Global Neurosurgery: A Retrospective Cohort Study to Compare the Effectiveness of Two Training Methods in Resource-Poor Settings

BACKGROUND AND OBJECTIVES

Many low- and middle-income countries are experiencing profound health care workforce shortages. Surgical subspecialists generally practice in large urban centers but are in high demand in rural areas. These subspecialists must be trained through sustainable programs to address this disparity. We quantitatively compared the relative effectiveness of 2 unique training models to advance neurosurgical skills in resource-poor settings where formally trained neurosurgeons are unavailable.

METHODS

Neurosurgical procedure data were collected from 2 hospitals in Tanzania (Haydom Lutheran Hospital [HLH] and Bugando Medical Centre [BMC]), where 2 distinct training models ("Train Forward" and "Back-to-Back," respectively) were incorporated between 2005 and 2012.

RESULTS

The most common procedures performed were ventriculoperitoneal shunt (BMC: 559, HLH: 72), spina bifida repair (BMC: 187, HLH: 54), craniotomy (BMC: 61, HLH: 19), bone elevation (BMC: 42, HLH: 32), and craniotomy and evacuation (BMC: 18, HLH: 34). The number of annual procedures at BMC increased from 148 in 2008 to 357 in 2012; at HLH, they increased from 18 in 2005 to 80 in 2010. Postoperative complications over time decreased or did not significantly change at both sites as the diversity of procedures increased.

CONCLUSION

The Train Forward and Back-to-Back training models were associated with increased surgical volume and complexity without increased complications. However, only the Train Forward model resulted in local, autonomous training of surgical subspecialists after completion of the initial training period. Incorporating the Train Forward method into existing training programs in low- and middle-income countries may provide unique benefits over historic training practices.

Interactive microsurgical anatomy education using photogrammetry 3D models and an augmented reality cube

OBJECTIVE

This study sought to assess the use of an augmented reality (AR) tool for neurosurgical anatomical education.

METHODS

Three-dimensional models were created using advanced photogrammetry and registered onto a handheld AR foam cube imprinted with scannable quick response codes. A perspective analysis of the cube anatomical system was performed by loading a 3D photogrammetry model over a motorized turntable to analyze changes in the surgical window area according to the horizontal rotation. The use of the cube as an intraoperative reference guide for surgical trainees was tested during cadaveric dissection exercises. Neurosurgery trainees from international programs located in Ankara, Turkey; San Salvador, El Salvador; and Moshi, Tanzania, interacted with and assessed the 3D models and AR cube system and then completed a 17-item graded user experience survey.

RESULTS

Seven photogrammetry 3D models were created and imported to the cube. Horizontal turntable rotation of the cube translated to measurable and realistic perspective changes in the surgical window area. The combined 3D models and cube system were used to engage trainees during cadaveric dissections, with satisfactory user experience. Thirty-five individuals (20 from Turkey, 10 from El Salvador, and 5 from Tanzania) agreed that the cube system could enhance the learning experience for neurosurgical anatomy.

CONCLUSIONS

The AR cube combines tactile and visual sensations with high-resolution 3D models of cadaveric dissections. Inexpensive and lightweight, the cube can be effectively implemented to allow independent co-visualization of anatomical dissection and can potentially supplement neurosurgical education.

Neurosurgical capacity building in the developing world through focused training

OBJECT

In Tanzania, there are 4 neurosurgeons for a population of 46 million. To address this critical shortage of neurosurgical care, the authors worked with local Tanzanian health care workers, neurosurgeons, the Ministry of Health and Social Welfare, and the Office of the President of Tanzania to develop a train-forward method for sustainable, self-propagating basic and emergency neurosurgery in resource-poor settings. The goal of this study was to assess the safety and effectiveness of this method over a 6-year period.

METHODS

The training method utilizes a hands-on bedside teaching technique and was introduced in 2006 at a remote rural hospital in northern Tanzania. Local health care workers were trained to perform basic and emergency neurosurgical procedures independently and then were taught to train others. Outcome information was retrospectively collected from hospital records for the period from 2005 (1 year before method implementation) through 2010. Analysis of de-identified data included descriptive statistics and multivariable assessment of independent predictors of complications following a patient's first neurosurgical procedure.

RESULTS

By 2010, the initial Tanzanian trainee had trained a second Tanzanian health care worker, who in turn had trained a third. The number of neurosurgical procedures performed increased from 18 in 2005 to an average of 92 per year in the last 3 years of the study period. Additionally, the number of neurosurgical cases performed independently by Tanzanian health care providers increased significantly from 44% in 2005 to 86% in 2010 (p < 0.001), with the number of complex cases independently performed also increasing over the same time period from 34% to 83% (p < 0.001). Multivariable analysis of clinical patient outcome information to assess safety indicated that postoperative complications decreased significantly from 2005 through 2010, with patients who had been admitted as training progressed being 29% less likely to have postoperative complications (OR 0.71, 95% CI 0.52-0.96, p = 0.03).

