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R. Shane Tubbs, E. George Salter, John C. Wellons III, Jeffrey P. Blount and W. Jerry Oakes

Object. Reports describing surgical landmarks with which to identify the branches of the lumbar plexus found on the posterior abdominal wall are lacking in the English-language literature.

Methods. The authors examined 22 sides from six female and five male cadavers. Measurements were made between the branches of the lumbar plexus and various bone landmarks such as the midline vertebral bodies, supracristal plane—a horizontal line connecting the superior-most aspect of the left and right iliac crests approximating the L4–5 vertebrae—and anterior superior iliac spine (ASIS).

The mean distances from the midline and as they emerged through or lateral to the psoas major muscle to the subcostal, iliohypogastric, ilioinguinal, lateral femoral cutaneous, genitofemoral, and femoral nerves, were 5.5, 6, 6.5, 6, 4.5, and 4.5 cm, respectively. At a vertical line through the midpoint between the ASIS and the midline, the subcostal, iliohypogastric, and ilioinguinal nerves were superior to the supracristal plane at mean distances of 8, 4, and 5 cm, respectively. Inferior to the supracristal plane and in a vertical line through a midpoint between the ASIS and the midline, the lateral femoral and femoral nerves were found to have mean distances of 5 and 5.5 cm, respectively. The obturator nerve had a mean distance of 3 cm lateral to the midline. Additionally, the lateral femoral cutaneous nerve had a mean distance of 1.5 cm inferomedial to the ASIS.

Conclusions. A good working knowledge of the locations and anatomy of the nerves of the lumbar plexus on the posterior abdominal wall is necessary for the surgeon who operates in this region. The measurements provided herein will aid the surgeon who wishes to expose or avoid these nerves, thus precluding injury.

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R. Shane Tubbs, John C. Wellons III, Jeffrey P. Blount, Paul A. Grabb and W. Jerry Oakes

✓The authors report on three pediatric patients with ventriculoperitoneal (VP) shunts who presented with chronic right shoulder pain. Imaging revealed that the distal peritoneal catheter was positioned between the right hemidiaphragm and liver. Following surgical repositioning of the distal tubing, all patients experienced resolution of their shoulder pain, which has not recurred. Although seemingly rare, referred shoulder pain from a VP shunt should be added to the list of complications seen with this method of cerebrospinal fluid diversion. The clinician who cares for patients with VP shunts may wish to evaluate cases of shoulder pain without obvious neural or musculoskeletal cause by performing imaging of the distal shunt tubing.

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R. Shane Tubbs, John C. Wellons III, Jeffrey P. Blount, Paul A. Grabb and W. Jerry Oakes

✓The authors report on three pediatric patients with ventriculoperitoneal (VP) shunts who presented with chronic right shoulder pain. Imaging revealed that the distal peritoneal catheter was positioned between the right hemidiaphragm and liver. Following surgical repositioning of the distal tubing, all patients experienced resolution of their shoulder pain, which has not recurred. Although seemingly rare, referred shoulder pain from a VP shunt should be added to the list of complications seen with this method of cerebrospinal fluid diversion. The clinician who cares for patients with VP shunts may wish to evaluate cases of shoulder pain without obvious neural or musculoskeletal cause by performing imaging of the distal shunt tubing.

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R. Shane Tubbs, John C. Wellons III, Jeffrey P. Blount and W. Jerry Oakes

✓The authors present three children born with myelomeningocele and hydrocephalus. Each presented with symptoms/signs of ventriculoperitoneal shunt malfunction. All patients at the time of presentation exhibited significant urinary bladder infections and were appropriately treated for their infection. No patient was found to have an underlying shunt infection. All patients without medically threatening symptoms were carefully observed and noted to have resolution of their shunt dysfunction symptoms/signs following treatment of their urinary bladder infections and thus did not undergo a shunt operation.

Based on the courses of these patients, we believe that significant urinary bladder infection in patients with myelodysplasia in whom a shunt has been placed may often be enough to bring a subclinical shunt malfunction to clinical attention or even to be the cause of temporary distal peritoneal shunt malabsorption. Although the exact mechanism for this dysfunction is unclear, treatment of the bladder infection may address the symptomatic shunt dysfunction in some patients so as to avoid operative intervention. We emphasize, however, that careful observation of these patients should be performed during hospitalization because they often rely on adequate cerebrospinal fluid diversion. Only patients with mild symptomatology should be observed first as the initial line of treatment.

