Abstract
Osteochondroma is the most common benign tumor of bone that often produces no symptoms unless the enlarged mass affects nearby structures. Rarely, Horner syndrome can be caused by an osteochondroma. A five-year-old female with a past medical history of seizure-like activity presented to the emergency department on three separate occasions within one month. She exhibited neurological deficits, including miosis and ptosis, resulting in the diagnosis of Horner syndrome. Computerized tomography (CT) demonstrated a calcified and ossified lesion arising from the right first rib and transverse process that was suspicious for an osteochondroma or chondrosarcoma with neuroblastoma lower on the differential diagnosis. Given the patient's escalating clinical symptomatology and suspicious features of the lesion, a CT guided-bone biopsy was performed. Pathology revealed an osteochondroma that was eventually resected by neurologic and orthopedic surgeries. In this case report, we review the sympathetic innervation to the head, eye, and neck, the most common etiologies of Horner syndrome, and elucidate imaging modalities useful for diagnosing osteochondroma. Horner syndrome secondary to osteochondroma of the first rib has been documented only once before.