Prasad Vannemreddy

OBJECT: The goal of this study was to determine whether drilling out the occipital condyle facilitates surgery via the far-lateral approach by comparing data from 10 clinical cases with that from studies of eight cadaver heads. METHODS: During the last 6 years at Louisiana State University Health Sciences Center-Shreveport, 10 patients underwent surgery via the far-lateral approach to the foramen magnum. Six of these patients harbored anterior foramen magnum meningiomas, one patient a dermoid cyst, two patients vertebral artery (VA) aneurysms, and an additional patient suffered from rheumatoid disease of the craniocervical junction. The surgical approach consisted of retromastoid craniectomy and C-1 laminectomy. The seven tumors and the pannus of rheumatoid disease were completely excised, and the two aneurysms were clipped without drilling the occipital condyle. In one patient a chronic subdural hematoma was found 3 months after surgery, but no patient displayed any complication associated with surgery. It is significant that in no patient was a cerebrospinal fluid leak present. All patients experienced improved neurological function postoperatively. To compare surgical visibility, eight cadaveric specimens (16 sides) were studied, including delineation of the VA and its segments around the craniocervical junction. Increase in visibility as a function of fractional removal of the occipital condyle was quantified by measuring the degrees of visibility gained by removing one third and one half of the occipital condyle. Removal of one third of the occipital condyle produced a mean increase of 15.9 degrees visibility, and removal of one half produced a mean increase of 19.9 degrees. CONCLUSIONS: On the basis of their findings the authors conclude that removal of the occipital condyle is not necessary for the safe and complete resection of anterior intradural foramen magnum tumors.

OBJECT: Hydrocephalus is a notorious neurosurgical disease that carries the adage "once a shunt always a shunt." This study was conducted to review the treatment results of pediatric hydrocephalus. METHODS: Pediatric patients who underwent ventriculoperitoneal shunt surgery over the past 14 years were reviewed for shunt revisions. Variables studied included age at shunt placement, revision, or replacement; programmable shunts; infection; obstruction; and diagnosis (congenital, posthemorrhagic, craniospinal dysraphism, and others including trauma, tumors, and infection). Multiple regression analysis methods were used to determine independent risk factors for shunt failure and the number of shunt revisions. The Kaplan-Meier method of survival analysis was used to compare etiologies on the 5-year survival (revision-free) rate and the median 5-year survival time. RESULTS: A total of 253 patients were studied with an almost equal sex distribution. There were 92 patients with congenital hydrocephalus, 69 with posthemorrhagic hydrocephalus, 48 with craniospinal dysraphism, and 44 with other causes. Programmable shunts were used in 73 patients (other types of shunts were used in 180 patients). A total of 197 patients (78%) underwent revision surgeries due to shunt failures. The mortality rate was 1.6%. Age at first revision, the 5-year survival rate, and the median 5-year survival time were significantly less for both posthemorrhagic and craniospinal dysraphism than for either the congenital or "other" group (p < 0.05). The failure rate and number of revisions were not significantly reduced with programmable shunts compared with either pressure-controlled or no-valve shunts (p > 0.5). CONCLUSIONS: Posthemorrhagic hydrocephalus and craniospinal dysraphism hydrocephalus had significantly earlier revisions than congenital and other etiologies. Programmable systems did not reduce the failure rate or the average number of shunts revisions.

