Carlson, Matthew L.

Objectives: 1) Describe the genetic alterations discovered in a series of sporadic vestibular schwannomas (VS). 2) Identify if more clinically aggressive variants possess different genetic alterations compared to more indolent-behaving VS. Methods: Fresh frozen tumor and matched peripheral blood leukocytes from 23 individuals with sporadic VS were analyzed using whole-exome sequencing, tumor whole transcriptome expression profiling (mRNA-Seq), and tumor mate-pair analysis. Source cases included tumors with fast preoperative growth, giant tumors in young patients, tumors with macrocystic change, recurrent tumors following radiation or microsurgery, and indolent small tumors with minimal or no growth before surgery. Somatic and germ-line alterations of the NF2 gene and beyond the NF2 locus were identified and analyzed using complementing analyses. Results: Biallelic somatic events involving the NF2 gene were discovered in every analyzed tumor specimen with no concurrent NF2 variants identified in matching peripheral blood specimens. Thirteen tumors showed loss of one chromosome 22 (ch22), 4 tumors showed copy-neutral 22q loss of heterozygosity, and 31 unique small variants in the NF2 gene were discovered. Of the latter, 10 were essential splice site, 11 frame shift, 7 stop gain, 2 missense, and 1 in-frame mutation. No other common or recurring NF2 mutations were identified. However, several other notable large chromosomal aberrations were discovered including 2 tumors with loss of a chromosome 21, 3 with loss of an X or Y chromosome, 1 with copy-neutral loss of heterozygosity in chromosome 15, and 1 with loss of 18p and 16q. All of these other major chromosomal abnormalities only occurred in tumors demonstrating a more aggressive phenotype. Conclusions: To date, few studies have used whole-exome sequencing, mate-pair analysis, and RNA-seq to profile genome-wide alterations in sporadic VS. Using high-throughput deep sequencing, “two-hit” alterations in the NF2 gene were identified in every tumor and were not present in peripheral blood supporting that all events were somatic. Type of NF2 gene alteration and accessory mutations outside the NF2 locus may predict phenotypic expression and clinical course.

Objective: To characterize the risk of progression to nonserviceable hearing in patients with sporadic vestibular schwannomas (VS) who elect initial observation. Study Design: Retrospective case series. Setting: Two tertiary care centers. Patients: VS patients with serviceable hearing who underwent at least two audiograms and two MRI studies before intervention or loss to follow-up. Main outcome measure(s): Serviceable hearing, defined as the pure tone average ≤ 50 dB HL and word recognition score ≥ 50%. Results: Four-hundred sixty-six patients (median age of 57 yr and median tumor diameter of 7.3 mm) had serviceable hearing at presentation and were followed for a median of 2.3 years (IQR 1.0 – 4.0). Kaplan–Meier estimated rates of maintaining serviceable hearing (95% CI; number still at risk) at 1, 3, 5, 7, and 10 years following diagnosis were 94% (91–96; 357), 77% (73–82; 172), 66% (60–73; 81), 56% (49–65; 31), and 44% (33–59; 10), respectively. Each 10-dB increase in pure-tone averages at diagnosis was associated with a 2-fold increased likelihood of developing nonserviceable hearing (hazard ratio 2.07; p < 0.001). Each 10% decrease in word recognition score was associated with a 1.5-fold increased likelihood of developing nonserviceable hearing (hazard ratio 1.48; p < 0.001). Conclusions: Among patients with sporadic VS, good baseline word recognition score and low pure-tone average are jointly associated with maintenance of serviceable hearing. These data may be used to guide patient counseling and optimize management.

Objectives: Catecholamine-secreting jugular paragangliomas (JPs) represent a rare subset of head and neck paragangliomas that may present with hypertension, arrhythmia, or syncopal episodes. Subtotal resection to protect critical neurovascular structures may result in persistent catecholamine excess from residual tumor. Herein, we report our experience with stereotactic radiosurgery (SRS) for salvage treatment of catecholamine-secreting JP following subtotal microsurgical resection. Patients: Adult patients treated with SRS after subtotal microsurgical resection of catecholamine-secreting JP. Interventions: SRS. Main Outcome Measures: Post-treatment catecholamine and metanephrine levels, clinical outcomes, and tumor control. Results: Of 85 patients with JPs treated with primary or salvage radiosurgery between 1990 and 2017, 2 (2%) harbored nonmalignant secreting tumors. Patient 1 developed catecholamine excess with elevated norepinephrine (NE) at 475 mcg/24 hours (normal < 80 mcg/24 h). Following subtotal resection, she developed catecholamine excess with radiographic evidence of tumor growth and therefore underwent SRS. Three years post-SRS and beyond, catecholamine levels remained normalized (NE 62 mcg/24 h at 10 yr) and tumor volume remained stable on serial MRI studies over the 17-year follow-up period. Patient 2 developed symptomatic arrhythmia and was found to have a JP. Urine norepinephrine (NE) was elevated at 213 mcg/24 hours. She underwent nerve-sparing subtotal resection and upfront SRS was used to treat residual tumor. Twenty months following SRS, the area of residual JP had not enlarged in size and catecholamine levels remained normal (NE 46 mcg/24 h). Conclusions: Radiosurgery can be used in salvage treatment of catecholamine-secreting JP, providing durable tumor control and resolution of catecholamine excess. For patients with large catecholamine-secreting JP and normal lower cranial nerve function, aggressive nerve-sparing subtotal resection with adjuvant radiosurgery may offer a low-morbidity alternative to gross total resection. Further study of this subset of patients is warranted to substantiate these promising, yet preliminary findings.