On "malignant transformation of acoustic neuroma/vestibular schwannoma 10 years after gamma knife stereotactic radiosurgery" (skull base 2010;20:381-388)

Tumor Control Following Stereotactic Radiosurgery in Patients with Vestibular Schwannomas - A Retrospective Cohort Study

BACKGROUND

To better counsel vestibular schwannoma patients, it is necessary to understand the tumor control rates of stereotactic radiosurgery (SRS).

OBJECTIVES

To determine tumor control rates, factors determining control and complication rates following SRS.

METHODS

Tertiary hospital retrospective cohort.

RESULTS

579 tumors (576 patients) were treated with SRS. 477 tumors (474 patients, 82%) had ≥1 year follow up and 60% (344) ≥3 years follow up. 88% of tumors had primary SRS and 6.7% salvage SRS. Median follow up time was 4.6 years. At 3 years, the tumor control rate of primary SRS was 89% (258 of 290) in sporadic tumors compared to 43% in Neurofibromatosis type II (3 of 17) (p < 0.01). Our bivariable survival data analysis showed that Neurofibromatosis type II, documented pre-SRS growth, tumor measured by maximum dimension, SRS given as nonprimary treatment increased hazard of failure to control. There was one case of malignancy and another of rapid change following intra-tumoral hemorrhage. For tumors undergoing surgical salvage (25 of 59), 56% had a total or near-total resection, 16% had postoperative CSF leak, with 12% new facial paralysis (House-Brackmann grade VI) and worsening of facial nerve outcomes (House-Brackmann grade worse in 59% at 12 mo).

CONCLUSIONS

Control of vestibular schwannoma after primary SRS occurs in the large majority. Salvage surgical treatment was notable for higher rates of postoperative complications compared to primary surgery reported in the literature.

Evaluation and Management of Facial Nerve Schwannoma

Facial nerve schwannomas are benign peripheral nerve sheath tumors that arise from Schwann cells, and most commonly present with facial paresis and/or hearing loss. Computed tomography and MRI are critical to diagnosis. Management decisions are based on tumor size, facial function, and hearing status. Observation is usually the best option in patients with good facial function. For patients with poor facial function, the authors favor surgical resection with facial reanimation. There is growing evidence to support radiation treatment in patients with progressively worsening moderate facial paresis and growing tumors.

Role of diffusion-weighted imaging in skull base lesions: A pictorial review

Skull base lesions can be related to wide number of pathologies including infections, benign and malignant tumors. Accurate diagnosis and differentiation between these entities is important for prompt and appropriate treatment. However, computed tomography and routine magnetic resonance imaging techniques only provide information on the extent of the lesions, with limited ability to differentiate between benign and malignant lesions. Diffusion-weighted imaging can help in many such situations by providing additional information, including help in differentiating benign from malignant lesions, so that appropriate treatment can be initiated. In this review article, we illustrate the imaging findings of the spectrum of skull base lesions, emphasizing the role of diffusion-weighted imaging in this domain.