Neuronal responses to tactile stimuli and tactile sensations evoked by microstimulation in the human thalamic principal somatic sensory nucleus (ventral caudal).

The normal organization and plasticity of the cutaneous core of the thalamic principal somatosensory nucleus (ventral caudal, Vc) have been studied by single-neuron recordings and microstimulation in patients undergoing awake stereotactic operations for essential tremor (ET) without apparent somatic sensory abnormality and in patients with dystonia or chronic pain secondary to major nervous system injury. In patients with ET, most Vc neurons responded to one of the four stimuli, each of which optimally activates one mechanoreceptor type. Sensations evoked by microstimulation were similar to those evoked by the optimal stimulus only among rapidly adapting neurons. In patients with ET, Vc was highly segmented somatotopically, and vibration, movement, pressure, and sharp sensations were usually evoked by microstimulation at separate sites in Vc. In patients with conditions including spinal cord transection, amputation, or dystonia, RFs were mismatched with projected fields more commonly than in patients with ET. The representation of the border of the anesthetic area (e.g., stump) or of the dystonic limb was much larger than that of the same part of the body in patients with ET. This review describes the organization and reorganization of human Vc neuronal activity in nervous system injury and dystonia and then proposes basic mechanisms.

Fusion Revision Surgery With Reamer-Irrigator-Aspirator to Harvest Autograft After Spinal Pseudarthrosis.

Background and purpose Spinal pseudarthrosis (SPA) is a common complication after attempted cervical or lumbosacral spinal fusion surgery. Revision surgeries usually necessitate bone graft implementation as an adjunct to hardware revision. Iliac crest bone graft is the gold standard but availability can be limited and usage often leads to persistent postoperative pain at the donor site. There is scant literature regarding the use of reamer-irrigator-aspirator (RIA)-harvested bone graft in lumbar spinal fusion. This is a collaborative study between orthopedic surgery and neurosurgery departments to utilize femur intramedullary autograft harvested using the RIA system as an adjunct graft in SPA revision surgeries. Materials and methods A retrospective review was conducted at a single center between August 2014 and December 2017 of patients aged ≥ 18 years and diagnosed with cervical, thoracic, or lumbar SPA who underwent revision fusion surgery using femur intramedullary autograft harvested using the RIA system. Plain radiographs and CT scans were utilized to confirm successful fusion. Results Eleven patients underwent 12 SPA revision surgeries using the RIA system as a source for bone graft in addition to bone morphogenetic protein 2 (BMP-2) and allograft. The mean amount of graft harvested was 51.3 mL (range: 20-70 mL). Nine patients achieved successful fusion (81.8%). The average time to fusion was 9.1 months. Four patients (36.4%) had postoperative knee pain. Regarding patient position and approach for harvesting, 66.7% (n = 8) of cases were positioned prone and a retrograde approach was utilized in 91.7% (n = 11) of cases. Interpretation This is the first case series in known literature to report the RIA system as a reliably considerable source of autologous bone graft for SPA revision surgeries. It provides a useful adjunct to the known types of bone grafts. Patient positioning and the approach choice for graft harvesting can be adjusted according to the fusion approach and the surgeon's preference.

Pretruncal nonaneurysmal subarachnoid hemorrhage causing basilar artery vasospasm.

BACKGROUND: Pretruncal nonaneurysmal subarachnoid hemorrhage (PNSAH), more commonly known as perimesencephalic nonaneurysmal subarachnoid hemorrhage, is characterized by the presence of subarachnoid hemorrhage anterior to the midbrain with no evidence of an intracranial aneurysm on four vessel craniocervical angiogram. Although vasospasm is a common occurrence after aneurysmal subarachnoid hemorrhage and can lead to significant morbidity and mortality, vasospasm in the setting of PNSAH is rare. METHODS: The purpose of this report is to describe the case of a patient with PNSAH who developed significant radiographic vasospasm of the basilar artery that altered clinical management. The current literature on this uncommon disease entity and management considerations are discussed. RESULTS: A four-vessel cerebral angiogram was performed on hospital day (HD) two that did not demonstrate any apparent vascular abnormality or vasospasm. A repeat craniocervical angiogram on HD 8 demonstrated significant stenosis of the basilar artery consistent with vasospasm. The patient continued to be neurologically intact. A repeat cerebral angiogram performed on HD 15 demonstrated resolving vasospasm. There continued to be no evidence of a source of his initial hemorrhage. CONCLUSIONS: PNSAH is associated with an excellent clinical course that is rarely associated with long-term sequelae. Although cerebral vasospasm rarely develops radiographically or clinically in patients with PNSAH, evidence suggests that clinical observation comparable to that performed in patients with aneurysmal SAH should be performed until a second confirmatory study has conclusively ruled out an aneurysmal source and until clinical and radiographic evidence of resolution of severe vasospasm is obtained.

