Anatomic features of glioblastoma and their potential impact on survival.

BACKGROUND: Many reports on glioblastoma multiforme discuss the prognostic impact of anatomical features such as cysts, necrotic changes, extent of edema or subependymal spread of tumor cells. In the present study, we examined different growth patterns and their possible relations to patient survival. METHODS: To analyze whether anatomical characteristics are related to prognosis, we reviewed the prospectively collected pre- and postoperative MRIs of 83 patients in the 5-ALA study, provided by the 5-ALA Glioma Study Group. Following a standardized analytic work flow, the tumor volume and site, presence of necrosis or cysts, and perifocal edema were assessed preoperatively. In the same way, postoperative MRI and the MRI at first recurrence were analyzed. In addition, survival time of the patients was documented. RESULTS: Median survival time of all 83 patients was 15.1 months (range 1.5 to 70.1, mean 18). The site or volume of glioblastoma, as well as the presence of intratumoral necrosis or cysts, did not exert a significant effect on survival time; 96.4 % of recurrences occurred within the former resection margin. Tumors with initial contact with the subependymal zone had multifocal or ventricular recurrences significantly more often. In patients with residual tumor on early postoperative MRI, the follow-up images displayed enlargement of the remnants in 91.9 % of these cases. CONCLUSIONS: A merely anatomical analysis of the glioblastoma growth pattern cannot reliably provide prognostic information. The occurrence of most recurrences next to the resection margin and the high percentage of growing residual tumors underline the importance of complete resections.

Gestational diabetes predicts the risk of childhood overweight and abdominal circumference independent of maternal obesity.

AIM: Gestational diabetes mellitus is believed to be a risk factor for childhood overweight/obesity. We aimed to assess whether this association is either a reflection or independent of confounding by maternal BMI. METHODS: Data from 7355 mother-child dyads of the German Perinatal Prevention of Obesity cohort with full anthropometric information on mothers and children, gestational diabetes and confounding factors were obtained at school entry health examination. We calculated crude and adjusted logistic regression models for the association of gestational diabetes and childhood overweight/obesity and abdominal adiposity defined by age- and sex-specific percentiles for BMI and waist circumference. RESULTS: Among all children (mean age 5.8 years), 8.1% were overweight, 2.6% were obese and 15.5% had abdominal adiposity. The prevalence of overweight (obesity) was 21% (8.2%) in children of mothers with gestational diabetes and 10.4% (2.4%) in children of healthy mothers. Analyses with adjustment for maternal BMI and other potential confounders yielded an odds ratio of 1.81 (95% CI 1.23-2.65) and 2.80 (95% CI 1.58-4.99) for the impact of gestational diabetes on childhood overweight and obesity, respectively. Similar results were obtained for the risk of childhood abdominal adiposity (odds ratio 1.64, 95% CI 1.16-2.33) by maternal gestational diabetes. CONCLUSIONS: The postulated increased risk of overweight and abdominal adiposity in offspring of mothers with gestational diabetes cannot be explained by maternal BMI alone and may be stronger for childhood obesity than for overweight.

Training charter in epilepsy surgery added competence.

The present Training Charter in Epilepsy Surgery Added Competence constitutes the third stage of a program initiated by the European Society for Stereotactic and Functional Neurosurgery (ESSFN) and substantiated in close collaboration with the Union Européennedes Médecins Spécialists (UEMS) and the European Association of Neurosurgical Societies (EANS). This program aims to raise the standards of clinical practice by guiding education and quality control concepts. The particular sections of this Charter include: definitions and standards of added competence training, relations of the Epilepsy Unit with the Neurosurgical Department, duration of epilepsy surgery fellowship, institution and training program director requirements, operative totals for epilepsy surgery, educational program, individual requirements, and evaluation and qualification of the trainees. The specification of all these requirements is expected to improve harmonisation and quality of epilepsy surgery practice across Europe, and enhance the clinical activity and the scientific productivity of existing neurosurgical centres.

