Real-time navigation guidance with intraoperative CT imaging for pedicle screw placement using an augmented reality head-mounted display: a proof-of-concept study.

OBJECTIVE: Augmented reality (AR) has the potential to improve the accuracy and efficiency of instrumentation placement in spinal fusion surgery, increasing patient safety and outcomes, optimizing ergonomics in the surgical suite, and ultimately lowering procedural costs. The authors sought to describe the use of a commercial prototype Spine AR platform (SpineAR) that provides a commercial AR head-mounted display (ARHMD) user interface for navigation-guided spine surgery incorporating real-time navigation images from intraoperative imaging with a 3D-reconstructed model in the surgeon's field of view, and to assess screw placement accuracy via this method. METHODS: Pedicle screw placement accuracy was assessed and compared with literature-reported data of the freehand (FH) technique. Accuracy with SpineAR was also compared between participants of varying spine surgical experience. Eleven operators without prior experience with AR-assisted pedicle screw placement took part in the study: 5 attending neurosurgeons and 6 trainees (1 neurosurgical fellow, 1 senior orthopedic resident, 3 neurosurgical residents, and 1 medical student). Commercially available 3D-printed lumbar spine models were utilized as surrogates of human anatomy. Among the operators, a total of 192 screws were instrumented bilaterally from L2-5 using SpineAR in 24 lumbar spine models. All but one trainee also inserted 8 screws using the FH method. In addition to accuracy scoring using the Gertzbein-Robbins grading scale, axial trajectory was assessed, and user feedback on experience with SpineAR was collected. RESULTS: Based on the Gertzbein-Robbins grading scale, the overall screw placement accuracy using SpineAR among all users was 98.4% (192 screws). Accuracy for attendings and trainees was 99.1% (112 screws) and 97.5% (80 screws), respectively. Accuracy rates were higher compared with literature-reported lumbar screw placement accuracy using FH for attendings (99.1% vs 94.32%; p = 0.0212) and all users (98.4% vs 94.32%; p = 0.0099). The percentage of total inserted screws with a minimum of 5° medial angulation was 100%. No differences were observed between attendings and trainees or between the two methods. User feedback on SpineAR was generally positive. CONCLUSIONS: Screw placement was feasible and accurate using SpineAR, an ARHMD platform with real-time navigation guidance that provided a favorable surgeon-user experience.

An 8-Week Self-Administered At-Home Behavioral Skills-Based Virtual Reality Program for Chronic Low Back Pain: Double-Blind, Randomized, Placebo-Controlled Trial Conducted During COVID-19.

BACKGROUND: Chronic low back pain is the most prevalent chronic pain condition worldwide and access to behavioral pain treatment is limited. Virtual reality (VR) is an immersive technology that may provide effective behavioral therapeutics for chronic pain. OBJECTIVE: We aimed to conduct a double-blind, parallel-arm, single-cohort, remote, randomized placebo-controlled trial for a self-administered behavioral skills-based VR program in community-based individuals with self-reported chronic low back pain during the COVID-19 pandemic. METHODS: A national online convenience sample of individuals with self-reported nonmalignant low back pain with duration of 6 months or more and with average pain intensity of 4 or more/10 was enrolled and randomized 1:1 to 1 of 2 daily (56-day) VR programs: (1) EaseVRx (immersive pain relief skills VR program); or (2) Sham VR (2D nature content delivered in a VR headset). Objective device use data and self-reported data were collected. The primary outcomes were the between-group effect of EaseVRx versus Sham VR across time points, and the between-within interaction effect representing the change in average pain intensity and pain-related interference with activity, stress, mood, and sleep over time (baseline to end-of-treatment at day 56). Secondary outcomes were global impression of change and change in physical function, sleep disturbance, pain self-efficacy, pain catastrophizing, pain acceptance, pain medication use, and user satisfaction. Analytic methods included intention-to-treat and a mixed-model framework. RESULTS: The study sample was 179 adults (female: 76.5%, 137/179; Caucasian: 90.5%, 162/179; at least some college education: 91.1%, 163/179; mean age: 51.5 years [SD 13.1]; average pain intensity: 5/10 [SD 1.2]; back pain duration ≥5 years: 67%, 120/179). No group differences were found for any baseline variable or treatment engagement. User satisfaction ratings were higher for EaseVRx versus Sham VR (P<.001). For the between-groups factor, EaseVRx was superior to Sham VR for all primary outcomes (highest P value=.009), and between-groups Cohen d effect sizes ranged from 0.40 to 0.49, indicating superiority was moderately clinically meaningful. For EaseVRx, large pre-post effect sizes ranged from 1.17 to 1.3 and met moderate to substantial clinical importance for reduced pain intensity and pain-related interference with activity, mood, and stress. Between-group comparisons for Physical Function and Sleep Disturbance showed superiority for the EaseVRx group versus the Sham VR group (P=.022 and .013, respectively). Pain catastrophizing, pain self-efficacy, pain acceptance, prescription opioid use (morphine milligram equivalent) did not reach statistical significance for either group. Use of over-the-counter analgesic use was reduced for EaseVRx (P<.01) but not for Sham VR. CONCLUSIONS: EaseVRx had high user satisfaction and superior and clinically meaningful symptom reduction for average pain intensity and pain-related interference with activity, mood, and stress compared to sham VR. Additional research is needed to determine durability of treatment effects and to characterize mechanisms of treatment effects. Home-based VR may expand access to effective and on-demand nonpharmacologic treatment for chronic low back pain. TRIAL REGISTRATION: ClinicalTrials.gov NCT04415177; https://clinicaltrials.gov/ct2/show/NCT04415177. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): RR2-10.2196/25291.