CONCLUSIONS

The Madaktari Africa train-forward method is a reasonable and sustainable approach to improving specialized care in a resource-poor setting.

The use of IV-tubing as a closed-suction drainage system during neurosurgical cases in Tanzania

Background:

Commercial closed-suctions drainage systems are commonly used in the United States and many other countries for use in neurosurgical cases. However, in Tanzania and other developing nations with fewer resources, these are not available. This report explores another option for a closed-system drainage system utilizing inexpensive supplies found commonly in hospitals around the world.

Methods:

Sterile IV-tubing is cut, inserted into the wound, and brought out through an adjacent puncture incision. For suction, an empty plastic bottle can be attached to the tubing.

Results:

The IV-tubing closed-suction drainage system was applied in both cranial and spinal neurosurgical procedures, including as subdural, subgaleal, epidural, and suprafacial drains. It maintained suction and was an adequate substitute when commercial drains are unavailable.

Conclusions:

This report illustrates how sterile IV-tubing can be adapted for use as a closed-drainage system. It utilizes inexpensive supplies commonly found in many hospitals throughout the world and can be applied to both cranial and spinal neurosurgical procedures.

Decompressive craniectomy: technical note

Decompressive craniectomy is a neurosurgical technique in which a portion of the skull is removed to reduce intracranial pressure. The rationale for this procedure is based on the Monro-Kellie Doctrine; expanding the physical space confining edematous brain tissue after traumatic brain injury will reduce intracranial pressure. There is significant debate over the efficacy of decompressive craniectomy despite its sound rationale and historical significance. Considerable variation in the employment of decompressive craniectomy, particularly for secondary brain injury, explains the inconsistent results and mixed opinions of this potentially valuable technique. One way to address these concerns is to establish a consistent methodology for performing decompressive craniectomies. The purpose of this paper is to begin accomplishing this goal and to emphasize the critical points of the hemicraniectomy and bicoronal (Kjellberg type) craniectomy.

History and current state of neurosurgery at the Medical University of South Carolina

We review the development of neurosurgery at the Medical University of South Carolina (MUSC) and the emergence of MUSC as a leading academic neurosurgical center in South Carolina. Historical records from the Waring Historical Library were studied, former and current faculty members were interviewed, and the personal records of Dr Phanor J Perot were examined. Dr Frederick E Kredel was the first to perform cerebral revascularization in stroke patients using omental flaps and the first to culture glioma cells in artificial media. The MUSC Neurosurgery residency program was established in 1964 by its first formally trained neurosurgeon, Julian Youmans, MD. The first graduate of the program, Dr Russell Travis, went on to become the President of the American Association of Neurological Surgeons. In 1968, the longest serving chairman, Dr Perot, joined the department and conducted significant research in spinal cord injury, receiving a continuous, 20-year award from the National Institute of Neurological Disorders and Stroke. A major change in the neurosurgery program occurred in 2004 when Dr Sunil Patel accepted the chairmanship. He integrated neurosurgery, neurology, and basic neuroscience departments into a comprehensive Department of Neurosciences to provide integrated clinical care. This department now ranks second in the country in National Institutes of Health research funding. Recently, the Center for Global Health and Global Neurosurgery was established with a vision of caring for patients beyond national borders. Neurosurgery at MUSC has been influenced by Drs Kredel and Perot and the current leadership is moving forward with a uniquely integrated department with novel areas such as global neurosurgery.

The role of surgery for high-grade intracranial dural arteriovenous fistulas: importance of obliteration of venous outflow

Object

Surgical intervention may be required if endovascular embolization is insufficient to completely obliterate intracranial dural arteriovenous fistulas (DAVFs). The authors report their 14-year experience with 23 patients harboring diverse intracranial DAVFs that required surgical intervention.

Methods

Between 1993 and 2007, 23 patients underwent surgery for intracranial DAVFs. The following types of DAVFs were treated: superior petrosal sinus (in 10 patients); parietooccipital (in 3); confluence of sinuses and ethmoidal (in 2 each); and tentorial, falcine, occipital, transverse-sigmoid, superior sagittal, and cavernous sinuses (in 1 patient each). In all cases, the authors' goal was to obliterate the DAVF venous outflow by direct surgical interruption of the leptomeningeal venous drainage. Transarterial embolization was used primarily as an adjunct to decrease flow to the DAVF prior to definitive treatment.

Results

Complete angiographic obliteration of the DAVF was achieved in all cases. There were no complications of venous hypertension, venous infarction, or perioperative death. There were no recurrences and no further clinical events (new hemorrhages or focal neurological deficits) after a mean follow-up of 45 months.

Conclusions

The authors' experience emphasizes the importance of occluding venous outflow to obliterate intracranial DAVFs. Those that drain purely through leptomeningeal veins can be safely obliterated by surgically clipping the arterialized draining vein as it exits the dura. Radical excision of the fistula is not necessary.