Laminar screw fixation of the axis.

OBJECT: Laminar fixation of the axis with crossing bilateral screws has been shown to provide rigid fixation with a theoretically decreased risk of vertebral artery damage compared with C1-2 transarticular screw fixation and C-2 pedicle screw fixation. Some studies, however, have shown restricted rigidity of such screws compared with C-2 pedicle screws, and others note that anatomical variability exists within the posterior elements of the axis that may have an impact on successful placement. To elucidate the clinical impact of such screws, the authors report their experience in placing C-2 laminar screws in adult patients over a 2-year period, with emphasis on clinical outcome and technical placement. METHODS: Sixteen adult patients with cervical instability underwent posterior cervical and cervicothoracic fusion procedures at our institution with constructs involving C-2 laminar screws. Eleven patients were men and 5 were women, and they ranged in age from 28 to 84 years (mean 57 years). The reasons for fusion were degenerative disease (9 patients) and treatment of trauma (7 patients). In 14 patients (87.5%) standard translaminar screws were placed, and in 2 (12.5%) an ipsilateral trajectory was used. All patients underwent preoperative radiological evaluation of the cervical spine, including computed tomography scanning with multiplanar reconstruction to assess the posterior anatomy of C-2. Anatomical restrictions for placement of standard translaminar screws included a deeply furrowed spinous process and/or an underdeveloped midline posterior ring of the axis. In these cases, screws were placed into the corresponding lamina from the ipsilateral side, allowing bilateral screws to be oriented in a more parallel, as opposed to perpendicular, plane. All patients were followed for >2 years to record rates of fusion, instrumentation failure, and other complications. RESULTS: Thirty-two screws were placed without neurological or vascular complications. The mean follow-up duration was 27.3 months. Complications included 2 revisions, one for pseudarthrosis and the other for screw pullout, and 3 postoperative infections. CONCLUSIONS: Placement of laminar screws into the axis from the standard crossing approach or via an ipsilateral trajectory may allow a safe, effective, and durable means of including the axis in posterior cervical and cervicothoracic fusion procedures.

Frameless image-guided stereotactic brain biopsy procedure: diagnostic yield, surgical morbidity, and comparison with the frame-based technique.

OBJECT: The gold standard for stereotactic brain biopsy target localization has been frame-based stereotaxy. Recently, frameless stereotactic techniques have become increasingly utilized. Few authors have evaluated this procedure, analyzed preoperative predictors of diagnostic yield, or explored the differences in diagnostic yield and morbidity rate between the frameless and frame-based techniques. METHODS: A consecutive series of 110 frameless and 160 frame-based image-guided stereotactic biopsy procedures was reviewed. Associated variables for both techniques were reviewed and compared. All stereotactic biopsy procedures were included in a risk factor analysis of nondiagnostic biopsy sampling. Frameless stereotaxy led to a diagnostic yield of 89%, with a total permanent morbidity rate of 6% and a mortality rate of 1%. Larger lesions were fivefold more likely to yield diagnostic tissues. Deep-seated lesions were 2.7-fold less likely to yield diagnostic tissues compared with cortical lesions. Frameless compared with frame-based stereotactic biopsy procedures showed no significant differences in diagnostic yield or transient or permanent morbidity. For cortical lesions, more than one needle trajectory was required more frequently to obtain diagnostic tissues with frame-based as opposed to frameless stereotaxy, although this factor was not associated with morbidity. CONCLUSIONS: With regard to diagnostic yield and complication rate, the frameless stereotactic biopsy procedure was found to be comparable to or better than the frame-based method. Smaller and deep-seated lesions together were risk factors for a nondiagnostic tissue yield. Frameless stereotaxy may represent a more efficient means of obtaining biopsy specimens of cortical lesions but is otherwise similar to the frame-based technique.

