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John Diaz Day and Anil Nanda

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David E. Connor Jr., Menarvia Nixon, Anil Nanda and Bharat Guthikonda

Object

The authors conducted a study to evaluate the published results of vagal nerve stimulation (VNS) for medically refractory seizures according to evidence-based criteria.

Methods

The authors performed a review of available literature published between 1980 and 2010. Inclusion criteria for articles included more than 10 patients evaluated, average follow-up of 1 or more years, inclusion of medically refractory epilepsy, and consistent preoperative surgical evaluation. Articles were divided into 4 classes of evidence according to criteria established by the American Academy of Neurology.

Results

A total of 70 publications were reviewed, of which 20 were selected for review based on inclusion and exclusion criteria. There were 2 articles that provided Class I evidence, 7 that met criteria for Class II evidence, and 11 that provided Class III evidence.

The majority of evidence supports VNS usage in partial epilepsy with a seizure reduction of 50% or more in the majority of cases and freedom from seizure in 6%–27% of patients who responded to stimulation. High stimulation with a gradual increase in VNS stimulation over the first 6 weeks to 3 months postoperatively is well supported by Class I and II data. Predictors of positive response included absence of bilateral interictal epileptiform activity and cortical malformations.

Conclusions

Vagal nerve stimulation is a safe and effective alternative for adult and pediatric populations with epilepsy refractory to medical and other surgical management.

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Alexander R. Vaccaro

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Ali Nourbakhsh, Shashikant Patil, Prasad Vannemreddy, Alan Ogden, Debi Mukherjee and Anil Nanda

Object

Anterior screw fixation of the Type II odontoid fracture stabilizes the odontoid without restricting the motion of the cervical spine. The metal screw may limit bone remodeling because of stress shielding (if not placed properly) and limit imaging of the fracture. The use of bioabsorbable screws can overcome such shortcomings of the metal screws. The purpose of this study was to compare the strength of a 5-mm bioabsorbable screw with single 4-mm metal and double 3.5-mm lag screw fixation for Type II fractures of the odontoid process.

Methods

Three different modalities of anterior screw fixation were used in 19 C-2 vertebrae. These fixation methods consisted of a single 5-mm cannulated bioabsorbable lag screw (Group A), a single 4-mm cannulated titanium lag screw (Group B), and two 3.5-mm cannulated titanium lag screws (Group C). Anteroposterior (AP) stiffness and rotational stiffness were evaluated in all constructs.

Results

There was no statistical difference among the ages of the cadavers in each group (p = 0.52). The AP bending stiffness in Groups A, B, and C was 117 ± 86, 66 ± 43, and 305 ± 130 Nm/mm, respectively. The AP bending stiffness in Group C was significantly higher than that in Groups A and B (p = 0.01 and p = 0.001, respectively). The difference in AP bending stiffness values of bioabsorbable and 4-mm metal screws was not statistically significant (p = 0.23). The rotational stiffness of the double 3.5-mm metal screws was significantly greater than that of the 5-mm bioabsorbable and the 4-mm titanium screws.

Conclusions

Double screw fixation with 3.5-mm screws provides the stiffest construct in Type II odontoid fractures. Bioabsorbable lag screws (5 mm) have the same AP bending and rotational stiffness as the single titanium lag screw (4 mm) in odontoid fractures.

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Anil Nanda, Vijayakumar Javalkar and Anirban Deep Banerjee

Object

Petroclival meningiomas are notoriously difficult lesions to manage surgically, given the critical neurovascular structures that are intimately associated with the tumors. In this paper, the authors' aim was to review their series of patients with petroclival meningiomas who underwent surgical treatment; emphasis was placed on evaluating modes of presentation, postoperative neurological outcome, complications, and recurrence rates.

Methods

Fifty patients underwent surgical treatment for petroclival meningiomas. The majority of the patients were women (72%). The authors retrospectively reviewed the patients' medical records, imaging studies, and pathology reports to analyze presentation, surgical approach, neurological outcomes, complications, and recurrence rates.

