Characterized by miosis, upper eyelid ptosis, facial anhidrosis, and hyperemia, Horner syndrome is caused by an injury to the oculosympathetic chain. Iatrogenic Horner syndrome secondary to tonsillectomy is rarely reported, particularly in the ophthalmologic literature. We report a case of acquired Horner's syndrome following radiofrequency tonsil ablation.
A 2.5-year-old boy presented with a 5-month history of pupil asymmetry. Complete history revealed that he also had a mild drooping in the left upper eyelid, but it gradually resolved in 5 months. Both of these symptoms developed after an adenoidectomy and radiofrequency tonsil ablation surgery under general anesthesia.
On examination, he had 20/20 visual acuity in both eyes with Allen figure optotypes. Evaluation of the pupils revealed 1 mm of miosis in the left eye under natural light that increased to 2 mm in the dark (Figure 1A). The rest of the ophthalmological examination was unremarkable. Instillation of apraclonidine 0.5% eye drops in both eyes resulted in reverse anisocoria due to dilatation of the affected left pupil and confirmed the diagnosis of Horner syndrome (Figure 1B). Magnetic resonance imaging of the head, neck, and upper chest were performed to rule out any ominous etiology, and the results were normal. The patient was diagnosed as having iatrogenic Horner syndrome secondary to radiofrequency tonsil ablation surgery, and had persistent miosis at 1 year of follow-up.
(A) Left-sided miosis. (B) Anisocoria is reversed after instillation of 0.5% apraclonidine.
Horner syndrome is a relatively rare disease with an estimated incidence of 1.42 per 100,000 children and develops secondary to the interruption of the oculosympathetic nerve pathway along the hypothalamus and the orbit.1 Although the more well-known causes of Horner syndrome include neoplasms and trauma, postoperative complications of the neck and thorax constitute the most common etiology in acquired cases.2
Tonsillectomy is one of the most frequently performed operations in childhood. The close anatomical relationship between the palatine tonsil and the superior cervical ganglion puts the oculosympathetic pathway at risk during this surgery. However, isolated Horner syndrome as a complication of tonsillectomy is a rare entity, with only 13 cases reported in the English literature.3–7 The potential mechanisms underlying this complication include the peritonsillar infiltration of local anesthesia, postoperative hematoma or abscess compressing the ganglion, and direct injury to the sympathetic chain or superior cervical ganglion. Because local anesthetic drugs were not used and symptoms developed after an uneventful surgery, the most likely cause of Horner syndrome in our patient was direct damage to the superior cervical ganglion and surrounding tissues.
Several different techniques, including monopolar and bipolar diathermy, bipolar scissors, KTP-532 laser, carbon dioxide laser, and radiofrequency ablation and coablation techniques, have been used in an attempt to reduce the operative time, hemorrhage, and postoperative pain associated with tonsillectomy.8 Our patient was treated with radiofrequency tonsil ablation, a relatively new and effective technique that uses ionizing energy to break down the intercellular bonds and reduce tonsillary volume. The resultant thermal effect of this procedure is much lower than electrocautery, but it can still lead to temperatures as high as 85°C in the neighboring tissues and result in collateral damage.9 To our knowledge, this is the third reported case of Horner syndrome developing after radiofrequency ablation.7
This case report highlights a rare complication of a common surgery. Ophthalmologists should be aware of the possibility of Horner syndrome after tonsil ablation surgery.
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