Graffeo, Christopher S.

Abstract BACKGROUND The lateral craniopharyngeal or Sternberg's canal (SC) originates from superior orbital fissure (SOF) and traverses the sphenoid body into the nasopharynx. A remnant of the canal, Sternberg's defect (SD), has been debated as a source of cerebrospinal fluid (CSF) leak. The canal was described in 1888, and there is limited accurate visual illustration in the literature. OBJECTIVE To provide a detailed anatomic and radiological illustration of the canal in pediatric and adult population including the mechanism undermining the incidence of the canal, and the possibility of the canal as a source of CSF leak. METHODS A total of 195 high-resolution computed tomographies (CT) of patients (50 3-yr-old, 20 5-yr-old, and 125 adults) and 43 dry adult skulls (86 sides) were analyzed for a canal matching the description of the SC. RESULTS A SC was identified in 86% of the 3-yr-old and 40% of 5-yr–old patients. The diameter and length were 2.12 mm and 12 mm, respectively. The incidence of the canal decreased with age as sinus pneumatization extended into the sphenoid sinus. Only 0.8% of the adult skull on CT had the canal. The canal was not present on the dry adult skulls examination, but SD was found in 4.65%. CONCLUSION SC exists with high incidence in the pediatric group. Sinus pneumatization obliterates the canal in the adult population, leaving a defect in 4.65% of cases, which given the location and related anatomic structures, is unlikely to be a source of CSF leak.

Abstract BACKGROUND Hypopituitarism is the most frequent complication after pituitary adenoma stereotactic radiosurgery (SRS) and is correlated with increasing radiation to the pituitary gland. Biological effective dose (BED) is a dosimetric parameter that incorporates a time component to adjust for mechanisms of deoxyribonucleic acid repair activated during treatment. OBJECTIVE To assess mean gland BED as a predictor of post-SRS hypopituitarism, as compared to mean gland dose, in a contemporary cohort study of patients undergoing single-fraction SRS for pituitary adenoma. METHODS Cohort study of 97 patients undergoing single-fraction SRS from 2007 to 2014. Eligible patients had no prior pituitary irradiation, normal pre-SRS endocrine function, and >24 mo of endocrine follow-up. Cox proportional hazards analysis was used to assess mean gland dose and BED as predictors of new post-SRS hypopituitarism. RESULTS Median post-SRS follow-up was 48 mo (interquartile range [IQR], 34-68). A total of 27 patients (28%) developed new hypopituitarism at a median 22 mo (IQR, 12-36). Actuarial rates of new endocrinopathy were 17% at 2 yr (95% CI 10%-25%) and 31% at 5 yr (95% CI 20%-42%). On univariate analysis, sex ( P = .02), gland volume ( P = .03), mean gland dose ( P < .0001), and BED significantly predicted new hypopituitarism ( P < .0001). After adjusting for sex and gland volume, BED > 45 Gy 2.47 and mean gland dose > 10 Gy were significantly associated increased risk of hypopituitarism (hazard ratio [HR] = 14.32, 95% CI = 4.26-89.0, P < .0001; HR = 11.91, 95% CI = 3.54-74.0, P < .0001). CONCLUSION BED predicted hypopituitarism more reliably than mean gland dose after pituitary adenoma SRS, but additional studies are needed to confirm these results.

