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Background and Objectives: The utility of oral 5-aminolevulinic acid (5-ALA)/protoporphyrin fluorescence for the resection of high-grade gliomas is well documented, but the problem of false-negative observations remains. This study compares high-grade glioma visualization with low/standard dose 5-ALA (<30 mg/kg) to high-dose 5-ALA (>40 mg/kg) to see if by using this higher dose, it is possible to reduce the rate of false-negative observations without increasing the rate of false-positive (FP) observations and therefore increase the sensitivity., Methods: This is a prospective study of consecutive patients with radiological evidence of presumed high-grade glioma. We reviewed the data from patients who received preoperative low/standard doses and patients who received a preoperative high dose of 5-ALA. Adverse events, dose to observation time, intensity of tumor fluorescence, and results of biopsies in areas of tumor and tumor bed under deep blue light were recorded., Results: A total of 22 patients with high-grade glioma received a dose >40 mg/kg (high-dose) and 9 patients received <30 mg/kg (low/standard dose). There were no serious adverse events related to 5-ALA in any subject. There was a very high sensitivity and specificity of 5-ALA for the presence of tumor in both groups. There were no FP observations (fluorescence with no tumor) in either group. The specificity and the positive predictive value were 100% in both groups. The sensitivity and the negative predictive value were 53.3% and 30.0% in the low/standard dose group and 59.5% and 31.8% in the high-dose group, respectively., Conclusion: High-dose oral 5-aminolevulinic/protoporphyrin fluorescence is a safe and effective aid to the intraoperative detection of high-grade gliomas with high sensitivity and specificity. False-negative observations with a high dose do not seem to be less than that with a low/standard dose. The rate of FP observations with both groups remains very low., (Copyright © Congress of Neurological Surgeons 2024. All rights reserved.)

Cranial dermoids have the tendency to occur in the midline, especially near fontanelles and sutures early in the life of a patient. Here we present an unusual case of an intraosseous dermoid that presented initially as a lytic lesion, off of the midline and not associated with cranial sutures or fontanelles. The diameter of the lesion grew to approx 15 mm over time, thus the decision was made to take the child to surgery for removal of dermoid with the use of neuronavigation and cranioplasty. A dermoid cyst was confirmed on histopathologic analysis., Competing Interests: Conflict of Interest None declared., (The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. ( https://creativecommons.org/licenses/by-nc-nd/4.0/ ).)

Objective: Anterior cervical diskectomy and fusion (ACDF) is a highly successful procedure to treat spinal cord or nerve root compression; however, complications can still occur. With advancements in imaging, 3-dimensional (3D) reconstruction allows real-time instrument tracking in a surgical field relative to the patient's anatomy. Here, we compare plate positioning and short-term outcomes when using 3D navigation to fluoroscopy in ACDF for degenerative spine disease., Methods: All ACDFs for cervical spondylosis performed by 6 surgeons at a single center between 2010 and 2018 were included. ACDFs were divided into those performed using 3D navigation or fluoroscopy. Records were assessed for patient demographics, American Society of Anesthesiology score, number of operated interspaces, operative time, length of stay, perioperative complications, and 90-day readmissions. Postoperative images were reviewed for lateral and angular plate deviations., Results: A total of 193 ACDFs performed with 3D navigation and 728 performed with fluoroscopy were included. After controlling for demographics and surgical characteristics, using 3D navigation was associated with less lateral plate deviation (P = 0.048) and longer operative times per interspace (P < 0.001) but was not associated with angular plate deviation (P = 0.724), length of stay (P = 0.393), perioperative complications (P = 0.844), and 90-day readmissions (P = 0.539)., Conclusions: Using 3D navigation in ACDF for degenerative disease is associated with slightly more midline plate positioning and comparable short-term outcomes as using fluoroscopy and can be a suitable alternative. Advantages of using this technology, such as improved visualization of anatomy, should be weighed against disadvantages, such as increased operative time, on a per-patient basis., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Purpose: Prior research has examined predictors of shunt failure in children with hydrocephalus and concluded that the majority of shunts do not survive long-term. However, risk factors such as etiology, birth weight, and gestational age may vary across institutions and populations. We sought to identify the social, clinical, and neonatal factors associated with initial ventriculoperitoneal (VP) shunt failure in the intraventricular hemorrhage (IVH) patient population and the patient population with an etiology other than IVH (non-IVH)., Methods: A retrospective review of patients, born during 2000-2005 diagnosed and treated for hydrocephalus at Children's of Alabama was conducted. Survival analysis identified factors associated with time to shunt failure., Results: Analyses were done separately for the IVH and non-IVH cohorts. Age and weight at initial VP shunt insertion were found to be associated with shunt failure in the non-IVH group (p < .05). Of the 238 patients in the non-IVH cohort, 108 failed within 2 years of their initial insertion. Fifty of those shunt failures occurred within 3 months of initial shunt placement. In the IVH cohort, 56 out of 100 failed within 2 years; 36 of those failed within 3 months post initial shunt insertion. When controlling for type of shunt failure, age at initial shunt placement was associated with time to shunt failure (p = .0004)., Conclusion: This study confirms previously published studies on the IVH population. A prospective cohort study and standardized clinical decision making are necessary to further assess the impact that shunting has on this patient population.