Basilar tip aneurysm - adenosine induced asystole for the treatment of a basilar tip aneurysm following failure of temporary clipping

We report on a giant basilar tip aneurysm in a 48-year-old woman that could not be clipped despite temporary occlusion of the basilar trunk. Adenosine induced cardiac asystole reduced the aneurysm's wall tension and coupled with increased exposure resulting from brain relaxation allowed for the aneurysm to be satisfactorily occluded via an extended right pterional craniotomy. In difficult vascular cases, adenosine induced cardiac standstill is a useful technique which may allow for technical success when other methods such as temporary clipping fail. It acts to both reduce aneurysm wall tension and increase operative exposure by reducing vascular, and hence brain volume.

Delayed re-opening of an STA-MCA bypass graft

We describe the case of a 47-year-old female with symptomatic right MCA stenosis who had undergone cerebral revascularization through a superficial temporal artery-to-middle cerebral artery (STA-MCA) bypass. Despite clear patency in the operating room, post-operative angiography showed no flow in the bypass. Her ipsilateral internal carotid artery (ICA) was widely patent. She remained asymptomatic and follow-up angiography four years later showed a widely patent bypass graft in the setting of critical stenosis of the ipsilateral ICA. That the graft was found opened up and supplying the hemisphere was presumably stimulated by an increased "demand" and flow gradient promoting its patency.

Principles of cerebral oxygenation and blood flow in the neurological critical care unit

Cerebrovascular disease and trauma are leading causes of death in the United States. In addition to the initial insult to the brain, disturbances of cerebral oxygenation and metabolism underlie many of the secondary pathophysiological processes that increase both morbidity and mortality. Therefore, researchers and clinicians have sought to obtain a more thorough understanding of the physiological and biochemical principles of cerebral oxygenation and metabolism. New technologies capable of offering continuous and quantitative assessment of cerebral oxygenation may improve clinical outcomes. In this article, we review the physiological principles of cerebral metabolism, cerebral blood flow and their metabolic coupling, and cerebral oxygenation, with particular emphasis on variables that could be monitored and managed in an intensive care unit setting.

Contrast ultrasonographic assessment of cerebral perfusion in patients undergoing decompressive craniectomy for traumatic brain injury

Object

The aims of this study were to determine whether contrast-enhanced ultrasonography (CEU) could be used for noninvasive evaluation of cerebral perfusion in patients with traumatic brain injury (TBI) and to assess the effect of decompressive surgery on cerebral perfusion as measured by CEU.

Methods

Contrast-enhanced ultrasonography with intravenous administration of a microbubble contrast agent was performed in six patients with TBI undergoing decompressive craniectomy. Contrast-enhanced ultrasonography was performed through a bur hole before craniectomy and through the calvarial defect immediately after craniectomy and on postoperative Days 1 and 2. For the latter two studies, patients were placed in the recumbent position and at a 35° incline to investigate changes in perfusion produced by modulation of intracranial pressure (ICP). Cerebral microvascular blood flow increased by almost threefold immediately after craniectomy, from a mean of 7.5 ± 6.9 (standard deviation [SD]) to 20.9 ± 11.6 (p < 0.05), and further improved on postoperative Day 1 (mean 37.1 ± 13.9 [SD], p < 0.05, compared with postcraniectomy microvascular blood flow) without subsequent change on Day 2. The change in microvascular perfusion correlated inversely with the initial ICP (p < 0.01), indicating less recovery of flow when preoperative ICP was markedly elevated. On postoperative Days 1 and 2, head-of-bed elevation produced an increase in microvascular perfusion on CEU (mean 37 ± 11 compared with 51 ± 20, p < 0.05) and a small decrease in ICP (mean 16 ± 5 mm Hg compared with 12 ± 4 mm Hg, p < 0.05). In patients with parenchymal hematoma, CEU provided spatial information on perfusion abnormalities in the hemorrhagic core and surrounding tissues.

Conclusions

Contrast-enhanced ultrasonography has potential for the intraoperative and bedside assessment of cerebral perfusion in patients with TBI. The technique may be appropriate for evaluating responses to therapies aimed at preventing secondary ischemia and for assessing regional perfusion abnormalities.

Neuromonitoring in Neurological Critical Care

In this article, we review technologies available for direct monitoring of cerebral oxygenation and metabolic status, including jugular venous oxygen saturation, brain tissue oxygen tension, transcranial cerebral oximetry with near-infrared spectroscopy, Positron emission tomography oxidative metabolism, single-photon emission computed tomography/computed tomography perfusion and functional imaging, and cerebral metabolite measurement using microdialysis. We also introduce a novel method of monitoring cerebral perfusion that may substitute for direct monitoring of oxygenation in the future.

Pioneers in the development of neurological surgery in Auckland, New Zealand: Robertson, Wrightson, and Mackenzie

OBJECTIVE

To demonstrate the development of neurosurgery in Auckland, New Zealand, which has diverse roots and was influenced by geographical, socioeconomic, and international forces.

