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Object: The quantitative analysis of odontoid process angulation has had scant attention in the Chiari I malformation population. In this study the authors sought to elucidate the correlation between posterior angulation of the odontoid process and patients with Chiari I malformation., Methods: Magnetic resonance images of the craniocervical junction obtained in 100 children with Chiari I malformation and in 50 children with normal intracranial anatomy (controls) were analyzed. Specific attention was focused on measuring the degree of angulation of the odontoid process and assigning a score to the various degrees. Postoperative outcome following posterior cranial fossa decompression was then correlated to grades of angulation. Other measurements included midsagittal lengths of the foramen magnum and basiocciput, the authors' institutions' previously documented pB-C2 line (a line drawn perpendicular to one drawn between the basion and the posterior aspect of the C-2 body), level of the obex from a midpoint of the McRae line, and the extent of tonsillar herniation. Higher grades of odontoid angulation (retroflexion) were found to be more frequently associated with syringomyelia and particularly holocord syringes. Higher grades of angulation were more common in female patients and were often found to have obices that were caudally displaced greater than three standard deviations below normal., Conclusions: These results not only confirm prior reports of an increased incidence of a retroflexed odontoid process in Chiari I malformation but quantitatively define grades of inclination. Grades of angulation were not found to correlate with postoperative outcome. It is the authors' hopes that these data add to our current limited understanding of the mechanisms involved in hindbrain herniation.

Objective: Cadaveric studies of the blood supply to the human cervical sympathetic chain and ganglia are lacking in the English literature. This study seeks to elucidate the gross blood supply of the cervical sympathetic chain so as to avoid surgical disruption of these vessels and thus decrease the risk of vascular insufficieny and subsequent dysfunction of thoracolumbar autonomic outflow to the head and neck., Methods: Twelve (24 sides) human cadavers (8 male and 4 female) were dissected and their brachiocephalic veins, internal carotid arteries, and vertebral arteries cannulated. Red and blue latex was injected into the arteries and veins respectively. Dissection of the neck was carefully performed and the blood supply of the cervical sympathetic chain identified., Results: The primary arterial supply to the sympathetic chain and ganglia were from superior to inferior the ascending pharyngeal, ascending cervical, thyrocervical trunk, and supreme intercostal arteries. The primary venous drainage of these structures was primarily by direct posterior branches into the internal jugular vein. In addition, we have found an area at the junction of the lower two-thirds and upper one-third of the neck, which is deficient in blood supply (both arterial and venous)., Conclusions: Although sympathetic injury is a rare consequence of cervical operations, the current data should be useful to the surgeon who operates in the cervical region so as to avoid potential complications from disruption of the primary blood supply of the cervical sympathetic chain and ganglia. Also, future techniques of selective iatrogenic disruption of the blood supply to portions of these structures e.g. stellate ganglion may be helpful in treating entities such as hyperhydrosis.

Objective: This study tests the hypothesis that the ability of Hering's nerve stimulation (HNS) to blunt seizure activity is dependent on the availability of dopamine in the amygdala., Methods: In 10 rats, Hering's nerve (HN) on the right side was isolated and placed on an electrode and penicillin was locally placed on each rat's left frontoparietal region to induce seizures. After the initiation of seizures, HN was stimulated. After the recurrence of seizure activity, the left basolateral amygdala was injected with 1.0 microl of normal saline, dopamine, haloperidol or 1% lidocaine in sequential tests. HN was stimulated after each injection and the latency and amplitude of the seizure activity were assessed., Results: Focal cortical penicillin induced seizures that resulted in tonic-clonic movement of the limbs and face that lasted 35-45 min. Tonic-clonic movements of the limbs and face of similar latency and amplitude were induced by repeated reapplication of penicillin in untreated rats. HNS decreased seizure activity, but infusion of haloperidol or lidocaine into the basolateral amygdala blocked this antiseizure effect of HNS. In contrast, infusion of saline or dopamine had no effect on the ability of HNS to blunt seizure activity. None of the amygdala injections altered the latency or amplitude of seizure activity., Conclusion: These results demonstrate that the ability of HNS to blunt seizure activity in the rat is dependent on an intact dopamine system in the basolateral amygdala. These data will hopefully be useful in furthering our understanding of the circuitry that allows peripheral nerve stimulation to alter seizure activity., (Copyright 2002 S. Karger AG, Basel)

