Preservation of Pituitary Function after Endonasal Craniopharyngioma Surgery: Case Report and Review of the Literature

Craniopharyngiomas comprise approximately 3% of all intracranial tumors. Preservation of pituitary function after resection represents a significant challenge due to their location in the anterior skull base and aggressive local behavior. We report a case of a 79-year-old woman with a large suprasellar craniopharyngioma who presented with visual loss. MRI revealed a suprasellar cystic mass with mass effect on the optic chiasm and pituitary gland. Following endoscopic endonasal gross total resection of the tumor, the patient’s pituitary function returned to normal.


Introduction
Craniopharyngiomas are histologically benign epithelial tumors that arise along the path of the craniopharyngeal duct and are derived from the epithelial remnants of Rathke's pouch [1]. Given the anatomical location of these tumors in the anterior skull base and close relation to vital structures, including the optic chiasm, pituitary gland, hypothalamus, and anterior cerebral artery, surgical resection is a significant challenge [2].
Pituitary function is especially difficult to maintain after surgery as these tumors frequently abut or strongly adhere to the pituitary gland [2]. Preservation of the infundibulum and pituitary gland often results in subtotal resection due to tumor infiltration. Thus, pituitary function is often sacrificed during surgery in order to achieve gross total resection (GTR). Here, we present a unique case of craniopharyngioma, in which the pituitary function was able to be preserved following GTR through endoscopic endonasal surgery.

Case Presentation
A 79-year-old female presented with a complaint of visual disturbances over the past eight months. Signed informed patient consent was obtained prior to treatment. Upon examination, the patient was found to have a visual loss in her left eye, normal endocrine function, and intact mental status. MRI with the injection of contrast media revealed a lobulated cystic lesion centered in the suprasellar cistern measuring 2.2 x 1.6 x 2.0 cm (AP x transverse x CC). The mass demonstrated broad vascular contact with the circle of Willis as well as a mass effect on the optic chiasm, left optic nerve, and pituitary gland (Figures 1-2). CT revealed several small foci of calcification.  The patient underwent endoscopic endonasal transsphenoidal resection of the tumor using a transtuberculum approach [2][3][4]. The tumor was identified and removed from the anterior skull base with no evidence of residual tumor. A gasket seal closure was used, covered by nasoseptal flap [5][6][7]. A lumbar drain was left in place for 24 hours. Postoperative MRI confirmed gross total resection of the tumor (Figures 3-4). The diagnosis from surgical pathology was craniopharyngioma, WHO Grade 1. The patient did not have any complications from the procedure and was found not to have diabetes insipidus postoperatively. She did not require hormone replacement and was cleared for discharge home two days after undergoing surgery. She also reported subjective improvement in her vision.

Discussion
Craniopharyngiomas are histologically benign epithelial tumors that arise along the path of the craniopharyngeal duct and are derived from the epithelial remnants of Rathke's pouch [1].
Treatment of craniopharyngiomas is traditionally centered on gross total resection (GTR), although recent evidence suggests that subtotal resection and adjuvant therapy may also provide comparable control of the tumor [11]. Given the anatomical location of these tumors in the anterior skull base and close relation to vital structures, including the optic chiasm, pituitary gland, hypothalamus, and anterior cerebral artery, surgical resection is a significant challenge [2].
Pituitary function is especially difficult to maintain after surgery as these tumors frequently abut or strongly adhere to the pituitary gland [2]. Preservation of the infundibulum and pituitary gland often results in subtotal resection due to tumor infiltration. In this case, her pituitary function was able to be preserved after gross total resection through endoscopic endonasal surgery.
The endoscopic endonasal approach to the resection of craniopharyngiomas has been recently developed as an alternative to the open transcranial approach. A review of the literature suggests that the endoscopic endonasal approach may result in a greater rate of pituitary function preservation. Higher rates of pituitary function preservation may arise from improved visualization of the stalk and superior hypophyseal arteries.
A 2012 meta-analysis comparing the approaches found that the rates of permanent diabetes insipidus and hypopituitarism were 54.8% and 48.1%, respectively, in the open transcranial cohort versus 27.7% and 47.1%, respectively, in the endoscopic endonasal cohort. It also found that the endoscopic endonasal cohort had a greater rate of GTR and improved visual outcome compared to the open transcranial cohort and concluded that that endoscopic endonasal approach is a safe and effective alternative for the treatment of craniopharyngiomas [12].
In recent publications looking at outcomes of the endoscopic endonasal approach, new onset diabetes insipidus was reported in 42-48% of patients and new onset hypopituitarism was reported in 38-58% [13][14][15]. In recent publications looking at outcomes of the open transcranial approach, new onset diabetes insipidus was reported in 66.7-93.2% of patients, new onset ACTH deficiency was reported in 56.5-83.8%, and new onset thyroid insufficiency was reported in 30.8-83.8% [16][17].

Conclusions
Preservation of pituitary function after resection of craniopharyngioma is a significant challenge due to the location of the tumor and its frequent adherence to the pituitary gland. Endoscopic endonasal surgery can be an effective approach to gross total resection and may lead to higher rates of pituitary function preservation compared with transcranial surgeries.