Intracranial aneurysm following radiation therapy during childhood for a brain tumor. Case report and review of the literature.

Ionizing radiation therapy is associated with pathological vascular changes in intracranial vessels, most commonly in the form of vessel thrombosis and occlusion. The development of an intracranial aneurysm following such therapy, however, is far less common. In this report the authors describe a 24-year-old man in whom a distal middle cerebral artery aneurysm developed 15 years after radiotherapy, which was given as adjuvant treatment following resection of a medulloblastoma. The patient underwent a craniotomy for microsurgical trapping of the aneurysm and was discharged without any neurological deficit. This case serves to remind clinicians of the possibility, albeit rare, that intracranial aneurysms may form following cranial radiotherapy.

Translaminar screw fixation in the upper thoracic spine.

OBJECT: The use of pedicle screws (PSs) for instrument-assisted fusion in the cervical and thoracic spine has increased in recent years, allowing smaller constructs with improved biomechanical stability and repositioning possibilities. In the smaller pedicles of the upper thoracic spine, the placement of PSs can be challenging and may increase the risk of damage to neural structures. As an alternative to PSs, translaminar screws can provide spinal stability, and they may be used when pedicular anatomy precludes successful placement of PSs. The authors describe the technique of translaminar screw placement in the T-1 and T-2 vertebrae. METHODS: Seven patients underwent cervicothoracic fusion to treat trauma, neoplasm, or degenerative disease. Nineteen translaminar screws were placed, 13 at T-1 and six at T-2. A single asymptomatic T-2 screw violated the ventral laminar cortex and was removed. The mean clinical and radiographic follow up exceeded 14 months, at which time there were no cases of screw pullout, screw fracture, or progressive kyphotic deformity. CONCLUSIONS: Rigid fixation with translaminar screws offers an attractive alternative to PS fixation, allowing the creation of sound spinal constructs and minimizing potential neurological morbidity. Their use requires intact posterior elements, and care should be taken to avoid violation of the ventral laminar wall.

Preoperative imaging of cervical spine hemangioblastomas using three-dimensional fusion digital subtraction angiography. Report of two cases.

Angiography is often performed to identify the vascular supply of hemangioblastomas prior to resection. Conventional two-dimensional (2D) digital subtraction (DS) angiography and three-dimensional (3D) DS angiography provides high-resolution images of the vascular structures associated with these lesions. However, such 3D DS angiography often does not provide reliable anatomical information about nearby osseous structures, or when it does, resolution of vascular anatomy in the immediate vicinity of bone is sacrificed. A novel angiographic reconstruction algorithm was recently developed at The Johns Hopkins University to overcome these inadequacies. By combining two separate sequences of images of bone and blood vessels in a single 3D representation, 3D fusion DS (FDS) angiography provides precise topographic information about vascular lesions in relation to the osseous environment, without a loss of resolution. In this paper, the authors present the cases of two patients with cervical spine hemangioblastomas who underwent preoperative evaluation with FDS angiography and then successful gross-total resection of their tumors. In both cases, FDS angiography provided high-resolution 3D images of the hemangioblastoma anatomy, including each tumor's topographic relationship with adjacent osseous structures and the location and size of feeding arteries and draining veins. These cases provide evidence that FDS angiography represents a useful adjunct to magnetic resonance imaging and 2D DS angiography in the preoperative evaluation and surgical planning of patients with vascular lesions in an osseous environment, such as hemangioblastomas in the spinal cord.

Independent predictors of morbidity after image-guided stereotactic brain biopsy: a risk assessment of 270 cases.