A report on neurosurgical workforce in the countries of the EU and associated states. Task Force "Workforce Planning", UEMS Section of Neurosurgery.

AIM: Aim of this report was to present recently collected data on neurosurgical workforce in the countries of the EU and associated states. METHODS: Data were obtained from 27 countries by means of a questionnaire developed by members of a working group of the UEMS Section of Neurosurgery (UEMS = Union Europénne des Médecins Spécialistes; European Union of Medical Specialists). Most data originate from 2005/2006. Results were discussed, amended, and approved by the countries' delegates of the UEMS Section of Neurosurgery. RESULTS: The number of Neurosurgeons (NS) per population varies considerably among these countries. The mean is one neurosurgeon per 99,152 population. The number of neurosurgical operations per population per year varies similarly with a mean of 1,642 operations per million population/year. Countries with fewer neurosurgeons per population tend to have less neurosurgical operations per population and vice versa. The average number of operations performed by one neurosurgeon per year (annual caseload) is between 56 and 300 with a mean of 154. A numerus clausus for neurosurgical training is reported in 13 countries, another 13 countries have no numerus clausus. The annual intake of new trainees is between 2.4 and 10.3% of the number of accredited neurosurgeons with a mean of approx. 5.2%. The average yearly loss rate due to retirement, sickness, other activities, etc. can only be estimated and lies in the range between 2.3 and 3.36% of the number of accredited NS. According to the figures provided by the countries, the total number of accredited NS in 2005/2006 was approx. 6,280 for a population of about 504.7 millions. These countries had an annual intake of approx. 332 new trainees.

The revised European neurosurgical electronic logbook of operations.

The revised electronic neurosurgical logbook is a standalone windows application supporting multiple languages that allows the neurosurgeon in training to enter all operations he is involved in. This data can be summarised and printed as required by the UEMS at the end of the training period.

Evaluation of 177Lu[Lu]-CHX-A″-DTPA-6A10 Fab as a radioimmunotherapy agent targeting carbonic anhydrase XII.

INTRODUCTION: Due to their infiltrative growth behavior, gliomas have, even after surgical resection, a high recurrence tendency. The approach of intracavitary radioimmunotherapy (RIT) is aimed at inhibiting tumor re-growth by directly administering drugs into the resection cavity (RC). Direct application of the radioconjugate into the RC has the advantage of bypassing the blood-brain barrier, which allows the administration of higher radiation doses than systemic application. Carbonic anhydrase XII (CA XII) is highly expressed on glioma cells while being absent from normal brain and thus an attractive target molecule for RIT. We evaluated a CA XII-specific 6A10 Fab (fragment antigen binding) labelled with 177Lu as an agent for RIT. METHODS: 6A10 Fab fragment was modified and radiolabelled with 177Lu and characterized by MALDI-TOF, flow cytometry and radio-TLC. In vitro stability was determined under physiological conditions. Biodistribution studies, autoradiography tumor examinations and planar scintigraphy imaging were performed on SCID-mice bearing human glioma xenografts. RESULTS: The in vitro CA XII binding capacity of the modified Fab was confirmed. Radiochemical purity was determined to be >90% after 72 h of incubation under physiological conditions. Autoradiography experiments proved the specific binding of the Fab to CA XII on tumor cells. Biodistribution studies revealed a tumor uptake of 3.0%ID/g after 6 h and no detectable brain uptake. The tumor-to-contralateral ratio of 10/1 was confirmed by quantitative planar scintigraphy. CONCLUSION: The radiochemical stability in combination with a successful in vivo tumor uptake shows the potential suitability for future RIT applications with the 6A10 Fab.

Neurological impairment in rats after transient middle cerebral artery occlusion: a comparative study under various treatment paradigms.