METHODS

Historical records were examined, and interviews were conducted to determine the factors that shaped the development of neurological surgery in Auckland, New Zealand.

RESULTS

Sir Carrick Robertson, a Scotsman, was one of the more enterprising general surgeons in Auckland. As early as the 1920s, he performed and published the results of several neurosurgical procedures. Later, Donald Mackenzie, another Auckland general surgeon, went abroad to gain neurosurgical experience from his North American and British colleagues. He returned and founded the Auckland Neurosurgical Department in 1945. David Robertson and Phillip Wrightson later joined the department, and they were instrumental in conducting early research on shunt systems, head injury, and pituitary tumors. The neurosurgical department Mackenzie founded went on to become the largest in New Zealand and presently serves metropolitan Auckland as well as both rural areas of New Zealand's North Island and many smaller Pacific island nations.

CONCLUSION

Neurological surgery in Auckland was influenced largely by Great Britain, Australia, and North America, as well as by geographical and socioeconomic factors unique to the South Pacific. The achievements of these earlier pioneers in neurosurgery highlight their tremendous abilities and sheer determination to succeed.

Characterization of genetically defined types of Charcot-Marie-Tooth neuropathies by using magnetic resonance neurography

Object. Charcot-Marie-Tooth (CMT) disease is a collection of related genetic disorders affecting peripheral nerves with an incidence of one in every 2500 individuals. A diagnosis of CMT disease has classically relied on a medical history, examination, and measurement of nerve conduction velocities. Advancements in genetic testing and magnetic resonance (MR) imaging techniques may provide clinicians with a more precise diagnostic armamentarium. The authors investigated MR neurography as a possible method to characterize CMT subtypes.

Methods. The authors performed MR neurography to evaluate sciatic nerves in the mid-thigh area of seven patients with genetically defined subtypes of CMT, one patient with chronic inflammatory demylinating polyneuropathy, and one patient without neuropathy. The authors correlate their findings with normal nerve conduction velocities (NCVs) and present their results as a descriptive case series.

Although MR neurography could not be used to distinguish subtypes of CMT disease on nerve area or fascicle number, it appears to characterize phenotypic features and disease progression noninvasively in patients with some subtypes.

Conclusions. In conjunction with NCV measurements, MR neurography may be useful in the diagnosis of CMT neuropathies and in monitoring disease progression.

Imaging tumor angiogenesis with contrast ultrasound and microbubbles targeted to alpha(v)beta3

BACKGROUND

Angiogenesis is a critical determinant of tumor growth and metastasis. We hypothesized that contrast-enhanced ultrasound (CEU) with microbubbles targeted to alpha(v)-integrins expressed on the neovascular endothelium could be used to image angiogenesis.

METHODS AND RESULTS

Malignant gliomas were produced in 14 athymic rats by intracerebral implantation of U87MG human glioma cells. On day 14 or day 28 after implantation, CEU was performed with microbubbles targeted to alpha(v)beta3 by surface conjugation of echistatin. CEU perfusion imaging with nontargeted microbubbles was used to derive tumor microvascular blood volume and blood velocity. Vascular alpha(v)-integrin expression was assessed by immunohistochemistry, and microbubble adhesion was characterized by confocal microscopy. Mean tumor size increased markedly from 14 to 28 days (2+/-1 versus 35+/-14 mm2, P<0.001). Tumor blood volume increased by approximately 35% from day 14 to day 28, whereas microvascular blood velocity decreased, especially at the central portions of the tumors. On confocal microscopy, alpha(v)beta3-targeted but not control microbubbles were retained preferentially within the tumor microcirculation. CEU signal from alpha(v)beta3-targeted microbubbles in tumors increased significantly from 14 to 28 days (1.7+/-0.4 versus 3.3+/-1.0 relative units, P<0.05). CEU signal from alpha(v)beta3-targeted microbubbles was greatest at the periphery of tumors, where alpha(v)-integrin expression was most prominent, and correlated well with tumor microvascular blood volume (r=0.86).

CONCLUSIONS

CEU with microbubbles targeted to alpha(v)beta3 can noninvasively detect early tumor angiogenesis. This technique, when coupled with changes in blood volume and velocity, may provide insights into the biology of tumor angiogenesis and be used for diagnostic applications.

Intrasellar Schwannomas: Report of Two Cases

OBJECTIVE AND IMPORTANCE

The complex regional anatomic features surrounding the sella turcica make the differential diagnosis of intrasellar and parasellar lesions complicated. Sellar and parasellar schwannomas are rare. With the exclusion of parasellar schwannomas arising from cranial nerves within the cavernous sinus and extending into the sella, there have been only two reported cases of true intrasellar schwannomas.

CLINICAL PRESENTATION

We describe the clinical, radiological, and pathological features of two cases in which the histopathological diagnosis of schwannoma was confirmed with immunohistochemical analyses and/or electron microscopy.