OBJECT: Image-guided stereotactic brain biopsy is associated with transient and permanent incidences of morbidity in 9 and 4.5% of patients, respectively. The goal of this study was to perform a critical analysis of risk factors predictive of an enhanced operative risk in frame-based and frameless stereotactic brain biopsy. METHODS: The authors reviewed the clinical and neuroimaging records of 270 patients who underwent consecutive frame-based and frameless image-guided stereotactic brain biopsies. The association between preoperative variables and biopsy-related morbidity was assessed by performing a multivariate logistic regression analysis. Transient and permanent stereotactic biopsy-related morbidity was observed in 23 (9%) and 13 (5%) patients, respectively. A hematoma occurred at the biopsy site in 25 patients (9%); 10 patients (4%) were symptomatic. Diabetes mellitus (odds ratio [OR] 3.73, 95% confidence interval [CI] 1.37-10.17, p = 0.01), thalamic lesions (OR 4.06, 95% CI 1.63-10.11, p = 0.002), and basal ganglia lesions (OR 3.29, 95% CI 1.05-10.25, p = 0.04) were in'dependent risk factors for morbidity. In diabetic patients, a serum level of glucose that was greater than 200 mg/dl on the day of biopsy had a 100% positive predictive value and a glucose level lower than 200 mg/dl on the same day had a 95% negative predictive value for biopsy-related morbidity. Pontine biopsy was not a risk factor for morbidity. Only two (4%) of 45 patients who had epilepsy before the biopsy experienced seizures postoperatively. The creation of more than one needle trajectory increased the incidence of neurological deficits from 17 to 44% when associated with the treatment of deep lesions (those in the basal ganglia or thalamus; p = 0.05), but was not associated with morbidity when associated with the treatment of cortex lesions. CONCLUSIONS: Basal ganglia lesions, thalamic lesions, and patients with diabetes were independent risk factors for biopsy-associated morbidity. Hyperglycemia on the day of biopsy predicted morbidity in the diabetic population. Epilepsy did not predispose to biopsy-associated seizure. For deep-seated lesions, increasing the number of biopsy samples along an established track rather than performing a second trajectory may minimize the incidence of morbidity. Close perioperative observation of glucose levels may be warranted.

Accuracy of frameless and frame-based image-guided stereotactic brain biopsy in the diagnosis of glioma: comparison of biopsy and open resection specimen.

OBJECTIVES: Tissue heterogeneity and rapid tumor progression may decrease the accuracy a prognostic value of stereotactic brain biopsy in the diagnosis of gliomas. Correct tumor grading is therefore dependent on the accuracy of biopsy needle placement. There has been a dramatic increase in the utilization of frameless image-guided stereotactic brain biopsy; however, its accuracy in the diagnosis of glioma remains unstudied. METHODS: The diagnoses of 21 astrocytic brain tumors were derived using image-guided stereotactic biopsy (12 frame-based, nine frameless) and followed by open resection of the lesion 1.5 (0.5-4) months later. The histologic diagnoses yielded by the biopsy were compared with subsequent histologic diagnosis from open tumor resection. RESULTS: Histology of 21 stereotactic biopsies accurately represented the greater lesion at open resection a median of 45 days later in 16 (76%) cases and correctly guided therapy in 19 (91%) cases. Biopsy accuracy of frameless versus frame-based stereotaxis was similar (89 versus 66%, p=0.21). In three (14%) cases, biopsy specimens were adequate to diagnose glioma; however, histology was insufficient for definitive tumor grading. Anaplastic oligodendroglioma (ODG) was under-graded as low-grade ODG in one (5%) case. Biopsy of new onset glioblastoma multiforme (GBM) yielded necrosis/gliosis and was termed non-diagnostic in one patient. Tumors <50 cm(3) were 8-fold less likely to accurately represent the grade of the entire lesion at resection compared with lesions <50 cm(3) (OR, 8.8; 95% CI, 0.9-100, p=0.05). DISCUSSION: Both frameless and frame-based MRI-guided stereotactic brain biopsy are safe and accurately represent the larger glioma mass sufficiently to guide subsequent therapy. Large tumor volume had a higher incidence of non-concordance. Increasing the number of specimens taken through the long dimension of large tumors may improve diagnostic accuracy.

Spinal pelvic reconstruction after total sacrectomy for en bloc resection of a giant sacral chordoma. Technical note.

Although radical resection prolongs the disease-free survival period, surgical management of primary sacral tumors is challenging because of their location and often large size. Moreover, in cases of lesions for which a radical resection necessitates total sacrectomy, reconstruction is required. The authors have previously described a modified Galveston technique in which a liaison between the spine and pelvis is achieved using lumbar pedicle screws and Galveston rods embedded into the ilia; additionally, a transiliac bar reestablishes the pelvic ring. Although this reconstruction technique achieves stabilization, several biomechanical limitations exist. In the present report the authors present the case of a patient who underwent spinal pelvic reconstruction after a total sacrectomy was performed to remove a giant sacral chordoma. They describe a novel spinal pelvic reconstruction technique that addresses some of the biomechanical limitations.

