Shin, Masahiro

BACKGROUND Acinic cell carcinomas (AcCCs), rare malignancies of the salivary glands, often recur and metastasize, particularly in the skull base. Conventional radical resection can be invasive for skull base AcCCs adjacent to cranial nerves and major vasculature, and the effectiveness of stereotactic radiosurgery (SRS) as an alternative is not well established. OBSERVATIONS This case report details the application of SRS for recurrent skull base AcCCs. A 71-year-old male with a history of resection for a right mandibular AcCC 23 years earlier experienced tumor recurrence involving the right cavernous sinus and nasal cavity. He underwent endoscopic transnasal surgery followed by SRS targeting different tumor locations—the cavernous sinus to the pterygopalatine fossa, maxillary sinus, and clivus—each with a prescribed dose of 20 Gy to the 40% to 50% isodose line. After the first skull base metastasis, additional sessions of localized SRS after endoscopic surgery led to a 12-year survival without sequela. LESSONS This is a report indicating that SRS for skull base AcCCs can achieve favorable local control, functional preservation, and long-term survival. SRS may be suitable for skull base AcCC given the lesion’s tendency toward multiple local recurrences. Further investigation is needed to validate the treatment’s efficacy.

OBJECTIVE Chronic subdural hematoma (CSDH) is known to occur after endoscopic endonasal surgery (EES); however, the detailed clinical picture remains unclear. In this study, the authors aimed to examine the incidence of and risk factors for post-EES CSDH, with a focus on the quantitative evaluation of postoperative pneumocephalus. METHODS The authors retrospectively collected data on consecutive patients who, between November 2016 and December 2022, had undergone EES during which intraoperative cerebrospinal fluid (CSF) leakage occurred. Using CT images obtained immediately after surgery (CT0), the authors measured the extent of pneumocephalus in detail. The locations of pneumocephalus were divided into two groups: remote and local. Remote pneumocephalus was further subdivided into convexity and ventricular. The incidence of post-EES CSDH was calculated, and its risk factors were analyzed. RESULTS Among the 159 EES patients included in the study, Esposito grade 1, 2, and 3 intraoperative CSF leakage was confirmed in 22 (14%), 27 (17%), and 110 (69%) patients, respectively. CSDH occurred in 6 patients (3.8%). One patient (0.6%) required unilateral burr hole surgery, whereas the hematomas spontaneously disappeared in the others. All CSDHs occurred in patients with Esposito grade 3 CSF leakage and convexity pneumocephalus on CT0. In the multivariate analysis of 149 sides with convexity pneumocephalus on CT0, the product of the diameter and the thickness of convexity pneumocephalus on CT0 was significantly associated with subsequent CSDH (OR 1.21, 95% CI 1.06–1.38, p = 0.004). Using a cutoff value of 10 cm2, CSDH development could be predicted with a sensitivity of 0.82 and specificity of 0.74. CONCLUSIONS The incidence of post-EES CSDH is acceptably low, and surgery is rarely required. Patients with extensive convexity pneumocephalus on immediate postoperative CT are prone to develop CSDH and thus should be carefully monitored.

Stereotactic radiosurgery (SRS) is known to provide excellent tumor control with functional preservation for vestibular schwannomas (VS), but its efficacy in the other major intracranial schwannomas including trigeminal (TS), facial (FS), and jugular foramen schwannomas (JFS) has not been established yet due to their rarity. We retrospectively analyzed data of 514 consecutive patients who had intracranial schwannomas (460 VS, 22 TS, 7 FS, and 25 JFS) and underwent SRS. The 5- and 10-year tumor control rates were 97% and 94% for VS, 100% and 100% for TS, 80% and 80% for FS, and 100% and 80% for JFS. Radiation-induced complications included one hydrocephalus for TS (4.5%), no cases for FS (0%), and one hydrocephalus and one lower palsy for JFS (8.0%). Through matched cohort analysis between patients with VS and each of the non-VS, we found no statistical difference in tumor control and radiation-induced adverse events. SRS seems to provide long-term tumor control with functional preservation for TS, FS and JFS and the efficacies are similar to VS.

