Gompel, Jamie J. Van

OBJECTIVE Historically, performing neurosurgery with the patient in the sitting position offered advantages such as improved visualization and gravity-assisted retraction. However, this position fell out of favor at many centers due to the perceived risk of venous air embolism (VAE) and other position-related complications. Some neurosurgical centers continue to perform sitting-position cases in select patients, often using modern monitoring techniques that may improve procedural safety. Therefore, this paper reports the risks associated with neurosurgical procedures performed in the sitting position in a modern series. METHODS The authors reviewed the anesthesia records for instances of clinically significant VAE and other complications for all neurosurgical procedures performed in the sitting position between January 1, 2000, and October 8, 2013. In addition, a prospectively maintained morbidity and mortality log of these procedures was reviewed for instances of subdural or intracerebral hemorrhage, tension pneumocephalus, and quadriplegia. Both overall and specific complication rates were calculated in relation to the specific type of procedure. RESULTS In a series of 1792 procedures, the overall complication rate related to the sitting position was 1.45%, which included clinically significant VAE, tension pneumocephalus, and subdural hemorrhage. The rate of any detected VAE was 4.7%, but the rate of VAE requiring clinical intervention was 1.06%. The risk of clinically significant VAE was highest in patients undergoing suboccipital craniotomy/craniectomy with a rate of 2.7% and an odds ratio (OR) of 2.8 relative to deep brain stimulator cases (95% confidence interval [CI] 1.2–70, p = 0.04). Sitting cervical spine cases had a comparatively lower complication rate of 0.7% and an OR of 0.28 as compared with all cranial procedures (95% CI 0.12–0.67, p < 0.01). Sitting cervical cases were further subdivided into extradural and intradural procedures. The rate of complications in intradural cases was significantly higher (OR 7.3, 95% CI 1.4–39, p = 0.02) than for extradural cases. The risk of VAE in intradural spine procedures did not differ significantly from sitting suboccipital craniotomy/craniectomy cases (OR 0.69, 95% CI 0.09–5.4, p = 0.7). Two cases (0.1%) had to be aborted intraoperatively due to complications. There were no instances of intraoperative deaths, although there was a single death within 30 days of surgery. CONCLUSIONS In this large, modern series of cases performed in the sitting position, the complication rate was low. Suboccipital craniotomy/craniectomy was associated with the highest risk of complications. When appropriately used with modern anesthesia techniques, the sitting position provides a safe means of surgical access.

ABSTRACTBACKGROUND/PURPOSEBrain herniation into presumed arachnoid granulations (BHAG) is an increasingly recognized entity. Though it has previously been described as isointense to brain matter on magnetic resonance imaging (MRI), we have encountered 21 cases in our clinical practice, many of which have signal abnormality in the herniated or adjacent parenchyma. We performed a systematic analysis on these cases to further understand the clinical significance.METHODSThis is a retrospective analysis of cases collected from our clinical MRI practice. Each case was evaluated for location, size, lobe of origin, associated signal abnormality, symptoms, and the presence or absence of intracranial hypertension.RESULTSTwenty‐one cases of BHAG identified in 16 patients. Seven cases (7/21, 33%) demonstrated signal abnormality in the herniated or underlying parenchyma. On serial imaging, the size of herniation either fluctuated (2/10, 20%) or stayed the same (8/10, 80%). The associated signal abnormalities increased (1/5, 20%), decreased (1/5, 20%), or remained stable (3/5, 60%). Four patients (4/16, 25%) had signs/symptoms that could be associated with the BHAG. Ten patients (10/16, 63%) had either imaging findings or clinical signs that could be associated with intracranial hypertension.CONCLUSIONIn contrast to previously reported cases, our study demonstrates that BHAG can be associated with MRI signal abnormalities of the herniated and adjacent brain. Symptoms are typically absent, though may be present in a small subset of patients, regardless of the presence of signal change or encephalomalacia of the involved brain. Indirect evidence of intracranial hypertension is present in a majority of patients but completely lacking in others.