INTERVENTION

The two cases were grossly resected via a transsphenoidal approach. Follow-up monitoring revealed no evidence of recurrence.

CONCLUSION

Schwannomas may atypically occur in the sellar region, in which they demonstrate the typical light microscopic, immunohistochemical, and ultrastructural features observed in the peripheral nervous system. New and existing hypotheses regarding the histopathogenesis of intrasellar and parasellar schwannomas are presented.

Intrasellar schwannomas: report of two cases

OBJECTIVE AND IMPORTANCE

The complex regional anatomic features surrounding the sella turcica make the differential diagnosis of intrasellar and parasellar lesions complicated. Sellar and parasellar schwannomas are rare. With the exclusion of parasellar schwannomas arising from cranial nerves within the cavernous sinus and extending into the sella, there have been only two reported cases of true intrasellar schwannomas.

CLINICAL PRESENTATION

We describe the clinical, radiological, and pathological features of two cases in which the histopathological diagnosis of schwannoma was confirmed with immunohistochemical analyses and/or electron microscopy.

INTERVENTION

The two cases were grossly resected via a transsphenoidal approach. Follow-up monitoring revealed no evidence of recurrence.

CONCLUSION

Schwannomas may atypically occur in the sellar region, in which they demonstrate the typical light microscopic, immunohistochemical, and ultrastructural features observed in the peripheral nervous system. New and existing hypotheses regarding the histopathogenesis of intrasellar and parasellar schwannomas are presented.

Anemia, testosterone, and pituitary adenoma in men

OBJECT

Older men with clinically nonfunctioning pituitary tumors have been noted to be anemic, to have hypopituitarism, and to have low serum levels of testosterone. The authors hypothesized that men with pituitary adenomas and hypogonadism have a physiologically related decrease in hematocrit.

METHODS

A retrospective analysis was conducted of 216 patients older than 50 years of age who harbored pituitary adenomas. In 100 men serum testosterone levels and a complete blood (cell) count (CBC) were obtained before treatment; a CBC was also acquired in a series of women with pituitary adenomas. Using clinical laboratory standards, anemia was defined as a hematocrit less than 40% in men and less than 35% in women. Thirty-one (46.3%) of 67 men with low serum concentrations of testosterone were anemic. In men with low levels of testosterone, the average hematocrit was 39.9%, compared with 45.6% for men with normal testosterone levels (p < 0.001). Men with macroadenomas were most likely to have both anemia and a low serum concentration of testosterone. Anemia was associated with a low level of testosterone, adjusting for tumor size (odds ratio 19, 95% confidence interval 4.86-77.03). Of patients with anemia, 84% were men and 16% were women (p < 0.001). The prevalence of anemia in women was low and was not correlated with tumor size. Men receiving testosterone replacement therapy had a significantly higher hematocrit value than men with low or normal testosterone levels.

CONCLUSIONS

These findings support a direct relationship between serum testosterone levels and hematopoiesis in men, and demonstrate that hematopoiesis is compromised in men who have low concentrations of testosterone due to a pituitary adenoma.

Use of FloSeal hemostatic sealant in transsphenoidal pituitary surgery: technical note

OBJECTIVE

Bleeding during transsphenoidal pituitary surgery can lead to a variety of operative difficulties. When the endonasal transsphenoidal approach is used, even mild intraoperative hemorrhage can lessen visibility in the confined operative field of view. This technical note describes the use of a hemostatic agent we have found of benefit in obtaining prompt hemostasis during this operation.

METHODS

Operative records were reviewed for an 18-month period for all patients who underwent transsphenoidal surgery since we began using FloSeal hemostatic sealant in January 2000.

RESULTS

During the study period, 293 transsphenoidal operations were performed for pituitary lesions. Of these, 20 procedures involved vigorous or persistent bleeding. When the standard techniques for hemostasis failed or were inadequate, FloSeal, a sterile mixture of a gelatin matrix and thrombin component mixed at the time of use, was applied to the site of hemorrhage by use of a 14-gauge angiocatheter to reach the sella. We observed complete hemostasis immediately on application of FloSeal in all cases except one, which required a second application. Hemostasis was obtained immediately after the second application. No operations were aborted during this period as a consequence of undue bleeding.

CONCLUSION

We detail the method in which we use FloSeal in transsphenoidal surgery and report our impression of its effectiveness. FloSeal has been demonstrated to be safe and biocompatible as compared with hemostatic agents currently in use.

Surgical salvage of microcatheter-induced aneurysm perforation during coil embolization

We report a case of iatrogenic aneurysm rupture during coil embolization in a 55-year-old woman. Surgical intervention resulted in a good clinical outcome. To our knowledge, this technique for the salvage of catheter-induced aneurysm perforation has not been previously reported.