Abstract BACKGROUND High-definition vascular imaging is desirable for treatment planning in Gamma Knife radiosurgery (GKRS; Elekta AB) for brain arteriovenous malformations (BAVMs). Currently, rotational angiography (RA) provides the clearest 3-dimensional visualization of niduses with high spatial resolution; however, its efficacy for GKRS has not been clarified. At our institution, RA has been integrated into GKRS (RA-GKRS) for better treatment planning and outcomes since 2015. OBJECTIVE To evaluate RA-GKRS outcomes of BAVMs and compare them with conventional GKRS (c-GKRS) outcomes. METHODS We retrospectively analyzed the radiosurgical outcomes of 50 BAVMs treated with RA-GKRS compared with the 306 BAVMs treated with c-GKRS. Considering possible differences in the baseline characteristics, we also created propensity score-matched cohorts and compared the radiosurgical outcomes between them to ensure comparability. RESULTS The obliteration time was shorter in the RA-GKRS group (cumulative rate, 88% vs 65% at 4 yr [ P = .001]). Multivariate Cox proportional hazards analysis demonstrated that the RA-GKRS group (hazard ratio 2.38, 95% CI 1.58-3.60; P = .001) had a better obliteration rate. The cumulative 4-yr post-GKRS hemorrhage rates were 4.0% and 2.6% in the RA-GKRS and c-GKRS groups, respectively ( P = .558). There was a trend toward early post-GKRS signal change in the RA-GKRS group compared with the c-GKRS group (cumulative rate, 38% vs 29% at 2 yr; P = .118). Those results were also confirmed in the matched cohort analyses. CONCLUSION The integration of RA into GKRS is promising and may provide earlier nidus obliteration.

Little is known about delayed postoperative hyponatremia (DPH) accompanied with transsphenoidal surgery for non-adenomatous skull base tumors (NASBTs). Consecutive data on 30 patients with parasellar NASBT was retrospectively reviewed with detailed analyses on perioperative serial sodium levels. Serological DPH (sodium ≤ 135 mmol/L) was observed in eight (27%), with four (13%) of them being symptomatic. DPH developed on postoperative day 7–12 where the mean sodium levels were 134 mmol/L (a mean of 7 mmol/L drop from the baseline) in asymptomatic and 125 mmol/L (a mean of 17.5 mmol/L drop from the baseline) in symptomatic DPH. Serological DPH was accompanied with “weight loss and hemoconcentration (cerebral salt wasting type)” in four (50%), “weight gain and hemodilution (syndrome of inappropriate antidiuretic hormone secretion type)” in three (38%), and no significant weight change in one. Intraoperative extradural retraction of the pituitary gland was the only significant factor for serological DPH (p = 0.035; odds ratio, 12.25 (95% confidence interval, 1.27–118.36)). DPH should be recognized as one of the significant postsurgical complications associated with TSS for NASBTs. Although the underlying mechanism is still controversial, intraoperative extradural compression of the pituitary gland and subsequent dysregulation of the hypothalamo-hypophyseal axis may be responsible.

OBJECTIVE The major concern about ruptured arteriovenous malformations (rAVMs) is recurrent hemorrhage, which tends to preclude stereotactic radiosurgery (SRS) as a therapeutic modality for these brain malformations. In this study, the authors aimed to clarify the role of SRS for rAVM as a stand-alone modality and an adjunct for a remnant nidus after surgery or embolization. METHODS Data on 410 consecutive patients with rAVMs treated with SRS were analyzed. The patients were classified into groups, according to prior interventions: SRS-alone, surgery and SRS (Surg-SRS), and embolization and SRS (Embol-SRS) groups. The outcomes of the SRS-alone group were analyzed in comparison with those of the other two groups. RESULTS The obliteration rate was higher in the Surg-SRS group than in the SRS-alone group (5-year cumulative rate 97% vs 79%, p < 0.001), whereas no significant difference was observed between the Embol-SRS and SRS-alone groups. Prior resection (HR 1.78, 95% CI 1.30–2.43, p < 0.001), a maximum AVM diameter ≤ 20 mm (HR 1.81, 95% CI 1.43–2.30, p < 0.001), and a prescription dose ≥ 20 Gy (HR 2.04, 95% CI 1.28–3.27, p = 0.003) were associated with a better obliteration rate, as demonstrated by multivariate Cox proportional hazards analyses. In the SRS-alone group, the annual post-SRS hemorrhage rates were 1.5% within 5 years and 0.2% thereafter and the 10-year significant neurological event–free rate was 95%; no intergroup difference was observed in either outcome. The exclusive performance of SRS (SRS alone) was not a risk for post-SRS hemorrhage or for significant neurological events based on multivariate analyses. These results were also confirmed with propensity score–matched analyses. CONCLUSIONS The treatment strategy for rAVMs should be tailored with due consideration of multiple factors associated with the patients. Stand-alone SRS is effective for hemorrhagic AVMs, and the risk of post-SRS hemorrhage was low. SRS can also be favorably used for residual AVMs after initial interventions, especially after failed resection.