Foix-Alajouanine syndrome has become a well-known entity since its initial report in 1926. The traditional understanding of this clinical syndrome is as a progressive spinal cord venous thrombosis related to a spinal vascular lesion, resulting in necrotic myelopathy. However, spinal venous thrombosis is extremely rare and not a feature of any common spinal vascular syndrome. A translation and review of the original 42-page French report revealed 2 young men who had presented with progressive and unrelenting myelopathy ultimately leading to their deaths. Pathological analysis demonstrated endomesovasculitis of unknown origin, including vessel wall thickening without evidence of luminal narrowing, obliteration of cord vessels, or thrombosis. Foix and Alajouanine also excluded the presence of intramedullary arteriovenous malformations. At the time, dural arteriovenous fistulas (dAVFs) had not been described, and therefore this type of lesion was not specifically sought. In retrospect, it seems possible that both patients had progressive myelopathy due to Type I dAVFs. In the decades since that original report, numerous authors have included spinal cord venous thrombosis as a central feature of Foix-Alajouanine syndrome. The inclusion of thrombosis in the clinical picture of this syndrome is not only incorrect but may leave one with the impression of therapeutic futility, thus possibly preventing successful surgical or endovascular therapy.

Introduction: Malfunction of cerebrospinal shunts is common and due to multiple etiologies. We hypothesize that opening of the spinal dura may prompt shunt failure in select individuals with previously unrecognized tenuous shunt function., Case Reports: The authors describe five patients with shunted hydrocephalus who underwent procedures in which the spinal dura mater was opened. All patients had acute dysfunction of their ventriculoperitoneal shunt that required shunt revision. All shunt valves were functioning properly at operative inspection but all patients were found to have adherent intracranial catheters with ingrowth of choroid plexus., Conclusions: We theorize that the siphoning effect caused from cerebrospinal fluid egress from the opened spinal subarachnoid space resulted in acute shunt failure. Such alterations in cerebrospinal fluid flow may precipitate complete failure of a shunt that is functioning suboptimally. Clinicians should be aware that spinal procedures that violate the subarachnoid space in shunted hydrocephalic patients may result in acute shunt failure. These patients may warrant more careful observation in the early postoperative period, particularly as shunt failure may compromise spinal wound closures.

Purpose: We report a case of increased cerebrospinal fluid (CSF) production in a child with concomitant mycoplasma meningitis., Materials and Methods: This 4-year-old boy presented with a 2-week history of body aches, malaise, and headaches. He developed sudden onset of obtundation, apnea, left eye deviation, and bilateral dilated and unreactive pupils. A ventriculostomy was placed initially for a poor neurologic examination in the setting of likely meningitis. Initial intracranial pressure was high, and CSF production was supraphysiologic for the first few days of empiric, broad-spectrum treatment. Mycoplasma meningitis was diagnosed. The ventriculostomy was weaned after adequate treatment for mycoplasma meningitis., Results and Conclusions: At 4 months follow-up, the child remains shunt-free with only mild cognitive-linguistic impairment. Untreated mycoplasma meningitis may cause raised intracranial pressure (possibly as a result of increased CSF production) and result in a poor neurological examination. In this setting, CSF diversion in the form of an external ventricular drain may be beneficial to preserve neurologic function during treatment with antibiotics.

