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Eric M. Horn, Nicholas Theodore, Neil R. Crawford, Nicholas C. Bambakidis and Volker K. H. Sonntag

Object

Lateral mass screws are traditionally used to fixate the subaxial cervical spine, while pedicle screws are used in the thoracic spine. Lateral mass fixation at C-7 is challenging due to thin facets, and placing pedicle screws is difficult due to the narrow pedicles. The authors describe their clinical experience with a novel technique for transfacet screw placement for fixation at C-7.

Methods

A retrospective chart review was undertaken in all patients who underwent transfacet screw placement at C-7. The technique of screw insertion was the same for each patient. Polyaxial screws between 8- and 10-mm-long were used in each case and placed through the facet from a perpendicular orientation. Postoperative radiography and clinical follow-up were analyzed for aberrant screw placement or construct failure.

Results

Ten patients underwent C-7 transfacet screw placement between June 2006 and March 2007. In all but 1 patient screws were placed bilaterally, and the construct lengths ranged from C-3 to T-5. One patient with a unilateral screw had a prior facet fracture that precluded bilateral screw placement. There were no intraoperative complications or screw failures in these patients. After an average of 6 months of follow-up there were no hardware failures, and all patients showed excellent alignment.

Conclusions

The authors present the first clinical demonstration of a novel technique of posterior transfacet screw placement at C-7. These results provide evidence that this technique is safe to perform and adds stability to cervicothoracic fixation.

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Sam Safavi-Abbasi, Mehmet Senoglu, Nicholas Theodore, Ryan K. Workman, Alireza Gharabaghi, Iman Feiz-Erfan, Robert F. Spetzler and Volker K. H. Sonntag

Object

The authors conducted a study to evaluate the clinical characteristics and surgical outcomes in patients with spinal schwannomas and without neurofibromatosis (NF).

Methods

The data obtained in 128 patients who underwent resection of spinal schwannomas were analyzed. All cases with neurofibromas and those with a known diagnosis of NF Type 1 or 2 were excluded. Karnofsky Performance Scale (KPS) scores were used to compare patient outcomes when examining the anatomical location and spinal level of the tumor. The neurological outcome was further assessed using the Medical Research Council (MRC) muscle testing scale.

Results

Altogether, 131 schwannomas were treated in 128 patients (76 males and 52 females; mean age 47.7 years). The peak prevalence is seen between the 3rd and 6th decades. Pain was the most common presenting symptom. Gross-total resection was achieved in 127 (97.0%) of the 131 lesions. The nerve root had to be sacrificed in 34 cases and resulted in minor sensory deficits in 16 patients (12.5%) and slight motor weakness (MRC Grade 3/5) in 3 (2.3%). The KPS scores and MRC grades were significantly higher at the time of last follow-up in all patient groups (p = 0.001 and p = 0.005, respectively).

Conclusions

Spinal schwannomas may occur at any level of the spinal axis and are most commonly intradural. The most frequent clinical presentation is pain. Most spinal schwannomas in non-NF cases can be resected totally without or with minor postoperative deficits. Preoperative autonomic dysfunction does not improve significantly after surgical management.

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Tejas Sankar, Rachid Assina, John P. Karis, Nicholas Theodore and Mark C. Preul

✓Mannitol is widely considered the hyperosmolar therapy of choice in routine neurosurgical practice for the reduction of intracranial pressure (ICP). The authors present a unique case of a patient with a large meningioma treated with mannitol, in which mannitol accumulation within the tumor and its surrounding parenchyma was shown using in vivo magnetic resonance spectroscopy (MRS). This rare appearance of mannitol on MRS was characterized by a wide-based peak at 3.8 ppm, which remained detectable several hours after the last dose. These findings provide the first in vivo evidence in support of the prevailing theory that mannitol leakage into the peritumoral edematous region may contribute to rebound increases in ICP and suggest that this phenomenon has the potential to occur in extraaxial tumors. Judicious use of mannitol in the setting of elevated ICP due to tumor may be indicated to avoid potentially deleterious side effects caused by its accumulation.

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Nicholas C. Bambakidis, John Butler, Eric M. Horn, Xukui Wang, Mark C. Preul, Nicholas Theodore, Robert F. Spetzler and Volker K. H. Sonntag

✓ The development of an acute traumatic spinal cord injury (SCI) inevitably leads to a complex cascade of ischemia and inflammation that results in significant scar tissue formation. The development of such scar tissue provides a severe impediment to neural regeneration and healing with restoration of function. A multimodal approach to treatment is required because SCIs occur with differing levels of severity and over different lengths of time. To achieve significant breakthroughs in outcomes, such approaches must combine both neuroprotective and neuroregenerative treatments. Novel techniques modulating endogenous stem cells demonstrate great promise in promoting neuroregeneration and restoring function.

