PMON96 A Curious Case of Isolated Oculomotor Nerve Palsy From a Non-Functional Gonadotroph Adenoma

INTRODUCTION: Pituitary adenoma typically presents with signs and symptoms of hormone hypersecretion and only 30% of cases present clinically as nonfunctioning adenomas. Furthermore, amongst these less than 5% are associated with ocular nerve palsies. We report a rare case of isolated, unilateral oculomotor nerve palsy due to a non-functional gonadotroph adenoma expanding into the left cavernous sinus. CASE: 48 years old male with a pertinent medical history of Type 2 Diabetes Mellitus presented to the ER with 3 days of intractable generalized headache associated with double vision, nausea, and increased lethargy. On initial examination, he had findings of oculomotor nerve palsy on the left eye (ptosis, the eye being down and out, and non-reactive pupil to direct or consensual light stimulation) while the rest of his examination was normal. His initial blood work was non-revealing and normal. He underwent extensive imaging including an initial CT scan showing a pituitary macroadenoma, followed by a pituitary-focused MRI brain revealing a hyperplastic pituitary lesion measuring 17.8 mm×22.5 mm in axial axis and 16.4 mm×14.4 mm in sagittal axis with extension into the left cavernous sinus. Biochemical workup was done to evaluate the pituitary function and it revealed a low total testosterone level (95 ng/ml) with a suppressed LH (2.1IU/l) and FSH (1.76 mIU/ml), a low fT4 (0.58 ng/dl) with a suppressed TSH (0.68 mIU/l), low cortisol (1.2 mcg/dl) with a suppressed ACTH of < 5 pg/ml and normal IGF-1 and prolactin levels. He was given stress dose steroids and underwent transsphenoidal resection of the pituitary mass. Pathology of the specimen showed immunoreactivity for SF1 and ASU which was suggestive of a gonadotroph adenoma. The patient showed no signs or symptoms of diabetes insipidus post-operatively, however, was managed for secondary adrenal insufficiency, hypothyroidism, and hypogonadism. He was discharged home on hydrocortisone, levothyroxine, and metformin. He followed up at the Neuroendocrine clinic within a week of discharge and maintained a regular outpatient follow-up where he showed gradual improvement in his symptoms. CONCLUSION: Visual impairment from a non-secreting pituitary adenoma is usually from chiasmal compression. Very rarely, pituitary macroadenoma expands laterally into the cavernous sinus and compresses the oculomotor nerve causing signs and symptoms of third nerve palsy. This case highlights the importance of recognizing different presentations of nonfunctional pituitary adenoma early as this could improve both the morbidity and mortality associated with them. REFERENCE: Choong, K., Lee, S L. Pituitary Macroadenoma with invasion into the cavernous sinus, cranial nerve palsies (Endocrine Today) Presentation: Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.