Introduction: Previously, the Seldinger technique has been used for insertion of difficult-to-place vascular catheters. The authors describe the use of this technique in exchanging difficult-to-place ventricular catheters in a child with multiloculated hydrocephalus and ventriculoperitoneal shunt infection., Patient and Methods: A thin, flexible, hydrophilic catheter (Radifocus Glidewire, Terumo Medical, NJ, USA) was truncated to 35 cm, and the angled tip was transected. This modified wire was then used to cannulate two existing ventricular catheters. Each catheter was exchanged for a ventriculostomy over the glidewire. No complications were observed., Results: Catheter placement was identical to preoperative location on postoperative imaging., Conclusions: The authors believe that the modified Seldinger technique may be of use in selected cases of ventricular catheter exchange. With the increase use of endoscopy to place intracranial catheters, holes in intracranial catheters are more common and, thus, the Seldinger technique may increase in its usage.

Introduction: The authors previously conducted a retrospective study regarding deaths from CSF shunt failure to identify circumstances surrounding shunt malfunction-related deaths in children in the modern era., Materials and Methods: Using the same methodology, we conducted a follow-up study to determine whether recent policy and procedural changes instituted since the time of the first study had effected a change in the mortality rate of our shunted patient population., Results: Thirty-nine original patient records (of patients seen at Children's Hospital who died with the diagnosis of hydrocephalus between 1998 and 2004) were identified and reviewed for inclusion into the study. Only four (10.3%) were found to have died directly as a result of shunt malfunction., Conclusions: Our rate of shunt malfunction death has decreased over time. It is reasonable to attribute part of this decline to continued improvements in diagnostic and therapeutic techniques and to the use of surveillance scans to identify asymptomatic patients with shunt failure. However, we believe the majority of this decline is due to two additional factors: (1) increased nursing staff and (2) effective patient/family education.

Object: The suprascapular nerve may become entrapped as it travels deep to the suprascapular ligament, necessitating decompression. The present study was performed to verify the feasibility of a minimally invasive, endoscopically assisted technique for decompressing the suprascapular nerve in the supraspinous fossa., Methods: The authors performed dissection and decompression of the suprascapular ligament using an endoscopically assisted technique via a 3-cm skin incision in 10 adult cadavers (20 sides). Measurements were also made of the depth from the skin to the suprascapular ligament., Results: A mean depth of 4 cm was necessary to reach the suprascapular ligament from the skin surface. With the authors' approach, no obvious injury occurred to the suprascapular or other vicinal neurovascular structures (such as the spinal accessory nerve and suprascapular vessels)., Conclusions: The results of this cadaveric study demonstrate that access to the suprascapular nerve can be obtained endoscopically via a small suprascapular incision. This approach obviates a large incision, entry into the glenohumeral joint, and reduces the risk of spinal accessory nerve injury in the posterior cervical triangle, or atrophy of the trapezius or supraspinatus muscles from a standard larger dissection. To the authors' knowledge an endoscopically assisted approach to decompressing the suprascapular nerve as it courses deep to the suprascapular ligament has not been reported previously.

The authors report an unusual case of cortical herniation into a chronic subdural hematoma (SDH). The patient was successfully treated with good outcome. A 4-month-old boy with a history of macrocrania and very large bilateral chronic SDHs underwent subduroperitoneal shunt treatment shortly after presentation. Eight months later he developed a new-onset seizure disorder, which was localized by electroencephalography to the right frontal region. Neuroimaging demonstrated the development of a focal herniation of the brain through a subdural membrane into the subdural space. The patient underwent a craniotomy to resect the seizure focus and the herniated cortex. The subdural shunt was subsequently replaced. After 2 years of follow-up, the patient remains free of seizures, is on no medication regimen, and is neurologically and developmentally normal. To the authors' knowledge, this is only the fourth report in the medical literature of cortical herniation through a chronic subdural membrane and the first in which successful treatment with a good outcome is described.