The subdiaphragmatic part of the phrenic nerve - morphometry and connections to autonomic ganglia.

Few anatomical textbooks offer much information concerning the anatomy and distribution of the phrenic nerve inferior to the diaphragm. The aim of this study was to identify the subdiaphragmatic distribution of the phrenic nerve, the presence of phrenic ganglia, and possible connections to the celiac plexus. One hundred and thirty formalin-fixed adult cadavers were studied. The right phrenic nerve was found inferior to the diaphragm in 98% with 49.1% displaying a right phrenic ganglion. In 22.8% there was an additional smaller ganglion (right accessory phrenic ganglion). The remaining 50.9% had no grossly identifiable right phrenic ganglion. Most (65.5% of specimens) exhibited plexiform communications with the celiac ganglion, aorticorenal ganglion, and suprarenal gland. The left phrenic nerve inferior to the diaphragm was observed in 60% of specimens with 19% containing a left phrenic ganglion. No accessory left phrenic ganglia were observed. The left phrenic ganglion exhibited plexiform communications to several ganglia in 71.4% of specimens. Histologically, the right phrenic and left phrenic ganglia contained large soma concentrated in their peripheries. Both phrenic nerves and ganglia were closely related to the diaphragmatic crura. Surgically, sutures to approximate the crura for repair of hiatal hernias must be placed above the ganglia in order to avoid iatrogenic injuries to the autonomic supply to the diaphragm and abdomen. These findings could also provide a better understanding of the anatomy and distribution of the fibers of that autonomic supply.

Harvest of autologous clavipectoral fascia for use in duraplasty: cadaveric feasibility study.

Techniques and materials for repair of dural defects following neurosurgical procedures vary. Given higher complication rates with nonautologous duraplasty materials, most authors strongly recommend autologous grafts. To expand the arsenal of possible materials available to the neurosurgeon, we propose the use of autologous clavipectoral fascia as an alternative donor for duraplasty. Eight embalmed adult cadavers underwent dissection of the pectoral region. A 12-cm curvilinear skin incision was made 2 cm inferior to the nipple in males and along the inferior breast edge in females. Dissection was continued until the clavipectoral fascia was encountered, and a tissue plane was developed between this fascia and the deeper pectoralis major muscle. Sections of clavipectoral fascia were used for duraplasty in the same specimens. In all specimens, removal of clavipectoral fascia was easily performed with tissue separation between the overlying fascia and underlying muscle. Only small adhesions were found between the fascia and underlying muscle, and these were easily transected. No obvious gross neurovascular injuries were identified. Large portions of clavipectoral fascia were available, and at least a 10 × 10-cm piece (average thickness, 1.2 mm) was easily harvested for all specimens. Clavipectoral fascia shares characteristics with materials such as pericranium and fascia lata that have been used successfully in duraplasty, and most importantly, it is autologous. Theoretically, using clavipectoral fascia would reduce the risk of muscle herniation. It offers an alternative source for autologous dural grafting when other sources are unavailable or exhausted. Clinical experience with this fascia is warranted.

External landmarks for identifying the drainage site of the vein of Labbé: application to neurosurgical procedures.