Objective: We recently found that Hering's nerve stimulation (HNS) effectively blunts seizure activity. This study characterizes the cortical areas that are activated by HNS., Methods: Hering's nerve (HN) was stimulated in 3 dogs and 6 pigs, and then the brains of the animals were removed. The insular and mesial temporal cortices were removed and evaluated for increased neuronal activity by examining Fos-like activity., Results: In both the dogs and pigs, Fos activity was elevated in the anterior insular and mesial temporal cortices. Increased cortical activity was not noted in adjacent areas such as the frontal cortex., Conclusion: This study demonstrates that the mesial temporal and anterior insular cortices are selectively activated by stimulation of HN, thus suggesting cortical loci at which HNS might blunt seizure activity., (Copyright 2002 S. Karger AG, Basel)

Introduction: Sagittal synostosis has been found to occur in families at a low frequency. All previous reports of sagittal synostosis in twins have been of males., Case Report: We now report a case of female twins concordant for sagittal synostosis., Conclusion: Our hopes are that this information will further our understanding of the genetics of sagittal synostosis not only in single births but also in that of twins.

Dolichoodontoid is defined as hypertrophy of the apical portion of the odontoid process of the axis. We report the first case of a dolichoodontoid process in a pediatric patient with other congenital anomalies. This rare entity has had three previous citations in the literature. Our patient presented with scoliosis in which subsequent MRI demonstrated a Chiari I malformation, a small thoracic syrinx and a dolichoodontoid process. The diagnosis of this malformation should be entertained in cases of craniocervical anomalies., (Copyright 2002 S. Karger AG, Basel)

There has been almost no evaluation or discussion of the symmetry of tonsillar ectopia in the medical literature. We measured the degree of left and right tonsillar herniation in 42 pediatric patients with a symptomatic Chiari I malformation and made clinical/radiological correlations. 18% of all patients with tonsillar asymmetry had clinical symptoms or physical findings referable to the inequality of their hindbrain herniation. In addition, 95% of patients with a coexisting syringomyelia had a right cerebellar tonsillar herniation greater than the left. We hypothesize that slight differences in posterior cranial fossa morphology may physically allow for greater unilateral herniation of the left or right cerebellar tonsil, which may be manifested in a patient's clinical presentation., (Copyright 2002 S. Karger AG, Basel)

Object: The medial tubercles of the atlas serve as the attachments of the transverse ligament and provide an important anchoring site for which no discussion of their fine anatomy is published in the literature. In this study the authors examine this anatomy along with its osseous relationships., Methods: One hundred dry cadaveric atlantal tubercles were assessed for size and relationship to nearby anatomical osseous structures. In addition, eight cadaveric specimens were evaluated for their anatomy in this area. All specimens exhibited atlantal tubercles for the attachment of the transverse portion of the cruciate ligament of the atlas. Right-sided tubercles tended to be of a larger caliber. Overall, right-sided vertical distances between these tubercles and the superior articular facets and inferior articular facets were greater, although distances from each tubercle to the lateral margin of the dental facets anteriorly were found to be constant, as were intertubercular distances. The mean angle formed between both tubercles and the dental facet was 75 degrees., Conclusions: The data derived in this study should be useful to the clinician for whom the craniocervical junction is a vital anatomical area.

The authors describe the use of autogenetic posterior atlantooccipital (PAO) membrane for duraplasty following after posterior cranial fossa surgery. The PAO membrane is routinely exposed for procedures of the posterior cranial fossa and merely needs to be dissected free of the underlying dura mater. Recently this membrane was obtained in several pediatric patients following procedures of the posterior cranial fossa such as duraplasty in case of Chiari I malformation. No postoperative complications were found at 6-month follow-up examination. The advantages of this intervention include less manipulation of muscle and fascia than that involved in other procedures and, therefore, seemingly less postoperative pain and the negation of issues inherent with foreign-body graft sources. The authors believe this structure to be of use as a dural substitute in small dural openings of the posterior cranial fossa.