The assessment of the functional outcome - in addition to the conventional endpoints as histomorphometry of the ischemic brain damage - for the evaluation of cerebroprotective therapies is increasingly recommended, although there is little consensus on appropriate procedures. We evaluated a battery of sensorimotor tasks in rats after transient middle cerebral artery occlusion (MCAO) to select those with the highest potential to discriminate between various degrees of neuronal damage. A total of 40 Sprague-Dawley rats were subjected to 90 min of MCAO and assigned to one of four treatment arms: (1) sham-operated controls, (2) vehicle-treated controls, (3) moderately effective neuroprotection by 2x100 mg/kg alpha-phenyl-N-tert-butyl nitrone (PBN), (4) highly effective neuroprotection by mild hypothermia (33 degrees C). Functional deficits were daily quantified using the beam balance task (1.5 cm, 2.5 cm diameter rectangular and 2.5 cm diameter cylindrical beam), the prehensile traction task, the rotarod, and a six-point neuro-score. Infarction of cerebral cortex and basal ganglia was assessed one week after ischemia. Treatment with PBN significantly reduced cortical infarction (-31%), while treatment with hypothermia resulted in a significantly smaller infarct volume of cortex (-94%) and basal ganglia (-27%). Beam balance, prehensile traction and rotarod failed to demonstrate any difference in motor performance. The six-point neuro-score showed a significant correlation with cortical infarction from day 2 and with total infarct volume from day 3. The smaller the reduction of infarct volume, the later the corresponding difference in neuro-score became apparent. Functional outcome after MCAO in rats can be assessed by a relatively simple measurement of neurological deficit. The slope of functional recovery is closely related with the degree of the morphological, particularly cortical damage. If expected treatment effects are small, an observation period of at least 3 days should be planned for the study design. The functional impairment from focal brain ischemia and its subsequent recovery could provide valuable information for future studies evaluating the neuroprotective potential of novel agents and procedures.

Neuroprotective efficacy of combination therapy with two different antioxidants in rats subjected to transient focal ischemia.

The vascular endothelium and parenchyma of the brain have both potential pathways to generate free radicals under pathological conditions. We evaluated the neuroprotective efficacy of two different antioxidants, a microvascularly acting 21-aminosteroid (U-74389G) and a brain-penetrating pyrrolopyrimidine (U-101033E) alone and in combination. Forty Sprague-Dawley rats were randomly assigned to one of four treatment groups: (1) vehicle-treated controls, (2) U-74389G, (3) U-101033E, (4) U-74389G+U-101033E. Drugs were administered in a dosage of 3x3 mg/kg i.v. before, during, and after ischemia. All animals were subjected to 90 min of middle cerebral artery occlusion. Local cortical blood flow (LCBF) was continuously recorded by bilateral laser Doppler flowmetry. Functional deficits were quantified by daily neurological examinations. Infarct volume was assessed after 7 days. There were no significant differences in LCBF among groups. U-101033E improved neurological function from postoperative day 4 to 7, while U-74389G did not improve neurological recovery. Animals treated with both drugs showed significantly less deficits from postoperative day 1 to 7. U-101033E and combination therapy reduced total infarct volume by 53% and 54% (P<0.05). U-74389G non-significantly reduced total infarct volume by 25%. Cortical infarct volume was significantly reduced in all treatment groups but only U-101033E and combination therapy protected the basal ganglia from infarction. In conclusion, brain-penetrating antioxidants have superior neuroprotective properties compared to microvascularly acting agents. Combination therapy, affording antioxidation plus radical scavenging in blood vessels and brain parenchyma, might yield the highest degree of neuronal protection from peroxidative damage. The neuroprotective efficacy seems to be independent of CBF.

Localization of the precentral gyrus in the computed tomogram and its clinical application.

In 30 patients the anatomical configurations of the precentral and central sulcus and gyrus were examined by computed tomography and could be determined with great accuracy. The distances between the coronal suture and the central and precentral fissure, and the angle between the longitudinal fissure and the central fissure were measured. These data are used in the precise localization for a surgical approach to a mass lesion.