Object: There is conflicting information in the literature regarding the increased risk of ventriculoperitoneal (VP) shunt infection after abdominal surgical procedures such as gastrostomy tube (GT) placement and Nissen fundoplication (NF) in the young patient. To further elucidate this potential association, the authors reviewed their institutional experience with such cases., Methods: The authors retrospectively reviewed the records of all patients with shunted hydrocephalus who also underwent NF procedures and/or GT placements over a 9-year period., Results: During this 9-year period, 3065 cerebrospinal fluid (CSF) shunts were placed and 1630 NF procedures/GT placements were performed. Ninety-six patients were identified who received both a CSF shunt and NF procedures/GT placements. Seventy-nine patients had a functioning VP shunt (without recent [< 6 months] CSF infection or shunt revision) at the time of their abdominal procedure (NF procedure or GT placement). Of this latter cohort, there were 38 males and 41 females with a mean age of 6.4 months; 12.7% of these patients developed a shunt infection and 60% of these infections were due to Staphylococcus species., Conclusions: Based on this study, an NF procedure/GT placement in a child with a VP shunt appears to carry approximately the same risk of shunt infection as a shunt placement operation. Moreover, the microbiology observed in these patients with infection did not differ significantly from the usual microorganisms responsible for VP shunt infections in infants/neonates. Finally, but not conclusively, an open NF procedure/GT placement may carry a higher infection risk than a laparoscopic-assisted NF procedure/GT placement.

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.

Object: There is scant literature regarding the long-term outcome in patients with cranial vault encephaloceles, and what literature there is may underestimate long-term deficits. The goal of this study was to address this lack of information., Methods: The authors performed a retrospective chart review of cranial vault encephaloceles performed at our institution between 1989 and 2003. Fifty-two total patients were identified and 44 of these cases were reviewed. Additionally, 34 of the 44 patients were contacted and given an outcome survey (Hydrocephalus Outcome Questionnarie [HOQ]) to evaluate physical, emotional, cognitive, and overall health outcomes., Results: The mean age for patients in this cohort was 9.6 years (range 4-17 years) and the mean follow-up time was 9.2 years. There was an equal sex distribution and there were no deaths. Hydrocephalus was found in 60% of occipital and 14% of frontal encephaloceles, and epilepsy was confirmed in 17% of occipital and 7% of frontal lesions. Outcome assessments performed using the HOQ showed that 50% of the patients with occipital encephaloceles had overall HOQ health scores of 0.5 or less and 55% had HOQ cognitive scores of 0.3 or less, compared with 0% of patients in both categories who had frontal encephaloceles. It was also found that the presence of hydrocephalus and epilepsy independently and significantly lowered the overall health scores., Conclusions: Occipital encephaloceles carry a worse prognosis than frontal encephaloceles, with higher rates of hydrocephalus and seizure. Based on this study, the presence of hydrocephalus and epilepsy are significant additive adverse prognostic factors. Approximately half of the patients with occipital encephaloceles will be severely debilitated and will probably be unable to live and function independently in society. These data may be useful to clinicians in counseling patients and predicting long-term outcome following repair of cranial vault encephaloceles.

Object: Postoperative epidural morphine is commonly used to control pain in children following dorsal rhizotomy for spasticity. The authors report their experience in using a regimen of scheduled minor analgesic drugs to manage postoperative pain, with the goal of avoiding opiate use following a spinal intradural procedure., Methods: Postoperative pain scores were analyzed in a group of 22 children who underwent a partial dorsal rhizotomy. According to a preestablished standard regimen for postoperative pain control after dorsal rhizotomy, in each patient an intraoperative epidural catheter was placed for the potential infusion of postoperative morphine. Additionally, this cohort underwent a scheduled regimen of acetaminophen (10 mg/kg) and ibuprofen (10 mg/kg), alternating every 2 hours. For comparison, a retrospective chart review was performed in 20 patients with rhizotomies completed prior to the use of this oral analgesic protocol. Only one patient received a postoperative dose of morphine epidurally. None of the remaining patients required postoperative epidural morphine for pain control. Pain scores were significantly lower in this group compared with a retrospective review of patients treated according to the standard regimen. Length of hospital stay was shorter in these patients and antiemetic requirements were lower., Conclusions: A regimen of minor analgesic therapy, when given in alternating doses every 2 hours immediately after partial dorsal rhizotomy for spasticity and throughout hospitalization, significantly reduced postoperative pain scores, hospitalization, and antiemetic requirements in these patients.