A novel rat model for the study of intraosseous metastatic spine cancer.

OBJECT: Although metastatic spinal disease constitutes a significant percentage of all spinal column tumors, an accessible and reproducible animal model has not been reported. In this study the authors describe the technique for creating an intraosseous spinal tumor model in rats and present a functional and histological analysis. METHODS: Eighteen female Fischer 344 rats were randomized into two groups. Group 1 animals underwent a transabdominal exposure and implantation of CRL-1666 breast adenocarcinoma into the L-6 vertebral body (VB). Animals in Group 2 underwent a sham operation. Hindlimb function was tested daily by using the Basso-Beattie-Bresnahan scale. Sixteen days after tumor implantation, animals were killed and their spines were removed for histological assessment. Statistical analysis was performed using the Wilcoxon signed-rank test. By Day 15 functional analysis showed a significant decrease in motor function in Group 1 animals (median functional score 2 of 21) compared with Group 2 rats (median functional score 21 of 21) (p = 0.0217). The onset of paraparesis in Group 1 occurred within 14 to 16 days of surgery. Histopathological analysis showed tumor proliferation through the VB and into the spinal canal, with marked osteolytic activity and spinal cord compression. CONCLUSIONS: Analysis of these findings demonstrates the consistency of tumor growth in this model and validates the utility of functional testing for onset of paresis. This new rat model allows for the preclinical evaluation of novel therapeutic treatments for patients harboring metastatic spine disease.

En bloc resection of primary sacral tumors: classification of surgical approaches and outcome.

OBJECT: En bloc resection with adequate margins is associated with the highest probability of long-term tumor control or cure in most cases of primary sacral malignancies. The authors present their experience with a systematic approach to these lesions. They provide a novel classification of surgical techniques based on the level of nerve root sacrifice and evaluate the functional and oncological outcomes. METHODS: Seventy-eight consecutive patients underwent 94 resections of sacral neoplasms at The University of Texas M. D. Anderson Cancer Center in Houston between August 1993 and June 2002. The records of 29 consecutive patients who underwent en bloc resection of primary sacral tumors were retrospectively reviewed. The median follow-up period was 55 months (range 1-103 months). Chordoma was the most frequent tumor type (16 cases). Midline sacral amputation was performed in 25 patients (eight low, four middle, seven high, and five total sacrectomies; one hemicorporectomy). Lateral sacrectomy was undertaken in four patients (two unilateral excisions of the sacroiliac joint and two hemisacrectomies). The surgical margins were wide in 19 cases, marginal in nine, and contaminated in one. The type of sacrectomy correlated with characteristic outcomes with respect to bladder, bowel, and ambulatory functions. Duration of hospital stay was related to the extent of sacrectomy (p = 0.003, Wilcoxon signed-rank test). The median Kaplan-Meier disease-free survival for patients with chordoma was 68 months (95% confidence interval 46-90 months). CONCLUSIONS: Classification of en bloc sacral resection techniques by the level of nerve root transection is useful in predicting postoperative function and the potential for morbidity. Adequate surgical margins should not be compromised to preserve function when they are necessary to affect tumor control.

Ventriculoperitoneal shunt malfunction presenting with pleuritic chest pain.

BACKGROUND: Ventriculoperitoneal (VP) shunts are widely used for treating hydrocephalus. These devices are prone to malfunction with up to 70% requiring revision. Shunt infection and obstruction comprise the majority of malfunctions and usually present dramatically. However, rare presentations occur. METHODS/RESULTS: We report a rare case of VP shunt malfunction presenting with pleuritic chest pain. A 13-year-old girl with a VP shunt placed at birth for congenital hydrocephalus presented on multiple occasions with pleuritic chest pain, cough, and fever. She was diagnosed with an upper respiratory tract infection and discharged home. She returned with respiratory compromise, and chest x-ray depicted the shunt catheter in the pleural space with an associated pleural effusion and infiltrate. The patient fully recovered with intravenous antibiotics, thoracentesis, and placement of a new shunt system. CONCLUSIONS: VP shunt malfunction usually presents with signs and symptoms of increased intracranial pressure and/or infection. However, unusual presentations of malfunction may occur with signs and symptoms which appear unrelated to the shunt. Thus, all patients with VP shunts warrant a comprehensive evaluation.