[Cerebral vasoparalysis, arterial hypertension and brain edema (author's transl)]. / Cerebrale Vasoparalyse, arterielle Hypertension und Hirnödem

The present studies were performed in order to determine whether "filtration edema" will develop as a consequence of cerebral vasoparalysis, vasoparalysis in combination with arterial hypertension or arterial hypertension alone. A series of dogs, anaesthetised with i.v. Chloralose-Urethane were exposed 1) to cerebral vasoparalysis, produced by hypercapnia (PaCO2 about 150 mm Hg) and hypoxaemia (PaO2 40-60 mm Hg); 2) to arterial hypertension and 3) to a combination of cerebral vasoparalysis and arterial hypertension. Following cerebral vasoparalysis and arterial hypertension, a significant decrease of total cerebrovascular resistance and moderate increase of venous resistance was observed. Regional cerebral blood flow (133Xe), intracranial pressure, as well as the pressure in postcapillary venous outflow (sinus sagittalis wedge pressure and confluence sinuum pressure) were increased. Neither normotonic vasoparalysis nor vasoparalysis in combination with slight arterial hypertension (MABP more than 90 min above 180 mm Hg) resulted in cerebral edema. In contrast, cerebral vasoparalysis in combination with severe arterial hypertension (MABP more than 90 min above 220 mm Hg) resulted in a statistically significant increase in the water content in the white matter without evidence of protein extravasation. Multiple small foci of Evans blue extravasates, however, were found in the cortex following arterial hypertension in combination with vasodilation, indicating a damage of the blood brain barrier. In these blue stained cortical areas the water content was significantly in creased. The following conclusions were drawn from the results. Vasoparalysis during normotension does not produce brain edema despite the slightly elevated hydrostatic pressure gradient between intravasal and extracellular space. Only considerable increase of this hydrostatic pressure gradient caused by a combination of vasoparalysis with severe arterial hypertension is able to produce brain edema in the white matter. In addition, acute hypertension may cause minor multifocal damage of the blood brain barrier in the cerebral cortex. It is concluded that so-called brain swelling, which has been described by several authors in states of cerebral vasoparalysis, is not predominantly caused by brain edema but by vascular congestion. The clinical aspects of the result are discussed.

The effect of arterial hypertension of focal ischemic edema. An experimental study.

The middle cerebral artery (MCA) of cats was occluded permanently for 24h to study the influence of arterial hypertension during the early phase of focal ischemia upon the development of endema and changes of the blood-brain barrier (BBB). In normotensive animals MCA occlusion results in a hemispheric weight increase of about 8% and marked water and electrolyte alterations in both the grey and white matter of the MCA territory. The RISA space increases mainly in the grey matter. Hypertension aggravates these changes significantly, whereby water and electrolyte changes in the grey matter are predominantly concerned, while there is a preferential increase of the RISA space in the white matter. It is suggested that arterial hypertension aggravates the ischemic edema and enhances a vasogenic type of edema in the white matter.

EEG burst suppression is not necessary for maximum barbiturate protection in transient focal cerebral ischemia in the rat.

Barbiturates have been demonstrated to reduce the cerebral metabolic rate (CMR) in a dose-dependent manner but investigations of a dose-response relationship for their neuroprotective efficacy are scant. It has been suggested that barbiturates possess other mechanism of action that may be critical to their protective effect. If so, it is conceivable that the peak effect of such mechanisms does not parallel the reduction in CMR. Thus, maximal neuroprotection may be achieved with a substantially lower dose of the drug. Thirty Sprague-Dawley rats were subjected to 2 h of middle cerebral artery occlusion while either anesthetized with (1) halothane (control) or (2) intravenous thiopental titrated to cause mild EEG suppression or (3) thiopental titrated to maintain EEG burst suppression. Cortical blood flow was recorded by continuous bilateral laser Doppler flowmetry (LDF). Infarct volume was assessed after 3 h of reperfusion. Low-dose thiopental decreased blood flow to 80% of baseline and high-dose thiopental to 70% of baseline. LDF did not indicate improvement of blood flow by thiopental in the ischemic area. Compared to controls, low-dose thiopental significantly decreased infarct volume by 28% and high-dose thiopental by 29%. The results of this study and a review of literature indicate that barbiturates provide cerebral protection but that the magnitude of this effect has been overestimated. Other mechanisms than CMR reduction seem to contribute to their beneficial effects, and high doses administered to the point of burst suppression may not be required to obtain maximal protection.

