(14.01) Oculomotor Nerve Palsy as Initial Manifestation of Pituitary Macroadenoma

Pituitary adenomas may present with loss of vision or visual field in 40-60% of patients but presentation with ptosis is unusual. In this patient, right leg weakness was a red herring that was due to radiculopathy.

Case(s) Description :

85-year-old female presented with a month history of diplopia, and ptosis of the left eye. She reported falls, photophobia, headache, nausea, numbness in the right half of her body and right leg weakness.

She had no features of Cushing syndrome, hyperprolactinemia, acromegaly or thyroid dysfunction.

On physical exam, she had ptosis and failure to adduct the left eye, but no other cranial nerve or visual field deficits. There was right leg weakness, normal passive range of motion but diminished sensation and right foot drop. The concern was for a midbrain stroke, but MRI revealed 2.2 cm sellar and suprasellar mass extending into the left para-cavernous region with mild mass effect on the optic chiasm. The differentials were pituitary macroadenoma or meningioma.

Laboratory tests showed negative myasthenia gravis panel, Total T3 82, Total T4 6.89, TSH 0.76, free T4 0.51, prolactin 20.7, cortisol 8.3, ACTH 36.1, growth hormone 4.2, IGF-1 227, LH 0.2, FSH 2.1, prolactin with hook effect testing was 13.

She underwent endoscopic endonasal resection of pituitary macroadenoma, with intraoperative evidence of cavernous sinus invasion and left oculomotor compression. She commenced hydrocortisone postop.

Pathology revealed lactotroph adenoma, densely granulated subtype, positive for Pit1, Prolactin (multifocal, cytoplasmic), Cam 5.2: (patchy), Ki-67 index: 1-2% while SF1, Tpit, FSH, LH, GH, TSH, and ACTH were negative.

Postop, the diplopia and ptosis improved, and cortisol was 8.9, prolactin 11.4. MRI showed interval transsphenoidal resection of pituitary mass with fat grafting. Residual enhancing pituitary tissue was demonstrated in the right aspect of the sella turcica with interval resolution of mass effect upon the optic chiasm.

The plan is for repeat pituitary MRI, pituitary hormone monitoring and right L4-5 laminectomy for acute right L5 radiculopathy diagnosed on EMG.

Discussion :

Pituitary adenoma has a prevalence of 1 per 1000 in the general population, about 40% are non-functioning, and incidentally discovered pituitary adenomas occur in 0.016 per 1000.

Pituitary macroadenomas (≥10 mm in size) occur in 48% of tumors and may cause mass effect such as visual field defects, headache, or hypopituitarism in 18-78%, 17-75%, or 34-89% of patients, respectively.

In this case of histologically confirmed prolactinoma without hyperprolactinemia, the initial presentation of ptosis, right lower extremity weakness, and involvement of the cavernous sinus made a pituitary mass a less likely consideration as a sellar mass would not affect the midbrain. This case highlights the importance of physical examination and knowledge of anatomy. It is important to consider a pituitary adenoma in the differential of oculomotor palsy, but motor weakness should prompt a search for an additional diagnosis.