Intraoperative transabdominal MEPs: four case reports.

Four recent cases utilizing transabdominal motor-evoked potentials (TaMEPs) are presented as illustrative of the monitoring technique during lumbosacral fusion, sciatic nerve tumor resection, cauda equina tumor resection, and lumbar decompression. Case 1: In a high-grade lumbosacral spondylolisthesis revision fusion, both transcranial motor-evoked potentials (TcMEPs) and TaMEPs detected a transient focal loss of left tibialis anterior response in conjunction with L5 nerve root decompression. Case 2: In a sciatic nerve tumor resection, TcMEPs responses were lost but TaMEPs remained unchanged, the patient was neurologically intact postoperatively. Case 3: TaMEPs were acquired during an L1-L3 intradural extramedullary cauda equina tumor resection utilizing a unique TaMEP stimulation electrode. Case 4: TaMEPs were successfully acquired with little anesthetic fade utilizing an anesthetic regimen of 1.1 MAC Sevoflurane during a lumbar decompression. While the first two cases present TaMEPs and TcMEPs side-by-side, demonstrating TaMEPs correlating to TcMEPs (Case 1) or a more accurate reflection of patient outcome (Case 2), no inference regarding the accuracy of TaMEPs to monitor nerve elements during cauda equina surgery (Cases 3) or the lumbar decompression presented in Case 4 should be made as these are demonstrations of technique, not utility.

The maxillary artery and its variants: an anatomical study with neurosurgical applications.

BACKGROUND: The maxillary artery (MA) has gained attention in neurosurgery particularly in cerebral revascularization techniques, intracranial endonasal approaches and endovascular procedures. OBJECTIVES: To describe and illustrate the anatomy of the MA and its neurosurgical importance in a detailed manner. METHODS: Six cadaveric heads (12 MAs) were injected with latex. The arteries and surrounding structures were dissected and studied using microsurgical techniques. The dimensions, course and branching patterns of the MA were recollected. In addition, 20 three-dimensional reconstruction CT head and neck angiograms (3D CTAs) of actual patients were correlated with the cadaveric findings. RESULTS: The MA can be divided in three segments: mandibular, pterygoid and pterygopalatine. Medial and lateral trunk variants regarding its course around the lateral pterygoid muscle can be found. The different branching patterns of the MA have a direct correlation with the course of its main trunk at the base of the skull. Branching and trunk variants on one side do not predict the findings on the contralateral side. CONCLUSION: In this study the highly variable course, branching patterns and relations of the MA are illustrated and described in human cadaveric heads and 3D CTAs. MA 3D CTA with bone reconstruction can be useful preoperatively for the identification of the medial or lateral course variants of this artery, particularly its pterygoid segment, which should be taken into account when considering the MA as a donor vessel for an EC-IC bypass.

Intracranial injectable tumor model: technical advancements.

Background and Objectives Few simulation models are available that provide neurosurgical trainees with the challenge of distorted skull base anatomy despite increasing importance in the acquisition of safe microsurgical and endoscopic techniques. We have previously reported a unique training model for skull base neurosurgery where a polymer is injected into a cadaveric head where it solidifies to mimic a skull base tumor for resection. This model, however, required injection of the polymer under direct surgical vision via a complicated alternative approach to that being studied, prohibiting its uptake in many neurosurgical laboratories. Conclusion We report our updated skull base tumor model that is contrast-enhanced and may be easily and reliably injected under fluoroscopic guidance. We have identified a map of burr holes and injection corridors available to place tumor at various intracranial sites. Additionally, the updated tumor model allows for the creation of mass effect, and we detail the variation of polymer preparation to mimic different tumor properties. These advancements will increase the practicality of the tumor model and ideally influence neurosurgical standards of training.

Acute subdural hematoma from bridging vein rupture: a potential mechanism for growth.

