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Jimmy D. Miller and Remi Nader

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.

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Ahmad Hafez, Remi Nader and Ossama Al-Mefty

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.

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Iman Feiz-Erfan, Benjamin D. Fox, Remi Nader, Dima Suki, Indro Chakrabarti, Ehud Mendel, Ziya L. Gokaslan, Ganesh Rao and Laurence D. Rhines

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.

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Remi Nader, Brent T. Alford, Haring J. W. Nauta, Wayne Crow, Eric Vansonnenberg and Alexander G. Hadjipavlou

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.

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Hematogenous pyogenic facet joint infection of the subaxial cervical spine

A report of two cases and review of the literature

Anthony J. Muffoletto, Remi Nader, Richard M. Westmark, Haring J. W. Nauta, Kim J. Garges and Alexander G. Hadjipavlou

✓ Two cases of hematogenous, pyogenic, subaxial cervical facet joint infection are reported, and the literature is reviewed. Infection of the cervical facet joint is a rarely diagnosed condition; only one case has been reported in the literature. Lumbar facet joint infections are also rare but more commonly reported. Approximately one fourth of facet joint infections in the lumbar spine are complicated by epidural abscess formation, which can lead to a neurological deficit. Because of the paucity of reports on cervical facet joint infections, the clinical characteristics of this entity are not well known.

Both patients presented with an acute onset of unilateral neck pain that radiated into the ipsilateral shoulder. Frank radicular pain was initially absent. Unilateral upper-extremity motor weakness that was attributed to associated epidural abscess or granulation tissue formation was also demonstrated in both patients. Leukocyte count and erythrocyte sedimentation rate were elevated in both cases. Magnetic resonance imaging was necessary to obtain an accurate diagnosis. Staphylococcus aureus was identified as the offending pathogen in both cases. Decompressive surgery and antibiotic therapy were required to cure the condition. One patient recovered completely and the other sustained a permanent motor deficit.

Hematogenous cervical facet joint infection is a rare clinical entity that has many characteristics in common with the more-common lumbar homolog. All three reported cases, however, have been complicated by epidural abscess or granulation tissue formation that has led to a neurological deficit. This finding suggests that a facet joint infection in the cervical spine may have a less benign clinical course than that in the lumbar spine.

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Stephen J. Hentschel, Remi Nader, Dima Suki, Amer Dastgir, David L. Callender and Franco DeMonte

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.

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Daryl R. Fourney, Donald F. Schomer, Remi Nader, Jennifer Chlan-Fourney, Dima Suki, Kamran Ahrar, Laurence D. Rhines and Ziya L. Gokaslan

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 3volume 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.

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Skull base tumor model

Laboratory investigation

Cristian Gragnaniello, Remi Nader, Tristan van Doormaal, Mahmoud Kamel, Eduard H. J. Voormolen, Giovanni Lasio, Emad Aboud, Luca Regli, Cornelius A. F. Tulleken and Ossama Al-Mefty

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.