Objective: We report the control of hydrocephalus in children with presumed tectal plate gliomas by the use of endoscopic third ventriculostomy (ETV)., Methods: The hospital records, office charts, and imaging studies from children who underwent ETV at the Children's Hospital of Alabama were reviewed. Thirteen children with the diagnosis of tectal plate glioma and hydrocephalus were identified. ETV was the primary therapy instituted for all but one of these children. Successful treatment outcome was defined as shunt freedom, improvement in symptoms, and reduced ventricular size., Results: Thirteen children underwent a total of 15 ETVs, and all children were shunt-free at their most recent follow-up examinations. One child underwent successful secondary ETV, one child underwent shunt removal concomitant with the initial ETV, and one child underwent shunt removal concomitant with secondary ETV. Symptoms and signs resolved in all patients. All postoperative cranial imaging studies revealed normal or reduced ventricular size as compared with preoperative cranial imaging scans. The median follow-up period was 31 months., Conclusion: In our surgical experience, ETV has been uniformly successful in the management of hydrocephalus caused by tectal plate gliomas in children. ETV should be considered the treatment of choice for hydrocephalus in pediatric patients with tectal plate gliomas.

Background: Innovations in shunt technology and neuroendoscopy have been increasingly applied to shunt management. However, the relative life span of shunts and the etiology of shunt failure have not been characterized recently., Methods: We reviewed the records of all shunting procedures at our institution between January 1992 and December 1998. Independent predictors of shunt failure were analyzed via multivariate Cox regression analysis in 836 shunting procedures. Independent predictors of the etiology of failure (infection, proximal obstruction, distal malfunction) were analyzed via multivariate logistic regression analysis in the 383 shunts which failed., Results: A total of 353 pediatric patients underwent 308 shunt placements and 528 revisions. The risk (hazard ratio; HR) of shunt failure decreased as a function of time in both primary placements and revised shunts. In failed shunts, the odds of infection decreased 4-fold per year of shunt function, while the odds of distal malfunction increased 1.45-fold per year. Increasing number of shunt revisions (HR 1.31, p < 0.05), decreasing patient age in years (HR 1.04, p < 0.001), gestational age <40 weeks (HR 2.15, p < 0.001) but not the etiology of hydrocephalus were associated with an increased risk of shunt failure. Revisions versus primary placements, Dandy-Walker cysts and gestational age <40 weeks were independently associated with proximal, distal and infectious causes of failure, respectively., Conclusions: The long-term shunt revision rates observed here are similar to those reported over the past 2 decades. Shunt life span remains poorer in shunt revisions and in younger patients. Patient characteristics may suggest a specific risk and mechanism of failure, aiding in the long-term management of shunted hydrocephalus., (Copyright 2002 S. Karger AG, Basel)

The horizontal sacrum has never been described as an indicator of a tethered spinal cord following myelomeningocele closure. We retrospectively analyzed 30 children with a myelomeningocele for this progressive change and its correlation with symptoms. At least two lateral radiographs over time were examined and the lumbosacral angle (LSA) was measured. We found that the majority of these children had an LSA that was greater than would be expected in patients with late and decreased ambulatory abilities. Also, we observed that the LSA was often inappropriately increased at the time many of these patients presented with symptoms indicative of a tethered spinal cord. We hypothesize that the LSA in this group of children is altered by a tethered spinal cord and that the horizontal nature of the sacrum may predate the clinically appreciable symptoms of a tethered spinal cord., (Copyright 2002 S. Karger AG, Basel)