Blood use in cerebrovascular neurosurgery

BACKGROUND AND PURPOSE

This study reviews the perioperative use of red blood cell transfusion in cerebrovascular neurosurgery. The current algorithm for preoperative ordering of red cells is historical and dated. More blood is ordered than is actually transfused, and considerable variability exists between different institutions. We determine the use of blood transfusion in cerebrovascular surgery to develop a rational blood ordering practice.

METHODS

Records of 301 patients undergoing cerebrovascular neurosurgery at the University of Virginia were reviewed to quantitatively evaluate red blood cell transfusion practices. The amount and reason for transfusion were noted in each case.

RESULTS

In 126 patients undergoing carotid endarterectomy, there were no preoperative or intraoperative transfusions and 5 postoperative transfusions (4.0%). In 71 ruptured aneurysm patients, there were 2 preoperative blood transfusions (2.8%), 4 intraoperative transfusions (5.6%), and 15 postoperative transfusions (21.1%). Forty-seven patients underwent surgery for unruptured aneurysms, with no preoperative transfusions, 2 intraoperative transfusions (4.3%), and 8 postoperative blood transfusions (17.0%). Of the 54 patients undergoing surgery for arteriovenous malformations, 5 patients (9.3%) were transfused preoperatively, 4 were transfused intraoperatively (7.4%), and 22 were transfused postoperatively (40.7%). None of the 3 patients undergoing surgery for concomitant arteriovenous malformations and aneurysms received intraoperative blood transfusions, but 1 received blood both preoperatively and postoperatively, and another received a transfusion postoperatively only. The overall ratio of perioperative cross-match to transfusion in this series is 41.4.

CONCLUSIONS

In vascular neurosurgery at our institution, blood has routinely been ordered excessively. We recommend an ABO-Rh type and antibody screen for aneurysm and arteriovenous malformation surgery and no screen for carotid endarterectomy to efficiently utilize transfusion therapy in cerebrovascular surgery.

The long-term significance of microscopic dural invasion in 354 patients with pituitary adenomas treated with transsphenoidal surgery

OBJECT

Pituitary adenomas are considered benign tumors; however, they may infiltrate surrounding tissues including the dura mater. In this paper the authors analyze the clinical significance of microscopically confirmed dural invasion by comparing a range of variables (age and sex of patients, adenoma type, adenoma size on magnetic resonance [MR] images, remission, residual pituitary disease, recurrence, survival, and disease-free interval after surgery) between patients with noninvasive adenomas and those with invasive ones.

METHODS

Between 1992 and 1997 dural specimens were obtained in 354 patients with pituitary adenomas who underwent transsphenoidal surgery performed by the senior author (E.R.L.). Dural specimens were examined using routine histological methods and assessed for invasion by pituitary adenoma tissue. The dura was invaded by the pituitary adenoma in 161 patients (45.5%), and in 192 patients (54.5%) no evidence of dural invasion was found. Dural invasion was present significantly more frequently in the repeated surgery group (69%, 55 patients) than in the primary transsphenoidal surgery group (41%, 291 patients). The mean age of patients undergoing primary transsphenoidal surgery was significantly older in cases of invasive adenomas (50 years) compared with cases of noninvasive adenomas (43 years), and these age differences also correlated with adenoma size. Women tend to develop clinically evident, smaller adenomas at a younger age than men. Of the patients with pituitary adenomas that were 20 mm or smaller, 117 (76%) of 154 were women, whereas of the patients with adenomas that were larger than 20 mm, 74 (54%) of 137 were men. The frequency of dural invasion increased with increasing size of the pituitary adenoma as measured on MR images. In 291 patients who underwent primary pituitary surgery, the frequency of dural invasion according to adenoma size was 24% (< or = 10 mm), 35% (> 10 to < or = 20 mm), 55% (> 20 to < or = 40 mm), and 70% (> 40 mm). In patients who underwent primary transsphenoidal surgery, dural invasion was present in more than 50% of those with nonfunctioning adenomas and in 30 to 35% of patients with endocrinologically active adenomas. The mean diameter of the gonadotrophic adenomas and null-cell adenomas was significantly larger than that of each of the endocrinologically active adenomas. In 58 (20%) of 291 patients who underwent primary pituitary surgery there was residual pituitary disease postsurgery, and 20% of this subset of patients showed clinical improvement to such an extent that no further management was recommended. After pituitary surgery, residual tumor tissue was demonstrable significantly more frequently in patients with invasive adenomas than in those with noninvasive adenomas. Recurrences after initial remission (cure) of pituitary disease occurred in 18 (8.8%) of 205 patients between 2 and 79 months after primary pituitary surgery (median 25 months). The recurrence rate was not related to dural invasion in a consistent or significant fashion. Seven patients died between 14 and 79 months after pituitary surgery and all had invasive adenomas identified on gross observation at surgery and on microscopy. The survival rate was slightly but significantly decreased for patients with invasive adenomas (91%) compared with patients with noninvasive adenomas (100%) at 6 years postsurgery.