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R. Shane Tubbs, John C. Wellons III, Jeffrey P. Blount and W. Jerry Oakes

✓The authors present three children born with myelomeningocele and hydrocephalus. Each presented with symptoms/signs of ventriculoperitoneal shunt malfunction. All patients at the time of presentation exhibited significant urinary bladder infections and were appropriately treated for their infection. No patient was found to have an underlying shunt infection. All patients without medically threatening symptoms were carefully observed and noted to have resolution of their shunt dysfunction symptoms/signs following treatment of their urinary bladder infections and thus did not undergo a shunt operation.

Based on the courses of these patients, we believe that significant urinary bladder infection in patients with myelodysplasia in whom a shunt has been placed may often be enough to bring a subclinical shunt malfunction to clinical attention or even to be the cause of temporary distal peritoneal shunt malabsorption. Although the exact mechanism for this dysfunction is unclear, treatment of the bladder infection may address the symptomatic shunt dysfunction in some patients so as to avoid operative intervention. We emphasize, however, that careful observation of these patients should be performed during hospitalization because they often rely on adequate cerebrospinal fluid diversion. Only patients with mild symptomatology should be observed first as the initial line of treatment.

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R. Shane Tubbs, Cheryl R. Killingsworth, Dennis L. Rollins, William M. Smith, Raymond E. Ideker, John C. Wellons III, Jeffrey P. Blount and W. Jerry Oakes

Object. Vagus nerve stimulation is known to decrease the frequency, duration, and intensity of some types of intracranial seizures in both humans and animals. Although many theories abound concerning the mechanism for this action, the true cause remains speculative. To potentially elucidate a pathway in which vagus nerve stimulation aborts seizure activity, seizures were initiated not in the cerebral cortex but in the spinal cord and then vagus nerve stimulation was performed.

Methods. Ten pigs were anesthetized and placed in the lateral position, and a small laminectomy was performed in the lumbar region. Topical penicillin, a known epileptogenic drug to the cerebral cortex and spinal cord, was applied to the dorsal surface of the exposed cord. With the exception of two animals that were used as controls, once seizure activity was discernible via motor convulsion or increased electrical activity the left vagus nerve, which had been previously isolated in the neck, was stimulated. Following multiple stimulations of the vagus nerve and with seizure activity confirmed, the cord was transected in the midthoracic region and vagus nerve stimulation was performed.

Vagus nerve stimulation resulted in cessation of spinal cord seizure activity in all (87.5%) but one experimented animal. Transection of the spinal cord superior to the site of seizure induction resulted in the ineffectiveness of vagus nerve stimulation to cause cessation of seizure activity in all study animals.

Conclusions. The effects of vagus nerve stimulation on induced spinal cord seizures involve descending spinal pathways. The authors believe that this experiment is the first to demonstrate that spinal cord neuronal hyperactivity can be suppressed by stimulation of a cranial nerve. These data may aid in the development of alternative mechanisms for electrical stimulation in patients with medically intractable seizures. Further studies are now necessary to isolate which specific tracts, nuclei, and neurotransmitters are involved in this process.

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R. Shane Tubbs, Cheryl R. Killingsworth, Dennis L. Rollins, William M. Smith, Raymond E. Ideker, John C. Wellons III, Jeffrey P. Blount and W. Jerry Oakes

Object

Vagus nerve stimulation is known to decrease the frequency, duration, and intensity of some types of intracranial seizures in both humans and animals. Although many theories abound concerning the mechanism for this action, the true cause remains speculative. To potentially elucidate a pathway in which vagus nerve stimulation aborts seizure activity, seizures were initiated not in the cerebral cortex but in the spinal cord and then vagus nerve stimulation was performed.

Methods

Ten pigs were anesthetized and placed in the lateral position, and a small laminectomy was performed in the lumbar region. Topical penicillin, a known epileptogenic drug to the cerebral cortex and spinal cord, was applied to the dorsal surface of the exposed cord. With the exception of two animals that were used as controls, once seizure activity was discernible via motor convulsion or increased electrical activity the left vagus nerve, which had been previously isolated in the neck, was stimulated. Following multiple stimulations of the vagus nerve and with seizure activity confirmed, the cord was transected in the midthoracic region and vagus nerve stimulation was performed.

Vagus nerve stimulation resulted in cessation of spinal cord seizure activity in all (87.5%) but one experimented animal. Transection of the spinal cord superior to the site of seizure induction resulted in the ineffectiveness of vagus nerve stimulation to cause cessation of seizure activity in all study animals.

