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Dachling Pang and Paul A. Grabb

✓ Long-term patency of the ventricular catheter of a cerebrospinal fluid shunt depends on the positioning of the hole-bearing segment of the catheter. Placement of this segment near the choroid plexus or injured ependyma increases the probability of obstruction. Proper positioning for a coronal shunt in turn depends on the ventricular catheter length and target coordinates. The authors describe a method of calculating the catheter length based on bone landmarks on skull radiographs, and a technique for accurate ventricular catheter placement using free-hand passage guided by simple stereotactic coordinates based on visible and palpable surface anatomy. The insertion trajectory is aligned with the coronal obliquity of the lateral ventricle so that, even with slit ventricles, the entire hole-bearing segment of the catheter can be reliably situated within the anterior horn. The predetermined catheter length also fixes the tip at the foramen of Monro, away from the choroid plexus and injured ependyma.

Of 160 children undergoing ventriculoperitoneal shunt insertion using this technique, only three required catheter revision during a mean follow-up period of 39 months. Radiographic grading of the ventricular catheter position in 112 children showed a satisfactory placement rate of 93.2%; all three children with occlusion showed poor catheter positioning. Thus, this method results in accurate ventricular catheter placement with a 1.9% obstruction rate, which compares favorably to the 16% to 18% incidence of proximal obstruction reported in the literature. This technique is applicable to patients of all ages but is particularly suitable for children because of the greater variability in head size.

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Paul A. Grabb, A. Leland Albright and Basil J. Zitelli

✓ The authors present an unusual case in which increased intracranial pressure developed because of multiple-suture craniosynostosis and megaloencephaly in a child with a previously undiagnosed lysosomal storage disease, α-d-mannosidase deficiency. This 3-year-old boy presented with a history of frequent naps, headaches, florid papilledema, enlarged head (> 95th percentile), elevated opening pressure by lumbar puncture, a “beaten copper” appearance on skull radiographs, and no hydrocephalus. Multiple synostectomies were performed. Postoperatively, the child's headaches and papilledema resolved and his level of physical activity increased dramatically. The authors discuss the paradoxical presentation of prematurely fused sutures and macrocrania in light of this lysosomal storage disease and its subsequent management.

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Paul A. Grabb and Mark R. Gilbert

✓ The authors investigated the effects of glioma cells and pharmacological agents on the permeability of an in vitro blood-brain barrier (BBB) to determine the following: 1) whether malignant glia increase endothelial cell permeability; 2) how glucocorticoids affect endothelial cell permeability in the presence and absence of malignant glia; and 3) whether inhibiting phospholipase A2, the enzyme that releases arachidonic acid from membrane phospholipids, would reduce any malignant glioma—induced increase in endothelial cell permeability.

Primary cultures of rat brain capillary endothelium were grown on porous membranes; below the membrane, C6, 9L rat glioma, T98G human glioblastoma, or no cells (control) were cocultured. Dexamethasone (0.1 µM), bromophenacyl bromide (1.0 µM), a phospholipase A2 inhibitor, or nothing was added to culture media 72 hours prior to assaying the rat brain capillary endothelium permeability. Permeability was measured as the flux of radiolabeled sucrose across the rat brain capillary endothelium monolayer and then calculated as an effective permeability coefficient (Pe). When neither dexamethasone nor bromophenacyl bromide was present, C6 cells reduced the Pe significantly (p < 0.05), whereas 9L and T98G cells increased Pe significantly (p < 0.05) relative to rat brain capillary endothelium only (control). Dexamethasone reduced Pe significantly for all cell preparations (p < 0.05). The 9L and T98G cell preparations coincubated with dexamethasone had the lowest Pe of all cell preparations. The Pe was not affected in any cell preparation by coincubation with bromophenacyl bromide (p > 0.45).

These in vitro BBB experiments showed that: 1) malignant glia, such as 9L and T98G cells, increase Pe whereas C6 cells probably provide an astrocytic influence by reducing Pe; 2) dexamethasone provided significant BBB “tightening” effects both in the presence and absence of glioma cells; 3) the in vivo BBB is actively made more permeable by malignant glia and not simply because of a lack of astrocytic induction; 4) tumor or endothelial phospholipase A2 activity is probably not responsible for glioma-induced increased in BBB permeability; and 5) this model is useful for testing potential agents for BBB protection and for studying the pathophysiology of tumor-induced BBB disruption.

