MON-122 A Rare Sight: Isolated Third Nerve Palsy as the Sole Presentation of a Non-Functional Pituitary Adenoma

Abstract Disclosure: J. Aboytes: None. J. Loayza: None. I. Mollogon: None. I. Cantu: None. Introduction: Hypopituitarism is a condition where the pituitary gland produces insufficient hormones due to either impaired synthesis or disrupted transport. Pituitary tumors account for about 15% of intracranial tumors, with pituitary adenomas being the leading cause of hypopituitarism in adults. These tumors can be functional (hormonally active) or non-functional, with the latter being rare in children and most common in individuals aged 60-65. Non-functional adenomas often cause symptoms like visual field deficits, headaches, and hypopituitarism, with cranial nerve palsies occurring when the tumor extends into the cavernous sinuses. A rare but notable manifestation of pituitary adenomas is isolated oculomotor (third nerve) palsy. This report highlights such a case where third nerve palsy was the first sign of a non-functional pituitary adenoma. Case: A 46-year-old man with uncontrolled type 2 diabetes presented with acute right-sided headache, diplopia, ptosis, and right leg weakness. His symptoms began with a headache that worsened throughout the morning. On examination, he had right-sided ptosis, a non-reactive right pupil, facial drooping, and weakness in his right leg. Given his symptoms, he received thrombolytic therapy, resulting in partial improvement of his leg weakness, but the right eye pain and diplopia persisted. A CT scan showed no acute ischemic or hemorrhagic events but revealed a right-sided mass near the sella. Further imaging with MRI confirmed a 2.1 cm tumor affecting the optic chiasm and invading the right cavernous sinus, with no infarction or hemorrhage.Laboratory results showed signs of hypopituitarism and a hemoglobin A1c of 11.1%. ACTH: 55.5 pg/mL (Reference: 7.2-63.3), Cortisol: 4.1 µg/dL (Reference: 5.0-25.0), TSH: 0.196 µIU/mL (Reference: 0.358-3.740), Free T4: 0.64 ng/dL (Reference: 0.76-1.46), LH: 0.4 (Reference: 1.5-9.3), Prolactin: 0.9 ng/mL (Reference: 2.1-17.7), Growth Hormone: 0.1 (Reference: 0.0-10.0), IGF-1: 68 ng/mL (Reference: 81-263). He was treated with hydrocortisone, levothyroxine, insulin and atorvastatin. Neurosurgical consultation recommended surgery after stabilization, with follow-up scheduled post-discharge. Endocrinology follow-up was also scheduled. Discussion: Isolated third nerve palsy is a rare but important presentation of non-functional pituitary adenomas. This case emphasizes the need to include pituitary tumors in the differential diagnosis of cranial nerve deficits to prevent misdiagnosis and treatment delays. Given the potential for diagnostic anchoring bias, clinicians should maintain a broad perspective when assessing neurological deficits. Prompt imaging and endocrine assessment are essential for timely diagnosis and management, ensuring appropriate intervention before significant complications arise. Presentation: Monday, July 14, 2025