OBJECTIVE The objective of this study was to examine operative outcomes in cases of microvascular decompression (MVD) of cranial nerve (CN) VIII for tinnitus through a critical review of the literature. METHODS Forty-three English-language articles were gathered from PubMed and analyzed. In this review, two different case types were distinguished: 1) tinnitus-only symptomatology, which was defined as a patient with tinnitus with or without sensorineural hearing loss; and 2) mixed symptomatology, which was defined as tinnitus with symptoms of other CN dysfunction. This review reports outcomes of those with tinnitus-only symptoms. RESULTS Forty-three tinnitus-only cases were found in the literature with a 60% positive outcome rate following MVD. Analysis revealed a 5-year cutoff of preoperative symptom duration before which a good outcome can be predicted with 78.6% sensitivity, and after which a poor outcome can be predicted with 80% specificity. CONCLUSIONS As the 60% success rate is more promising than several other therapeutic options open to the chronic tinnitus sufferer, future research into this field is warranted.

OBJECTIVE Vagus nerve and sympathetic chain cervical schwannomas (VNCSs and SCCSs) are benign nerve sheath tumors that arise in the head and neck. Despite similar presentations that make accurate preoperative diagnosis more difficult, the potential for morbidity following resection is significantly higher for patients with VNCS. Therefore, the authors analyzed a retrospective case series and performed a comparative analysis of the literature to establish diagnostic criteria to facilitate more accurate preoperative diagnoses. METHODS The authors conducted a blinded review of imaging studies from retrospectively collected, operatively confirmed cases of VNCS and SCCS. They also performed a systematic review of published series that reported patient-specific preoperative imaging findings in VNCS or SCCS. RESULTS Nine patients with VNCS and 11 with SCCS were identified. In the study cohort, splaying of the internal carotid artery (ICA) and internal jugular vein (IJV) did not significantly predict the nerve of origin (p = 0.06); however, medial and lateral ICA displacement were significantly associated with VNCS and SCCS, respectively (p = 0.01 and p = 0.003, respectively). Multivariate analysis demonstrated that ICA and IJV splaying with medial ICA displacement carried an 86% probability of VNCS (p = 0.001), while the absence of splaying with lateral ICA displacement carried a 91% probability of SCCS (p = 0.006). The presence of vocal cord symptoms or peripheral enhancement significantly augmented the predictive probability of VNCS, as did Horner's syndrome or homogeneous enhancement for SCCS. A review of the literature produced 25 publications that incorporated a total of 106 patients, including the present series. Splaying of the ICA and IJV was significantly, but not uniquely, associated with VNCS (p < 0.0001); multivariate analysis demonstrated that ICA and IJV splaying with medial ICA displacement carries a 75% probability of VNCS (p < 0.0001), while the absence of such splaying with lateral ICA displacement carries an 87% probability of SCCS (p = 0.0003). CONCLUSIONS ICA and IJV splaying frequently predicts VNCS; however, this finding is also commonly observed in SCCS and, among the 9 cases in the present study, was observed more often than previously reported. When congruent with splaying, medial or lateral ICA displacement significantly enhances the reliability of preoperative predictions, empowering more accurate prognostication.

The function and connectivity of human brain is disrupted in epilepsy. We previously reported that the region of epileptic brain generating focal seizures, i.e., the seizure onset zone (SOZ), is functionally isolated from surrounding brain regions in focal neocortical epilepsy. The modulatory effect of behavioral state on the spatial and spectral scales over which the reduced functional connectivity occurs, however, is unclear. Here we use simultaneous sleep staging from scalp EEG with intracranial EEG recordings from medial temporal lobe to investigate how behavioral state modulates the spatial and spectral scales of local field potential synchrony in focal epileptic hippocampus. The local field spectral power and linear correlation between adjacent electrodes provide measures of neuronal population synchrony at different spatial scales, ∼1 and 10 mm, respectively. Our results show increased connectivity inside the SOZ and low connectivity between electrodes in SOZ and outside the SOZ. During slow-wave sleep, we observed decreased connectivity for ripple and fast ripple frequency bands within the SOZ at the 10 mm spatial scale, while the local synchrony remained high at the 1 mm spatial scale. Further study of these phenomena may prove useful for SOZ localization and help understand seizure generation, and the functional deficits seen in epileptic eloquent cortex.