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Paul A. Grabb, A. Leland Albright, Robert J. Sclabassi and Ian F. Pollack

The authors reviewed the results of continuous intraoperative electromyographic (EMG) monitoring of muscles innervated by cranial nerves in 17 children whose preoperative imaging studies showed compression or infiltration of the fourth ventricular floor by tumor to determine how intraoperative EMG activity correlated with postoperative cranial nerve morbidity. Bilateral lateral rectus (sixth) and facial (seventh) nerve musculature were monitored in all children. Cranial nerve function was documented immediately postoperatively and at 1 year.

Of the 68 nerves monitored, nine new neuropathies occurred in six children (sixth nerve in four children and seventh nerve in five). In five new neuropathies, intraoperative EMG activity could be correlated in one of four sixth nerve injuries and four of five seventh nerve injuries. Electromyographic activity could not be correlated in four children with new neuropathies. Of 59 cranial nerves monitored that remained unchanged, 47 had no EMG activity. Twelve cranial nerves (three sixth nerves and nine seventh nerves) had EMG activity but no deficit. Of four children with lateral rectus EMG activity, three had new seventh nerve injuries.

Lateral rectus EMG activity did not predict postoperative abducens injury. The absence of lateral rectus EMG activity did not assure preserved abducens function postoperatively. Likely because of the close apposition of the intrapontine facial nerve to the abducens nucleus, lateral rectus EMG activity was highly predictive of seventh nerve injury. Although facial muscle EMG activity was not an absolute predictor of postoperative facial nerve dysfunction, the presence of facial muscle EMG activity was associated statistically with postoperative facial paresis. The absence of facial muscle EMG activity was rarely associated with facial nerve injury. The authors speculate that EMG activity in the facial muscles may have provided important intraoperative information to the surgeon so as to avoid facial nerve injury.

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Paul A. Grabb, A. Leland Albright, Robert J. Sclabassi and Ian F. Pollack

✓ The authors reviewed the results of continuous intraoperative electromyographic (EMG) monitoring of muscles innervated by cranial nerves in 17 children whose preoperative imaging studies showed compression or infiltration of the fourth ventricular floor by tumor to determine how intraoperative EMG activity correlated with postoperative cranial nerve morbidity. Bilateral lateral rectus (sixth) and facial (seventh) nerve musculatures were monitored in all children. Cranial nerve function was documented immediately postoperatively and at 1 year.

Of the 68 nerves monitored, nine new neuropathies occurred in six children (sixth nerve in four children and seventh nerve in five). In five new neuropathies, intraoperative EMG activity could be correlated in one of four sixth nerve injuries and four of five seventh nerve injuries. Electromyographic activity could not be correlated in four children with new neuropathies. Of 59 cranial nerves monitored that remained unchanged, 47 had no EMG activity. Twelve cranial nerves (three sixth nerves and nine seventh nerves) had EMG activity but no deficit. Of four children with lateral rectus EMG activity, three had new seventh nerve injuries.

Lateral rectus EMG activity did not predict postoperative abducens injury. The absence of lateral rectus EMG activity did not assure preserved abducens function postoperatively. Likely because of the close apposition of the intrapontine facial nerve to the abducens nucleus, lateral rectus EMG activity was highly predictive of seventh nerve injury. Although facial muscle EMG activity was not an absolute predictor of postoperative facial nerve dysfunction, the presence of facial muscle EMG activity was associated statistically with postoperative facial paresis. The absence of facial muscle EMG activity was rarely associated with facial nerve injury. The authors speculate that EMG activity in the facial muscles may have provided important intraoperative information to the surgeon so as to avoid facial nerve injury.

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Bermans J. Iskandar, Gary L. Hedlund, Paul A. Grabb and W. Jerry Oakes

Object. To provide more information about this rare condition, the authors describe five cases of syringohydromyelia without hindbrain herniation. Preoperative magnetic resonance imaging with and without gadolinium—diethylenetriamine pentaacetic acid revealed no evidence of spinal cord tumor, arachnoiditis, or spinal dysraphism.

Methods. Craniocervical decompression was performed in all patients, after which there was resolution of the symptoms in the four symptomatic patients, and all five showed marked reduction in the size of the syrinx.