There is minimal information in the literature regarding the tectorial membrane. Further, information in the literature regarding the anatomy and function of this structure is often contradictory. We performed the current study to elucidate further this structure's detailed anatomy, function, and histology. Thirteen adult cadavers underwent dissection of their tectorial membranes and detailed observations and measurements were made of them. Ranges of motion of the craniocervical junction were performed before and after transection of this structure. Histological analysis was performed on all membranes. The tectorial membrane was found to attach much more superiorly than previously described and was found to be firmly adherent to the cranial base and body of the axis but not to the posterior aspect of the odontoid process. The mean thickness of this membrane was found to be 1 mm. Flexion of the head made the tectorial membrane fully taut at 15 degrees and extension made it fully taut at 20 degrees; however, there was a buckling effect (redundant tectorial membrane) noted at the level of the odontoid process in extension. With the alar and transverse ligaments cut and with flexion of the head, the middle portion of this membrane was stretched over the odontoid process, thus acting as a "hammock" that inhibited the odontoid process from moving posteriorly. The tectorial membrane did not limit cervical flexion per se but rather helped to insure that the odontoid process did not impinge into the cervical canal. Lateral flexion was not found to be limited by this structure. Histologically, parallel collagen fibers with spindle-shaped fibrocytes were observed within this membrane and near its attachment to the posterior axis, the collagen fibers were noted to be more homogenous with larger non-spindled fibrocytes. At the cranial attachment of the tectorial membrane, multiple calcified areas were noted that interdigitated with the underlying bone. Also near this cephalic bony attachment, there was an increase in the number of elastic fibers, which were found running parallel with the surrounding Type III collagen fibers. The tectorial membrane was found to attach much more superiorly than previously described. We would propose that the tectorial membrane provides for a second line of defense, preventing the odontoid process from compressing the spinal cord and by doing so, secondarily limits movement of the craniocervical juncture. This hypothesis is strengthened by the finding of many elastic fibers in the tectorial membrane. To our knowledge, our study is the first to perform a detailed histological analysis of the tectorial membrane. We hope that these data are useful to the clinician who investigates this ligament of the craniocervical region.

Introduction: Stability of the atlantooccipital joint is of vital importance. The ligaments of this region, for the most part, have been thoroughly investigated, except for the lateral atlantooccipital ligament (LAO), which is not described in most modern texts., Materials and Methods: The authors examined 20 adult cadaveric specimens to observe the morphology of the LAO., Results: All specimens were found to have an LAO, bilaterally, immediately posterior to the rectus capitis lateralis muscle with a fiber direction more or less opposite to this muscle. The LAO was found in intimate contact with the vertebral artery posteriorly and with the contents of the jugular foramen anteriorly. In all specimens, the origin of this ligament was from the anterolateral aspect of the transverse process of the atlas and the insertion onto the jugular process of the occipital bone. The fibers of the LAO had a mean angle of 26 degrees from the midline. The mean length and width of this ligament was 2.2 and 0.5 cm, respectively. The mean thickness of the LAO was 2 mm. The average tensile strength of this band was 37.5 degrees N. The LAO remained lax with flexion and extension of the craniocervical junction. With contralateral lateral flexion of the craniocervical junction, the LAO became fully taut at a mean of 8 degrees . Partial, but never complete, tautness was observed with rotation of the occipital on the atlas bilaterally. Following sectioning of the LAO, approximately an additional 3 degrees -5 degrees of contralateral lateral flexion was observed., Conclusions: The LAO is a constant anatomical structure of the craniocervical junction that might be of concern to the clinician. This ligament inhibits lateral flexion of the atlantooccipital joint and its disruption appears to add to instability at this articulation.

Object: Facial nerve injury with resultant facial muscle paralysis is disfiguring and disabling. Reanimation of the facial nerve has been performed using different regional nerves. The nerve to the mylohyoid has not been previously explored as a donor nerve for facial nerve reanimation procedures., Methods: Five fresh adult human cadavers (10 sides) were dissected to identify an additional nerve donor candidate for facial nerve neurotization. Using a curvilinear cervicofacial skin incision, the nerve to the mylohyoid and facial nerve were identified. The nerve to the mylohyoid was transected at its point of entrance into the anterior belly of the digastric muscle. Measurements were made of the length and diameter of the nerve to the mylohyoid, and this nerve was repositioned superiorly to the various temporofacial and cervicofacial parts of the extracranial branches of the facial nerve. All specimens had a nerve to the mylohyoid. The mean length of this nerve available inferior to the mandible was 5.5 cm and the mean diameter was 1 mm. In all specimens, the nerve to the mylohyoid reached the facial nerve stem and the temporofacial and cervicofacial trunks without tension. No gross evidence of injury to surrounding neurovascular structures was identified., Conclusions: To the authors' knowledge, the use of the nerve to the mylohyoid for facial nerve reanimation has not been explored previously. Based on the results of this cadaveric study, the use of the nerve to the mylohyoid may be considered for facial nerve reanimation procedures.

