Rapid improvement in visual field with cabergoline in suprasellar tumor in a young adult: Clinical dilemma solved and surgery averted.

Sir,

We report a case of suprasellar mass with visual compromise, hypogonadism and hyperprolactinemia, where weekly visual perimetry after dopamine agonist (cabergoline) therapy helped to differentiate between pituitary adenoma (macroprolactinoma) and craniopharyngioma with stalk compression syndrome. This case highlights the use of simple clinical test of visual perimetry to help in quick and reliable decision making, regarding surgery.

A 24-year-old male was presented to the neurosurgery department with a history of headache, diminution of vision of 4 months’ duration. His MRI of the brain revealed 20 × 21 × 19 mm sized, well-defined, smoothly marginated ovoid lesion in suprasellar region diagnosed as craniopharyngioma [Figures 1a and b]. The lesion was compressing and displacing the optic chiasm and circle of Willis superiorly, pituitary gland and stalk inferiorly and supraclinoid internal carotid artery laterally. He was then referred to the endocrinology department for hormonal evaluation in view of suprasellar mass before transcranial removal of tumor. He also gave a history of decreased libido, decreased frequency of shaving and postural giddiness. His general and systemic examination was unremarkable except decreased bilateral lateral visual field. Sexual maturity score was of a normal adult (P5G5) and bilateral testicular volume was 20 ml. His hormonal profile revealed hypogonadotropic hypogonadism (LH/FSH - 3.02/2.43; S. testosterone - 0.5 ng/ml), secondary hypothyroidism (FT4 - 0.96 ng/ml; TSH - 0.01 μIU/ml), secondary adrenal insufficiency (basal and post-ACTH cortisol-2.29 / 12.3 μg/dl), and hyperprolactinemia (178 ng/ml; normal<25). His visual perimetry revealed bitemporal hemianopia with additional restriction of field of vision in left inferior quadrant [Figure 2, baseline]. He was diagnosed as a case of macroprolactinoma with remote possibility of craniopharyngioma with pituitary stalk compression. We advised him to defer the surgery for 4 weeks and started on cabergoline with rapid increase to 0.5 mg twice-weekly alongwith thyroxin and hydrocortisone. After 2 weeks, there was subjective and objective improvement of vision. His visual perimetry showed bitemporal superior quadrantanopia with minimal involvement of inferior lateral quadrants [Figure 2]. In view of the dramatic response to dopamine agonists, we decided to hold the surgery and patient was continued on tab cabergoline and planned for follow-up after 4 weeks. After 6 weeks of exhibition of cabergoline, his repeat visual perimetry was near normal [Figure 2] and repeat MRI brain showed reduction in size of lesion (16 × 16 × 19 mm3), with stalk [Figure 1c] and optic chiasma [Figure 1d] clearly visible to be separated from the tumor. His prolactin had normalized to 3.48 ng/ml and hypopituitarism completely recovered with hormonal parameters of LH/FSH/testosterone -8.44/4.95/4.9 ng/ ml; serum cortisol basal/post-ACTH -8.7 / 26.4 μg/dl and FT4 -2.33 ng/ ml (0.8-1.7), TSH -4.4 μIU/ml without any replacement.

Figure 1

Coronal and sagittal section in post-gadolinium T2W MRI before (a, b) and after 6 weeks (c, d) of cabergoline therapy. Pituitary stalk and optic chiasma are clearly visible and separated from tumor in image c and d, respectively

Figure 2

Visual field by perimetry at baseline, after 2 and 6 weeks of cabergoline therapy

Both neoplastic and non-neoplastic sellar masses may arise from regions within and adjacent to the hypothalamus and pituitary. Prolactin>100 ng/ml can be caused by prolactinoma, sellar masses with stalk compression and use of drugs. Prolactin levels above 250 ng/ml are almost exclusively caused by prolactinomas.[1] In our patient, possible causes of hyperprolactinemia were restricted to either a prolactinoma or suprasellar mass (? craniopharyngioma) with stalk compression.

Prolactinomas are the most common secretary pituitary adenomas.[2] Males usually present with macroadenomas, often with headache, visual symptoms, or both, in addition to hypogonadism. Non-functioning sellar masses also present with similar symptoms. In view of the diagnostic dilemma, we decided to expose our patient to dopamine agonist therapy (cabergoline). As the patient was quite apprehensive about finding of a tumor in the brain, and persistent headache and visual loss, he was explained about rationale of therapy to allay his anxiety. Though he had a diagnosis of craniopharyngioma with stalk compression, we decided to give a trial of dopamine agonist therapy to avoid unnecessary surgery with a view that it was prolactinoma. Classical differentiation between prolactinoma and suprasellar mass with raised prolactin levels is done by assessing decrease in the size of adenoma after dopamine agonist therapy as assessed by MRI of the brain after 1-3 months or visual perimetry after 2-3 months.[3-4] We here, report this case where we followed-up our patient with visual perimetry to assess response to therapy very early during the course of the disease, thus the decreased time lag before taking the final decision. Visual perimetry is cheap, easily accessible, and has clinical correlate in form of visual confrontation test.This case also highlights rapid reversibility of hypopituitarism due to stalk compression which was confirmed on imaging.