INTRODUCTION: The vein of Labbé is an important structure of the lateral cortical surface. However, to date, studies aimed at providing external landmarks for aiding in its identification have been scant. Therefore, the present study focussed on establishing reliable bony landmarks for localizing this deeper lying venous structure. MATERIALS AND METHODS: Fifteen adult cadavers (30 sides) underwent dissection of the lateral cortical brain surface with special attention given to the drainage site of the vein of Labbé into the transverse sinus. Measurements of the distance from this site to surrounding external bony landmarks were then made. RESULTS: We found that this drainage site into the transverse sinus was 0.8-1.5 cm (mean 1.1 cm, SD 0.567) superior to the superior border of the zygomatic arch and 2 - 5 cm (mean 2.9 cm, SD 0.713) posterior to the opening of the external auditory meatus. Statistically, there was no significance between left and right sides or between sexes. CONCLUSIONS: We found that the junction between the vein of Labbé and transverse sinus may be variable. Nonetheless, additional landmarks found in this study for identifying the junction may aid in its earlier identification during surgery, potentially decreasing operative morbidity.

Anatomy of the ilioinguinal and iliohypogastric nerves with observations of their spinal nerve contributions.

Proper anesthesia and knowledge of the anatomical location of the iliohypogastric and ilioinguinal nerves is important during hernia repair and other surgical procedures. Surgical complications have also implicated these nerves, emphasizing the importance of the development of a clear topographical map for use in their identification. The aim of this study was to explore anatomical variations in the iliohypogastric and ilioinguinal nerves and relate this information to clinical situations. One hundred adult formalin fixed cadavers were dissected resulting in 200 iliohypogastric and ilioinguinal nerve specimens. Each nerve was analyzed for spinal nerve contribution and classified accordingly. All nerves were documented where they entered the abdominal wall with this point being measured in relation to the anterior superior iliac spine (ASIS). The linear course of each nerve was followed, and its lateral distance from the midline at termination was measured. The ilioinguinal nerve originated from L1 in 130 specimens (65%), from T12 and L1 in 28 (14%), from L1 and L2 in 22 (11%), and from L2 and L3 in 20 (10%). The nerve entered the abdominal wall 2.8 ± 1.1 cm medial and 4 ± 1.2 cm inferior to the ASIS and terminated 3 ± 0.5 cm lateral to the midline. The iliohypogastric nerve originated from T12 on 14 sides (7%), from T12 and L1 in 28 (14%), from L1 in 20 (10%), and from T11 and T12 in 12 (6%). The nerve entered the abdominal wall 2.8 ± 1.3 cm medial and 1.4 ± 1.2 cm inferior to the ASIS and terminated 4 ± 1.3 cm lateral to the midline. For both nerves, the distance between the ASIS and the midline was 12.2 ± 1.1 cm. To reduce nerve damage and provide sufficient anesthetic for nerve block during surgical procedures, the precise anatomical location and spinal nerve contributions of the iliohypogastric and ilioinguinal nerves need to be considered.

Patient-specific virtual reality technology for complex neurosurgical cases: illustrative cases.

BACKGROUND: Virtual reality (VR) offers an interactive environment for visualizing the intimate three-dimensional (3D) relationship between a patient's pathology and surrounding anatomy. The authors present a model for using personalized VR technology, applied across the neurosurgical treatment continuum from the initial consultation to preoperative surgical planning, then to intraoperative navigation, and finally to postoperative visits, for various tumor and vascular pathologies. OBSERVATIONS: Five adult patients undergoing procedures for spinal cord cavernoma, clinoidal meningioma, anaplastic oligodendroglioma, giant aneurysm, and arteriovenous malformation were included. For each case, 360-degree VR (360°VR) environments developed using Surgical Theater were used for patient consultation, preoperative planning, and/or intraoperative 3D navigation. The custom 360°VR model was rendered from the patient's preoperative imaging. For two cases, the plan changed after reviewing the patient's 360°VR model from one based on conventional Digital Imaging and Communications in Medicine imaging. LESSONS: Live 360° visualization with Surgical Theater in conjunction with surgical navigation helped validate the decisions made intraoperatively. The 360°VR models provided visualization to better understand the lesion's 3D anatomy, as well as to plan and execute the safest patient-specific approach, rather than a less detailed, more standardized one. In all cases, preoperative planning using the patient's 360°VR model had a significant impact on the surgical approach.

