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There are scant data in the literature regarding distances from the midline to the suboccipital segment of the vertebral artery, and to our knowledge, none addressing this measurement in the pediatric population. This study seeks to establish age-related distances (Y) from the laterally placed vertebral artery to the midline at the level of the posterior arch of the atlas in children. Measurements from the midline to the most medial portion of the vertebral artery at the level of the posterior arch of the atlas were made in 50 children who underwent CT imaging of the cervical spine. For all left sides, Y = 12-23 mm (mean 17 mm). For all right sides, Y = 10-25 mm (mean 17.5 mm). For girls, Y = 12-16 mm (mean 12.7 mm) for left sides and Y = 12-25 mm (mean 18.5 mm) for right sides. For boys, Y = 12-20 mm (mean 16 mm) for left sides and Y = 10-21 mm (mean 16.7 mm) for right sides. We have found that the most medial portion of the vertebral artery from the midpoint of the posterior arch of the atlas for all ages was approximately 17 and 17.5 mm for left and right sides, respectively. This distance was generally less for left sides, except in the 16-19 years age group. However, as a group, this distance did not vary more than 2.8 mm between left and right sides. These data should assist the neurosurgeon who operates in the suboccipital region in children., (Copyright 2003 S. Karger AG, Basel)

The authors report a patient with type II split cord malformation (SCM) and Klippel-Feil syndrome (KFS). Considering our review of the medical literature and present case report, we believe lumbar SCM and KFS in the same patient not to be coincidental findings but rather embryologically related entities. We propose that KFS in at least one of its phenotypes represents a forme fruste of occult spinal dysraphism., (Copyright 2003 S. Karger AG, Basel)

Objective: We review our experience of endoscopic third ventriculocisternostomy (ETV) in children with hydrocephalus from central nervous system (CNS) infection or intraventricular hemorrhage to better elucidate success rates and predictors of success in these children., Methods: We performed a retrospective review of 12 children less than 21 years of age with ETV treated from 1999 to 2002 with a minimum follow-up of 12 months. Children selected for surgery had been diagnosed with hydrocephalus from perinatal germinal matrix hemorrhage or CNS infection and had neuroimaging consistent with obstruction of the aqueduct, fourth ventricular outlets or both at the time of ETV. Charts and imaging studies were reviewed to determine clinical outcomes and predictors of successful ETV. An ETV was deemed successful if the child did not require placement or replacement of a ventriculoperitoneal shunt., Results: Thirteen ETV were performed in 12 patients (7 boys and 5 girls; mean age 9.2 years, range 3.8-21 years), with an overall success rate of 60% for those with CNS infections and 71% for those with perinatal intraventricular hemorrhage at initial presentation. There were no significant complications from the procedure., Conclusions: ETV is a safe procedure, which in carefully selected children with etiologies of hydrocephalus thought to be 'communicating' in nature carries a satisfyingly high success rate. Further application and study of this modality in larger groups of patients with these causes of hydrocephalus is warranted., (Copyright 2003 S. Karger AG, Basel)

We report a pediatric patient who presented with hypogonadism and diabetes insipidus. Further evaluation revealed hypothyroidism. MRI of the brain revealed a suprasellar mass. Following frontal craniotomy for mass biopsy, histological analysis of the mass revealed benign lymphoid hyperplasia. The patient has had no progression of his mass or symptoms at most recent follow-up (10 months). We review this unusual case and other similar conditions. We believe this to be the first reported case of lymphoid hyperplasia without malignant cells of the suprasellar region., (Copyright 2003 S. Karger AG, Basel)

We report a 2-week-old male with a large cystic mass in the left cervical and face region. No connection to the brain or spinal cord was discernable either at operation or on imaging. Histological study of this mass revealed central nervous tissue including neuroglia, ependymal cells, non-neuroblastic neurons, pigmented retinal epithelium, and choroid plexus. This case represents the rare ectopic 'brain'. We review this case as well as the literature concerning these unusual masses., (Copyright 2003 S. Karger AG, Basel)

The subgaleal shunt has been used for the temporary bypass of the normal cerebrospinal fluid (CSF) pathways. We retrospectively reviewed all subgaleal shunts placed at the Children's Hospital, Birmingham, Ala., USA, from 1997 to the present and examined all uses (e.g. indication, length of follow-up) of the subgaleal shunt outside its use for temporary CSF diversion in premature infants with intraventricular hemorrhage and subsequent hydrocephalus. The average length of survival of the primary subgaleal shunt in this population was 32.2 days. We have had good success with subgaleal shunts in children with malignant brain tumors, intraventricular abscesses, chronic truncal wounds, chronic subdural hygromas and meningitis. However, the greatest utility has been in those scenarios in which the peritoneal cavities were not currently, but with time would be, candidates for distal shunt implantation. Examples of these instances are patients with hydrocephalus and necrotizing enterocolitis or hydrocephalus and preoperative abdominal wall pathology such as omphalocele., (Copyright 2003 S. Karger AG, Basel)