Abstract Background The far-lateral approach is an effective skull base technique that provides access to the lower clivus and premedullary area. This approach is also useful for maximal visualization and resection of large posterior fossa tumors with extensive medial extension, especially when aggressive resection is ideal for a malignant tumor in a young patient, or it is technically challenging because of tumor calcification. We demonstrate a microsurgical operative video to describe technical pearls in this difficult situation. Case Presentation A 45-year-old man with history of “hoarseness” for up to two decades was presented with imbalance and mild dysphagia over 3 years. Imaging demonstrated a 55-mm left cerebellopontine angle (CPA) tumor extending medially across the midline with severe calcification (Figs. 1 and 2). His neurological examination revealed left facial numbness, complete left facial weakness, left deafness, complete left vocal paralysis, as well as severe left hemibody ataxia. The tumor was resected via a left suboccipital craniotomy with far lateral approach including drilling to the occipital condyle and C1 laminectomy. Initial manipulation of the inferior pole of the tumor resulted in asystole which was managed successfully with glycol pyrolate. Pathology demonstrated IDH-1 wild type, MGMT-methylated glioblastoma. The patient subsequently underwent adjuvant chemoradiation. Conclusion The far-lateral approach is an effective approach for maximal safe resection of a malignant brainstem, cerebellar, and CPA tumor.The link to the video can be found at: https://youtu.be/AIGebJPJEnw.

OBJECTIVE Intracranial facial nerve schwannomas (FNS) requiring treatment are frequently recommended for surgery or stereotactic radiosurgery (SRS). The objective of this study was to compare facial nerve function outcomes between these two interventions for FNS via a systematic review and meta-analysis. METHODS A search of the Ovid EMBASE, PubMed, SCOPUS, and Cochrane databases from inception to July 2019 was conducted following PRISMA guidelines. Articles were screened against prespecified criteria. Facial nerve outcomes were classified as improved, stabilized, or worsened by last follow-up. Incidence was pooled by random-effects meta-analysis of proportions. RESULTS Thirty-three articles with a pooled cohort of 519 patients with FNS satisfied all criteria. Twenty-five articles described operative outcomes in 407 (78%) patients; 10 articles reported SRS outcomes in 112 (22%). In the surgical cohort, facial nerve function improved in 23% (95% CI 15%–32%), stabilized in 41% (95% CI 32%–50%), and worsened in 30% (95% CI 21%–40%). In the SRS cohort, facial nerve function was improved in 20% (95% CI 9%–34%), stable in 66% (95% CI 54%–78%), and worsened in 9% (95% CI 3%–16%). Compared with SRS, microsurgery was associated with a significantly lower incidence of stable facial nerve function (p < 0.01) and a significantly higher incidence of worsened facial nerve function (p < 0.01). Tumor progression and complication rates were comparable. Outcome certainty assessments were very low to moderate for all parameters. CONCLUSIONS Unfavorable facial nerve function outcomes are associated with surgical treatment of intracranial FNS, whereas stable facial nerve function outcomes are associated with SRS. Therefore, SRS should be recommended to patients with FNS who require treatment, and surgery should be reserved for patients with another indication, such as decompression of the brainstem. Further study is required to definitively optimize and validate management strategies for these rare skull base tumors.

OBJECTIVE Residency interviews are integral to the recruitment process yet imperfect. Through surveys of neurosurgery residency applicants, the authors describe interview content and the perceived utility and stress of topics from the applicant’s perspective. METHODS All 2018–2019 neurosurgery resident applicants applying to three particular programs were surveyed. Across 10 interview topics, survey questions assessed topic frequency and the applicant’s opinion of the utility and stress of each topic (Likert scale 1–5). Analyses included descriptive statistics, Spearman’s rank correlation, and logistic regression. RESULTS One hundred thirty-three of 265 surveyed US residency applicants (50%) responded. Extracurricular activities, research, future career, non-medicine interests, and small talk were discussed in all interviews. The least frequent topics included neurosurgical knowledge assessment (79%) and manual dexterity tests (45%). The most useful topics according to respondents were future career objectives (4.78 ± 0.49) and prior research (4.76 ± 0.50); the least useful were neurosurgical knowledge assessment (2.67 ± 1.09) and manual dexterity tests (2.95 ± 1.05). The most stressful topics were neurosurgical knowledge assessment (3.66 ± 1.23) and ethical/behavioral scenarios (2.94 ± 1.28). The utility and stress of manual dexterity tests and neurosurgical knowledge assessments were inversely correlated (r = −0.40, p < 0.01; r = −0.36, p < 0.01), whereas no such correlation existed for ethical/behavioral questions (r = −0.12, p = 0.18), indicating that ethical/behavioral questions may have been stressful but were potentially useful topics. Respondents who attended ≥ 15 interviews were more likely to be asked about the three most stressful topics (each p < 0.05). Respondents with children were less likely to be asked about ethical/behavioral scenarios (OR 0.13, 95% CI 0.03–0.52, p < 0.01). CONCLUSIONS Applicants found several of the most frequently discussed topics to be less useful, indicating a potential disconnect between applicant opinion and the faculty’s preferred questions. Ethical/behavioral scenarios were rated as stressful but still useful, representing a potentially worthwhile type of question. These data provide several avenues for potential standardization and improvement of the interview process.