A paramedian tangential approach to lumbosacral extraforaminal disc herniations.

OBJECTIVE: Extraforaminal disc herniations today are operated on via the so-called lateral approach. Clinical experience has shown that in contrast to levels L2/3-L4/5, this approach may become extremely difficult at the L5-S1 level. According to new microanatomic studies, the previous lateral approaches at this level often do not allow access to the neuroforamen without partial or total destruction of the L5-S1 facet joint. Postoperatively, this may lead to joint irritation with consecutive low back and pseudoradicular pain. To preserve the facet joint, a new approach was developed based on an anatomic study. METHODS: The approach was first considered with the help of bone specimens including ilium, vertebra 5, and sacrum. Thereafter, lumbar maceration specimens were prepared leaving ligaments, intervertebral discs, and joints intact. From these specimens, bony and ligamentous landmarks were deduced. Finally, the approach was tested on seven cadavers. Subsequently, the approach was performed on 13 patients and the intraoperative findings, the clinical feasibility, and the postoperative results were analyzed. APPROACH: After a transverse skin incision above the dorsal curvature of the ilium, the paravertebral muscles are dissected from the ilium medially toward the spinous process. Lateral from the apophyseal joint, a canal is drilled through the spongiosa of the sacrum. Primarily, a thin layer of inner cortex is spared to protect the content of the neuroforamen. Subsequently, it can easily be removed with the dissector to enter the extraforaminal space. In the depth of the drilled canal, the nerve root is found, because it is fixed at the sacrum near the disc space by the anterior lumbosacral ligaments. Riding on the nerve root, the intertransverse ligament and muscle can be removed with the punch. It is then possible to see the neuroforamen and extraforaminal space in front of the joint. Free fragments and contained discs can then easily be found and removed. CONCLUSION: Using this new approach, the L5-S1 joint remains intact. Space for instrumental manipulations is created in areas not essential for joint function. For this procedure, newly defined anatomic landmarks, such as the ileolumbar ligament, upper edge of the sacrum, lateral rim of the apophyseal joint, and para-articular notch, guide the operative route. In accordance with the preliminary anatomic studies, this approach was successfully used in 13 patients, and we think that it is a promising alternative that helps to preserve joint function and dorsal root ganglion integrity.

Microsurgical anatomy of the lateral approach to extraforaminal lumbar disc herniations.

OBJECTIVE: During the "lateral" approach to extraforaminal lumbar disc herniations, the surgeon may be confronted with considerable variations in anatomy, making this approach extremely difficult in some patients. An anatomic study, therefore, was undertaken to examine the bony boundaries of the operative target, the medial intertransverse space. METHODS: In 31 lumbar spine specimens taken from cadavers of people who had been between 30 and 93 years old at death, the relevant distances and proportions of the operative window were measured at the levels L1-L2 to L5-S1. RESULTS: Measurements revealed that the operative window in a systematic fashion becomes progressively smaller as the approach moves from L1-L2 toward L5-S1: 1) from L1 to L5, the medial boundary, the isthmus laminae, gradually extends farther laterally and eventually covers the waist of the respective vertebral body; 2) the lower boundary, the facet joint, gradually overlaps the disc space in an upward and lateral direction; 3) the upper boundary, the transverse process, gradually moves downward. Anatomic variations and abnormalities are found particularly often at the L5-S1 level. CONCLUSION: The anatomic findings led to important conclusions regarding the microsurgical approach to extraforaminal lumbar disc herniations; at levels L1-L2 to L3-L4, the midline approach with lateral retraction of the paraspinal muscles allows for efficient exposure of the lateral neural foramen and avoidance of trauma to the facet joint. Often at level L4-L5, and nearly always at level L5-S1, a tangential route through a paramedian transmuscular approach offers many advantages.