Early Experience With Virtual and Synchronized Augmented Reality Platform for Preoperative Planning and Intraoperative Navigation: A Case Series.

BACKGROUND: Virtual reality (VR) allows for presurgical planning. Intraoperatively, augmented reality (AR) enables integration of segmented anatomic information with neuronavigation into the microsurgical scene to provide guidance without workflow disruption. Combining VR and AR solutions may help guide microsurgical technique to improve safety, efficiency, and ergonomics. OBJECTIVE: To describe a VR/AR platform that provides VR planning and intraoperative guidance via microscope ocular injection of a comprehensive AR overlay of patient-specific 360°/3D anatomic model aligned and synchronized with neuronavigation. METHODS: Custom 360° models from preoperative imaging of 49 patients were utilized for preoperative planning using a VR-based surgical rehearsal platform. Each model was imported to SyncAR, the platform's intraoperative counterpart, which was coregistered with Medtronic StealthStation S8 and Zeiss or Leica microscope. The model was injected into the microscope oculars and referenced throughout by adjusting overlay opacity. For anatomic shifts or misalignment, the overlay was reregistered via manual realignment with known landmarks. RESULTS: No SyncAR-related complications occurred. SyncAR contributed positively to the 3D understanding of patient-specific anatomy and ability to operate. Preoperative planning and intraoperative AR with 360° models allowed for more precise craniotomy planning and execution. SyncAR was useful for guiding dissection, identifying critical structures including hidden anatomy, understanding regional anatomy, and facilitating resection. Manual realignment was performed in 48/49 surgeries. Gross total resection was achieved in 34/40 surgeries. All aneurysm clipping and microvascular decompression procedures were completed without complications. CONCLUSION: SyncAR combined with VR planning has potential to enhance surgical performance by providing critical information in a user-friendly, continuously available, heads-up display format.

Self-Administered Behavioral Skills-Based At-Home Virtual Reality Therapy for Chronic Low Back Pain: Protocol for a Randomized Controlled Trial.

BACKGROUND: Chronic pain is one of the most common and debilitating health conditions. Treatments for chronic low back pain typically focus on biomedical treatment approaches. While psychosocial treatments exist, multiple barriers prevent broad access. There is a significant unmet need for integrative, easily accessible, non-opioid solutions for chronic pain. Virtual reality (VR) is an immersive technology allowing innovation in the delivery of behavioral pain treatments. Behavioral skills-based VR is effective at facilitating pain management and reducing pain-related concerns. Continued research on these emerging approaches is needed. OBJECTIVE: In this randomized controlled trial, we seek to test the efficacy of a self-administered behavioral skills-based VR program as a nonpharmacological home-based pain management treatment for people with chronic low back pain (cLBP). METHODS: We will randomize 180 individuals with cLBP to 1 of 2 VR programs: (1) EaseVRx (8-week skills-based VR program); or (2) Sham VR (control condition). All participants will receive a VR headset to minimize any biases related to the technology's novelty. The Sham VR group had 2D neutral content in a 3D theater-like environment. Our primary outcome is average pain intensity and pain-related interference with activity, stress, mood, and sleep. Our secondary outcomes include patient-reported physical function, sleep disturbance, pain self-efficacy, pain catastrophizing, pain acceptance, health utilization, medication use, and user satisfaction. We hypothesize superiority for the skills-based VR program in all of these measures compared to the control condition. Team statisticians blinded to treatment assignment will assess outcomes up to 6 months posttreatment using an approach suitable for the longitudinal nature of the data. RESULTS: The study was approved by the Western Institutional Review Board on July 2, 2020. The protocol (NCT04415177) was registered on May 27, 2020. Recruitment for this study was completed in July 2020, and data collection will remain active until March 2021. In total, 186 participants were recruited. Multiple manuscripts will be generated from this study. The primary manuscript will be submitted for publication in the winter of 2020. CONCLUSIONS: Effectively delivering behavioral treatments in VR could overcome barriers to care and provide scalable solutions to chronic pain's societal burden. Our study could help shape future research and development of these innovative approaches. TRIAL REGISTRATION: ClinicalTrials.gov NCT04415177; https://clinicaltrials.gov/ct2/show/NCT04415177. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): RR1-10.2196/25291.

Correction: Self-Administered Behavioral Skills-Based At-Home Virtual Reality Therapy for Chronic Low Back Pain: Protocol for a Randomized Controlled Trial.