Objective: Gamma knife radiosurgery (GKRS) is commonly used to treat vestibular schwannomas (VSs). The risk of complications from GKRS decreases at lower doses, but it is unknown if long-term tumor control is negatively affected by dose reduction. Study Design: This was a retrospective case review and analysis of patient data. Setting: Tertiary referral center. Patients: Patients with VSs who underwent GKRS between 1990 and 2007 at the authors’ institution. Intervention(s): The subjects were divided into two cohorts based on the prescribed doses of radiation received: a 12 Gy cohort (96 patients) with a follow-up period of 124 months and a >12 Gy cohort (118 patients) with a follow-up period of 143 months. Main Outcome Measures: Tumor control rates at 10 to 15 years, frequency of facial and trigeminal nerve complications, and hearing function. Results: The 10 to 15-year tumor control rates were 95% in the 12 Gy cohort and 88% in the > 12 Gy cohort, but the differences were not significant. Compared with the >12 Gy cohort, facial and trigeminal nerve deficits occurred significantly less frequently in the 12 Gy cohort, with the 10-year cumulative, permanent deficit-free rates being 2% and 0%, respectively. Multivariate analyses revealed that treatment doses exceeding 12 Gy were associated with a significantly higher risk for cranial nerve deficits. The percentage of subjects retaining pure-tone average ≤ 50 dB at the final follow-up did not significantly differ between the cohorts (12 Gy cohort, 30% and >12 Gy cohort, 33%; p = 0.823). Conclusions: Dose reduction to 12 Gy for GKRS to treat VSs decreased facial and trigeminal nerve complications without worsening tumor control rates.

The efficacy of radiosurgery for neurofibromatosis type 2 (NF2)-associated vestibular schwannoma (VS) remains debatable. We retrospectively analyzed radiosurgical outcomes for NF2-associated VS compared to sporadic VS using our database of 422 consecutive VS patients. Twenty-five patients with 30 NF2-associated VSs with a mean follow-up of 121 months were identified. NF2-associated VSs exhibited excellent tumor control (10-year cumulative rate, 92% vs. 92% in sporadic VSs; p = 0.945) and worse overall survival (73% vs. 97%; p = 0.005), mainly due to tumor progression other than the treated VSs. The presence of NF2 was not associated with failed tumor control via multivariate Cox proportional hazard analyses. No difference in radiation-induced adverse events (RAEs) was confirmed between cohorts, and prescription dose (hazard ratio 8.30, 95% confidence interval 3.19–21.62, p < 0.001) was confirmed as a risk for cranial nerve injuries via multivariate analysis. Further analysis after propensity score matching using age, volume, and sex as covariates showed that NF2-associated VSs exhibited excellent local control (100% vs. 93%; p = 0.240) and worse overall survival (67% vs. 100%; p = 0.002) with no significant difference in RAEs. Excellent long-term tumor control and minimal invasiveness may make radiosurgery a favorable therapeutic option for NF2 patients with small to medium VS, preferably with non-functional hearing or deafness in combination with postoperative tumor growth or progressive non-operated tumors, or with functional hearing by patients’ wish.