Most acute subdural hematomas (ASDHs) develop after rupture of a bridging vein or veins. The anatomy of the bridging vein predisposes to its tearing within the border cell layer of the dura mater. Thus, the subdural hematoma actually forms within the dura. The hematoma grows by continued bleeding into the border cell layer. However, the venous pressure would not be expected to cause a large hematoma. Therefore, some type of mechanism must account for the hematoma's expansion. Cerebral venous pressure (CVP) has been demonstrated in animal models to be slightly higher than intracranial pressure (ICP), and CVP tracks the ICP as pressure variations occur. The elevation of CVP as the ICP increases is thought to result from an increase in outflow resistance of the terminal portion of the bridging veins. This probably results from a Starling resistor model or, less likely, from a muscular sphincter. A hypothesis is derived to explain the mechanism of ASDH enlargement. Tearing of one or more bridging veins causes these vessels to bleed into the dural border cell layer. Subsequent ICP elevation from the ASDH, cerebral swelling, or other cause results in elevation of the CVP by increased outflow resistance in the intact bridging veins. The increased ICP causes further bleeding into the hematoma cavity via the torn bridging veins. Thus, the ASDH enlarges via a positive feedback mechanism. Enlargement of an ASDH would cease as blood within the hematoma cavity coagulates. This would stop the dissection of the dural border cell layer, and pressure within the hematoma cavity would equalize with that in the torn bridging vein or veins.

Surgical treatment of sacral metastases: indications and results.

OBJECT: Hematogenous metastases to the sacrum can produce significant pain and lead to spinal instability. The object of this study was to evaluate the palliative benefit of surgery in patients with these metastases. METHODS: The authors retrospectively reviewed all cases involving patients undergoing surgery for metastatic disease to the sacrum at a single tertiary cancer center between 1993 and 2005. RESULTS: Twenty-five patients (21 men, 4 women) were identified as having undergone sacral surgery for hematogenous metastatic disease during the study period. Their median age was 57 years (range 25-71 years). The indications for surgery included palliation of pain (in 24 cases), need for diagnosis (in 1 case), and spinal instability (in 3 cases). The most common primary disease was renal cell carcinoma. Complications occurred in 10 patients (40%). The median overall survival was 11 months (95% CI 5.4-16.6 months). The median time from the initial diagnosis to the diagnosis of metastatic disease in the sacrum was 14 months (95% CI 0.0-29.3 months). The numerical pain scores (scale 0-10) were improved from a median of 8 preoperatively to a median of 3 postoperatively at 90 days, 6 months, and 1 year (p < 0.01). Postoperative modified Frankel grades improved in 8 cases, worsened in 3 (due to disease progression), and remained unchanged in 14 (p = 0.19). Among patients with renal cell carcinoma, the median overall survival was better in those in whom the sacrum was the sole site of metastatic disease than in those with multiple sites of metastatic disease (16 vs 9 months, respectively; p = 0.053). CONCLUSIONS: Surgery is effective to palliate pain with acceptable morbidity in patients with metastatic disease to the sacrum. In the subgroup of patients with renal cell carcinoma, those with the sacrum as their solitary site of metastatic disease demonstrated improved survival.

Novel simulation for training trauma surgeons.

BACKGROUND: Clinical training in operative technique is important to boost self-confidence in residents in all surgical fields but particularly in trauma surgery. The fully trained trauma surgeon must be able to provide operative intervention for any injury encountered in practice. In this report, we describe a novel training model using a human cadaver in which circulation in the major vessels can be simulated to mimic traumatic injuries seen in clinical practice. METHODS: Fourteen human cadavers were used for simulating various life-threatening traumatic injuries. The carotid and femoral arteries and the jugular and femoral vein were cannulated and connected to perfusate reservoirs. The arterial reservoir was connected to an intra-aortic balloon pump, which adds pulsatile flow through the heart and major arteries. Fully trained trauma surgeons evaluated the utility of this model for repairing various injuries in the thoracic and abdominal cavity involving the heart, lungs, liver, and major vessels while maintaining emergent airway control. RESULTS: Surgeons reported that this perfused cadaver model allowed simulation of the critical challenges faced during operative trauma while familiarizing the student with the operative techniques and skills necessary to gain access and control of hemorrhage associated with major vascular injuries. CONCLUSION: In this report, we describe a novel training model that simulates the life-threatening injuries that confront trauma surgeons. An alternative to living laboratory animals, this inexpensive and readily available model offers good educational value for the acquisition and refinement of surgical skills that are specific to trauma surgery.

Preservation of the superior petrosal sinus during the petrosal approach.

