Abducens nerve palsy during pegvisomant therapy in an acromegalic patient

Pegvisomant is a recent treatment modality of acromegaly, which is most effective in regulating IGF-1 levels. Tumor growth has been reported in 5% of the acromegaly cases treated with pegvisomant. Herein we report a case of acromegaly resistant to surgical treatment, radiotherapy and medical therapy with a somatostatin analogue and cabergolin. Due to presence of pituitary tumor with cavernous sinus invasion and unremitting disease activity pegvisomant therapy was initiated. She developed left abducens nerve palsy after pegvisomant treatment. The objective of this report is to emphasize the value of close follow-up of the acromely cases under pegvisomant therapy, especially if they have cavernous sinus infiltrating tumor. A 44-year-old woman with acromegaly presented with visual defect and diplopia on left lateral gaze. Her complaint developed 3 years after initiation of pegvisomant therapy. Her neurologic examination was consistent with mild abducens nerve palsy on left side. Other causes for abducens nerve palsy were excluded. Pegvisomant was discontinued upon patient request. Although sella MRI did not reveal a tumor growth, even minimal growth within cavernous sinus can cause cranial nerve involvement. Therefore close and careful follow-up of cavernous sinus infiltrating tumors after pegvisomant therapy is crucial to early recognition of complications.