Acceptable cavities for the distal portion of a cerebrospinal fluid diversion shunt include the peritoneal, pleural, and atrial cavities. The authors report on a patient in whom placement into the peritoneal cavity failed, the pleural cavity was not an option, and access to the right atrium was not technically possible via standard cannulation techniques into the veins of the neck and shoulder regions. A right ventriculoatrial shunt was thus placed into the right atrium via the ipsilateral femoral vein. Eight months postoperatively, the patient's condition was at baseline and there were no signs of shunt malfunction. This technique may prove useful when other measures have failed.

In certain highly selected circumstances, division of a distally nonfunctional or dysfunctional cord can be a means of definitive untethering that spares and protects more rostral neurological function and results in definitive untethering. The authors reviewed their institutional experience with such cases and evaluated the limited literature. Based on their experience, treatment can be effective in carefully selected patients who undergo spinal cord transection, and the rate of repetitive tethered spinal cord can be decreased.

Accessory nerve meningiomas are exceedingly rare. We present a case of a nine-year-old patient with neurofibromatosis type 2 who had radiologic evidence of spinal cord compression from an upper cervical/foramen magnum lesion. He was asymptomatic from this lesion, but it progressed in size. The tumor was resected and histologic investigation revealed frequent tight whorls and psammoma bodies consistent with meningioma. To the authors' knowledge, this is the first reported spinal accessory nerve meningioma in a pediatric patient.

Object: New information regarding nerve branches of the brachial plexus can be useful to the surgeon performing neurotization procedures following patient injury. Nerves in the vicinity of the axillae have been commonly used for neural grafting procedures, with the exception of the lower subscapular nerve (LSN)., Methods: The authors dissected and measured the LSN in 47 upper extremities (left and right sides) obtained in 27 adult cadavers, and determined distances between the LSN and surrounding nerves to help quantify it for possible use in neurotization procedures. The mean diameter of the LSN was 2.3 mm. The mean length of the LSN from its origin at the posterior cord until it branched to the subscapularis muscle was 3.5 cm, and the mean distance from this branch until its termination in the teres major muscle was 6 cm. Therefore, the mean length of the entire LSN from the posterior cord to the teres major was 9.5 cm. When the LSN was mobilized to explore its possible use in neurotization, it reached the entrance site of the musculocutaneous nerve into the coracobrachialis muscle in all but three sides and was within 1.5 cm from this point in these three. In the other specimens, the mean length of the LSN distal to this site of the musculocutaneous nerve was 2 cm. The mobilized LSN reached the axillary nerve trunk as it entered the quadrangular space in all specimens. The mean length of the LSN distal to this point on the axillary nerve was 2.5 cm. Furthermore, on all but one side the LSN was found within the confines of an anatomical triangle previously described by the authors., Conclusions: The authors hope that these data will prove useful to the surgeon for both identifying the LSN and planning for potential neurotization procedures of the brachial plexus.

Object: Surgical exposure of the extracranial part of the vertebral artery (VA) is occasionally necessary. Historically, the greater portion of the extracranial portion of the VA has been approached by traversing the anterior cervical triangle. The authors speculated that this entire segment of the VA could be reached with equal efficacy via the posterior cervical triangle (PCT)., Methods: Six adult cadavers underwent dissection of the left and right VAs via the PCT. The entire extracranial VA was easily exposed through this approach. Only three of 12 sides required the transection of the clavicular head of the sternocleidomastoid muscle for exposure of the most proximal segment of the VA as it originated from the subclavian artery. No gross injury to the VA or other regional vessels or nerves was noted., Conclusions: The authors found that the extracranial VA can be exposed easily through the PCT. Following confirmation of this technique in vivo, this approach may be added to the surgeon's armamentarium for exposing the extracranial segment of the VA.