Abstract BACKGROUND Central nervous system (CNS) germ cell tumors (GCT) are rare and complex pediatric neoplasms, the optimal management of which remains an area of active investigation. OBJECTIVE To present an updated cohort study, with particular attention to novel diagnostic methods and posttreatment clinical phenotypes. METHODS A single-institution cohort study of 80 primary, neurosurgically managed, CNS GCTs was conducted at Mayo Clinic, 1988-2017. RESULTS Postchemotherapy resection (eg, second-look surgery) was frequently required (27.0%), especially after adjuvant therapies for nongerminomatous GCTs (NGGCTs; 14 of 28 cases, excluding mature teratoma) and significantly associated with pineal lesions, as compared to neurohypophyseal or bifocal lesions (43.6% vs 5.9% vs 6.7%, P = .004), a finding that retained statistical significance after adjusting for index extent of resection and histology ( P = .04). Essentially every NGGCT case underwent at least 1 craniotomy, either on presentation, as second-look surgery, or following local recurrence. Mature teratomatous tissue was highly incident in second-look specimens (84.2%), even among lesions initially diagnosed as germinomas. Pretreatment cerebrospinal fluid (CSF) cell fraction analysis demonstrated an association between single lesions and neutrophil predominance, whereas nongerminomatous GCTs were associated with increased monocyte fractions. CONCLUSION CNS GCTs are clinically heterogeneous lesions, resulting in numerous opportunities for improved understanding and clinical management via novel diagnostic and therapeutic protocols. Samples from second-look surgeries for recurrent germinomas frequently demonstrate teratomatous tissue, suggesting possible underdiagnosis of mixed GCTs—particularly among pineal lesions. GCT subtypes demonstrate differential cell fraction distributions on CSF analysis, a novel and perhaps diagnostically helpful finding that requires validation in external cohorts.

OBJECTIVE Recent population-based and hospital cohort studies have reported a decreasing incidence of aneurysmal subarachnoid hemorrhage (aSAH) and declining aSAH-associated case-fatality rates. Principal drivers of these trends are debated, but improvements in smoking cessation and hypertension control may be critical factors. METHODS The population-based medical records linkage system of the Rochester Epidemiological Project was used to document aSAH incidence and 30-day case fatality rates during a 20-year study period (1996–2016) in Olmsted County, Minnesota. Incidence rates in the study period were compared with data from a previous Olmsted County study concerning aSAH incidence from 1965 to 1995 and with regional trends in tobacco use. RESULTS One hundred nineteen incident cases of aSAH were included. The median age at hemorrhage was 59 years (range 16–94 years), and 74 patients were female (62.2%). The overall average annual aSAH incidence rate was 4.2/100,000 person-years (P-Y). The aSAH incidence rate decreased from 5.7/100,000 in 1996 to 3.5/100,000 P-Y in 2011–2016. The overall aSAH-associated 30-day case-fatality rate was 21.9% and declined by approximately 0.5% annually. An accelerated decline in the fatality rate (0.9%/year) was observed from 2006–2016. Smoking among adult Olmsted County residents decreased from 20.4% in 2000 to 9.1% in 2018. CONCLUSIONS A decline in the incidence of aSAH and 30-day case-fatality rate from 1996 to 2016 was observed, as well as an accelerated decline of the fatality rate from 2006 to 2016. These findings confirm and extend the trends reported by prior studies in the same population. The decrease in aSAH in the years studied paralleled a noticeable reduction in the population smoking rates.