Introduction: The removal of the choroid plexus from the lateral ventricles was attempted by Dandy in the early 20th century but later discarded as complications arose and other methods of cerebrospinal fluid (CSF) diversion were introduced. We compare our experience with a variation of this operation to CSF diversion in patients with hydranencephaly or near hydranencephaly., Methods: The hospital and office charts of patients with a diagnosis of hydranencephaly were reviewed from the two institutions spanning the career of the senior author. Thirteen patients were identified, of whom 9 underwent CSF diversionary procedures (group A) and 4 underwent choroid plexectomy (group B)., Results: The mean number of reoperations (2 in group A, 0 in group B), neurosurgical readmissions (1.5 in group A, 0 in group B) and days of hospitalization related to neurosurgical readmissions (43.5 in group A, 0 in group B) were all less in patients who underwent choroid plexectomy. The total incidence of complications related to surgery was also lower in this group (7 in group A, 0 in group B)., Conclusion: In our experience, choroid plexectomy in patients with hydranencephaly reduces the incidence of reoperation and readmission, the number of days of hospitalization related to the surgical procedure and the total number of complications in comparison to patients undergoing CSF diversion. Further neurosurgical intervention is minimized as is the financial burden from multiple emergency department visits and radiological procedures for shunt evaluation. Choroid plexectomy is a viable alternative to CSF diversion in patients with hydranencephaly and a rapidly enlarging head. It avoids the chronic issues and complications surrounding CSF diversion in this difficult group of patients., (Copyright 2002 S. Karger AG, Basel)

Complications of posterior cranial fossa decompression for Chiari malformations are uncommon. We present three patients who developed infratentorial supracerebellar hygromas causing acute hydrocephalus after posterior cranial fossa decompression., (Copyright 2002 S. Karger AG, Basel)

Oxidative stress is known to play an important role in the response of brain to traumatic insults. We tested the hypothesis that increased extracellular superoxide dismutase (EC-SOD) expression can reduce injury in a mouse model of closed head injury. Neurologic, cognitive, and histologic outcomes were compared between transgenic mice exhibiting a fivefold increase in EC-SOD activity and wild-type littermate controls. Severe or moderate transcranial impact was induced in anesthetized and physiologically controlled animals. After severe impact, transgenic mice had better neurological outcome at 24 hr postinjury (p = 0.038). Brain water content was increased, but there was no difference between groups. Moderate impact resulted in predominantly mild neurologic deficits in both groups at both 24 hr and 14 days postinjury. Morris water maze performance, testing cognitive function at 14-17 days after trauma, was better in EC-SOD overexpressors (p = 0.018). No differences were observed between groups for histologic damage in hippocampal CA1 and CA3. We conclude that EC-SOD has a beneficial effect on behavioral outcome after both severe and moderate closed head injury in mice. Because EC-SOD is believed to be predominantly located in the extracellular space, these data implicate an adverse effect of extracellular superoxide anion on outcome from closed head injury.

Background: Although reduction of cerebral metabolic rate is thought to contribute to anesthetic neuroprotection, histologic evidence to support this concept has not been provided. In this study, histologic outcome was evaluated in rats subjected to different durations of severe forebrain ischemia while anesthetized with volatile anesthetics that have substantially different effects on cerebral metabolic rate., Methods: Normothermic rats that underwent fasting were anesthetized with 0.75 minimum alveolar concentration (MAC) isoflurane-60% nitrous oxide (N2O) or 0.75 MAC halothane-60% N2O. Ischemia was induced with use of a combination of bilateral carotid occlusion and controlled hypotension. Rats in the isoflurane group were subjected to 6.5 min or 8.0 min ischemia, whereas the halothane group received 6.5 min ischemia. Histologic damage was assessed 4 days later., Results: With 6.5 min ischemia, mean +/- SD, hippocampal CA1 percent of dead (% dead) neurons was reduced with isoflurane-N2O (45 +/- 18) versus halothane-N2O (60 +/- 23, P = 0. 023). Eight minutes of ischemia increased % dead neurons in the isoflurane-N2O group (60 +/- 17, P = 0.017). There was no difference between the isoflurane 8.0-min and halothane 6.5-min groups (P = 0. 935). A similar pattern was observed in hippocampal CA4 and the neocortex. Striatal damage was not affected by anesthetic or ischemic duration., Conclusions: At 6.5 min ischemia, isoflurane provided improved outcome versus halothane. Previous research has shown that 0.75 MAC isoflurane-N2O increases the time to onset of ischemic depolarization by 1.5 min and reduces cerebral metabolic rate by 42% versus 0.75 MAC halothane-N2O. In the current study, when the duration of ischemia was increased by 1.5 min in the isoflurane-N2O group, histologic outcome became similar to that in halothane-N2O-anesthetized rats. These results provide evidence that cerebral metabolic rate reduction has an advantageous effect on outcome from severe brain ischemia, but also suggest that such benefit is likely to be small.