OBJECT: The purpose of this study was to evaluate the feasibility of the criteria described in the literature as the indications for surgery for acute Type II odontoid fractures. METHODS: The authors searched the PubMed database for studies in which the fusion rate of acute Type II odontoid fractures following external immobilization (halo vest or collar) or surgery (posterior C1-2 fusion or anterior screw fixation) was reported. The only studies included reported the fusion rate for either 1) groups of patients whose age was either more or less than a certain age range (45-55 years); or 2) groups of patients with a fracture displacement of either more or less than a certain odontoid fracture displacement (4-6 mm) or the direction of displacement (see Methods section of text for more details). A meta-analysis in which the random effect model was used was conducted to analyze the data. RESULTS: There was a statistically significantly higher fusion rate for operative management compared with external immobilization (85 vs 60%, p = 0.01) for the patients > 45-55 years. However, the overall fusion rate was > 80% for the patients whose age was < 45-55 years, regardless of treatment modality, and no significant differences were observed between surgically and nonsurgically treated patients (89 and 81%, respectively; p = 0.29). The result of operation (overall fusion rate 89%) was superior to external immobilization (44%) when the fracture was posteriorly displaced (p < 0.001), but for anteriorly displaced fractures, the results of operative and nonoperative management were identical (p = 0.15). The overall fusion rate of operative management of both anteriorly and posteriorly displaced fractures proved to be > 85%, and no statistically significant difference was observed (p = 0.50). For all degrees of displacement (either > or < 4-6 mm) the operation proved to provide significantly better results than conservative treatment. The fusion rate of conservatively treated fractures with < 4-6 mm displacement was significantly better than in fractures with > 4-6 mm displacement (76 vs 41%, p = 0.002). CONCLUSIONS: Operative treatment (posterior C1-2 fixation or anterior screw fixation) provides a better fusion rate than external immobilization for acute odontoid Type II fractures, although in certain situations, such as anterior displacement of the fracture and for younger (< 45-55 years of age) patients, conservative management (halo vest or collar immobilization) can be as effective as surgery. Operative management is recommended in older patients, in cases of posterior displacement of the fracture, and when there is displacement of > 4-6 mm.

OBJECTIVE: The outcome of subarachnoid hemorrhage associated with cocaine abuse is reportedly poor. However, no study in the literature has reported the use of a statistical model to analyze the variables that influence outcome. METHODS: A review of admissions during a 6-year period revealed 14 patients with cocaine-related aneurysms. This group was compared with a control group of 135 patients with ruptured aneurysms and no history of cocaine abuse. Age at presentation, time of ictus after intoxication, Hunt and Hess grade of subarachnoid hemorrhage, size of the aneurysm, location of the aneurysm, and the Glasgow Outcome Scale score were assessed and compared. RESULTS: The patients in the study group were significantly younger than the patients in the control group (P < 0.002). In patients in the study group, all aneurysms were located in the anterior circulation. The majority of these aneurysms were smaller than those of the control group (8 +/- 6.08 mm versus 11 +/- 5.4 mm; P = 0.05). The differences in mortality and morbidity between the two groups were not significant. Hunt and Hess grade (P < 0.005) and age (P < 0.007) were significant predictors of outcome for the patients with cocaine-related aneurysms. CONCLUSION: Cocaine use predisposed aneurysmal rupture at a significantly earlier age and in much smaller aneurysms. Contrary to the published literature, this group did reasonably well with aggressive management.

OBJECTIVES: We present patient test outcomes to show that on-off control of deep brain stimulation sequences in essential tremor patients is achievable in a self-adaptive manner via non-invasive surface-electromyography, to prevent tremors in these patients. METHOD: In our study, an essential tremor patient, who underwent bilateral deep brain stimulation implantation 8 years earlier, was subjected to deep brain stimulation at 130 pulses/second, with a 90-microsecond pulse-width, in packets of durations from 20 to 73 seconds and was monitored with surface-electromyography. RESULTS: At the end of these stimulation packets, tremor-free intervals followed, averaging over 20 seconds, before tremor reappeared. Wavelet analysis of the eletromyographic signals allowed predicting onset of tremors at the end of the tremor-free intervals and was successful in all test cycles. Furthermore, once stimulation was restarted, the tremors disappeared within 0.5 seconds on average. When restarting stimulation approximately 2 seconds ahead of the end of tremor-free post-simulation intervals as predicted by visual inspection of unprocessed electromyograms, no tremors occurred during three successive cycles of stimulation-on and stimulation-off. Maximal ratio of tremor-free duration to stimulation duration was computed, to determine a best DBS (deep brain stimulation) duration range (20-35 seconds). CONCLUSIONS: We show existence of a tremor-free interval averaging over 20 seconds that follows applying stimulation packets of 20-35 seconds and that surface electomyogram allows predicting onset of tremor to facilitate activation of a next stimulation packet before tremor reappears. This establishes the feasibility of electromyographic-based predictive on-off control of deep brain stimulation in certain essential tremor patients. Best tremor-free duration to stimulation duration ratio may differ over the progression of the disorder and from patient to patient.