Anterior perforated substance region aneurysms: review of a series treated with microsurgical technique.

Aneurysms arising from the distal carotid, proximal A1, and proximal M1 that project posteriorly and superiorly toward the anterior perforated substance (APS) are rare. Their open surgical treatment is particularly difficult due to poorly visualized origin of the aneurysm and the abundance of surrounding perforators. We sought to analyze the anatomical and clinical characteristics of APS aneurysms and discuss surgical nuances that can optimize visualization, complete neck clip obliteration, and preservation of adjacent perforators. Thirty-two patients with 36 APS aneurysms were surgically treated between November 2000 and September 2017. Patients were prospectively enrolled in a cerebral aneurysm database and their clinical, imaging, and surgical records were retrospectively reviewed. Twenty-seven aneurysms originated from the distal ICA, 7 from the proximal A1, and 2 from the proximal M1; 15 patients presented with subarachnoid hemorrhage. Careful intraoperative dissection revealed 4 aneurysms originating at the takeoff of a perforator; another 25 had at least 1 adherent perforator. All aneurysms were clipped except for one that was trapped. Postoperatively, 3 patients had radiographic infarctions in perforator territory with only 1 developing delayed clinical hemiparesis. Good outcome (modified Rankin Scale, 0-2) was achieved in 28 patients (88%). APS aneurysms present a challenging subset of aneurysms due to their complex anatomical relationship with surrounding perforators. These should be identified on preoperative imaging based on location and projection. Successful microsurgical clipping relies on optimization of the surgical view, meticulous clip reconstruction, preservation of all perforators, and electrophysiological monitoring to minimize ischemic complication.

Automatic image processing pipeline for tracking longitudinal vessel changes in magnetic resonance angiography.

BACKGROUND: Cerebral vessel diameter changes objectively and automatically derived from longitudinal magnetic resonance angiography (MRA) facilitate quantification of vessel changes and further modeling. PURPOSE: To characterize longitudinal changes in intracranial vessel diameter using time-of-flight (TOF) MRA. STUDY TYPE: Retrospective longitudinal study. SUBJECT POPULATION: IN all, 112 pediatric patients, aged 9.96 ± 4.59 years, with craniopharyngioma from 2006-2011 scanned annually. FIELD STRENGTH/SEQUENCE: 1.5T and 3T TOF MRA. STATISTICAL TESTS: Chi-square and Wilcoxon-Mann-Whitney tests. ASSESSMENT: Manual measurements using interventional angiography was established as a reference standard for diameter measurements. Constant and linear quantile regression with absolute difference, percentage difference, and relative difference was used for outlier detection. RESULTS: Major vessels surrounding the circle of Willis were successfully segmented except for posterior communicating arteries, mostly due to disease-related hypoplasia. Diameter measurements were calculated at 1-mm segments with a median computed vessel diameter of 1.25 mm. Diameter distortion due to registration was within 0.04 mm for 99% of vessel segments. Outlier detection using quantile regression detected less than 4.34% as being outliers. Outliers were more frequent in smaller vessels and proximity to bifurcations (P < 0.001). DATA CONCLUSION: Using the proposed method, objective changes in vessel diameter can be acquired noninvasively from routine longitudinal imaging. High-throughput analyses of imaging-derived vascular trees combined with clinical and treatment parameters will allow rigorous modeling of vessel diameter changes. LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;50:1063-1074.

Basal ganglia neurons dynamically facilitate exploration during associative learning.

The basal ganglia (BG) appear to play a prominent role in associative learning, the process of pairing external stimuli with rewarding responses. Accumulating evidence suggests that the contributions of various BG components may be described within a reinforcement learning model, in which a broad repertoire of possible responses to environmental stimuli are evaluated before the most profitable one is chosen. The striatum receives diverse cortical inputs, providing a rich source of contextual information about environmental cues. It also receives projections from midbrain dopaminergic neurons, whose phasic activity reflects a reward prediction error signal. These coincident information streams are well suited for evaluating responses and biasing future actions toward the most profitable response. Still lacking in this model is a mechanistic description of how initial response variability is generated. To investigate this question, we recorded the activity of single neurons in the globus pallidus internus (GPi), the primary BG output nucleus, in nonhuman primates (Macaca mulatta) performing a motor associative learning task. A subset (29%) of GPi neurons showed learning-related effects, decreasing firing during the early stages of learning, then returning to higher baseline rates as associations were mastered. On a trial-by-trial basis, lower firing rates predicted exploratory behavior, whereas higher rates predicted an exploitive response. These results suggest that, during associative learning, BG output is initially permissive, allowing exploration of a variety of responses. Once a profitable response is identified, increased GPi activity suppresses alternative responses, sharpening the response profile and encouraging exploitation of the profitable learned behavior.

Morphometric Comparison of the Pterional Trans-Sylvian and the Pretemporal Trans-Clinoidal Approaches to the Posterior Communicating Artery.