Complications following cerebrospinal fluid (CSF) diversion procedures are protean. The formation of pseudoaneurysms after the placement of a ventricular catheter as part of a CSF diversion procedure is presumably quite rare. The authors report the case of a child in whom a pericallosal artery pseudoaneurysm developed following the endoscopic insertion of a ventricular catheter as part of a ventriculoperitoneal shunt placement procedure. Significant intraventricular bleeding signaled vascular injury. Angiography revealed a right pericallosal artery pseudoaneurysm. The patient subsequently underwent surgical trapping of his pseudoaneurysm and physical therapy for left leg monoparesis. This appears to be the first reported case of pseudoaneurysm formation following the placement of a ventricular catheter for a CSF diversion procedure. This case underlines a rare but serious risk involved with the routine placement of CSF shunts.

Myosin heavy chains (MyHCs) are highly conserved ubiquitous actin-based motor proteins that drive a wide range of motile processes in eukaryotic cells. MyHC isoforms expressed in skeletal muscles are encoded by a multigene family that is clustered on syntenic regions of human and mouse chromosomes 17 and 11, respectively. In an effort to gain a better understanding of the genomic organization of the skeletal MyHC genes and its effects on the regulation, function, and molecular genetics of this multigene family, we have constructed high-resolution physical maps of both human and mouse loci using PCR-based marker content mapping of P1-artificial chromosome clones. Genes encoding six MyHC isoforms have been mapped with respect to their linear order and transcriptional orientations within a 350-kb region in both human and mouse. These maps reveal that the order, transcriptional orientation, and relative intergenic distances of these genes are remarkably conserved between these species. Unlike many clustered gene families, this order does not reflect the known temporal expression patterns of these genes. However, the conservation of gene organization since the estimated divergence of these species (approximately 75-110 million years ago) suggests that the physical organization of these genes may be significant for their regulation and function.

Myosin in adult murine skeletal muscle is composed primarily of three adult fast myosin heavy chain (MyHC) isoforms. These isoforms, MyHC-IIa, -IId, and -IIb, are >93% identical at the amino acid level and are broadly expressed in numerous muscles, and their genes are tightly linked. Mice with a null mutation in the MyHC-IId gene have phenotypes that include growth inhibition, muscle weakness, histological abnormalities, kyphosis (spinal curvature), and aberrant kinetics of muscle contraction and relaxation. Despite the lack of MyHC-IId, IId null mice have normal amounts of myosin in their muscles because of compensation by the MyHC-IIa gene. In each muscle examined from IId null mice, there was an increase in MyHC-IIa- containing fibers. MyHC-IIb content was unaffected in all muscles except the masseter, where its expression was extinguished in the IId null mice. Cross-sectional fiber areas, total muscle cross-sectional area, and total fiber number were affected in ways particular to each muscle. Developmental expression of adult MyHC genes remained unchanged in IId null mice. Despite this universal compensation of MyHC-IIa expression, IId null mice have severe phenotypes. We conclude that despite the similarity in sequence, MyHC-IIa and -IId have unique roles in the development and function of skeletal muscle.

The three adult fast myosin heavy chains (MyHCs) constitute the vast majority of the myosin in adult skeletal musculature, and are >92% identical. We describe mice carrying null mutations in each of two predominant adult fast MyHC genes, IIb and IId/x. Both null strains exhibit growth and muscle defects, but the defects are different between the two strains and do not correlate with the abundance or distribution of each gene product. For example, despite the fact that MyHC-IIb accounts for >70% of the myosin in skeletal muscle and shows the broadest distribution of expression, the phenotypes of IIb null mutants are generally milder than in the MyHC-IId/x null strain. In addition, in a muscle which expresses both IIb and IId/x MyHC in wild-type mice, the histological defects are completely different for null expression of the two genes. Most striking is that while both null strains exhibit physiological defects in isolated muscles, the defects are distinct. Muscle from IIb null mice has significantly reduced ability to generate force while IId null mouse muscle generates normal amounts of force, but has altered kinetic properties. Many of the phenotypes demonstrated by these mice are typical in human muscle disease and should provide insight into their etiology.