Planned Subtotal Resection in Benign Skull Base Tumors Followed by Gamma Knife Surgery: Preliminary Results

Aim: The management of large lesions of the skull base, such as vestibular schwannomas (VS), meningiomas (MEN), or pituitary adenomas (PA), is challenging, with microsurgery remaining the main treatment option. Planned subtotal resection is now being increasingly considered to reduce the risk of neurological deficits following complete resection. The residual part of the tumor can then be treated with Gamma-Knife Radiosurgery (GKR) to achieve long-term growth control.

Methods: This case series documents early results with planned subtotal resection followed by GKR in Lausanne University Hospital, between July 2010 and March 2012. There were 24 patients who underwent surgery, with 22 having already undergone GKR and 2 waiting for GKR. We analyzed clinical symptoms for all patients, as well as audiograms, ophthalmological, and endocrinological tests, when indicated.

Results: Nine patients had VS surgery (mean diameter 35 mm; range 30 to 44.5) through a retrosigmoid approach. There were no postoperative facial nerve deficits. Of the 3 patients who had useful hearing preoperatively, this was improved in 2 and remained stable in 1. Four patients with clinoid MEN (mean diameter 26.5 mm; range 17 to 42) underwent subtotal resection of the tumor, and the component in the cavernous sinus was later treated with GKR. The visual status remained stable in three patients and one had complete visual recovery. Four patients underwent subtotal resection of petroclival MEN (mean diameter 36 mm; range 32 to 42); three had House-Brackmann (HB) grade 2 facial function that recovered completely; one continues to have HB grade 4 facial deficit following surgery. Of the seven patients with PA (mean diameter 34.5 mm; range 20 to 54.5), two had acromegaly, the others were nonfunctional PA. Six patients underwent transsphenoidal surgery, while one patient had a transcavernous sinus resection of the tumor (with prior staged transsphenoidal surgery). Visual status improved in three patients while the others remained stable. Two patients had transient diabetes insipidus following surgery. Up to now, no additional deficit or worsening has been reported after GKR.

Conclusions: Our data suggest that planned subtotal resection has an excellent clinical outcome with respect to preservation of cranial nerves, and other neurological functions, and a good possibility of recovery of many of the preoperative cranial nerve dysfunctions. The results in terms of tumor control following GKR need further long-term evaluation.