Ectopic recurrence of craniopharyngioma after an interhemispheric transcallosal approach: case report.

OBJECTIVE AND IMPORTANCE: Ectopic recurrence of a craniopharyngioma is a rare postoperative complication. We present a case of a craniopharyngioma that ectopically recurred along the tract of a previous surgical route. CLINICAL PRESENTATION: A 73-year-old female patient presented 8 years earlier with a suprasellar craniopharyngioma. She underwent a right frontal craniotomy, with an interhemispheric transcallosal approach, for total microsurgical resection of the tumor. No postoperative radiotherapy was administered. Four years after surgery, magnetic resonance imaging studies revealed a well-circumscribed, heterogeneously enhancing, parasagittal mass with significant vasogenic edema in the right frontal lobe. Enlargement of the lesion was noted in subsequent radiological evaluations until 8 years after surgery, when the patient experienced a significant decline in neurocognitive status and the mass was surgically resected. INTERVENTION: Gross total resection of a histologically confirmed craniopharyngioma was achieved. CONCLUSION: To our knowledge, only eight previous case reports described the ectopic recurrence of a craniopharyngioma. Transplantation of tumor cells along the tract of a previous surgical route in six cases and dissemination in cerebrospinal fluid in two cases are presumed to be the primary mechanisms by which these ectopic recurrences occurred. The results of our literature review led us to conclude that total surgical resection, combined with careful inspection and irrigation of the surgical field, is the optimal treatment for preventing ectopic recurrences. Furthermore, it is recommended that, after primary craniopharyngioma resection, patients undergo long-term clinical and radiological follow-up monitoring for the rare development of an ectopically recurring tumor.

Outcome and cost of craniotomy performed to treat tumors in regional academic referral centers.

OBJECTIVE: Improved clinical and economic outcomes for high-risk surgical procedures have been previously cited in support of regionalization. The goal of this study was to examine the effects of regionalization by analyzing the cost and outcome of craniotomy for tumors and to compare the findings in academic medical centers versus community-based hospitals. METHODS: Outcomes and charges were analyzed for all adult patients undergoing craniotomy for tumor in 33 nonfederal acute care hospitals in Maryland using the Maryland Health Service Cost Review Commission database for the years 1990 to 1996. A total of 4723 patients who underwent craniotomy for tumor were selected on the basis of Diagnostic Related Group 1 (craniotomy except for trauma, age 18 or older) and International Classification of Diseases-9th Revision diagnosis code for benign tumor, primary malignant neoplasm, or secondary malignant neoplasm (codes 191, 192, 194, 200, 225, 227, 228, 237, and 239). Hospitals were categorized as high-volume hospitals (>50 craniotomies/yr) or low-volume hospitals (

Decompressive craniectomy for intractable cerebral edema: experience of a single center.

Several case reports and small clinical series have reported benefits of decompressive hemicraniectomy in patients with intractable cerebral edema and early clinical herniation. Specific indications and timing for this intervention remain unclear. We present our experience with this procedure in a subset of 18 patients with massive cerebral edema refractory to medical management, treated with decompressive craniectomy over a 3-year period (1997 to 2000). Computerized tomography (CT) scans were independently analyzed by a neuroradiologist blinded to clinical outcome. Eleven male and seven female patients, ages 20 to 69 years (mean +/- SEM, 46 +/- 14 years), underwent hemicraniectomy for the following diagnoses: 12 hemispheric infarcts, 3 traumatic intracerebral hemorrhages/contusions, 2 nontraumatic intraparenchymal hemorrhages (ICH), and 1 subdural empyema. This population included four patients with aneurysmal subarachnoid hemorrhage (SAH). Patients were followed for a mean of 10 months. Clinical factors including age, side of lesion, preoperative herniation signs, and early surgery (<12 or <24 hours) were not significantly associated with mortality or Glasgow outcome score (GOS). Preoperative CT evidence of transtentorial herniation (present in 5/17 patients) was associated with mortality ( = 0.04), while preoperative uncal herniation (8/17 patients) was associated with poor outcome (GOS > 1) ( = 0.01). Favorable outcome (GOS > 3) occurred in six patients, three with spontaneous or traumatic focal hematomas. Of four patients with SAH, one died while the others were severely disabled (GOS 3). Seven of nine patients with malignant MCA infarctions unrelated to SAH had poor outcomes. The overall mortality was 4/18 (22%). Patients with refractory cerebral swelling secondary to focal hematomas may have better outcomes following decompressive craniectomy. Patients with preexisting SAH seem to have poor outcomes, possibly related to other neurologic comorbidities. Hemicraniectomy requires definition of proper timing. Preoperative CT findings, especially transtentorial and uncal herniation may be useful in defining when decompressive surgery should not be performed.