[This corrects the article DOI: 10.2196/25291.].

The clinical anatomy of the sinutubular junction.

Specific sites of atherosclerotic processes due to hemodynamic changes and resultant stress, including how these normal anatomical structures become problematic in certain individuals, have yet to be acknowledged. One of these areas of the cardiovascular system occurs at the sinutubular junction (SJ), causing altercation in an otherwise normal flow status. The anatomy of the SJ was examined in 100 adult human hearts during the gross anatomy course at St George's University, during the years 2006-2007. All hearts were examined in situ, using a General Electric model 3200S ultrasound machine with a 5 MHz linear probe. The aforementioned cadavers were also examined using a Stryker laparoscopic unit. Serial transverse histological sections were made through the SJ perpendicular to its axis, and stained with eosin-hematoxylin, van Gieson, Masson trichrome, and Orcein methods. In addition, an immunohistochemical analysis was performed for the detection of positive smooth muscle cells stained areas. During gross and endoscopic examination we were able to identify the SJ in all adult heart specimens. Neonatal and fetal hearts did not exhibit any gross evident SJ; however, a SJ was evident histologically. Ultrasonographically we were able to identify the SJ in all adult heart specimens examined, and a sinutubular ridge in 62%. A significant association was present between the thickness of the ridge and the age of the specimens. The SJ was found to exhibit atherosclerotic changes and plaque formation in an age-related manner. In older subjects, the SJ was marked with local calcification and hemorrhages. In contrast, the SJ of neonatal hearts appeared to have intimal thickening with focal fragmentation and absent or duplicate internal elastic lamina. Intuitively speaking, the presence of a sinutubular ridge, an inevitable fate in humans based on the results of this study, provides an irreversible atherosclerotic process as there is no evidence that the promoting ridge regresses. This is an alarming situation in those individuals who will eventually develop cardiovascular risk factors, whether through inevitable genetic manifestations or by means of exogenous environmental causes.

An endoscopic and anatomical approach to the septal papillary muscle of the conus.

Many authors have questioned the gross anatomy of the septal papillary muscle of the conus known as the papillary muscle complex (PMC) during the past century. An anatomical investigation was conducted to identify the morphology and the topography of the PMC. Our study involved 200 formalin fixed adult human hearts. The PMC was present in 82% of the hearts, while in the remaining 18% of specimens, it was replaced by tendinous chords. The PMC was connected with the septal (59.7%), anterior (20.7%), or both septal and anterior leaflets (19.5%) with single (29.8%) or multiple chordae tendinae (70.1%). The PMC was also found to be present as a single papilla (51.8%), double papilla (32.9%) or triple papilla (15.2%). In addition to the PMC, we observed accessory single septal papillary muscles 42 specimens, double septal papillary muscles 32 specimens and triple septal papillary muscles 26 specimens. In the right ventricular inflow tract, the location of the PMC was consistently found to be in a position below the junction of the anterior and septal leaflets of the tricuspid valve. In the right ventricular outflow tract, we were able to identify 73 specimens in which the PMC was located at the junction formed superiorly by the inferior border of the subpulmonary infundibulum and inferiorly by the superior-lateral border of the septal band, extending into the region of the subpulmonary infundibulum. In the remaining 27%, the PMC was located primarily at the area occupied by the superiolateral border of the septal band without extending to the subpulmonary infundibulum. The present study describes the topography of the PMC according to its surrounding anatomical structures such as the tricuspid valve, subpulmonary infundibulum and septal band of the right ventricle. This anatomical data could have important clinical significance for cardiac surgeons operating in this area.

Suprascapular nerve as a donor for extracranial facial nerve reanimation procedures: a cadaveric feasibility study.

OBJECTIVES: Facial nerve injury with resultant facial muscle paralysis is disfiguring and disabling. To the authors' knowledge, neurotization of the facial nerve using a branch of the brachial plexus has not been previously performed. METHODS: In an attempt to identify an additional nerve donor candidate for facial nerve neurotization, 5 fresh adult human cadavers (10 sides) underwent dissection of the suprascapular nerve distal to the suprascapular notch where it was transected. The facial nerve was localized from the stylomastoid foramen onto the face, and the cut end of the suprascapular nerve was tunneled to this location. Measurements were made of the length and diameter of the supra-scapular nerve. In 2 of these specimens prior to transection of the nerve, a nerve-splitting technique was used. RESULTS: All specimens were found to have a suprascapular nerve with enough length to be tunneled, tension free, superiorly to the extracranial facial nerve. Connections remained tensionless with left and right head rotation of up to 45 degrees . The mean length of this part of the suprascapular nerve was 12.5 cm (range 11.5-14 cm). The mean diameter of this nerve was 3 mm. A nerve-splitting technique was also easily performed. No gross evidence of injury to surrounding neurovascular structures was identified. CONCLUSIONS: To the authors' knowledge, the suprascapular nerve has not been previously explored as a donor nerve for facial nerve reanimation procedures. Based on the results of this cadaveric study, the authors believe that use of the suprascapular nerve may be considered for surgical maneuvers.