OBJECT: The petrosal approach is based on sectioning the superior petrosal sinus (SPS) and the tentorium. However, the venous anatomy in certain situations forbids this maneuver. The authors have derived a technique that enables the SPS to be spared during the performance of the petrosal approach. They describe the anatomical basis of this technique and report on 2 cases in which the technique was applied. METHODS: Five alcohol-preserved cadaveric heads injected with colored silicone were used for bilateral dissection and demonstration of the technique. The described method was thoroughly investigated in these cadavers to assess its advantages, variabilities, and limitations. Subsequently, the technique was applied during the resection of petroclival tumors in 2 patients. RESULTS: The authors were able to demonstrate that the approach provides good access to the petroclival area through both the middle and posterior fossa in cadavers. By deriving a new technique of applying the combined petrosal approach without cutting the SPS, the senior author (O.A.M.) managed to achieve total resection of a dumbbell-shaped trigeminal schwannoma in a 19-year-old woman and of a petroclival meningioma in a 49-year-old man. CONCLUSIONS: This modification of the petrosal approach involving sparing of the SPS or cutting of the tentorium is an effective means for cases in which the venous anatomy mandates preservation of these structures.

Optic canal involvement in tuberculum sellae meningiomas: influence on approach, recurrence, and visual recovery.

BACKGROUND: Tuberculum sellae meningiomas frequently extend into the optic canals. OBJECTIVE: To emphasize the high frequency of optic canal (OC) involvement in tuberculum sellae meningiomas; the importance of opening the OC and of removing tumor within the canal; and the effect of this maneuver on visual outcome, recurrence rates, and surgical approach selection. METHODS: A retrospective review of 58 patients with tuberculum sellae meningiomas treated surgically by the senior author (O.A.M) between 1993 and 2009 was performed. The frequency of involvement of the OC was documented, as well as the impact of removal of this part of the tumor on visual outcome and recurrence. RESULTS: Total resection (Simpson grade 1) was achieved in 51 of 58 patients (87.9%). The tumor invaded the optic canal in 67%. Tumor resection from the optic nerve was achieved in all cases, and most (92%) underwent deroofing of the OC for this purpose. The dura over the tuberculum sella and/or planum sphenoidale was removed in all patients. Eighty-three percent required removal of affected hyperostotic bone. Vision was improved and/or spared in 88%. The average follow-up period was 23 months with 1 recurrence detected. CONCLUSION: In the majority of cases, tuberculum sellae meningiomas extend into 1 or both OCs. Opening the OC for resection of the intracanalicular portion of the tumor enabled us to achieve excellent visual outcome. The supraorbital craniotomy remains the favored approach for removal of such tumors because it allows unroofing of both OCs, wide excision of the dura, and drilling of the affected bone.

Skull base tumor model.

OBJECT: Resident duty-hours restrictions have now been instituted in many countries worldwide. Shortened training times and increased public scrutiny of surgical competency have led to a move away from the traditional apprenticeship model of training. The development of educational models for brain anatomy is a fascinating innovation allowing neurosurgeons to train without the need to practice on real patients and it may be a solution to achieve competency within a shortened training period. The authors describe the use of Stratathane resin ST-504 polymer (SRSP), which is inserted at different intracranial locations to closely mimic meningiomas and other pathological entities of the skull base, in a cadaveric model, for use in neurosurgical training. METHODS: Silicone-injected and pressurized cadaveric heads were used for studying the SRSP model. The SRSP presents unique intrinsic metamorphic characteristics: liquid at first, it expands and foams when injected into the desired area of the brain, forming a solid tumorlike structure. The authors injected SRSP via different passages that did not influence routes used for the surgical approach for resection of the simulated lesion. For example, SRSP injection routes included endonasal transsphenoidal or transoral approaches if lesions were to be removed through standard skull base approach, or, alternatively, SRSP was injected via a cranial approach if the removal was planned to be via the transsphenoidal or transoral route. The model was set in place in 3 countries (US, Italy, and The Netherlands), and a pool of 13 physicians from 4 different institutions (all surgeons and surgeons in training) participated in evaluating it and provided feedback. RESULTS: All 13 evaluating physicians had overall positive impressions of the model. The overall score on 9 components evaluated--including comparison between the tumor model and real tumor cases, perioperative requirements, general impression, and applicability--was 88% (100% being the best possible achievable score where the evaluator strongly agreed with the proposed factor). Individual components had scores at or above 80% (except for 1). The only score that was below 80% was related to radiographic visibility of the model for adequate surgical planning (score of 74%). The highest score was given to usefulness in neurosurgical training (98%). CONCLUSIONS: The skull base tumor model is an effective tool to provide more practice in preoperative planning and technical skills.

