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We present a 4 year old child with Pendred syndrome and bilateral sixth nerve palsy. To our knowledge this association has not been previously reported. In addition, this patient developed unilateral corneal ulceration with associated corneal anaesthesia following squint surgery. We will discuss the pathophysiology of this unusual complication following squint surgery.
This patient presented when he was 6 months old with right convergent squint. He was diagnosed with Pendred syndrome (sensorineural hearing loss and thyroid dysfunction) by the paediatricians and the otolaryngologists following abnormal thyroid function tests and a computed tomograph (CT) scan of the temporal bones showing Mondini malformations of both cochleas. At presentation his visual acuities were 6/60 right eye and 6/36 left eye using the Cardiff acuity cards. He had bilateral alternating esotropia with an inability to abduct either eye. There was no globe retraction or abnormal lid movements and a magnetic resonance imaging (MRI) scan had shown congenital absence of the auditory nerves but no other abnormality. A diagnosis of bilateral sixth nerve palsy was made. The squint was cosmetically poor and measured at 45 prism dioptres in the distance and near. He had low hypermetropia with no significant anisometropia. Funduscopy was normal. He was reviewed regularly in the paediatric eye clinic over the next 3 years during which time his visual acuities were within normal limits, the best recorded acuity being 6/9 right eye and 6/9 left eye using singles.
When he was 4 years old, he underwent bilateral superior rectus and inferior rectus lateral transpositions under general anaesthesia, which was uneventful with no immediate postoperative complications, and a cosmetically acceptable alternating convergent squint of 15 prism dioptres for distance and near.
Two months later he developed a left inferior corneal ulcer (Fig 1) with surrounding punctate epitheliopathy which surprisingly did not seem to cause him as much distress as expected. The left corneal sensation was definitely reduced compared to the right which appeared normal. Sensation was assessed clinically (an anaesthesiometer was not available), and was consistently reproducible by different ophthalmologists. There was no exophthalmos or any other sign of thyroid orbitopathy. The right eye remained asymptomatic. Empirical therapy with topical ofloxacin and lubricants was unhelpful. He proceeded to have glue tarsorrhaphy which transiently aided the healing of the corneal ulcer. However, the ulcer quickly recurred when the tarsorrhaphy reversed. He subsequently had left inferior lid shortening with a canthal sling to elevate the lower lid to protect the corneal epithelium. The ulcer resolved leaving an area of corneal scarring. He is being reviewed regularly in the eye clinic.
Pendred syndrome is an autosomal recessive disorder characterised by congenital deafness and thyroid goitre. The hearing loss is usually severe and is present at birth, and the goitre generally appears at puberty or later but may be present in early childhood with an associated euthyroid or hypothyroid state.1–4 Affected individuals are reported to be otherwise normal.
The pathophysiology of the corneal anaesthesia and ulceration in this patient is uncertain. There are several possible reasons for the corneal anaesthesia. They include herpes simplex keratitis, postoperative anterior segment ischaemia, surgical trauma to the long posterior ciliary nerves or ciliary ganglion, congenital absence of sensation, and surgery reducing Bell’s phenomenon.
The clinical course was not typical of herpes simplex and there was no previous history of corneal pathology. Postoperative anterior ischaemic syndrome was unlikely as only two recti muscles were operated on and no anterior uveitis was observed. To our knowledge there are no reported cases of corneal anaesthesia after squint surgery. There was no evidence of pupillary involvement, which one may expect with trauma to the long posterior ciliary nerves or ciliary ganglion.
Congenital absence of corneal sensation was the most likely cause, especially in view of his unusual cranial nerve anomalies, and we believe he had pre-existing corneal anaesthesia before squint surgery despite the absence of any other fifth cranial nerve signs. Following the lateral transposition of the superior rectus his Bell’s phenomenon was noted to be absent thereby compromising his corneal protection. In addition, he was observed to have significant lagophthalmos while asleep. We believe that the combination of corneal anaesthesia, abolished Bell’s phenomenon, and lagophthalmos compromised his corneal integrity resulting in corneal ulceration.
This case highlights the importance of determining corneal sensation before transposition surgery on the superior rectus as Bell’s phenomenon may be abolished therefore compromising corneal protection. This is especially relevant in patients with unusual cranial neuropathy and lagophthalmos.