Intra-abdominal laparoscopic pudendal canal decompression - a feasibility study.

BACKGROUND: Pudendal canal syndrome (PCS) is induced by the compression or the stretching of the pudendal nerve within Alcock's canal. METHODS: Considering the difficulty and possible complications involved in exposing the pudendal canal and nerve by either transperineal, transgluteal or transischiorectal approaches, an intra-abdominal laparoscopic pudendal canal decompression (ILPCD) was employed. For this technique, 30 male adult human cadavers were examined. RESULTS: Measurements revealed an adequate working space in 16 (80%) of the 20 cadavers, while in four specimens the ischiococcygeus muscle was too large to be mobilized sufficiently. The mean working space was 24 mm with a range of 18 to 31 mm. It was considered that a working space of less than 20 mm would not be sufficient for manipulation of the instruments. With regards to pudendal nerve compression, it was observed that 7 (35%) of the 20 cadavers exhibited anatomic signs of PCS. In five (25%) specimens, the compression was observed between the sacrospinous and sacrotuberous ligaments, while the other two (10%) exhibited a broader compression, by the falciform portion of the sacrotuberous ligament. Under the guidance of a laparoscope, the peritoneum was cut laterally to the bladder, and fascia pelvis was identified. The latter was split and the internal iliac vein was traced to the opening of the pudendal canal allowing clear visualization of its contents. Subsequently, either the sacrospinous or sacrotuberous ligament was cut. CONCLUSIONS: Considering that none of the surgical procedures currently used are known to completely improve all the symptoms of PCS, ILPCD could theoretically reduce stretching of the pudendal nerve.

Histopathological basis for neurogenic thoracic outlet syndrome. Laboratory investigation.

OBJECT: To the best of the authors' knowledge, no report exists that has demonstrated the histopathological changes of neural elements within the brachial plexus as a result of cervical rib compression. METHODS: Four hundred seventy-five consecutive human cadavers were evaluated for the presence of cervical ribs. From this cohort, 2 male specimens (0.42%) were identified that harbored cervical ribs. One of the cadavers was found to have bilateral cervical ribs and the other a single right cervical rib. Following gross observations of the brachial plexus and, specifically, the lower trunk and its relationship to these anomalous ribs, the lower trunks were submitted for immunohistochemical analysis. Specimens were compared with two age-matched controls that did not have cervical ribs. RESULTS: The compressed plexus trunks were largely unremarkable proximal to the areas of compression by cervical ribs, where they demonstrated epi- and perineurial fibrosis, vascular hyalinization, mucinous degeneration, and frequent intraneural collagenous nodules. These histological findings were not seen in the nerve specimens in control cadavers. The epineurium was thickened with intersecting fibrous bands, and the perineurium appeared fibrotic. Many of the blood vessels were hyalinized. The nerve fascicles contained frequent intraneural collagenous nodules in this area, and focal mucinous degeneration was identified. CONCLUSIONS: Cervical ribs found incidentally may cause histological changes in the lower trunk of the brachial plexus. The clinician may wish to observe or perform further evaluation in such patients.

The surgical anatomy of ulnar and median nerve communications in the palmar surface of the hand.