Treatment of combined osteoporotic compression fractures and spinal stenosis: use of vertebral augumentation and interspinous process spacer.

STUDY DESIGN: Treatment of osteoporotic compression fractures has rapidly evolved with the use of kyphoplasty and vertebroplasty. Likewise, lumbar spinal stenosis is being treated with less invasive procedures such as interspinous process spacers. The combination of such minimally invasive procedures offers new advantages to selected patients. OBJECTIVE: Evaluation of vertebral augmentation combined with interspinous decompression procedure in the same sitting. SUMMARY OF BACKGROUND DATA: We present 2 cases of elderly females who had lumbar compression fractures with back pain, radicular pain and spinal stenosis. Initially, each was treated with an extension brace. In 1 patient, the brace relieved her back pain, but when she would stand or walk, she had severe pain radiating down her left leg preventing mobilization. The other, who lived by herself, had difficulty putting on her brace and did not wear it consistently. METHODS: On discussion with the patients and their families, the decision was made to proceed with vertebral body augmentation followed by placement of an interspinous process spacer in the same sitting. Both patients had rapid resolution of back and radicular pain. Each has had subsequent compression fractures, but the initially treated levels have remained unchanged. RESULTS: The combination of minimally invasive procedures resulted in rapid pain relief and mobilization in our elderly patients. Although other procedures to decompress the spinal canal, lateral recess and foramen, such as muscle splitting portals with removal of just enough bone to decompress the neural elements, could be advocated, use of an interspinous process spacer achieved the decompression with less dissection, less risk of harm to the thecal sac or nerve roots, minimal blood loss, and operative time. CONCLUSION: Combining vertebral augmentation and placement of an interspinous process spacer represents a viable option for treating such fragile patients.

Positive and negative prognostic variables for patients undergoing spine surgery for metastatic breast disease.

The histology of the primary tumor in metastatic spine disease plays an important role in its treatment and prognosis. However, there is paucity in the literature of histology-specific analysis of spinal metastases. In this study, prognostic variables were reviewed for patients who underwent surgery for breast metastases to the spinal column. Respective chart review was done to first identify all patients with breast cancer over an 8-year period at a major cancer center and then to select all those with symptomatic metastatic disease to the spine who underwent spinal surgery. Univariate and multivariate analyses were used to assess several prognostic variables. Presence of visceral metastases, multiplicity of bony lesions, presence of estrogen receptors (ER), and segment of spine (cervical, thoracic, lumbar, sacral) in which metastases arose were compared with patient survival. Eighty-seven patients underwent 125 spinal surgeries. Those with estrogen receptor (ER) positivity had a longer median survival after surgery compared to those with estrogen receptor negativity. Patients with cervical location of metastasis had a shorter median survival compared with those having metastases in other areas of the spine. The presence of visceral metastases or a multiplicity of bony lesions did not have prognostic value. In patients with spinal metastases from breast cancer, aggressive surgical management may be an option for providing significant pain relief and preservation/improvement of neurological function. Interestingly, in patients undergoing such surgery, cervical location of metastasis is a negative prognostic variable, and ER-positivity is associated with better survival, while presence of visceral or multiple bony lesions does not significantly alter survival.

Surgical treatment strategies and outcome in patients with breast cancer metastatic to the spine: a review of 87 patients.

