Ectopic Cervical Thymus Presenting as Horner's Syndrome

Abstract

Abstract: : Purpose: To review the presentation, differential diagnosis, and management of ectopic cervical thymus presenting as Horner's syndrome in the pediatric population. Methods: Case Report. Results: A 9-month old male presented to the pediatric ophthalmology clinic with Horner's syndrome. An MRI of his head and neck were negative, however an MRI of his chest demonstrated cervical extension of the thymus cephalad to the thoracic inlet indenting the left internal jugular vein. Ectopic cervical thymus is an uncommon etiology of Horner's syndrome in the pediatric population. There are prior reports of intrathoracic thymic cysts resulting in Horner's syndrome and only one case presentation of a cervical thymic rest causing Horner's syndrome. Fewer than 100 cases of ectopic cervical thymus have been reported in children who presented with primary neck masses. Malignant transformation to thymoma is rare, but has been reported in 11 cases in the literature in solid thymic masses only. The risk of surgical complications with biopsy and/or removal may exceed the likelihood of neoplastic transformation and can leave a patient asthymic. While some propose the diagnosis of ectopic cervical thymus can only be made histologically, magnetic resonance imaging is an excellent diagnostic tool. Conclusions: Ectopic cervical thymus is a uncommon etiology of both Horner's syndrome and primary neck masses in the pediatric population. Magnetic resonanance imaging, in conjunction with close clinical follow-up, is a useful tool in the diagnosis and management of rare cases of ectopic cervical thymus.

Keywords: neuro-ophthalmology: diagnosis • pupillary reflex • tumors