Abduction Deficit Mimicking Sixth Nerve Palsy due to Metastasis in Systemic Malignancy: Rare Case Report

Lateral rectus palsy presenting as abduction deficit resulting in diplopia is attributed to neurogenic causes. Metastasis as a cause of sixth cranial palsy is an extremely rare entity but cannot be overlooked. Cases of metastasis to lateral rectus secondary to lung and breast carcinoma have been reported. Primary adrenocortical carcinoma (ACC) metastasizing to lateral rectus muscle is extremely rare. Here, we report a case of ACC arising from the left adrenal gland that presented with left-sided abduction deficit in a 58-year-old male with vasculopathic risk factors. The case highlights the importance of neuroimaging in cases of isolated nontraumatic sixth nerve palsy or in cases with isolated ocular symptoms with associated systemic findings. The fact that all cases of muscle palsies may not be neurogenic and rare causes such as metastatic muscle involvement must be included as a differential diagnosis in suspected cases has been emphasized.