Aggressive surgical management of spinal metastatic disease can provide improvement of neurological function and significant pain relief. However, there is limited literature analyzing such management as is pertains to individual histopathology of the primary tumor, which may be linked to overall prognosis for the patient. In this study, clinical outcomes were reviewed for patients undergoing spinal surgery for metastatic breast cancer. Respective review was done to identify all patients with breast cancer over an eight-year period at a major cancer center and then to select those with symptomatic spinal metastatic disease who underwent spinal surgery. Pre- and postoperative pain levels (visual analog scale [VAS]), analgesic medication usage, and modified Frankel grade scores were compared on all patients who underwent surgery. Univariate and multivariate analyses were used to assess risks for complications. A total of 16,977 patients were diagnosed with breast cancer, and 479 patients (2.8%) were diagnosed with spinal metastases from breast cancer. Of these patients, 87 patients (18%) underwent 125 spinal surgeries. Of the 76 patients (87%) who were ambulatory preoperatively, the majority (98%) were still ambulatory. Of the 11 patients (13%) who were nonambulatory preoperatively, four patients were alive at 3 months postoperatively, three of which (75%) regained ambulation. The preoperative median VAS of six was significantly reduced to a median score of two at the time of discharge and at 3, 6, and 12 months postoperatively (P < 0.001 for all time points). A total of 39% of patients experienced complications; 87% were early (within 30 days of surgery), and 13% were late. Early major surgical complications were significantly greater when five or more levels were instrumented. In patients with spinal metastases specifically from breast cancer, aggressive surgical management provides significant pain relief and preservation or improvement of neurological function with an acceptably low rate of complications.

Craniofacial resections in the elderly: an outcome study.

OBJECT: The elderly population is increasing in number and is healthier now than in the past. The purpose of this study was to examine complications and outcomes following craniofacial resection (CFR) in elderly patients and to compare findings with those of a matched younger cohort. METHODS: All patients 70 years of age or older undergoing CFR at the M.D. Anderson Cancer Center (elderly group) between December 1992 and July 2003 were identified by examining the Department of Neurosurgery database. A random cohort of 28 patients younger than 70 years of age (control group) was selected from the overall population of patients who underwent CFR. There were 28 patients ranging in age from 70 to 84 years (median 74 years). Major local complications occurred in seven elderly patients (25%) and in six control patients (21%) (p = 0.75), and major systemic complications occurred in nine elderly patients (32%) and in three control patients (11%) (p = 0.05). There was one perioperative death in both groups of patients. The median duration of disease-specific survival for the elderly patients was not reached (mean 6.8 years); however, it was 8.3 years for control patients (p = 0.24). Predictors of poorer overall survival from a multivariate analysis of the elderly group included presence of cardiac disease (p = 0.005), a major systemic perioperative complication (p = 0.03), and a preoperative Karnofsky Performance Scale score less than 100 (p = 0.04). CONCLUSIONS: In this study of elderly patients who underwent CFR, there was no difference in disease-specific survival when compared with a matched cohort of younger patients. There was, however, an increased incidence of perioperative major systemic complications in the elderly group.

Metastatic sacral tumors.

Therapeutic approaches are still a matter of debate. Given the complexity of the sacral anatomy and the vicinity of major neural structures and vital organs, advantages of radical resection for local disease control must be weighed against the anticipated treatment morbidities and complications. It becomes imperative to establish a multidisciplinary team approach to provide the best environment for establishing individualized management plans.

Neuropathological and ultrastructural features of amebic encephalitis caused by Sappinia diploidea.

Here we present the neuropathological, ultrastructural, and radiological features of Sappinia diploidea, a newly recognized human pathogen. The patient was a 38-year-old man with visual disturbances, headache, and a seizure. Brain images showed a solitary mass in the posterior left temporal lobe. The mass was composed of necrotizing hemorrhagic inflammation that contained free-living amebae. Immunofluorescence microscopy showed that the organism was not a species of ameba previously known to cause encephalitis. Trophozoites had a highly distinctive double nucleus, and transmission electron microscopy confirmed that they contained 2 nuclei closely apposed along a flattened surface. The 2 nuclei were attached to each other by distinctive connecting perpendicular filaments. This and several other unique structural features led to the diagnosis of S. diploidea encephalitis. The patient was treated postoperatively with a sequential regimen of anti-amebic drugs (azithromycin, pentamidine, itraconazole, and flucytosine) and is alive after 5 years. Guidelines to recognize future cases of S. diploidea encephalitis are as follows. 1) It presented as a tumor-like cerebral mass without an abscess wall. 2) It had central necrotic and hemorrhagic inflammation that contained acute and chronic inflammatory cells without granulomas or eosinophils. 3) It contained trophozoites (40-70 microm diameter) that contained a distinctive double nucleus. 4) Cyst forms in the host were not excluded or definitely evident. 5) Trophozoites engulfed host blood cells and were stained brightly with Giemsa and periodic acid-Schiff. 6) Trophozoites often were present in viable brain parenchyma on the periphery of the mass without inflammatory response. 7) The prognosis after surgical excision and medical treatment was favorable in this instance.

