P-087 a Giant Prolactinoma Presenting With Strabismus

Abstract Introduction Giant prolactinoma (4 cm) is a rare entity, predominantly seen in men, and typically produces significant mass effect on surrounding structures. At presentation, its clinical features may mimic neurological disorders such as stroke. Most giant prolactinomas respond well to dopamine agonists. We report a case of giant prolactinoma presenting with strabismus. Clinical Case A 67-year-old male with hypertension, COPD, and atrial fibrillation presented with one year of headache and nausea, which had worsened in the past two days, accompanied by slurred speech and limitation of right eye movement. On examination, he was conscious, cooperative, and oriented. Eye exam revealed right esotropia in primary position, left orthophoria, isochoric pupils with intact light reflexes, and no other cranial nerve deficits. Motor strength was preserved in all extremities. Visual field testing showed right peripheral scotoma and left tubular vision loss. Brain MRI demonstrated a 35×65×38 mm mass (45 ml) extending into the sphenoid sinus and encasing the right cavernous ICA 360° and the left ICA 180°, consistent with pituitary macroadenoma. Initial laboratory results were: cortisol 0.835 µg/dL, ACTH 4 ng/L, IGF-1 113 µg/L, TSH 0.13 mIU/L, free T4 1.05, prolactin 23,500 µg/mL, FSH 3.7 IU/L, LH 4.15 IU/L, total testosterone 0.1 ng/mL, sodium 133 mmol/L, and glucose 119 mg/dL. These findings were consistent with pituitary insufficiency. The patient was diagnosed with giant prolactinoma and started on prednisolone 5 mg/day and cabergoline 1 mg/week under close neurosurgical and ophthalmological follow-up. After one week, prolactin decreased by 85% (3603 ng/mL). At one month, ocular and neurological symptoms improved, prolactin decreased to 770 µg/mL, and cortisol normalized (16.5 µg/dL). MRI showed tumor regression to 30×58×38 mm (33 ml, −33%). Prednisolone was discontinued and cabergoline increased to 2 mg/week. At six months, the patient was asymptomatic with normal neurological and visual function. Prolactin had normalized (19.5 µg/L), and MRI showed further regression to 35×45×25 mm (15 ml, −67%), surrounding the right ICA 90° with no left ICA contact. Clinical and biochemical remission with radiological regression was achieved, and cabergoline therapy was continued. Conclusion Giant prolactinomas usually respond to dopamine agonists, but PRL normalization may not always occur and residual tumor may persist. Our case illustrates a rare presentation with strabismus, most likely related to abducens nerve involvement, and shows a remarkable therapeutic response to cabergoline. These findings underline the need for long-term follow-up to monitor both hormonal and neurological outcomes.Figure 1:Clinical and Radiological FindingsPre-treatment, 1st-month, and 6th-month MRI results and ocular findings (from left to right)