Common Challenges and Solutions Associated with the Preparation of Silicone-Injected Human Head and Neck Vessels for Anatomical Study.

Neuroanatomy laboratory training is crucial for the education of neurosurgery residents and medical students. Since the brain is a complex and three-dimensional structure, it is challenging to understand the anatomical relationship of the cortex, internal structures, arteries, and veins without appropriate adjuncts. Several injection agents-including the inks/dyes, latex, polyester, acrylic resins, phenol, polyethylene glycol, and phenoxyethanol-have been explored. Colored silicon injection protocols for the head and neck vessels' perfusion have greatly aided the study of neuroanatomy and surgical planning. This report presents a colored silicone injection method in detail, and also highlights the technical shortcomings of the standard techniques and workarounds for common challenges during 35 human cadaveric head injections. The human cadaveric head preparation and the coloring of the head vessels are divided into decapitation, tissue fixation with 10% formalin, the placement of the Silastic tubing into the parent vessels, the cleaning of the vessels from clots, and the injection of the colored silicone into the vessels. We describe the technical details of the preparation, injection, and preservation of cadaveric heads, and outline common challenges during colored silicone injection, which include the dislocation of the Silastic tubing during the injection, the injection of the wrong or inappropriate colored silicone into the vessel, intracranial vessel perforation, the incomplete silicone casting of the vessel, and silicone leakage from small vessels in the neck. Solutions to these common challenges are provided. Ethyl alcohol fixed, colored human heads provided the long-term preservation of tissue, and improve the sample consistency and preservation for the teaching of neuroanatomy and surgical technique.

Genetic Predisposition to Symptomatic Lumbar Disk Herniation in Pediatric and Young Adult Patients.

STUDY DESIGN: Case-control whole-genome sequencing analysis of a highly select, young cohort with symptomatic lumbar disk herniation (LDH) compared with the standard variation in a large reference population. OBJECTIVE: To assess genetic influences predisposing pediatric and young adult patients to symptomatic LDH. SUMMARY OF BACKGROUND DATA: LDH has traditionally been attributed to natural weakening or mechanical insult, but recent literature supports a potential genetic influence. METHODS: Young patients with symptomatic, clinically confirmed LDH who underwent surgical treatment were included. Patients were younger than the average age of presentation, limiting the influence of environmental risks. DNA collected from these patients was compared with a reference genome (1000 Genomes Project). A genome-wide association study using whole-genome sequencing was used to characterize genetic mutations potentially associated with LDH. RESULTS: Among the 61 candidate genes flagged, 20 had missense mutations in 2 or more LDH cases. Missense mutations in collagen-encoding genes were observed in 12 of 15 patients (80%). A potential association with clinical presentation was indicated by odds ratios of key single-nucleotide polymorphism (SNP) variants in genes that encode collagen. Relative to the reference population, the LDH cohort demonstrated two statistically significant SNP variants in the gene encoding for aggrecan, a protein that facilitates load-bearing properties in the cartilaginous end plate. Aggrecan genes SNPs rs3817428 and rs11638262 were significantly associated with decreased odds of symptomatic LDH: odds ratio 0.05 (0.02-0.11) and 0.04 (0-0.26), respectively (P < 1 × 10 for both). CONCLUSION: These results suggest that collagen-encoding variants may be a genetic risk factor for LDH. They also shed new light on the role of variants that impact aggrecan, which sustains the cartilaginous end plate. Genetic predisposition to LDH may therefore be related to a multimodal combination of mutations that affect the nucleus pulposus, annulus fibrosus, and the cartilaginous end plates. LEVEL OF EVIDENCE: 4.

The Retrosigmoid Petrosal Fissure Transpeduncular Approach to Central Pontine Lesions.

BACKGROUND: The advent of improved surgical instruments and neuronavigation and descriptions of safe-entry zones have allowed neurosurgeons to resect brainstem lesions with an acceptable morbidity. The authors describe the technique of petrosal fissure dissection to the lateral transpeduncular safe-entry zone at the middle cerebellar peduncle (MCP) for resection of deep-seated central pontine pathologies. This approach allows the surgeon to obtain less cerebellar retraction and a more direct, more shallow, and shorter approach compared with the approach without opening this fissure. METHODS: An illustrative case is used to highlight the technique of dissecting the petrosal fissure to obtain a direct surgical corridor to the MCP. Anatomic dissections are used to define better the relative relationships of this fissure to the MCP and adjacent structures. RESULTS: Dissection of the petrosal fissure provides a direct trajectory to the lateral transpeduncular entry zone at the MCP and can enhance exposure of this structure, while minimizing morbidity to the corticospinal tract and cerebellum during approaches to central pontine pathologies. CONCLUSIONS: For resection of lesions within the pons via the retrosigmoid craniotomy, dissection of the petrosal fissure allows for a more direct and shorter route to the central pontine and lateral pontine lesion compared with an approach without expansion of this potential space.

The Influence of Common Medical Conditions on the Outcome of Anterior Lumbar Interbody Fusion.

STUDY DESIGN: The authors retrospectively reviewed a consecutive series of 231 patients with anterior lumbar interbody fusion (ALIF). OBJECTIVE: To determine the correlations among common medical conditions, demographics, and the natural history of lumbar surgery with outcomes of ALIF. SUMMARY OF BACKGROUND DATA: Multiple spinal disorders are treated with ALIF with excellent success rates. Nonetheless, adverse outcomes and complications related to patients' overall demographics, comorbidities, or cigarette smoking have been reported. METHODS: The age, sex, body mass index (BMI), comorbidities, history of smoking or previous lumbar surgery, operative parameters, and complications of 231 patients who underwent ALIF were analyzed. Regression analyses of all variables with complications and surgical outcomes based on total Prolo scores were performed. Two models predicting Prolo outcome score were generated. The first model used BMI and sex interaction, whereas the second model used sex, level of surgery, presence of diabetes mellitus, and BMI as variables. RESULTS: At follow-up, the rate of successful fusion was 99%. The overall complication rate was 13.8%, 1.8% of which occurred intraoperatively and 12% during follow-up. The incidence of complications failed to correlate with demographics, comorbidities, smoking, or previous lumbar surgery (P>0.5). ALIF at T12-L4 was the only factor significantly associated with poor patient outcomes (P=0.024). Both models successfully predicted outcome (P=0.05), although the second model did so only for males. CONCLUSIONS: Surgical level of ALIF correlated with poor patient outcomes as measured by Prolo functional scale. BMI emerged as a significant predictor of Prolo total score. Both multivariate models also successfully predicted outcomes. Surgical or follow-up complications were not associated with patients' preoperative status.