Pituitary Stalk Gangliogliomas

Background and Importance: Gangliogliomas rarely occur in the sella or parasellar region and are almost never seen in the pituitary stalk. Seven cases of gangliogliomas occurring in this region have been reported, and only one case involved a tumor within the pituitary stalk. Of the other six tumors, two occurred in the neurohypophysis, one was in the adenohypophysis, the location of one was unspecified, and two extensively invaded the optic chiasm, hypothalamus and brainstem. To our knowledge, this is only the second reported case of a pituitary stalk ganglioglioma.

Clinical Presentation: A 51-year old woman with an eleven-month history of polydipsia, polyuria and diagnosis of diabetes insipidus presented for evaluation. Magnetic Resonance Imaging of the brain revealed contrast-enhanced thickening and anterior bowing of the hypophyseal stalk. Transsphenoidal exploration found a firm, white mass, integral to the right side of the enlarged pituitary stalk. Pathologic analysis of the biopsy showed WHO grade I ganglioglioma. The patient tolerated the procedure well and required no endocrinologic treatment other than desmopressin.

Results: Including the 6 other reports of gangliogliomas presenting in the pituitary sella, the patient's ages ranged from 7 to 89 with a mean of 45.7 years. The most common presenting symptoms were headaches and vision changes. Three cases reported pathology grades, which was WHO grade 1 for all those cases. The most common endocrine abnormality was hyperprolactinemia, and there was only one other report of decreased vasopressin, though this occurred in a ganglioglioma of the neurohypophysis. The surgical approaches were evenly divided between endoscopic endonasal approach and craniotomy; with three cases each, while one patient was diagnosed on autopsy. Five cases reported the extent of resection; three had a gross total resection, and there were two cases of subtotal resection.

Discussion: Multiple theories have been postulated regarding the pathogenesis of gangliogliomas and ganglion cell tumors. Neuronal differentiation, pluripotent cells, or malformative neuronal lesions with glial components representing hamartomatous elements have all been suggested as origin pathways. Ongoing research studies into the molecular basis of gangliogliomas are shedding light on possible prognostic factors and therapeutic options. However, the predominant treatment modality for pituitary stalk gangliogliomas is surgical resection when possible. Two cases of pituitary stalk gangliogliomas with tumor extension to the optic-chiasm and hypothalamic pathway have utilized adjuvant radiotherapy. There have been reports of high-precision stereotactic conformal radiation therapy to a dose of 54 Gy in 30 fractions. Despite a reported 15-year overall survival rate of 94 percent, the rate of malignant degeneration of gangliogliomas have been noted to vary between 4 and 32 percent. Though adjuvant radiotherapy has been shown to prolong recurrence time without improving overall survival, a controversy with its use is the risk of accelerating malignant transformation of a previously benign ganglioglioma, several cases of which has been reported.

Conclusion: Pituitary stalk gangliogliomas are extremely rare entities. The diagnosis should be considered in patients who present with enlargement of the pituitary stalk. Since management differs for possible alternative diagnoses, biopsy should be performed for pathologic certainty.