Percutaneous vertebroplasty and kyphoplasty for painful vertebral body fractures in cancer patients.

OBJECT: The current North American experience with minimally invasive vertebro- and kyphoplasty is largely limited to the treatment of benign osteoporotic compression fractures. The objective of this study was to assess the safety and efficacy of these procedures for painful vertebral body (VB) fractures in cancer patients. METHODS: The authors reviewed a consecutive group of cancer patients (21 with myeloma and 35 with other primary malignancies) undergoing vertebro- and kyphoplasty at their institution. Ninety-seven (65 vertebro- and 32 kyphoplasty) procedures were performed in 56 patients during 58 treatment sessions. The mean patient age was 62 years (+/- 13 years [standard deviation]) and the median duration of symptoms was 3.2 months. All patients suffered intractable spinal pain secondary to VB fractures. Patients noted marked or complete pain relief after 49 procedures (84%), and no change after five procedures (9%); early postoperative Visual Analog Scale (VAS) pain scores were unavailable in four patients (7%). No patient was worse after treatment. Reductions in VAS pain scores remained significant up to 1 year (p = 0.02, Wilcoxon signed-rank test). Analgesic consumption was reduced at 1 month (p = 0.03, Wilcoxon signed-rank test). Median follow-up length was 4.5 months (range 1 day-19.7 months). Asymptomatic cement leakage occurred during vertebroplasty at six (9.2%) of 65 levels; no cement extravasation was seen during kyphoplasty. There were no deaths or complications related to the procedures. The mean percentage of restored VB height by kyphoplasty was 42 +/- 21%. CONCLUSIONS: Percutaneous vertebro- and kyphoplasty provided significant pain relief in a high percentage of patients, and this appeared durable over time. The absence of cement leakage-related complications may reflect the use of 1) high-viscosity cement; 2) kyphoplasty in selected cases; and 3) relatively small volume injection. Precise indications for these techniques are evolving; however, they are safe and feasible in well-selected patients with refractory spinal pain due to myeloma bone disease or metastases.

Preoperative embolization and intraoperative cryocoagulation as adjuncts in resection of hypervascular lesions of the thoracolumbar spine.

OBJECT: The purpose of this study was twofold. First the authors evaluated preoperative embolization alone to reduce estimated blood loss (EBL) when resecting hypervascular lesions of the thoracolumbar spine. Second, they compared this experience with intraoperative cryotherapy alone or in conjunction with embolization to minimize further EBL. METHODS: Twelve patients underwent 13 surgeries for hypervascular spinal tumors. In 10 cases the surgeries were augmented by preoperative embolization alone. In one patient, two different surgeries involved intraoperative cryocoagulation, and in one patient surgery involved a combination of preoperative embolization and intraoperative cryocoagulation for tumor resection. When cryocoagulation was used, its extent was controlled using intraoperative ultrasonography or by establishing physical separation of the spinal cord from the tumor. In the 10 cases in which embolization alone was conducted, intraoperative EBL in excess of 3 L occurred in five. Mean EBL was of 2.8 L per patient. In one patient, who underwent only embolization, excessive bleeding (> 8 L) required that the surgery be terminated and resulted in suboptimum tumor resection. In another three cases, intraoperative cryocoagulation was used alone (in two patients) or in combination with preoperative embolization (in one patient). In all procedures involving cryocoagulation of the lesion, adequate hemostasis was achieved with a mean EBL of only 500 ml per patient. No new neurological deficits were attributable to the use of cryocoagulation. CONCLUSIONS: Preoperative embolization alone may not always be satisfactory in reducing EBL in resection of hypervascular tumors of the thoracolumbar spine. Although experience with cryocoagulation is limited, its use, in conjunction with embolization or alone, suggests it may be helpful in limiting EBL beyond what can be achieved with embolization alone. Cryocoagulation may also assist resection by preventing spillage of tumor contents, facilitating more radical excision, and enabling spinal reconstruction. The extent of cryocoagulation could be adequately controlled using ultrasonography or by establishing physical separation between the tumor and spinal cord. Additionally, somatosensory evoked potential monitoring may provide early warning of spinal cord cooling.