Surgical resection of giant extrasellar thyrotropinoma: Use of orbitozygomatic and endoscopic endonasal approach.

Background: Thyrotropinomas (TSHoma) are rare pituitary adenomas.

Case Description: A 34-year-old female presented with mild bitemporal field defect in third trimester with intact pituitary function. MRI demonstrated an enhancing lesion from the posterior planum to suprasellar, interpeduncular and prepontine cisterns with chiasmal compression and right fetal posterior communicating artery encasement. With no sellar expansion, the differentials included meningioma or craniopharyngioma. She underwent a postpartum expanded endoscopic endonasal transtuberculum transchiasmatic sulcus approach [Video 1]. The lesion was debulked in the chiasmatic cistern to decompress the chiasm with preservation of superior hypophyseal perforators. Pituitary transposition and midclival approach to access the retrosellar component was not undertaken pending formal histology as the lesion encased the perforators and was atypical for the outlined differentials. In addition, the diaphragm was intact. Postoperatively, visual field normalized and the patient developed mild diabetes insipidus. Following the diagnosis of TSHoma (with an abnormal thyroid function test [TFT]) and due to patient preference and slightly increased risk of CSF leak with revisional endoscopic procedure, she underwent an orbitozygomatic craniotomy (pretemporal and transsylvian approach) without tentorial division to resect the disease in the interpeduncular and prepontine cisterns [Video 1]. The anatomical triangles and tumor characteristics facilitated this. A residual cuff was left along the base of the stalk and the floor of the third ventricle to preserve the superior hypophyseal and thalamoperforators. Postoperatively, the patient had normal TFT without any neurological deficit.

Conclusion: Operative treatment strategy is presented for a rare large challenging multicompartmental extrasellar TSHoma using endoscopic endonasal and open skull base approaches.