The paramedian supracerebellar transtentorial approach to the posterior fusiform gyrus.

BACKGROUND: The posterior fusiform gyrus lies in a surgically challenging region. Several approaches have been described to access this anatomical area. The paramedian supracerebellar transtentorial (SCTT) approach benefits from minimal disruption of normal neurovascular tissue. The aim of this study was to demonstrate its application to access the posterior fusiform gyrus. METHODS: Three brains and six cadaveric heads were examined. A stepwise dissection of the SCTT approach to the posterior fusiform gyrus was performed. Local cortical anatomy was studied. The operability score was applied for comparative analysis on surgical anatomy. RESULTS: The major posterior landmark used to identify the fusiform gyrus with respect to the medial occipitotemporal gyrus was the collateral sulcus, which commonly bifurcated at its caudal extent. Compared with other surgical approaches addressed to access the region, SCTT demonstrated the best operability in terms of maneuverability arc. Favorable tentorial anatomy is the only limiting factor. CONCLUSIONS: The supracerebellar transtentorial approach is able to provide access to the posterior fusiform gyrus via a minimally disruptive, anatomic, microsurgical corridor.

Defining the Border of the Subthalamic Nucleus for Deep Brain Stimulation: A Proposed Model Using the Symmetrical Sigmoid Curve Function.

BACKGROUND: The subthalamic nucleus (STN) is an important target during deep brain stimulation (DBS). Accurate lead placement is integral to achieving satisfactory clinical outcomes; however, the STN remains a structure whose visualization is highly variable with borders often difficult to define. We aimed to develop an objective method of evaluating the visibility of the STN on preoperative magnetic resonance imaging (MRI) to standardize future comparative assessments between imaging protocols and patient-specific parameters. METHODS: An imaging study of 64 prospectively collected patients undergoing bilateral DBS of the STN for various movement disorders was performed with institutional approval. MRI scans were acquired using a uniform protocol involving general anesthesia, cranial fixation in a Leksell stereotactic frame, and long acquisition times using a 3T MRI scanner. The images were analyzed using the iPlan Stereotaxy, version 2.6, workstation. High-resolution T2-weighted axial sections were evaluated, and the voxel values in the region of the presumed posterior border of the STN (as defined by the operating neurosurgeon) were obtained. A 4-parameter logistic symmetrical sigmoid curve was used to map the voxel values as they progressed from within to outside the region of the STN border. The inflection point and Hill coefficient of this symmetrical curve was calculated to provide objective information on the location and clarity of the STN border, respectively. These findings were compared with the surgeon's judgment of the STN border. To demonstrate the use of the sigmoid curve, the patients' head volumes were also calculated and evaluated to assess whether larger head volumes adversely affected STN visibility. RESULTS: The symmetrical sigmoid curve model provided objective information on the visibility of the STN on T2-weighted MRI scans and could be generated in 86% of the patients. The other 14% of patients had MRI scans that generated linear graphs, indicating the poorest scoring for STN image quality. No correlation between head volume and STN visibility was identified. CONCLUSIONS: Our proposed statistical model allows for standardized examination of the visibility of the STN border for DBS and has potential for both clinical and academic applications.

Bone graft substitutes in anterior cervical discectomy and fusion.

Anterior cervical discectomy with fusion is a common surgical procedure for patients suffering pain and/or neurological deficits and unresponsive to conservative management. For decades, autologous bone grafted from the iliac crest has been used as a substrate for cervical arthrodesis. However patient dissatisfaction with donor site morbidity has led to the search for alternative techniques. We present a literature review examining the progress of available grafting options as assessed in human clinical trials, considering allograft-based, synthetic, factor- and cell-based technologies.

Lateral extent and ventral laminar attachments of the lumbar ligamentum flavum: cadaveric study.