Results

Headache was the most common presentation (58%). The most commonly used approach was the transpetrous approach (in 16 patients), followed by the orbitozygomatic approach (in 13). Gross-total resection was performed in 14 patients (28%), and in the remaining patients there was residual tumor (72%). Eighteen patients with tumor remnants were treated with Gamma Knife surgery. New postoperative cranial neuropathies were noted in 22 patients (44%). The most common cranial nerve (CN) deficit following surgery was CN III dysfunction (in 11 patients) and facial weakness (in 10). In 9 patients, the CN dysfunction was transient (41%), and 7 patients had permanent dysfunction (32%). Eight patients developed hydrocephalus and all required placement of a ventriculoperitoneal shunt. A CSF leak was noted in only 2 patients (4%), and wound dehiscence was noted in 1. The CSF leaks and the wound dehiscence occurred in patients who were undergoing reoperations. Adequate radiographic follow-up (minimum 6 months) was available for 31 patients (62%). The mean follow-up was 22.1 months. In 6 patients, tumor progression or recurrences were noted. The median time to recurrence was 84 months. At the time of discharge from the hospital, 92% of the patients had good outcomes (Glasgow Outcome Scale Scores 4 and 5). Three patients died of causes not directly related to the surgery.

Conclusions

Petroclival meningiomas still pose a formidable challenge to neurosurgeons. In their series, the authors used multiple skull base approaches and careful microneurosurgical technique to achieve a good functional outcome (Glasgow Otcome Scale Score 4 or 5) in 92% of patients, although the extent of gross-total resection was only 28%. The authors' primary surgical goal was to achieve maximal tumor resection while maintaining or improving neurological function. The authors favor the treatment of residual tumor or recurrent tumor with stereotactic radiosurgery.

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Rishi Wadhwa, Samer Shamieh, Justin Haydel, Gloria Caldito, Mallory Williams and Anil Nanda

Object

As a result of spinal trauma, approximately 12,000 individuals become quadriplegic or paraplegic each year in the US. The cervical spine is the most frequently injured part of the spinal column, and approximately 60% of spinal cord injuries involve the cervical region. The cervical collar remains the best method of prehospital spinal stabilization. Following trauma, difficulty securing an airway, the shielding of life-threatening injuries, and pressure ulcers are just a few of the serious problems that may be encountered in patients placed in cervical collars. The authors' goal was to develop an efficient method of clearing the cervical spine, by incorporating flexion and extension CT scanning with reconstruction (FECTR) into a trauma protocol.

Methods

This prospective study reviewed consecutive patients evaluated by the neurosurgery and trauma services who underwent FECTR. Imaging studies were reviewed using the Picture Activating and Communication System. The incidence of injury detection was recorded, and detection of otherwise-missed cervical spinal injuries using FECTR and CT scanning were also recorded. This technique was also applied, without causing any new neurological complications, for comatose patients if the original CT showed no suspicion of unstable injury. The study end point was determination of the presence of cervical spinal column injury that would pose a threat of instability or injury to the patient.

Results

Seventy-seven consecutive patients who underwent FECTR were identified. Far superior visualization of the cervicothoracic junction was achieved compared with flexion-extension cervical spine radiographs. In this case series, the sensitivity and specificity, respectively, of both FECTR and CT were 80% and 98.6% for all radiographic abnormalities. More importantly, for clinically unstable injuries, FECTR had a sensitivity of 100%. The use of FECTR added approximately 10–12 minutes to the time required for CT scanning.

Conclusions

The authors' initial findings show FECTR to be a safe, effective, and efficient method of posttraumatic cervical spine clearance. In unconscious or obtunded patients, FECTR facilitates cervical spine clearance with a high degree of accuracy. A larger prospective study is needed to confirm these findings.

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Ali Nourbakhsh, Prashant Chittiboina, Prasad Vannemreddy, Anil Nanda and Bharat Guthikonda

Object

Transpedicular thoracic vertebrectomy (TTV) is a safe alternative to the more standard transthoracic approach. A TTV is most commonly used to address vertebral body fractures due to tumor or trauma.

