Vertebral Artery Compression by the Greater Cornu of the Thyroid Cartilage

Abstract

A case of symptomatic unilateral vertebral artery compression by the greater cornu of the thyroid cartilage is described. Imaging shows ossification of the greater cornu of the thyroid cartilage with compression of an aberrant vertebral artery that enters the transverse foramen at the level of C4. Diagnostic workup and surgical treatment are described. Laryngoplasty with a transverse cervical approach and resection of the greater cornu of the thyroid cartilage resulted in resolution of symptoms.

Introduction

The vertebral artery branches from the subclavian artery and travels cranially, entering the cervical spine at the level of C6 via the transverse foramen. As the artery courses superiorly to join the posterior circulation, it is protected in the cervical spine. Anatomic variations in the entry of this artery into the transverse foramen have been reported at C3, C4, and C5.^1,2 Entry at a level higher than C6 allows for extrinsic compression by structures within the neck. ¹ Compression or obstruction of the vertebral artery has been reported to cause Bow Hunter syndrome. Extrinsic compression can be from bony malformation, cervical spine instability, and compression by the greater cornu of the thyroid cartilage.^2,3 Dynamic occlusion of the vertebral artery can occur with normal head rotation and results in the symptoms of vertebrobasilar insufficiency including vertigo, dizziness, syncope, paresthesia, confusion, headache, and ataxia. ⁴ In the single case of symptomatic compression of an aberrant vertebral artery by the thyroid cartilage without an intrinsic abnormality of the contralateral vessel, the patient presented with a stroke. ² Here we describe a young patient whose vertebrobasilar insufficiency symptoms could only be attributed to dynamic unilateral compression of an aberrant vertebral artery by the greater cornu of the thyroid cartilage.

Case Report

An otherwise healthy 18-year-old male football player presented to the emergency department with a 2-month history of severe occipital headaches with radiation to the bitemporal regions, posterior neck pain, neck stiffness, and blurry vision. He had a past medical history of anxiety. The patient’s daily headaches lasted hours at a time, presenting with photophobia, phonophobia, nausea, and vomiting. Due to the severity of symptoms, he was unable to participate in football practice. The patient presented to the emergency department twice, once at an outside hospital, and at our institution. Physical and mental status exams were normal. His presentation was consistent with symptoms of vertebrobasilar insufficiency, but the differential diagnosis also included migraine headache.

During the first visit, computed tomography (CT) head without intravenous contrast was unremarkable. Computed tomography angiography of the head and neck was significant for ossification of the superior cornu of the right thyroid cartilage resulting in moderate-to-severe compression of the V1 segment of the right vertebral artery at the C5 level (Figure 1). Imaging also showed entry of the right vertebral artery into the transverse foramen at the C4 level and normal entry of the left vertebral artery at the C6 level. Two days later at our institution, CT angiography of the head and neck was similar (Figure 2). The artery was flattened between the right C5 transverse process and the triticeous cartilage, resulting in narrowing of the artery caliber. A right-sided Doppler ultrasound of the right vertebral artery was performed to assess for dynamic compression of the artery. With the head turned to the right, there was narrowing as evidenced by decreased color through the right vertebral artery.

Figure 1.

Axial CT angiogram of the neck at the level of C5 vertebra (A) and sagittal CT angiogram of the neck (B) demonstrating moderate compression (arrows) of the right vertebral artery by the right superior cornu of the right thyroid cartilage and the transverse process of C5. CT indicates computed tomography.

Figure 2.

Sagittal CT angiogram of the neck demonstrating normal entry of the left vertebral artery (A) at the C6 vertebra and entry of the right vertebral artery (B) into the transverse foramen at the level of C4 (arrow). CT indicates computed tomography.

Although the precise etiology of the patient’s headache remained unclear, secondary headache attributable to compressive vascular disease of the vertebral artery was the leading diagnosis over primary headache. Further, dynamic compression of the right vertebral artery posed a risk for embolic stroke. Treatment options included observation with anticoagulation and antiplatelet medications or surgical management. The patient’s age and extrinsic nature of the compression of the vertebral artery made surgical management with laryngoplasty an option. Laryngoplasty involved a right-sided horizontal incision beneath the thyroid notch. The right sternocleidomastoid muscle was lateralized, strap muscles were separated, and the carotid sheath was laterally retracted. The right superior cornu of the thyroid cartilage was identified and the superior horn was resected. At 10-day follow-up, he reported that his visual symptoms and headaches had resolved without recurrence.

Discussion

There has been 1 report in the literature of compression of the vertebral artery in the setting of a fully patent collateral vertebral artery, which consequently caused the patient to suffer a stroke. ² To our knowledge, our report is the first to describe transient symptoms of vertebrobasilar insufficiency caused solely by unilateral compression in the setting of a fully patent contralateral vertebral artery. The onset and process of ossification of the thyroid cartilage is variable but has been reported to start around the time of skeletal maturity and continue into old age. ⁵ Cartilage ossification starts at the posterior and inferior border of the thyroid cartilage and spreads cranially. ⁵ In the case report by Karle et al, the entire cartilage was ossified secondary to aging. In our young patient, the superior cornu’s close association with the vertebral artery may have resulted in ossification.

The patient’s symptoms of phonophobia, photophobia, nausea, and vomiting raise the suspicion for migraine; however, secondary headache attributable to vascular disease has been shown to present similarly to primary headaches. ⁶ Although the exact mechanism is not fully understood, the pain associated with vascular damage, such as carotid and vertebral artery dissection, is believed to be secondary to irritation of the arterial wall which leads to the release of pro-inflammatory neurotransmitters, causing diffuse pain, which may be distant from the area of damage. ⁷ Further, although the pain associated with cervical artery dissection has been reported as bilateral and diffuse, it may also mimic migraine. ⁸ In any case, The International Classification of Headache Disorders defines the diagnosis of “headache attributed to vascular disorder” as definite when the headache resolves within a specific time after its onset or after the acute phase of the disorder. ⁶ This patient’s rapid resolution of symptoms following therapeutic laryngoplasty favors the etiology of vertebral artery compression over primary headache.

The lifetime risk of stroke was a leading consideration in considering an operative intervention. Conservative management was considered with anticoagulation and antiplatelet therapy. Lifelong anticoagulation and antiplatelet therapy present potential for morbidity. The decision to resect the right ossified superior cornu of the thyroid cartilage was made with the intention to remedy the patient’s presenting symptoms, decrease the risk of future stroke, and avoid long-term anticoagulation.

The advantage of laryngoplasty over medical management is that it allows the patient to return to normal activity without the prolonged need for anticoagulation. The morbidity associated with lifelong anticoagulation is significant. As was the case with this patient, in the setting of an aberrant vertebral artery, symptoms of vertebrobasilar insufficiency may be secondary to mechanical compression. The lifetime risk of embolic stroke prompts consideration of a surgical approach over medical management in an otherwise healthy individual.

Supplemental Material

Supplemental Material, sj-pdf-1-ear-10.1177_01455613211002921 - Vertebral Artery Compression by the Greater Cornu of the Thyroid Cartilage

Supplemental Material, sj-pdf-1-ear-10.1177_01455613211002921 for Vertebral Artery Compression by the Greater Cornu of the Thyroid Cartilage by Walter Jongbloed, Alexander Gertel, Lawrence Kashat, Roshansa Singh and Kourosh Parham in Ear, Nose & Throat Journal