A computed tomography-based morphometric study of thoracic pedicle anatomy in a random United States trauma population.

OBJECT: The objective of this study was to establish normative data for thoracic pedicle anatomy in the US adult population. To this end, CT scans chosen at random from an adult database were evaluated to determine the ideal pedicle screw (PS) length, diameter, trajectory, and starting point in the thoracic spine. The role of patient sex and side of screw placement were also assessed. The authors postulated that this information would be of value in guiding safe implant size and placement for surgeons in training. METHODS: One hundred patients (50 males and 50 females) were selected via retrospective review of a hospital trauma registry database over a 6-month period. Patients included in the study were older than 18 years of age, had axial bone-window CT images of the thoracic spine, and had no evidence of spinal trauma. For each pedicle, the pedicle width, pedicle-rib width, estimated screw length, trajectory, and ideal entry point were measured using eFilm Lite software. Statistical analysis was performed using the Student t-test. RESULTS: The shortest mean estimated PS length was at T-1 (33.9 ± 3.3 mm), and the longest was at T-9 (44.9 ± 4.4 mm). Pedicle screw length was significantly affected by patient sex; men could accommodate a PS from T1-12 a mean of 4.0 ± 1.0 mm longer than in women (p < 0.001). Pedicle width showed marked variation by spinal level, with T-4 (4.4 ± 1.1 mm) having the narrowest width and T-12 (8.3 ± 1.7 mm) having the widest. Pedicle width had an obvious affect on potential screw diameter; 65% of patients had a least 1 pedicle at T-4 that was < 5 mm in diameter and therefore would not accept a 4.0-mm screw with 1.0 mm of clearance, as compared with only 2% of patients with a similar status at T-12. Sex variation was also apparent, as thoracic pedicles from T-1 to T-12 were a mean of 1.4 ± 0.2 mm wider in men than in women (p < 0.001). The PS trajectory in the axial plane was measured, showing a marked decrease from T-1 to T-4, stabilization from T-5 to T-10, followed by a decrease at T11-12. When screw trajectory was stratified by side of placement, a mean of 1.7° ± 0.5° of increased medialization was required for ideal pedicle cannulation from T-3 to T-12 on the left as compared with the right side, presumably because of developmental changes in the vertebral body caused by the aorta (p < 0.05 for T3-12, except for T-5, where p = 0.051). The junction of the superior articular process, lamina, and the superior ridge of the transverse process was shown to be a conserved surface landmark for PS placement. CONCLUSIONS: Preoperative CT evaluation is important in choosing PS length, diameter, trajectory, and entry point due to variation based on spinal level, patient sex, and side of placement. These data are valuable for resident and fellow training to guide the safe use of thoracic PSs.

Surgical management of two- versus three-column injuries of the cervicothoracic junction: biomechanical comparison of translaminar screw and pedicle screw fixation using a cadaveric model.

