Isolated Sixth Nerve Palsy as the First Manifestation of Cavernous Sinus Metastasis From Primary Breast Cancer

Cavernous sinus metastasis is a rare clinical finding, presenting most commonly with complaints of headache, diplopia, visual field defects, facial pain, and progressive neurological deficits. Many patients present with features of III, IV, and VI nerve palsies. We hereby report an unusual case of cavernous sinus metastasis from primary breast cancer in a 40-year-old female, who presented with binocular diplopia due to left VI nerve palsy as the first presenting complaint. The patient had a history of surgery for left breast cancer which was performed at another center. Contrast-enhanced computed tomography (CECT) scan of thorax and abdomen revealed a residual neoplastic left breast mass with satellite nodules, left axillary lymphadenopathy, and hepatic, splenic, and skeletal metastasis. Contrast-enhanced magnetic resonance imaging (CE-MRI) of brain and orbit showed enhancing lesion of 20 mm x 10 mm along the lateral wall of left cavernous sinus and left petrous apex. She was referred to radiation oncology department for further management. This case report highlights the importance of ophthalmologists in such life-threatening conditions, who may first present to them.