Loss of intrinsic and extrinsic motility of third nerve revealing breast cancer recurrence

Excerpt

A 30-year-old woman was referred for painless diplopia. Her only medical history was a breast cancer diagnosed 3 years earlier that had been treated with breast-conserving resection surgery with adjuvant chemotherapy. Breast cancer was considered in complete remission. Clinical examination only revealed mild weakness of adduction of the left eye; oculomotricity was otherwise normal. Pupils were normal. Hess–Lancaster test confirmed isolated weakness of the left medial rectus muscle. Visual acuity and fundoscopy did not reveal abnormalities. Other cranial nerves were intact. She had neither motor nor sensory weakness. Standard biological investigations, including sedimentation rate, angiotensin converting enzyme, and C-reactive protein were normal. Brain MRI only showed a discrete hypertrophy of the left medial rectus muscle. We first hypothesized that the patient had orbital myositis. Anti-nuclear, anti-neutrophil cytoplasmic, and anti-acetylcholine receptor antibodies were all negative. She was discharged home without specific treatment. Five months later, she presented in the emergency ward with painful left non-reactive mydriasis, persistent weakness of adduction of the left eye and a new weakness of the left inferior rectus muscle. Visual acuity was normal. There was no aneurysm on CT angiography. Repeated brain MRI showed left medial and inferior rectus muscles hypertrophy and hyperintensities on T2 weighted sequences and a small gadolinium-enhanced lesion at the left clinoid process level on T1 weighted-sequences (cf. Fig. 1a–d). We then hypothesized that the patient had breast cancer metastasis located on the third left nerve next to the clinoid process. CSF cytologic tests were negative for malignancy. Serum and CSF paraneoplastic antibodies were negative. …