STUDY DESIGN: An in vitro cadaveric biomechanical study. OBJECTIVE: To determine the stability of translaminar screws compared to pedicle screws at T1-T2 for constructs bridging the cervicothoracic junction. SUMMARY OF BACKGROUND DATA: Instrumented fixation of the cervicothoracic junction is challenging both biomechanically, due to the transition from the mobile cervical to the rigid thoracic spine, and technically, due to the anatomic constraints of the T1-T2 pedicles. For these reasons, an alternate fixation technique at T1-T2 that combines ease of screw insertion and a favorable safety profile with biomechanical stability would be clinically beneficial. METHODS: A 6-degree of freedom spine simulator was used to test multidirectional flexibility in 8 human cadaveric specimens. Flexion, extension, lateral bending, and axial rotation were tested in the intact condition, followed by destabilization via a simulated 2-column injury at C7-T1. Specimens were reconstructed using C5-C6 lateral mass screws and either translaminar or pedicle screws placed at T1, followed by caudal extension to T2. A 3-column injury at C7-T1 was then performed and specimens were tested using a posterior only approach with either translaminar or pedicle screws placed at T1 and T1-T2. Finally, anterior fixation at C7-T1 was added and multidirectional flexibility testing performed as previously described. RESULTS: Following a 2-column injury at C7-T1, there were no significant differences in segmental flexibility at C7-T1 between translaminar and pedicle screw fixation when placed at T1-T2 (P>0.05). For a 3-column injury treated posteriorly, translaminar screws at T1-T2 provided increased flexibility compared to pedicle screws in flexion/extension (P<0.05). There were no differences in segmental flexibility at C7-T1 between the 2 techniques following the addition of anterior fixation (P>0.05). CONCLUSION: Translaminar screws in the upper thoracic spine offer similar stability to pedicle screw fixation for constructs bridging the cervicothoracic junction. Small differences in range of motion must be weighed clinically against the potential benefits of translaminar screw insertion at T1-T2.

A computed tomography-based feasibility study of translaminar screw fixation in the upper thoracic spine.

OBJECT: Translaminar screws (TLSs) offer an alternative to pedicle screw (PS) fixation in the upper thoracic spine. Although cadaveric studies have described the anatomy of the laminae and pedicles at T1-2, CT imaging is the modality of choice for presurgical planning. In this study, the goal was to determine the diameter, maximal screw length, and optimal screw trajectory for TLS placement at T1-2, and to compare this information to PS placement in the upper thoracic spine as determined by CT evaluation. METHODS: One hundred patients (50 men and 50 women), whose average age was 41.7 +/- 19.6 years, were selected by retrospective review of a trauma registry database over a 6-month period. Patients were included in the study if they were over the age of 18, had standardized axial bone-window CT imaging at T1-2, and had no evidence of spinal trauma. For each lamina and pedicle, width (outer cortical and cancellous), maximal screw length, and optimal screw trajectory were measured using eFilm Lite software. Statistical analysis was performed using the Student t-test. RESULTS: The T-1 lamina was estimated to accommodate, on average, a 5.8-mm longer screw than the T-2 lamina (p < 0.001). At T-1, the maximal TLS length was similar to PS length (TLS: 33.4 +/- 3.6 mm, PS: 33.9 +/- 3.3 mm [p = 0.148]), whereas at T-2, the maximal PS length was significantly greater than the TLS length (TLS: 27.6 +/- 3.1 mm, PS: 35.3 +/- 3.5 mm [p < 0.001]). When the lamina outer cortical and cancellous width was compared between T-1 and T-2, the lamina at T-2 was, on average, 0.3 mm wider than at T-1 (p = 0.007 and p = 0.003, respectively). In comparison with the corresponding pedicle, the mean outer cortical pedicle width at T-1 was wider than the lamina by an average of 1.0 mm (lamina: 6.6 +/- 1.1 mm, pedicle: 7.6 +/- 1.3 mm [p < 0.001]). At T-2, however, outer cortical lamina width was wider than the corresponding pedicle by an average of 0.6 mm (lamina: 6.9 +/- 1.1 mm, pedicle: 6.3 +/- 1.2 mm [p < 0.001]). At T-1, 97.5% of laminae measured could accept a 4.0-mm screw with 1.0 mm of clearance, compared with 99.5% of T-1 pedicles; whereas at T-2, 99% of laminae met this requirement, compared with 94.5% of pedicles. The ideal screw trajectory was also measured (T-1: 49.2 +/- 3.7 degrees for TLS and 32.8 +/- 3.8 degrees for PS; T-2: 51.1 +/- 3.5 degrees for TLS and 20.5 +/- 4.4 degrees for PS). CONCLUSIONS: Based on CT evaluation, there are no anatomical limitations to the placement of TLSs compared with PSs at T1-2. Differences were noted, however, in lamina length and width between T-1 and T-2 that must be considered when placing TLS at these levels.