Objective: The posterior fossa (PF) has been found to be small in various forms of Chiari malformation. Explanations involving a connection between growth hormone deficiency (GHD) and Chiari I malformation (CIM) have been proposed. However, to date, no quantitative analysis of the PF of patients with CIM and GHD has been performed. Our study was performed to determine the geometry of the PF in children with GHD and CIM., Methods: Morphometric analysis of the PF was performed in 10 children with GHD and CIM (group 1), 20 children with GHD and no CIM (group 2) and 50 controls., Results: PF volumes for group 1 ranged from 128 to 259 +/- 33 ml, and for group 2, they ranged from 115 to 186.2 +/- 25.4 ml. Lengths of the foramen magnum for groups 1 and 2 had means of 36 and 38 mm, respectively. The mean basiocciput length and tentorial angle for groups 1 and 2 were 20 and 19 mm and 89 and 87.5 degrees, respectively., Conclusions: We have determined that children with GHD with or without CIM have no significant difference in their PF volume compared to controls. However, our data demonstrate significant underdevelopment of portions of the bony PF in both patients with GHD alone and in patients with GHD and CIM. Tentorial angles were elevated in noncontrol groups. We propose that this association is not due to an increased rate of 'midline' defects seen in GHD but rather a structurally distorted PF that is not capacious enough to house the entire developing rhombencephalon. These data will hopefully aid in the further understanding of the pathophysiology of CIM., (Copyright 2003 S. Karger AG, Basel)

We report two children with hemihypertrophy and Chiari I malformation (CIM) and review the extant medical literature regarding CIM and overgrowth disorders. We propose that these two entities do not represent a spurious association but rather share a common dysembryology of mesoderm., (Copyright 2003 S. Karger AG, Basel)

The subgaleal shunt has been and is currently used for the temporary bypass of the normal cerebrospinal fluid (CSF) pathways. We retrospectively reviewed all subgaleal shunts placed at the Children's Hospital, Birmingham, Ala., USA, from 1993 to the present and examined the life expectancy of revisions of this temporary method of CSF diversion. The average length of survival of primary, secondary and tertiary subgaleal shunts in this population was 37.4, 32.4 and 19.6 days, respectively. This current review demonstrates that the majority of patients in whom a subgaleal shunt is utilized may continue to obtain therapeutic diversion of their CSF for greater than 2.5 months with intermittent subgaleal shunt revisions. In the majority of cases, this length of time is sufficient to manage and resolve issues that would make ventriculoperitoneal shunting undesirable., (Copyright 2003 S. Karger AG, Basel)

The posterior atlanto-occipital membrane (PAO) contributes little to craniocervical stability and is generally underappreciated and incised with most suboccipital craniectomies. We report a case of a child who underwent posterior fossa decompression for Chiari I malformation with syringomyelia whose symptoms had not resolved months after surgery. A secondary exploratory operation revealed a healed constricting PAO which had been incised linearly at the initial operation. This patient's symptoms improved soon after the second surgery. We propose that attention be given to this membrane, and if it is incised with underlying dura mater as in a standard posterior fossa decompression, it should be removed or cauterized separately and laterally to inhibit its reformation., (Copyright 2003 S. Karger AG, Basel)

Background: Optimal surgical management of patients presenting with shunt failure in the age of neuroendoscopy remains complex. The value of replacing the entire shunt system as opposed to a single shunt component has not been assessed., Methods: We reviewed the records of all pediatric patients who underwent their first shunt revision between January 1992 and December 1998. Patients with primary shunt failure attributed solely to proximal catheter obstruction or distal catheter obstruction were included for analysis. Shunt revisions were classified as total (entire shunt replaced) or partial (only malfunctioning component replaced). Kaplan-Meier (shunt survival curves) and log rank analysis were used to compare failure rates between partially and totally revised shunts according to the underlying diagnosis and failed shunt part. Significant differences in univariate analysis were confirmed with a multivariate proportional hazards regression model., Results: 301 pediatric patients underwent primary shunt revision (183 total, 118 partial revisions). All shunts utilized distal slit peritoneal catheters. In shunt failures attributed to proximal obstruction, reutilization of the distal catheter was associated with a 57% increased risk of subsequent shunt failure (hazard ratio 1.57, 95% confidence interval 1.19-3.49). In shunt failures attributed to distal obstruction, subsequent shunt survival was not affected by reutilization of the proximal catheter (p = 0.581). When stratified according to the etiology of hydrocephalus, only patients with intraventricular hemorrhage (IVH) failed to demonstrate greater survival of totally revised shunts., Conclusions: In this series, in the setting of proximal shunt catheter obstruction, reutilizing the functional distal catheter was associated with an increase in subsequent shunt failure rates compared to revising the entire shunt system. Total revision was not associated with improved shunt survival in patients with IVH., (Copyright 2003 S. Karger AG, Basel)

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)

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)

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)

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.