CONCLUSIONS

The principal significance of dural invasion by pituitary adenoma is the persistence of tumor tissue after transsphenoidal surgery (incomplete adenomectomy; 20% in primary pituitary tumor resections). The increase in adenoma size with time and the concurrent development of dural invasion are the major factors that determine an incomplete adenomectomy. When the adenoma remains restricted to the sellar compartment or shows only moderate suprasellar extension, dural invasion may not yet have developed and conditions for complete selective adenomectomy are improved.

Acute spinal cord injury, part I: pathophysiologic mechanisms

Spinal cord injury (SCI) is a devastating and common neurologic disorder that has profound influences on modern society from physical, psychosocial, and socioeconomic perspectives. Accordingly, the present decade has been labeled the Decade of the Spine to emphasize the importance of SCI and other spinal disorders. Spinal cord injury may be divided into both primary and secondary mechanisms of injury. The primary injury, in large part, determines a given patient's neurologic grade on admission and thereby is the strongest prognostic indicator. However, secondary mechanisms of injury can exacerbate damage and limit restorative processes, and hence, contribute to overall morbidity and mortality. A burgeoning body of evidence has facilitated our understanding of these secondary mechanisms of injury that are amenable to pharmacological interventions, unlike the primary injury itself. Secondary mechanisms of injury encompass an array of perturbances and include neurogenic shock, vascular insults such as hemorrhage and ischemia-reperfusion, excitotoxicity, calcium-mediated secondary injury and fluid-electrolyte disturbances, immunologic injury, apoptosis, disturbances in mitochondrion function, and other miscellaneous processes. Comprehension of secondary mechanisms of injury serves as a basis for the development and application of targeted pharmacological strategies to confer neuroprotection and restoration while mitigating ongoing neural injury. The first article in this series will comprehensively review the pathophysiology of SCI while emphasizing those mechanisms for which pharmacologic therapy has been developed, and the second article reviews the pharmacologic interventions for SCI.

Acute spinal cord injury, part II: contemporary pharmacotherapy

Spinal cord injury (SCI) remains a common and devastating problem of modern society. Through an understanding of underlying pathophysiologic mechanisms involved in the evolution of SCI, treatments aimed at ameliorating neural damage may be developed. The possible pharmacologic treatments for acute spinal cord injury are herein reviewed. Myriad treatment modalities, including corticosteroids, 21-aminosteroids, opioid receptor antagonists, gangliosides, thyrotropin-releasing hormone (TRH) and TRH analogs, antioxidants and free radical scavengers, calcium channel blockers, magnesium replacement therapy, sodium channel blockers, N -methyl-D-aspartate receptor antagonists, alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid-kainate receptor antagonists, modulators of arachadonic acid metabolism, neurotrophic growth factors, serotonin antagonists, antibodies against inhibitors of axonal regeneration, potassium channel blockers (4-aminopyridine), paclitaxel, clenbuterol, progesterone, gabexate mesylate, activated protein C, caspase inhibitors, tacrolimus, antibodies against adhesion molecules, and other immunomodulatory therapy have been studied to date. Although most of these agents have shown promise, only one agent, methylprednisolone, has been shown to provide benefit in large clinical trials. Given these data, many individuals consider methylprednisolone to be the standard of care for the treatment of acute SCI. However, this has not been established definitively, and questions pertaining to methodology have emerged regarding the National Acute Spinal Cord Injury Study trials that provided these conclusions. Additionally, the clinical significance (in contrast to statistical significance) of recovery after methylprednisolone treatment is unclear and must be considered in light of the potential adverse effects of such treatment. This first decade of the new millennium, now touted as the Decade of the Spine, will hopefully witness the emergence of universal and efficacious pharmacologic therapy and ultimately a cure for SCI.

Cranioorbital fibrous dysplasia: with emphasis on visual impairment and current surgical management

Fibrous dysplasia is a benign but slowly progressive disorder of bone in which normal cancellous bone is replaced by immature woven bone and fibrous tissue. Significant deformity and both acute and chronic visual impairment can result. A contemporary understanding of fibrous dysplasia, emphasizing the origins of visual impairment, indications for decompressive surgery, and the techniques for correction of the cosmetic deformity are presented. In their experience and review of the literature, the authors found the most frequent clinical presentations to be exophthalmos, displacement of the globe, abnormalities of extraocular motility, cosmetic deformity, and visual impairment. Although traditionally the cause of visual impairment has been ascribed to impingement of the optic canal on the optic nerve, the authors' experience is that the most common cause of visual loss is cystic degeneration of the tumor, particularly with those involving the anterior clinoid process. Exophthalmos and optic canal stenosis are less common causes of visual impairment. Indications for surgical intervention include acute and/or serially radiographically documented and relentless visual impairment and significant cosmetic deformity. Individualized management strategies are also discussed.