Conclusions. The authors hypothesize the rare occurrence of syringohydromyelia resulting from a Chiari-like pathophysiological condition but lacking a hindbrain hernia. Patients with this condition may benefit from craniocervical decompression.

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Bermans J. Iskandar, Gary L. Hedlund, Paul A. Grabb and W. Jerry Oakes

Object

To provide more information about this rare condition, the authors describe five cases of syringohydromyelia without hindbrain herniation. Preoperative magnetic resonance imaging with and without gadolinium-diethylenetriamine pentaacetic acid revealed no evidence of spinal cord tumor, arachnoiditis, or spinal dysraphism.

Methods

Craniocervical decompression was performed in all patients, after which there was resolution of the symptoms in the four symptomatic patients, and all five showed marked reduction in the size of the syrinx.

Conclusions

The authors hypothesize the rare occurrence of syringohydromyelia resulting from a Chiari-like pathophysiological condition but lacking a hindbrain hernia. Patients with this condition may benefit from craniocervical decompression.

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R. Shane Tubbs, Paul Grabb, Alan Spooner, Wally Wilson and W. Jerry Oakes

Object. The authors conducted a study to describe the detailed anatomy of the apical ligament and to acknowledge or refute its historical description as a functionally significant contributor to craniocervical stability.

Methods. In 20 adult human cadavers measurements of the apical ligament were obtained, and its detailed anatomy was observed. Ranges of motion were also assessed to discern the function of the apical ligament.

Conclusions. Results of the study support the concept that the apical ligament is best described as a vestigial structure that offers no significant added stability to the craniocervical junction. In fact, this ligament was absent in 20% of the specimens examined. These data will aid physicians who frequently view images or manage clinical problems of the craniocervical junction because they may focus on other ligaments of this area and not the apical ligament.

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Michael J. Rauzzino, R. Shane Tubbs, Eben Alexander III, Paul A. Grabb and W. Jerry Oakes

Object

Neurenteric cysts are infrequently reported congenital abnormalities believed to be derived from an abnormal connection between the primitive endoderm and ectoderm. The authors report a series of 13 patients treated over a 50-year period.

Methods

Of the 13 patients, seven were female and six were male. Their ages at presentation ranged widely from 5 weeks to 52 years of age. Children presented more commonly with cutaneous stigmata of occult spinal dysraphism (OSD) whereas adults presented primarily with pain. Neurological deficit as a presenting symptom was less common in our series, a finding that reflects the slow growth of these lesions. In all but one patient some form of vertebral anomaly was associated with the cystic lesions, including two patients with Klippel–Feil abnormalities. There was a high incidence of associated forms of OSD including split cord malformation, lipoma, dermal sinus tract, and tethered spinal cord. In previous reports the authors have suggested that neurenteric cysts are more common in the cervical region and in a position ventral to the cord. In the present series these cysts most commonly occurred as intradural, extramedullary masses in the thoracolumbar region, situated dorsal to the spinal cord. The median follow-up period was 7.5 years, and postoperative outcome reflected a patient's preoperative neurological status; in no patient was outcome worsened due to surgery.

Conclusions

Complete excision of the neurenteric cyst remains the treatment of choice, as subtotal excision is associated with recurrence.

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R. Shane Tubbs, George Salter, Paul A. Grabb and W. Jerry Oakes

Object. The authors conducted a study to examine the detailed anatomy of the denticulate ligaments and to assess their classic role in spinal cord stability within the spinal canal.

Methods. Detailed observation of the denticulate ligaments in 12 adult cadavers was performed. Stress was applied in all major planes to discern when the ligaments would become taut, and at the same time, gross motion of the cord was observed at sites distal to the stresses applied. Tension necessary for avulsion of the ligaments in various areas of the spinal cord was also measured.

Conclusions. These results show that the denticulate ligaments do not inhibit cord motion to such discrete areas of the cord as was once thought. The authors have determined that the ligaments are stronger in the cervical region and that they decrease in strength as the spinal cord descends. These findings are demonstrative of the denticulate ligaments being more resistant to caudal compared with cephalad stresses in the cord. Anterior and posterior motion is constrained by these ligaments but to a limited degree, especially as one descends inferiorly along the cord. Further embryological and functional studies of these ligaments is needed in non—formalin fixed tissues.