Clinicopathological relations of cerebral cavernous angiomas: observations in eleven cases.

Eleven cases of cerebral cavernous angiomas (cavernomas) were observed within a period of 3 years. Two patients presented with cerebral hemorrhage, five with epilepsy, three each with a progressive focal neurological deficit, and one with papilledema. The unruptured lesions had a heterogeneous density on computed tomography with relatively little contrast enhancement. Two lesions contained major cysts. In one of these cases, the cyst measured 5.5 cm in diameter, had an enhancing membrane, and was surrounded by brain edema. Angiography did not show hypervascularity in any instance. During exploration and histological processing, special attention was paid to signs of previous silent hemorrhages and to the degree of encapsulation of the lesion. Iron deposits (signs of previous hemorrhages) were seen to varying degrees inside all cavernomas as well as in the surrounding gliotic cerebrum, and a causal relation between iron deposits and epileptic seizures seems likely. Encapsulation was minimal with the ruptured cavernomas and particularly prominent with the cystic lesions. The membrane of the giant cystic lesion with peripheral brain edema had a histological structure similar to that of the membranes of chronic subdural hematomas. It is suggested that continuous growth of cavernoma cysts is the result of recurrent hemorrhages from sinusoids of the malformation and from the neocapillary network of the cyst membranes.

The Neurosurgical Clinic at the Ludwig-Maximilians University in Munich.

ThE NEUROSURGICAL CLINIC at the Ludwig-Maximilians University in Munich began as a small unit of the university's surgical clinic. Eduard Weber, who in 1952 became the first surgeon fully trained in the specialty of neurosurgery to join the surgical clinic's faculty, worked, until his death in 1962, to advance the new specialty. Neurosurgery became an independent department of the university in 1965, and the neurosurgical clinic moved to a new location at Beethovenplatz. Further expansion led the neurosurgical clinic to move again, in 1975, to the newly constructed Klinikum Grosshadern at the periphery of Munich. Frank Marguth, chairman of the department of neurosurgery from 1964 to 1991, had superb skill as an organizer and greatly enhanced the reputation of the department of neurosurgery. Today, the faculty of the department consists of 10 full-time staff members, 10 joint appointment staff members, and 16 residents and fellows. Annually, 2200 to 2300 procedures are performed in the neurosurgical clinic. The current philosophy in the department places heavy emphasis on subspecialization and academic training. Political and economic changes in Germany during recent years have affected the nation's public health system and pose major challenges to the department of neurosurgery.

Transcallosal interforniceal-transforaminal approach for removing lesions occupying the third ventricular space: clinical and neuropsychological results.

OBJECTIVE: The present study was undertaken to describe the clinical and prospective neuropsychological results for our group of 30 patients who were treated using a transcallosal interforniceal-transforaminal microsurgical approach. METHODS: The transcallosal interforniceal and transcallosal-transforaminal approaches were used to treat 30 patients with space-occupying lesions located in the anterior part of the third ventricle. We used a modified anterior transcallosal microsurgical approach, as described recently. The patients underwent extensive, pre- and postoperative, prospective neuropsychological testing, using a specially designed test battery. RESULTS: Twenty-three of 30 patients (77%) experienced excellent clinical outcomes (Glasgow Outcome Scale Grade V). The surgical procedures described in this report did not themselves impair attentional function. In both the early and late postoperative neuropsychological testing sessions, deficits in verbal memory were only rarely observed and were not noted to be correlated with the surgical procedures. The most relevant neuropsychological results for individual patients are reported in detail. CONCLUSION: The approach described here can be successfully used for the resection of various space-occupying lesions in the anterior part of the third ventricle. The anatomic landmarks we recently defined and described (for example, the midline vessel on the trunk of the corpus callosum, to direct the callosotomy) guide the surgical path. Furthermore, we recommend the use of neuropsychological test batteries for both scientific and rehabilitative purposes.