OBJECT: Sensation in the palmar surface of the digits is supplied by the median and ulnar nerves, with the boundary classically being the midline of the ring finger. Overlap and variations of this division exist, and a communicating branch between the ulnar and median nerve could potentially explain further variations in digital sensory innervations. The aim of this study was to examine the origin and distribution of the communicating branch between the ulnar and median nerves and to apply such findings to the risk involved in surgical procedures in the hand. METHODS: The authors grossly and endoscopically examined 200 formalin-fixed adult human hands obtained in 100 cadavers, and a communicating branch was found to be present in 170 hands (85%). Of the specimens with communicating branches, the authors were able to identify four notable types representing different points of connections of the branches. The most common, Type I (143 hands, 84.1%), featured a communicating branch that originated proximally from the ulnar nerve and proceeded distally to join the median nerve. Type II (12 hands, 7.1%) designated a communicating branch that originated proximally from the median nerve and proceeded distally to join the ulnar nerve. Type III (six hands, 3.5%) designated a communicating branch that traversed perpendicularly between the median and ulnar nerves in such a way that it was not possible to determine which nerve served as the point of origin. Type IV (nine hands, 5.3%) designated a mixed type in which multiple communicating branches existed, arising from both ulnar and median nerves. CONCLUSIONS: According to the origin and distribution of these branching patterns, the investigators were able to define a risk area in which the communicating branch(es) may be subject to iatrogenic injury during common hand procedures.

Anatomy of the falcine venous plexus.

OBJECT: The superior and inferior sagittal sinuses have been well studied. Interestingly, other venous structures within the falx cerebri have received scant attention in the medical literature. The present study was performed to elucidate the presence and anatomy of these midline structures. METHODS: The authors examined 27 adult latex- or ink-injected cadaveric specimens to observe the morphological features of the sinuses within the falx cerebri (excluding the inferior and superior sagittal sinuses). RESULTS: All specimens were found to have an extensive network of small tributaries within the falx cerebri that were primarily concentrated in its posterior one third. In this posterior segment, these structures were usually more pronounced in the inferior two thirds. The portion of the falx cerebri not containing significant falcine venous sinus was termed a "safe area." These vascular channels ranged in size from 0.5 mm to 1.1 cm (mean 0.6 mm); 100% of these vessels communicated with the inferior sagittal sinus. Classification of the structures was then performed based on communication of the falcine venous sinus with the superior sagittal sinus. Type I falcine sinuses had no communication with the superior sagittal sinus, Type II falcine sinuses had limited communication with the superior sagittal sinus, and Type III falcine sinuses had significant communication with the superior sagittal sinus. Seventeen (63%) of 27 specimens communicated with the superior sagittal sinus (Types II and III). Further subdivision revealed 10 Type I, seven Type II, and 10 Type III falcine venous plexuses. CONCLUSIONS: There are other venous sinuses in the falx cerebri in addition to the superior and inferior sagittal sinuses. Neurosurgical procedures that necessitate incising or puncturing the falx cerebri can be done more safely via a described safe area. Given that the majority of specimens in the authors' study were found to have a plexiform venous morphology within the falx cerebri, they propose that these channels be referred to as the falcine venous plexus and not sinus. The falcine venous plexus should be taken into consideration by the neurosurgeon.

Surgical anatomy and landmarks for the basal vein of rosenthal.

OBJECT: The basal vein of Rosenthal (BV) courses from the premesencephalic cistern, through the ambient cistern, and terminates in the quadrigeminal cistern. The aim of this study was to describe and quantitate the surgical anatomy of this structure and specifically to provide landmarks for identifying this vessel along its course. These data may be of use, for example, to surgeons using subtemporal operative approaches through regions where this vessel is concealed. METHODS: The authors examined 15 latex-injected adult cadaveric brains (30 sides) to delineate the morphological characteristics of the BV. Dissections of the BV were then performed and measurements were made between this structure and the tentorial incisura at the anterior, middle, and posterior borders of the lateral midbrain. All specimens were found to have a left and right BV with varying morphological characteristics. The mean distance between the BV and posterior cerebral artery at the midpoint of the lateral midbrain was 16 mm. The BV was always found superomedial to the posterior cerebral artery along the lateral aspect of the midbrain, and the BV ranged in diameter from 1 to 5 mm. The BV drained into the vein of Galen in all but two specimens. The mean distances from the tentorial edge to the BV at the anterior, middle, and posterior borders of the lateral midbrain were 11, 1 3, and 4 mm, respectively. No statistically significant differences were found when comparing left and right sides or male and female specimens. CONCLUSIONS: The authors hope that these data will help the neurosurgeon operating near the BV to avoid injury to this important structure.

Giant intracranial lipoma.

Intracranial lipomas are rare and usually benign in their course. We report a case of a giant intracranial lipoma presenting with raised intracranial pressure. Additionally, this patient was found to have a large lipoma of the anterior fontanelle. The clinical course and outcome of this patient is presented and relevant literature reviewed.