Study Design. Review. Objective. To provide practicing spine surgeons a primer with key insights for reading, interpreting, and clinically integrating systematic reviews and meta-analyses. Summary of Background Data. Evidence-based medicine (EBM) refers to a family of standardized techniques for critical appraisal of clinical research. Within the contemporary spine literature, EBM is most commonly encountered in the form of systematic reviews and meta-analyses. Although these analytic techniques are potentially useful when appropriately applied to well-formulated questions with adequate primary data in the literature, the rapid and somewhat indiscriminate increase in volume of systematic reviews and meta-analyses published may be associated with an overall dilution in their quality, as well as misperceptions regarding the applicability of particular EBM studies to spine surgery in general. Methods. The collective experience of spine specialists with vested interests in advancing EBM and its utility was summarized into a primer. Results. We emphasize components that are pertinent methodologically (search strategy, study number, meta-analysis, bias, and certainty), and pertinent clinically (outcomes) to interpreting, and clinically integrating systematic reviews and meta-analyses into spine surgery practice. Conclusions. Armed with these insights into these five perspectives, we anticipate that practicing spine surgeons will be better equipped to interpret systematic reviews and meta-analyses in a fashion that will meaningfully impact their patient care. Level of Evidence: 2

Abstract BACKGROUND Stereotactic radiosurgery (SRS) is a safe and effective treatment for acromegaly. OBJECTIVE To improve understanding of clinical and dosimetric factors predicting biochemical remission. METHODS A single-institution cohort study of nonsyndromic, radiation-naïve patients with growth hormone-producing pituitary adenomas (GHA) having single-fraction SRS between 1990 and 2017. Exclusions were treatment with pituitary suppressive medications at the time of SRS, or <24 mo of follow-up. The primary outcome was biochemical remission—defined as normalization of insulin-like growth factor-1 index (IGF-1 i ) off suppression. Biochemical remission was assessed using Cox proportional hazards. Prior studies reporting IGF-1 i were assessed via systematic literature review and meta-analysis using random-effect modeling. RESULTS A total of 102 patients met study criteria. Of these, 46 patients (45%) were female. The median age was 49 yr (interquartile range [IQR] = 37-59), and the median follow-up was 63 mo (IQR = 29-100). The median pre-SRS IGF-1 i was 1.66 (IQR = 1.37-3.22). The median margin dose was 25 Gy (IQR = 21-25); the median estimated biologically effective dose (BED) was 169.49 Gy (IQR = 124.95-196.00). Biochemical remission was achieved in 58 patients (57%), whereas 22 patients (22%) had medication-controlled disease. Pre-SRS IGF-1 i ≥ 2.25 was the strongest predictor of treatment failure, with an unadjusted hazard ratio (HR) of 0.51 (95% CI = 0.26-0.91, P = .02). Number of isocenters, margin dose, and BED predicted remission on univariate analysis, but after adjusting for sex and baseline IGF-1 i , only BED remained significant—and was independently associated with outcome in continuous (HR = 1.01, 95% CI = 1.00-1.01, P = .02) and binary models (HR = 2.27, 95% CI = 1.39-5.22, P = .002). A total of 24 patients (29%) developed new post-SRS hypopituitarism. Pooled HR for biochemical remission given subthreshold IGF-1 i was 2.25 (95% CI = 1.33-3.16, P < .0001). CONCLUSION IGF-1 i is a reliable predictor of biochemical remission after SRS. BED appears to predict biochemical outcome more reliably than radiation dose, but confirmatory study is needed.