Cranioorbital fibrous dysplasia: with emphasis on visual impairment and current surgical management

Fibrous dysplasia is a benign but slowly progressive disorder of bone in which normal cancellous bone is replaced by immature woven bone and fibrous tissue. Significant deformity and both acute and chronic visual impairment can result. A contemporary understanding of fibrous dysplasia, emphasizing the origins of visual impairment, indications for decompressive surgery, and the techniques for correction of the cosmetic deformity are presented.

In their experience and review of the literature, the authors found the most frequent clinical presentations to be exophthalmos, displacement of the globe, abnormalities of extraocular motility, cosmetic deformity, and visual impairment. Although traditionally the cause of visual impairment has been ascribed to impingement of the optic canal on the optic nerve, the authors' experience is that the most common cause of visual loss is cystic degeneration of the tumor, particularly with those involving the anterior clinoid process. Exophthalmos and optic canal stenosis are less common causes of visual impairment. Indications for surgical intervention include acute and/or serially radiographically documented and relentless visual impairment and significant cosmetic deformity. Individualized management strategies are also discussed.

Radiosurgery for Cushing's disease after failed transsphenoidal surgery

OBJECT

Although transsphenoidal surgery has become the standard of care for Cushing's disease, it is often unsuccessful in normalizing cortisol production. In this study the authors investigate the safety and efficacy of gamma knife radiosurgery (GKRS) for Cushing's disease after failed transsphenoidal surgery.

METHODS

The records of all patients who underwent GKRS at the authors' institution after unsuccessful transsphenoidal surgery for Cushing's disease were retrospectively reviewed. Successful treatment was considered a normal or below-normal 24-hour urinary free cortisol (UFC) level. Records were also evaluated for relapse, new-onset endocrine deficiencies, interval change in tumor size, and visual complications. Forty-three patients underwent 44 gamma knife procedures with follow up ranging from 18 to 113 months (mean 39.1, median 44 months). Normal 24-hour UFC levels were achieved in 27 patients (63%) at an average time from treatment of 12.1 months (range 3-48 months). Three patients had a recurrence of Cushing's disease at 19, 37, and 38 months, respectively, after radiosurgery. New endocrine deficiencies were noted in seven patients (16%). Follow-up magnetic resonance images obtained in 33 patients revealed a decrease in tumor size in 24, no change in nine, and an increase in size in none of the patients. One patient developed a quadrantanopsia 14 months after radiosurgery despite having received a dose of only 0.7 Gy to the optic tract.

CONCLUSIONS

Gamma knife radiosurgery appears to be safe and effective for the treatment of Cushing's disease refractory to pituitary surgery. Delayed recurrences and new hormone deficiencies may occur, indicating the necessity for regular long-term follow up.

Modulation of macrophage and microglial responses to axonal injury in the peripheral and central nervous systems

OBJECTIVE

After axonal injury, macrophages rapidly infiltrate and become activated in the mammalian peripheral nervous system (PNS) but not the central nervous system (CNS). We used the dorsal root pathway to study factors that modulate the response of macrophages to degenerating axons in both the PNS and the CNS.

METHODS

Lewis rats underwent transection of dorsal roots (Group 1), stab within the spinal cord (Group II), crush at the dorsal root entry zone (Group III), transection of dorsal roots combined with a CNS lesion (Group IV), or systemic administration of a known activator of macrophages, lipopolysaccharide, alone (Group V) or combined with transection of dorsal roots (Group VI). ED-1 antibody stained for macrophages and activated microglia at 7, 14, and 42 days postinjury.

RESULTS

At early time points, Group I demonstrated ED-1 cells in the PNS but not the CNS portion of the degenerating dorsal roots. Group II revealed ED-1 cells near the stab lesion. Group III demonstrated ED-1 cells adjacent to the dorsal root entry zone crush site. Group IV revealed ED-1 cells along both the PNS and the CNS portions of the degenerating dorsal roots when the CNS lesion was placed near the transected roots. Group V demonstrated few ED-1 cells in the PNS and the CNS, whereas Group VI revealed a marked ED-1 cellular response along both the PNS and the CNS portions of the transected dorsal roots.

CONCLUSION

Local CNS trauma and systemic administration of lipopolysaccharide can "prime" macrophages/microglia, resulting in an enhanced response to degenerating axons in the CNS. Such priming might prove useful in promoting axonal regeneration.

Dorsal laminectomy in the adult mouse: a model for nervous system research

Animal strains with specific genetic mutations can serve as powerful tools to study normal and pathologic cellular and molecular processes. The mammalian species with the largest number of known genetic mutations is the mouse. In spinal cord research, mice have not been used as extensively as other species because of the difficulty in accessing and manipulating their spinal cord. We describe the technique of exposing and manipulating the spinal cord of normal mice and of mice with the severe combined immunodeficiency (scid) mutation. Surgical outcome and complications are discussed. We conclude that dorsal laminectomy with subsequent access and manipulation of the spinal cord and its roots can be accomplished consistently with practice.