Delayed Horner Syndrome and Accessory Nerve Weakness After Papillary Thyroid Carcinoma Surgery

Horner syndrome encompasses miosis, ptosis of the eyelid, enophthalmos, and facial anhidrosis resulting from sympathetic cervical nerve damage. Although a well-known entity, it is rarely encountered in the setting of thyroid surgery, with only anecdotal evidence in the literature. ^{1 -3} Variations in the anatomical relationship between the thyroid gland and surrounding neural structures may increase the odds of sympathetic chain lesion occurring during surgery. ⁴

A 26-year-old white female patient with a medical history of Hashimoto thyroiditis, Henoch-Schönlein purpura, and ulcerative colitis underwent total thyroidectomy and selective neck region VI dissection for thyroid papillary carcinoma treatment in May 2019. Preoperative ultrasonography showed a thyroid gland of normal volume, with a nodule in the upper left third of the left lobe, several reactive lymph nodes visible inferior to the thyroid in neck region VI. Histopathology revealed 2 intraglandular papillary carcinoma lesions (both ≤5 mm in diameter), and 1 occult lymph node metastasis identified in neck region VI. Regular postthyroidectomy follow-up ultrasonographic examination identified 2 lymph nodes in neck region IV bilaterally with a diameter of 12 mm on the left side and 10 mm on the right side. Fine-needle aspiration cytology confirmed metastatic papillary carcinoma in the neck bilaterally, with high levels of thyroglobulin in the samples taken from the nodes. Subsequent bilateral selective neck dissections were performed in July 2019, encompassing neck regions II to V. The surgery was uneventful, with no direct visualization of the right-sided sympathetic chain and direct visualization and preservation of the right-sided accessory nerve.

The early postoperative period was uneventful, but on the second postoperative day, right-sided Horner syndrome was observed, with eyelid ptosis, anhidrosis and miosis, without other neurological symptoms present. Vision was unaffected, and no other complications, such as bleeding, wound infection, vocal cord palsy, or hypoparathyroidism developed (Figure 1). The neck showed mild skin and soft-tissue edema, without postoperative hematoma or lymphostasis. The patient received intravenous methylprednisolone therapy dropping from 120 mg/d to 80 mg/d, converted to oral methylprednisolone from 80 mg/d, following a step-down protocol for another 9 days. Ultrasonography and color-Doppler showed absence of compression and normal carotid hemodynamics in the neck, and chest X-ray did not show any signs of aortic dissection. Several days later, a right-sided accessory nerve (cranial nerve XI) lesion was also noted, with the patient unable to elevate her right arm above 80° and complaining of pain in her right shoulder and neck. No brachial plexus lesion was noted. Follow-up electroneuromyography showed recovery of right-sided accessory nerve in December 2019, but Horner syndrome recovery still remains incomplete.

Figure 1.

Patient with right-sided Horner syndrome manifesting on postoperative day 2, with eyelid ptosis, anhidrosis, and miosis, without other neurological symptoms present. No significant neck edema present.

The cervical sympathetic trunk is not commonly encountered during neck dissection due to its anatomic location. Variations, however, have been documented and the presence of the sympathetic trunk within the carotid sheath has been shown in 2 (17%)/12 cadaveric dissections. ³ Horner syndrome following neck dissection is very rare, occurring in 4 (0.56%) of 714 patients undergoing neck dissection (levels II-VI) in a series of patients with laryngeal or hypopharyngeal tumors. The authors found no association between neurologic injury and clinical parameters or other complications (wound, vascular, or chyle-related). ⁴ Mobilization of carotid sheath structures in the course of neck dissection may expose the cervical sympathetic chain and its ganglia, most likely during removal of lymph nodes in neck levels II, III, and IV. Anteromedial retraction and deep cervical fascia dissection may injure the cervical sympathetic chain. Traction and compression injuries may result in a Sunderland type I (neurapraxia) or type II (axonotmesis) injury. ⁴ Postoperative hematoma compressing the cervical sympathetic chain and accessory nerve, ischemia-induced neural damage caused by a lateral ligature on the inferior thyroid artery trunk and damage to the communication between the cervical sympathetic chain and the recurrent laryngeal nerve have all been suggested as possible mechanisms previously. ⁵ However, all these actions are virtually unavoidable when performing thyroid surgery and neck dissection, and Horner syndrome still occurs only rarely. In the case discussed, the cervical sympathetic chain was not exposed, dissected, or knowingly injured, while the accessory nerve was visualized and preserved. We hypothesize the sympathetic chain experienced traction during retraction of lymph node contents, with postoperative tissue edema compression resulting in temporary dysfunction of the cervical sympathetic nervous system and accessory nerve. Although extent of surgery is the most obvious risk factor, literature cites instances where minimally invasive parathyroidectomy or video-assisted thyroidectomy may also cause Horner syndrome, with unknown underlying mechanisms. ^5,6