Transpedicular reconstruction of the anterior column with cage/bone traditionally requires unilateral thoracic nerve root sacrifice. In a cadaveric model, the authors evaluated the feasibility of transpedicular anterior column reconstruction without nerve root sacrifice. If feasible, this may be a reasonable approach that could be extended to the lumbar spine where nerve root sacrifice is not an option.

Methods

A TTV was performed in 8 fixed cadaveric specimens. In each specimen, an alternate vertebra (either odd or even) was removed so that single-level reconstruction could be evaluated. The vertebrectomy included facetectomy, adjacent discectomies, and laminectomy; however, the nerve roots were preserved. The authors then evaluated the feasibility of inserting a titanium mesh cage (Medtronic Sofamor Danek) without neural sacrifice.

Results

Transpedicular anterior cage reconstruction could be safely performed at all levels of the thoracic spine without nerve root sacrifice. The internerve root space varied from 18 mm at T2–3 to 27 mm at T11–12; thus, the size of the cage that was used also varied with level.

Conclusions

Cage reconstruction of the anterior column could be safely performed via the transpedicular approach without nerve root sacrifice in this cadaveric study. Removal of the proximal part of the rib in addition to a standard laminectomy with transpedicular vertebrectomy provided an excellent corridor for anterior cage reconstruction at all levels of the thoracic spine without nerve root sacrifice.

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Ali Nourbakhsh, Jinping Yang, Sean Gallagher, Anil Nanda, Prasad Vannemreddy and Kim J. Garges

Object

The purpose of this study was to find a landmark according to which the surgeon can dissect the cervical spine safely, with the lowest possibility of damaging the vertebral artery (VA) during anterior approaches to the cervical spine or the VA.

Methods

The “safe zone” for each level of the cervical spine was described as an area where the surgeon can start from the midline in that zone and dissect the soft tissue laterally to end up on the transverse process and cross the VA while still on the transverse process. In other words, safe zone signifies the narrowest width of the transverse process at each level. In such an approach, the VA is protected from the inadvertent deep penetration of the instruments by the transverse process. The surgical safe zone for each level was the common area among at least 95% of the safe zones for that level. For the purpose of defining the upper and lower borders of the safe zone for each level, the line passing from the upper vertebral border perpendicular to the midline (upper vertebral border line) was used as a reference.

Cervical spines of 64 formalin-fixed cadavers were dissected. The soft tissue in front of the transverse process and intertransverse space was removed. Digital pictures of the specimens were taken before and after removal of the transverse processes, and the distance to the upper and lower border of the safe zone from the upper vertebral border line was measured on the digital pictures with Image J software. The VA diameter and distance from the midline at each level were also measured. To compare the means, the authors used t-test and ANOVA.

Results

The surgical safe zone lies between 1 mm above and 1 mm below the upper vertebral border at the fourth vertebra, 2 mm above and 1 mm below the upper vertebral border at the fifth vertebra, and 1 mm above and 2 mm below the upper vertebral border of the sixth vertebra. The VA was observed to be tortuous in 13% of the intertransverse spaces. There is a positive association between disc degeneration and tortuosity of the VA at each level (p < 0.001). The artery becomes closer to the midline (p < 0.001) and moves posteriorly during its ascent.

Conclusions

Dissection of the soft tissue off the bone along the surgical safe zone and removal of the transverse process afterward can be a practical and safe approach to avoid artery lacerations. The findings in the present study can be used in anterior approaches to the cervical spine, especially when the tortuosity of the artery mandates exposure of the VA prior to uncinate process resection, tumor excision, or VA repair.

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Christina Notarianni, Prasad Vannemreddy, Gloria Caldito, Papireddy Bollam, Esther Wylen, Brian Willis and Anil Nanda

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.

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Ali Nourbakhsh, Runhua Shi, Prasad Vannemreddy and Anil Nanda

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.