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Mehmet Senoglu, Sam Safavi-Abbasi, Nicholas Theodore, Nicholas C. Bambakidis, Neil R. Crawford and Volker K. H. Sonntag

Object

In this study the authors investigated the anatomical, clinical, and imaging features as well as incidence of congenital defects of the C-1 arch.

Methods

The records of 1104 patients who presented with various medical problems during the time between January 2006 and December 2006 were reviewed retrospectively. The craniocervical computed tomography (CT) scans obtained in these patients were evaluated to define the incidence of congenital defects of the posterior arch of C-1. In addition, 166 dried C-1 specimens and 84 fresh human cadaveric cervical spine segments were evaluated for anomalies of the C-1 arch.

Results

Altogether, 40 anomalies (2.95%) were found in 1354 evaluated cases. Of the 1104 patients in whom CT scans were acquired, 37 (3.35%) had congenital defects of the posterior arch of the atlas. The incidence of each anomaly was as follows: Type A, 29 (2.6%); Type B, six (0.54%); and Type E, two (0.18%). There were no Type C or D defects. One patient (0.09%) had an anterior arch cleft. None of the reviewed patients had neurological deficits or required surgical intervention for their anomalies. Three cases of Type A posterior arch anomalies were present in the cadaveric specimens.

Conclusions

Most congenital anomalies of the atlantal arch are found incidentally in asymptomatic patients. Congenital defects of the posterior arch are more common than defects of the anterior arch.

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Sam Safavi-Abbasi, Joseph M. Zabramski, Pushpa Deshmukh, Cassius V. Reis, Nicholas C. Bambakidis, Nicholas Theodore, Neil R. Crawford, Robert F. Spetzler and Mark C. Preul

Object

The authors quantitatively assessed the effects of balloon inflation as a model of tumor compression on the brainstem, cranial nerves, and clivus by measuring the working area, angle of attack, and brain shift associated with the retrosigmoid approach.

Methods

Six silicone-injected cadaveric heads were dissected bilaterally via the retrosigmoid approach. Quantitative data were generated, including key anatomical points on the skull base and brainstem. All parameters were measured before and after inflation of a balloon catheter (inflation volume 4.8 ml, diameter 20 mm) intended to mimic tumor compression.

Results

Balloon inflation significantly shifted (p < 0.001) the brainstem and cranial nerve foramina (mean [± standard deviation] displacement of upper brainstem, 10.2 ± 3.7 mm; trigeminal nerve exit, 6.99 ± 2.38 mm; facial nerve exit, 9.52 ± 4.13 mm; and lower brainstem, 13.63 ± 8.45 mm). The area of exposure at the petroclivus was significantly greater with balloon inflation than without (change, 316.26 ± 166.75 mm2; p < 0.0001). Before and after balloon inflation, there was no significant difference in the angles of attack at the origin of the trigeminal nerve (p > 0.5).

Conclusions

This study adds an experimental component to the emerging field of quantitative neurosurgical anatomy. Balloon inflation can be used to model the effects of a mass lesion. The tumor simulation created “natural” retraction and an opening toward the upper clivus. The findings may be helpful in selecting a surgical approach to increase the working space for resection of certain extraaxial tumors.

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Iman Feiz-Erfan, Eric M. Horn, Nicholas Theodore, Joseph M. Zabramski, Jeffrey D. Klopfenstein, Gregory P. Lekovic, Felipe C. Albuquerque, Shahram Partovi, Pamela W. Goslar and Scott R. Petersen

Object

Skull base fractures are often associated with potentially devastating injuries to major neural arteries in the head and neck, but the incidence and pattern of this association are unknown.

Methods

Between April and September 2002, 1738 Level 1 trauma patients were admitted to St. Joseph's Hospital and Medical Center in Phoenix, Arizona. Among them, a skull base fracture was diagnosed in 78 patients following computed tomography (CT) scans. Seven patients had no neurovascular imaging performed and were excluded. Altogether, 71 patients who received a diagnosis of skull base fractures after CT and who also underwent a neurovascular imaging study were included (54 men and 17 women, mean age 29 years, range 1–83 years). Patients underwent CT angiography, magnetic resonance angiography, or digital subtraction angiography of the head and craniovertebral junction, or combinations thereof.

Results

Nine neurovascular injuries were identified in six (8.5%) of the 71 patients. Fractures of the clivus were very likely to be associated with neurovascular injury (p < 0.001). A high risk of neurovascular injury showed a strong tendency to be associated with fractures of the sella turcica–sphenoid sinus complex (p = 0.07).