BACKGROUND CONTEXT: Cadaveric descriptions of the deep layer of the lumbar ligamentum flavum (LF), extending between contiguous borders of adjacent laminae and into the lateral spinal canal region are limited. PURPOSE: To provide detailed descriptions of the lumbar LF. STUDY DESIGN: Cadaveric dissection. METHODS: The deep ligamentum flava of 14 formalin-fixed human cadaver lumbar spines (140 levels) were examined to assess their laminar attachments and lateral extents in relation to the intervertebral foramen. RESULTS: The variable attachment of the deep layer of the LF with respect to the cephalad and caudad laminae was identified and described. At each successive caudal level of the lumbar spine, the deep layer appeared to become a more prominent feature of the posterior vertebral column, lining more of the laminae to which it is attached and encroaching further into the posteroinferior region of the intervertebral foramen at its lateral margins. CONCLUSIONS: We describe our observations of the deep LF in the human lumbar spine. These observations have clinical relevance for the interpretation of radiologic imaging and the performance of adequate decompression in the setting of spinal stenosis.

Intracranial injectable tumor model: technical advancements.

Background and Objectives Few simulation models are available that provide neurosurgical trainees with the challenge of distorted skull base anatomy despite increasing importance in the acquisition of safe microsurgical and endoscopic techniques. We have previously reported a unique training model for skull base neurosurgery where a polymer is injected into a cadaveric head where it solidifies to mimic a skull base tumor for resection. This model, however, required injection of the polymer under direct surgical vision via a complicated alternative approach to that being studied, prohibiting its uptake in many neurosurgical laboratories. Conclusion We report our updated skull base tumor model that is contrast-enhanced and may be easily and reliably injected under fluoroscopic guidance. We have identified a map of burr holes and injection corridors available to place tumor at various intracranial sites. Additionally, the updated tumor model allows for the creation of mass effect, and we detail the variation of polymer preparation to mimic different tumor properties. These advancements will increase the practicality of the tumor model and ideally influence neurosurgical standards of training.

Biphasic calcium phosphate contained within a polyetheretherketone cage with and without plating for anterior cervical discectomy and fusion.

OBJECTIVE: To evaluate the properties of a combination bone graft consisting of biphasic calcium phosphate ceramic, polyetheretherketone (PEEK) cage in one- and two-level surgery. METHODS: Over a 12-month time period, a prospective single surgeon series of 75 patients were included in the study and 58 patients selected based on adequate data points. From these 58 patients, 32 were supplemented with anterior plate fixation and 26 patients without plating. Duration of clinical follow-up was a mean of 12.4 months (range, 6-26 months) in the Plated Group and 10.5 months (range, 6-21 months) in the Non-Plated Group. RESULTS: A 100% fusion rate with nil graft related complications was achieved in the Plated group compared with 96.2% fusion and 11.5% subsidence rates reported in the Non-Plated group. Patients in both groups experienced statistically significant improvement in pain and functional outcomes compared to their pre-operative status; however, there was no significant difference in outcome between the Plated and Non-Plated Groups. CONCLUSIONS: Biphasic calcium phosphate ceramic contained within a PEEK cage is an effective implant for use in anterior cervical surgery with high fusion rates and good clinical outcome.

Reconstruction versus no reconstruction of iliac crest defects following harvest for spinal fusion: a systematic review: A review.

OBJECT: Autologous bone from the iliac crest is commonly used for spinal fusion. However, its use is associated with significant donor site morbidity, especially pain. Reconstructive procedures of the iatrogenic defect have been investigated as a technique to alleviate these symptoms. The goal of this study was to assess the effects of reconstruction versus no reconstruction following iliac crest harvest in adults undergoing spine surgery. METHODS: The authors searched the Cochrane Central Register of Controlled Trials (The Cochrane Library 2011, Issue 4); MEDLINE (1948-Oct 2011); EMBASE (1947-Oct 2011); and the reference lists of articles. Randomized controlled trials (RCTs) or nonrandomized controlled trials (NRCTs) were included in the study. Two independent reviewers selected the studies, extracted data using a standardized collection form, and assessed for risk of bias. RESULTS: Three RCTs (96 patients) and 2 NRCTs (82 patients) were included. These had a moderate to high risk of bias. The results suggest that iliac crest reconstruction may be useful in reducing postoperative pain, minimizing functional disability, and improving cosmesis. No pattern of other clinical, radiological, or resource outcomes was identified. CONCLUSIONS: Although the available evidence is suboptimal, this systematic review supports the notion that iliac crest reconstruction following harvest for spinal fusion may reduce postoperative pain, minimize functional disability, and improve cosmesis.