A keyhole approach for endoscopically assisted pedicle screw fixation in lumbar spine instability.

OBJECTIVE: The standard approach for dorsal transpedicular fixation in lumbar spine instability requires extensive exposure of the vertebral column. This increases the risk of potential complications and possibly destabilizes healthy neighboring segments because of the dissection and denervation of paravertebral muscles. The majority of spinal disorders are currently treated successfully via limited and tailored approaches. Accordingly, a keyhole approach for dorsal fusion of the lumbar spine was developed on the basis of an anatomic study. METHODS: The new endoscopic technique entails the transmuscular insertion of a pedicle screw-rod fixation device via a rigid operating sheath. As a prerequisite, the endoscopic microanatomy of the target area, as visible through the operating sheath, was first evaluated on lumbar bone specimens. To localize the exact screw entry point into the pedicle, we identified the bony and ligamentous landmarks on partly macerated specimens. To determine the course of the pedicle screws, we deduced the corresponding angles of convergence from transparent polyester casting models of average vertebrae from T12 to S1. These angles were transferred into the operative situation and measured on-line with an inclinometer. The approach was finally tested on 12 cadavers for clinical feasibility and accuracy of screw placement and then successfully implemented in patients. RESULTS: After extracutaneous localization of the pedicles at lateral fluoroscopy, paramedian skin incisions were made above the pedicles of the motion segment to be stabilized. The operative windows were exposed by use of a rigid operating sheath (length, 50 mm; diameter, 15 mm), which was inserted transmuscularly in the pedicle axis. The screw entry point into the pedicles was localized by endoscopic dissection of the mamilloaccessory ligament, bridging the mamilloaccessory notch. The pilot holes were created via insertion of a blunt-tipped pedicle probe. The adequate angles of convergence were constantly controlled during hollowing of the pedicles by an inclinometer mounted to the pedicle probe handle. The pedicle screws were then inserted through the operating sheaths. After removal of the operating sheaths, the connecting rods were inserted transmuscularly and anchored in the pedicle screw heads. Posterior bone grafting was performed after completion of the dorsal instrumentation. The dorsal fusion site was exposed by reinserting the operating sheath and tilting it medially. CONCLUSION: This new approach significantly reduces surgical traumatization and destabilization of adjacent motion segments. An endoscopic operating sheath, adopted from thoracoscopic surgery, creates space for visualization and surgical manipulations. The newly defined anatomic landmarks provide guidance to the screw entry point into the pedicle in the center of the exposure. Observation of the exact corresponding angles of convergence during screw insertion by an inclinometer facilitates correct screw placement. In accordance with the initial anatomic studies, this approach was successfully performed on 12 cadavers and then used in six patients. Two illustrative cases are presented.

Orthodromic (intra/extracranial) neurography to monitor facial nerve function intraoperatively.

This report introduces the technique of orthodromic neurography for monitoring of facial nerve function during operation in the cerebellopontine angle. By stimulation of the intracisternal segment of the facial nerve, a compound nerve action potential with amplitudes of 15 to 480 microV can be recorded extracranially from the nerve near the stylomastoid foramen after 0.95 to 2.27 ms. Usually there is no need for signal averaging, and the method is independent of the effect of muscle relaxants. With the use of the same electrophysiological equipment as for evoked potential neuromonitoring, immediate and repeated localization of the facial nerve and its discrimination from the trigeminal and the lower cranial nerves during nerve preparation within the tumor capsule is possible.