic throat and ear pain; contact with the carotid artery can injure it; and narrowing of the jugular vein slows drainage from the brain.

The gap between the styloid process and C1

The first vertebra of the neck (C1, the atlas) has unusually wide transverse processes, bony projections that stick out on each side just below the skull. At the skull base, the internal jugular vein runs through the gap between the styloid process in front and the C1 transverse process behind56. When this gap is narrow, the vein can be squeezed between the two bones, a condition called atlanto-styloid or styloidogenic jugular compression.

In a series of 10 patients with this compression, the gap between the styloid and the C1 transverse process averaged 2.9 mm, compared with 9.9 mm in patients with raised intracranial pressure from other causes. The patients' styloids were also longer, averaging 31.0 mm against 19.0 mm7. Position matters as well as length: in a 2012 report of two patients, a prominent styloid process lying unusually far back pressed the vein against C16.

The gap changes with head position. Turning the head to the opposite side raised the pressure in the jugular vein in all 10 patients in the same series7. Soft tissues can add to the compression: the back part of the digastric muscle, the small muscles attached to the styloid, the occipital artery and the sheath of tissue around the vein8. In one reported patient, the internal carotid artery itself pressed the vein against the bone9. Narrowing of the jugular vein at this level is also common in people without any symptoms, so a narrow vein on a scan needs to be matched to symptoms and other tests5.

The angle of the styloid and the carotid artery

How close the styloid process lies to the internal carotid artery may matter more for the artery than how long the styloid is. A 2026 meta-analysis of five case-control studies, with 270 patients with carotid artery dissection and 377 controls, found that in the better-quality studies the styloid process lay closer to the artery on the side of the dissection. Neither the length nor the angle of the styloid was associated with dissection10. The studies were few and varied, and an association of this kind doesn't prove that the styloid caused the tear.

The diagnosis and imaging page explains how these measurements are made on CT.

References

1. Triantafyllou G, Paschopoulos I, Duparc F, Tsakotos G, Papadopoulos-Manolarakis P, Piagkou M. The anatomy of the stylohyoid chain: a systematic review with meta-analysis. Diagnostics (Basel). 2025;15(7):925. doi:10.3390/diagnostics15070925 PubMed ↩
2. Langlais RP, Miles DA, Van Dis ML. Elongated and mineralized stylohyoid ligament complex: a proposed classification and report of a case of Eagle's syndrome. Oral Surg Oral Med Oral Pathol. 1986;61(5):527-532. doi:10.1016/0030-4220(86)90400-7 PubMed ↩
3. Akçiçek G, Kara D, Uysal S, Zengin HY. Diagnostic accuracy of panoramic radiography in detecting styloid process elongation: a cone-beam computed tomography referenced retrospective study. BMC Oral Health. 2025;25(1):1969. doi:10.1186/s12903-025-07306-2 PubMed ↩
4. Cleveland Clinic. Eagle syndrome. Reviewed June 25, 2024. Accessed October 3, 2026. Source ↩
5. Bănică DA, Zamfirescu VI, Rusu MC, Brezean I. Compression syndromes of the stylohyoid complex: neural, arterial, and venous phenotypes in a dynamic neurovascular corridor. Tomography. 2026;12(9):127. doi:10.3390/tomography12090127 PubMed ↩
6. Dashti SR, Nakaji P, Hu YC, et al. Styloidogenic jugular venous compression syndrome: diagnosis and treatment: case report. Neurosurgery. 2012;70(3):E795-E799. doi:10.1227/NEU.0b013e3182333859 PubMed ↩
7. Zhao X, Cavallo C, Hlubek RJ, et al. Styloidogenic jugular venous compression syndrome: clinical features and case series. Oper Neurosurg. 2019;17(6):554-561. doi:10.1093/ons/opz012 PubMed ↩
8. Aghayev K, Demir H, Ozdol C, Comella Z, Vrionis FD. Bilateral circumferential internal jugular vein decompression for atlanto-styloid compression syndrome: report of 14 cases. Oper Neurosurg. Published online September 3, 2026. doi:10.1227/ons.0000000000002185 PubMed ↩
9. Aghayev K, Comella Z, Vrionis FD. Internal carotid artery anterior transposition for internal jugular vein decompression: illustrative case. J Neurosurg Case Lessons. 2026;12(9):CASE26599. doi:10.3171/CASE26599 PubMed ↩
10. Klail T, Kalioras E, von Gernler M, et al. Anatomical characteristics of the styloid process associated with internal carotid artery dissection: a systematic review and meta-analysis of controlled trials. Front Radiol. 2026;6:1788985. doi:10.3389/fradi.2026.1788985 PubMed ↩

Related pages

• Diagnosis and imagingHow Eagle syndrome is diagnosed: examination, CT with 3D reconstruction, CT angiography and venography, jugular pressure tests and reading a report.
• Jugular vein compressionJugular vein compression between the styloid and C1: how it happens, its link with intracranial hypertension, diagnosis, and surgery versus stenting.
• Vascular Eagle syndromeVascular Eagle syndrome: how the styloid process can compress or tear the carotid artery, the link with dissection and stroke, and how it is treated.
• Symptoms of Eagle syndromeEagle syndrome symptoms: throat and ear pain in the classic form, stroke warning signs with carotid involvement, and head pressure with jugular compression.