BACKGROUND: Posterior communicating (Pcom) aneurysms in the modern era have tended toward increased complexity and technical difficulties. The pretemporal approach is a valuable extension to the pterional approach for basilar apex aneurysms, but its advantages for Pcom aneurysms have not been previously elucidated. OBJECTIVE: To quantify characteristics of the pretemporal approach to the Pcom. METHODS: We dissected 6 cadaveric heads (12 sides) with a pretemporal transclinoidal approach and measured the following variables: (1) exposed length of internal carotid artery (ICA) proximal to the Pcom artery; (2) exposed circumference of ICA at the origin of Pcom; (3) deep working area between the optic nerve and tentorium/oculomotor nerve; (4) superficial working area; (5) exposure depth; and (6) the frontotemporal (superior posterolateral) and (7) orbito-sphenoidal (inferior anterolateral) angles of exposure. RESULTS: Compared with pterional craniotomy, the pretemporal transclinoidal approach increased the exposed length of the proximal ICA from 3.3 to 11.7 mm (P = .0001) and its circumference from 5.1 to 7.8 mm (P = .0003), allowing a 210° view of the ICA (vs 137.9°). The deep and superficial working areas also significantly widened from 53.7 to 92.4 mm2 (P = .0048) and 252.8 to 418.2 mm2 (P = .0001), respectively; the depth of the exposure was equivalent. The frontotemporal and spheno-Sylvian angles increased by 17° (P = .0006) and 10° (P = .0037), respectively. CONCLUSION: The pretemporal approach can be useful for complex Pcom aneurysms by providing easier proximal control, wider working space, improved aneurysm visualization, and more versatile clipping angles. Enhanced exposure results in a potentially higher rate of complete aneurysm obliteration and complication avoidance.

Minimizing Collateral Brain Injury Using a Protective Layer of Fibrin Glue: Technical Note.

BACKGROUND: Neurosurgical procedures expose the brain surface to a constant risk of collateral injury. We describe a technique where the brain surface is covered with a protective layer of fibrin glue and discuss its advantages. METHODS: A thin layer of fibrin glue was applied on the brain surface after its exposure in 34 patients who underwent different craniotomies for tumoral and vascular lesions. Data of 35 more patients who underwent standard microsurgical technique were collected as a control group. Cortical and pial injuries were evaluated using an intraoperative visual scale. Eventual abnormal signals at the early postoperative T2-weighted fluid-attenuated inversion recovery (T2FLAIR) magnetic resonance imaging (MRI) sequences were evaluated in oncological patients. RESULTS: Total pial injury was noted in 63% of cases where fibrin glue was not used. In cases where fibrin glue was applied, a significantly lower percentage of 26% (P < 0.01) had pial injuries. Only 9% had injuries in areas covered with fibrin glue (P < 0.0001). Early postoperative T2FLAIR MRI confirmed the differences of altered signal around the surgical field in the two populations. CONCLUSION: We propose beside an appropriate and careful microsurgical technique the possible use of fibrin glue as alternative, safe, and helpful protection during complex microsurgical dissections. Its intrinsic features allow the neurosurgeon to minimize the cortical manipulation preventing minor collateral brain injury.

Interhemispheric subdural electrodes: technique, utility, and safety.

BACKGROUND: Invasive monitoring using subdural electrodes is often valuable for characterizing the anatomic source of seizures in intractable epilepsy. Covering the interhemispheric surface with subdural electrodes represents a particular challenge, with a potentially higher risk of complications than covering the dorsolateral cortex. OBJECTIVE: To better understand the safety and utility of interhemispheric subdural electrodes (IHSE). METHODS: We retrospectively reviewed the charts of 24 patients who underwent implantation of IHSE by a single neurosurgeon from 2003 to 2010. Generous midline exposure, meticulous preservation of veins, and sharp microdissection were used to facilitate safe interhemispheric grid placement under direct visualization. RESULTS: The number of IHSE contacts implanted ranged from 10 to 106 (mean = 39.8) per patient. Monitoring lasted for 5.5 days on average (range, 2-24 days), with an adequate sample of seizures captured in all patients before explantation, and with a low complication rate similar to that reported for grid implantation of the dorsolateral cortex. One patient (of 24) experienced symptomatic mass effect. No other complications clearly related to grid implantation and monitoring, such as clinically evident neurological deficits, infection, hematoma, or infarction, were noted. Among patients implanted with IHSE, monitoring led to a paramedian cortical resection in 67%, a resection in a region not covered by IHSE in 17%, and explantation without resection in 17%. CONCLUSION: When clinical factors suggest the possibility of an epileptic focus at or near the midline, invasive monitoring of the paramedian cortex with interhemispheric grids can be safely used to define the epileptogenic zone and map local cortical function.

Minimalist cubital tunnel treatment.

OBJECTIVE: The surgical treatment of cubital tunnel syndrome by various techniques is often met with disappointing results. An optimal treatment is not agreed upon. The authors propose a collection of techniques which they believe optimizes outcome and minimizes iatrogenic injuries. METHODS: A combination of a novel skin incision which minimizes scar and iatrogenic cutaneous nerve injury, a technique of in situ decompression, and an atraumatic technique of ensuring complete nerve exploration proximal and distal to the incision is presented; these methods have been in use by the senior author for a number of years. RESULTS: Numerous reports have demonstrated that the success of in situ ulnar nerve release by division of Osborne's fascia is equivalent to the success rates of more invasive operations for the condition of ulnar neuropathy. The authors share this view in the majority of cases of ulnar neuropathy, and they present a technique that can be expanded, if necessary, on the basis of surgical findings, with only a few indications for the greater epicondylectomy or transposition procedures. CONCLUSION: The authors present a means of treating cubital tunnel syndrome. Failure of in situ cubital tunnel release, as with failure of any ulnar procedure, can be attributed to intraoperative ulnar nerve injury, injury to the medial antebrachial cutaneous nerve, inadequate longitudinal exploration and release, scar formation with recurrent compression and/or traction, and the possibility that decompression could lead to iatrogenic symptomatic nerve subluxation. The authors discuss the rationale for a minimalist open surgical approach for the treatment of cubital tunnel syndrome, and each of these concerns is addressed.