Conclusions

The effects of vagus nerve stimulation on induced spinal cord seizures involve descending spinal pathways. The authors believe that this experiment is the first to demonstrate that spinal cord neuronal hyperactivity can be suppressed by stimulation of a cranial nerve. These data may aid in the development of alternative mechanisms for electrical stimulation in patients with medically intractable seizures. Further studies are now necessary to isolate which specific tracts, nuclei, and neurotransmitters are involved in this process.

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R. Shane Tubbs, Matthew D. Smyth, John C. Wellons III and W. Jerry Oakes

Object. The literature contains scant data regarding variations in anatomy at the level of the foramen of Magendie in patients with Chiari I malformation and syringomyelia.

Methods. Based on their operative experience and hospital data, the authors detailed the incidence of arachnoid veils found in juxtaposition to the foramen of Magendie in patients with hindbrain herniation. Additionally, radiological studies were retrospectively reviewed in cases in which such an anomaly was noted intraoperatively.

Of 140 patients with Chiari I malformation who underwent decompressive surgery, an associated syrinx was demonstrated in 80 (57%). The foramen of Magendie was obstructed by an arachnoid veil in 10 (12.5%) of these patients; once the lesion was punctured, the cerebrospinal fluid drained freely from this median aperture. On retrospective review of imaging studies, none of these anomalous structures was evident. In all patients with an arachnoid veil and syringomyelia resolution of syringomyelia was revealed on postoperative imaging.

Conclusions. In the absence of a clear pathophysiology of syrinx production, the authors would recommend that patients with syringomyelia and Chiari I malformation undergo duraplasty so that, if present, these veils can be fenestrated.

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John C. Wellons III, Alyssa T. Reddy, R. Shane Tubbs, Hussein Abdullatif, W. Jerry Oakes, Jeffrey P. Blount and Paul A. Grabb

Object. Intracranial germinomas commonly occur in the pineal region, the floor of the third ventricle (hypothalamus), or both, and they are often associated with diabetes insipidus (DI). The authors conducted a study to correlate preoperative DI with the endoscopic and magnetic resonance (MR) imaging evidence of tumor on the third ventricle floor.

Methods. The authors reviewed hospital records, office charts, and MR imaging studies obtained in patients in whom a biopsy sampling procedure was performed with or without endoscopic third ventriculostomy (ETV) at Children's Hospital, Birmingham, Alabama between May 1998 and July 2002. Ten patients with the pathological diagnosis of pure germinoma were identified. Preoperative MR imaging findings and presenting symptoms were correlated with intraoperative neuroendoscopic findings.

Seven patients presented with symptomatic hydrocephalus and underwent concomitant ETV. Six patients presented with DI and MR imaging evidence of involvement of the third ventricle floor. Two patients presented with DI and no initial MR imaging evidence of neoplastic involvement of the third ventricle floor; in both there was endoscopic evidence of neoplastic involvement of the floor of the third ventricle. In two children without DI, neither MR imaging nor endoscopic evidence of involvement of the third ventricle floor was observed.

Conclusions. In the authors' experience with intracranial germinoma, endoscopic tumor biopsy sampling, and ETV provide an effective, safe, and minimally invasive means of obtaining diagnostic tissue and treating any concomitant hydrocephalus. The authors found that preoperative DI is an absolute predictor of neoplastic involvement of the hypothalamus regardless of MR imaging findings. Therefore, in the setting of DI and intracranial germinoma without neuroimaging evidence of hypothalamic involvement, germinomatous involvement of the hypothalamus should be assumed present, if not confirmed endoscopically at the time of biopsy sampling or third ventriculostomy, when devising adjuvant treatment plans for such patients.

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R. Shane Tubbs, John C. Wellons III, Jeffrey P. Blount, W. Jerry Oakes and Paul A. Grabb

✓ The authors report on the case of a patient evaluated for Valsalva maneuver—induced headache, dizziness, and ataxia. Neuroimaging revealed a Chiari I malformation without syringomyelia. A history of idiopathic hypertension was noted. After posterior fossa decompression, pathologically elevated blood pressure was absent, and at 24-month follow-up evaluation the patient remained normotensive. Although seemingly rare, this case illustrates that some patients with tonsillar ectopia may exhibit elevated blood pressure. Clinicians should consider hindbrain herniation a rare cause in idiopathic hypertension.