Conclusions

The risk of associated blunt neurovascular injury appears to be significant in Level 1 trauma patients in whom a diagnosis of skull base fracture has been made using CT. The incidence of neurovascular trauma is particularly high in patients with clival fractures. The authors recommend neurovascular imaging for Level 1 trauma patients with a high-risk fracture pattern of the central skull base to rule out cerebrovascular injuries.

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Sam Safavi-Abbasi, Leonardo B. C. Brasiliense, Ryan K. Workman, Melanie C. Talley, Iman Feiz-Erfan, Nicholas Theodore, Robert F. Spetzler and Mark C. Preul

✓In 25 years, the Mongolian army of Genghis Khan conquered more of the known world than the Roman Empire accomplished in 400 years of conquest. The recent revised view is that Genghis Khan and his descendants brought about “pax Mongolica” by securing trade routes across Eurasia. After the initial shock of destruction by an unknown barbaric tribe, almost every country conquered by the Mongols was transformed by a rise in cultural communication, expanded trade, and advances in civilization. Medicine, including techniques related to surgery and neurological surgery, became one of the many areas of life and culture that the Mongolian Empire influenced.

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Seref Dogan, Sam Safavi-Abbasi, Nicholas Theodore, Steven W. Chang, Eric M. Horn, Nittin R. Mariwalla, Harold L. Rekate and Volker K. H. Sonntag

Object

The authors evaluated the mechanisms and patterns of thoracic, lumbar, and sacral spinal injuries in a pediatric population as well as factors affecting the management and outcome of these injuries.

Methods

The records of 89 patients (46 boys and 43 girls; mean age 13.2 years, range 3–16 years) with thoracic, lumbar, or sacral injuries were reviewed. Motor vehicle accidents were the most common cause of injury. Eighty-two patients (92.1%) were between 10 and 16 years old, and seven (7.9%) were between 3 and 9 years old. Patient injuries included fracture (91%), fracture and dislocation (6.7%), dislocation (1.1%), and ligamentous injury (1.1%). The L2–5 region was the most common injury site (29.8%) and the sacrum the least common injury site (5%). At the time of presentation 85.4% of the patients were neurologically intact, 4.5% had incomplete injuries, and 10.1% had complete injuries. Twenty-six percent of patients underwent surgery for their injuries whereas 76% received nonsurgical treatment. In patients treated surgically, an anterior approach was used in six patients (6.7%), a posterior approach in 16 (18%), and a combined approach in one (1.1%). Postoperatively, six patients (26.1%) with neurological deficits improved, one of whom recovered fully from an initially complete injury.

Conclusions

Thoracic and lumbar spine injuries were most common in children older than 9 years. Multilevel injuries were common and warranted imaging evaluation of the entire spinal column. Most patients were treated conservatively. The prognosis for neurological recovery is related to the initial severity of the neurological injuries. Some pediatric patients with devastating spinal cord injuries can recover substantial neurological function.

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Rogerio Rocha, Sam Safavi-Abbasi, Cassius Reis, Nicholas Theodore, Nicholas Bambakidis, Evandro De Oliveira, Volker K. H. Sonntag and Neil R. Crawford

Object

The authors measured relevant quantitative anatomical parameters to define safety zones for the placement of C-1 posterior screws.

Methods

Nineteen linear, two angular, and four surface parameters of 20 dried atlantal specimens were evaluated. The Optotrak 3020 system was used to define the working area. Ideal angles for screw positioning were measured using digital radiographs and a free image-processing program. Six silicone-injected cadaveric heads were dissected bilaterally to study related neurovascular anatomy.

The depth (range 5.2–9.4 mm, mean 7.2 ± 1.1 mm) and width (range 5.2–8.1 mm, mean 6.5 ± 0.9 mm) of the transverse foramen varied considerably among specimens. The mean posterior working area was 43.3 mm2. All specimens accommodated 3.5-mm-diameter screws, and 93% accepted 4-mm-diameter screws. In 10 specimens (50%), partial removal of the posterior arch was necessary to accommodate a 4-mm screw. The mean maximum angle of medialization was 16.7 ± 1.3°; the mean maximum superior angulation was 21.7 ± 4.7°.

Conclusions

The anatomical configuration of the atlas and vertebral artery (VA) varied considerably among the cadaveric specimens. The heights of the C-1 pedicle, posterior arch, and posterior lamina determine the posterior working area available for screw placement. The inferior insertion of the posterior arch may have to be drilled to increase this working area, but doing so risks injury to the VA. A dense venous plexus with multiple anastomoses may cover the screw entry site, potentially obscuring the operative view and increasing the risk of hemorrhage.