Genetically engineered mice are increasingly important in stroke research. The strains on which these constructs are built are known to have inherent differential sensitivities to ischemic insults. This has been largely attributed to differences in vascular anatomy. This study compared the outcome from forebrain ischemia in two common murine background strains using two different types of ischemic insult. C57Bl/6 and SV129 mice were subjected to two vessel (bilateral carotid) occlusion (2VO) or 2VO plus systemic hypotension (2VO+Hypo; mean arterial pressure=30+/-2 mmHg) for 10-20 min. Ventilation and pericranial temperature were controlled. Cerebral blood flow (CBF) was determined by 14C-iodoantipyrine autoradiography. Histologic damage in forebrain structures was measured 3 days post-ischemia. During 2VO+Hypo, the EEG became isoelectric in all animals. During 2VO alone, EEG isoelectricity occurred in 73% of C57Bl/6 and 50% of SV129 mice. Forebrain CBF was reduced to a similar extent in both strains. Greater CBF variability was seen with 2VO alone versus 2VO+Hypo. CBF was less in the 2VO+Hypo model. SV129 mice had wider posterior communicating but smaller basilar artery diameters. With or without hypotension, SV129 mice had markedly less severe histologic damage than C57Bl/6 mice. A time-dependent increase in histologic damage was demonstrated in the 2VO+Hypo model but not with 2VO alone. The 2VO and 2VO+Hypo models produced similar magnitudes of histologic injury in C57Bl/6 mice subjected to 10-min ischemia. SV129 mice were resistant to ischemia in either model. The 2VO+Hypo model produced a more uniform severity of ischemia as defined by CBF and EEG examination. Despite this, the murine strain had a substantially greater impact on histologic outcome than did cerebrovascular anatomy or the type of model used to produce the ischemic insult.

A simple and safe technique for performing an endoscopic third ventriculocisternostomy is described using a small-diameter semirigid neuroendoscope in conjunction with a perforated ventricular catheter to bluntly fenestrate the floor of the third ventricle. All previous descriptions involve the initial use of an introducer sheath that in our experience lends to loss of cerebrospinal fluid, consequently distorting the anatomic landmarks of the third ventricle as well as compromising the crucial concave shape of its floor. Our technique limits the loss of cerebrospinal fluid volume, therefore, reducing the chance of basilar artery complex perforation as a consequence of distortion of third ventricular landmarks and loss of third ventricular floor concavity.

Optimal treatment of the hydrocephalic patient with symptomatic Dandy-Walker malformation or trapped fourth ventricle remains controversial. We describe 6 patients with symptomatic Dandy-Walker malformation or trapped fourth ventricle and hydrocephalus that were treated with an aggressive cyst fenestration. Four of the 6 patients had previously undergone five or more failed shunt procedures. There were no complications associated with surgery, and 5 of the 6 patients (83%) have remained asymptomatic with respect to their posterior fossa cysts. One patient has required subsequent fourth ventricular shunt placement. Median follow-up was 26 months (range 12-66 months). We suggest that suboccipital craniectomy and open fenestration is a valid treatment option in hydrocephalic patients with symptomatic Dandy-Walker malformation or trapped fourth ventricle. Although the associated lateral ventriculomegaly will probably still require a ventriculoperitoneal shunt, the absence of a cystoperitoneal shunt system seems to minimize the incidence of complications and reoperation.