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Georg Neuloh and Johannes Schramm

Object. The aims of this study were to compare the efficiency of motor evoked potentials (MEPs), somatosensory evoked potentials (SSEPs), and microvascular Doppler ultrasonography (MDU) in the detection of impending motor impairment from subcortical ischemia in aneurysm surgery; to determine their sensitivity for specific intraoperative events; and to compare their impact on the surgical strategy used.

Methods. Motor evoked potentials, SSEPs, and MDU were monitored during 100 operations for 129 aneurysms in 95 patients. Intraoperative events, monitoring results, and clinical outcome were correlated in a prospective observational design.

Motor evoked potentials indicated inadequate temporary clipping, inadvertent occlusion, inadequate retraction, vasospasm, or compromise to perforating vessels in 21 of 33 instances and deteriorated despite stable SSEPs in 18 cases. Microvascular Doppler ultrasonography revealed inadvertent vessel occlusion in eight of 10 cases and insufficient clipping in four of four cases. Stable evoked potentials (EPs) allowed safe, permanent vessel occlusion or narrowing despite reduced flow on MDU in five cases. Two patients sustained permanent and 10 showed transient new weakness, which had been detected by SSEPs in two of 12 patients and MEPs in 10 of 11 monitored cases. The surgical strategy was directly altered in 33 instances: by MEPs in 16, SSEPs in four, and MDU in 13.

Conclusions. Monitoring of MEPs is superior to SSEP monitoring and MDU in detecting motor impairment, particularly that from subcortical ischemia. Microvascular Doppler ultrasonography is superior to EP monitoring in detecting inadvertent vessel occlusion, but cannot assess remote collateral flow. Motor evoked potentials are most sensitive to all other intraoperative conditions and have a direct influence on the course of surgery in the majority of events. A controlled study design is required to confirm the positive effect of monitoring on clinical outcome in aneurysm surgery.

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Marec von Lehe and Johannes Schramm

Object

In this paper, the authors' goal was to summarize their experience with the surgical treatment of gliomas arising from the cingulate gyrus.

Methods

The authors analyzed preoperative data, surgical strategies, complications, and functional outcome in a series of 34 patients (mean age 42 years, range 12–69 years; 14 females) who underwent 38 operations between May 2001 and November 2008.

Results

In 7 cases (18%) the tumor was located in the posterior (parietal) part of the cingulate gyrus, and in 31 (82%) the tumor was in the anterior (frontal) part. In 10 cases (26%) the glioma was solely located in the cingulate gyrus, and in 28 cases (74%) the tumor extended to the supracingular frontal/parietal cortex. Most cases (23 [61%]) had seizures as the presenting symptom, 8 patients (24%) suffered from a hemiparesis/hemihypesthesia, and 4 patients (12%) had aphasic symptoms.

The authors chose an interhemispheric approach for tumor resection in 11 (29%) and a transcortical approach in 27 (71%) cases; intraoperative electrophysiological monitoring was applied in 23 (61%) and neuronavigation in 15 (39%) cases. A > 90% resection was achieved in 32 (84%) and > 70% in another 5 (13%) cases. Tumors were classified as low-grade gliomas in 11 cases (29%). A glioblastoma multiforme (WHO Grade IV, 10 cases [26%]) and oligoastrocytoma (WHO Grade III, 9 cases [24%]) were the most frequent histopathological results.

Postoperatively, patients in 13 cases suffered from a transient supplementary motor area syndrome (34%), all of whom had tumors in the anterior cingulate gyrus. In the early postoperative period (30 days) a new deficit occurred in 5 cases (13%, mild motor deficits or aphasic symptoms). One patient had a major bleeding episode 2 days after surgery and was in a persistent vegetative state.

Conclusions

Gliomas arising from the cingulate gyrus are rare. A gross-total resection is often possible and acceptably safe; intraoperative monitoring and neuronavigation are helpful adjuncts. In case of resection of gliomas arising from the anterior cingulate gyrus a supplementary motor area syndrome has to be considered, particularly when the tumor extends to the supracingular cortex

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Marec von Lehe and Johannes Schramm

Object

In this paper, the authors' goal was to summarize their experience with the surgical treatment of gliomas arising from the cingulate gyrus.

Methods

The authors analyzed preoperative data, surgical strategies, complications, and functional outcome in a series of 34 patients (mean age 42 years, range 12–69 years; 14 females) who underwent 38 operations between May 2001 and November 2008.

Results

In 7 cases (18%) the tumor was located in the posterior (parietal) part of the cingulate gyrus, and in 31 (82%) the tumor was in the anterior (frontal) part. In 10 cases (26%) the glioma was solely located in the cingulate gyrus, and in 28 cases (74%) the tumor extended to the supracingular frontal/parietal cortex. Most cases (23 [61%]) had seizures as the presenting symptom, 8 patients (24%) suffered from a hemiparesis/hemihypesthesia, and 4 patients (12%) had aphasic symptoms.

The authors chose an interhemispheric approach for tumor resection in 11 (29%) and a transcortical approach in 27 (71%) cases; intraoperative electrophysiological monitoring was applied in 23 (61%) and neuronavigation in 15 (39%) cases. A > 90% resection was achieved in 32 (84%) and > 70% in another 5 (13%) cases. Tumors were classified as low-grade gliomas in 11 cases (29%). A glioblastoma multiforme (WHO Grade IV, 10 cases [26%]) and oligoastrocytoma (WHO Grade III, 9 cases [24%]) were the most frequent histopathological results.

Postoperatively, patients in 13 cases suffered from a transient supplementary motor area syndrome (34%), all of whom had tumors in the anterior cingulate gyrus. In the early postoperative period (30 days) a new deficit occurred in 5 cases (13%, mild motor deficits or aphasic symptoms). One patient had a major bleeding episode 2 days after surgery and was in a persistent vegetative state.

Conclusions

Gliomas arising from the cingulate gyrus are rare. A gross-total resection is often possible and acceptably safe; intraoperative monitoring and neuronavigation are helpful adjuncts. In case of resection of gliomas arising from the anterior cingulate gyrus a supplementary motor area syndrome has to be considered, particularly when the tumor extends to the supracingular cortex

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Georg Neuloh, Ulrich Pechstein and Johannes Schramm

Object

Surgery for insular gliomas incurs a considerable risk of motor morbidity. In this study the authors explore the validity and utility of continuous motor tract monitoring to detect and reverse impending motor impairment during insular glioma resection.

Methods

Motor evoked potentials (MEPs) were successfully monitored during 73 operations to remove insular gliomas. Seventy-two cases were assessable, and one patient died during the early postoperative course. In this prospective observational approach, MEP monitoring results were correlated with intraoperative events and perioperative clinical data.

Intraoperative recordings of MEPs remained stable in 40 cases (56%), indicating unimpaired motor outcome and allowing safe completion of the hazardous steps of the procedure. Deterioration of MEPs occurred in 32 cases (44%). This deterioration was reversible after intervention in 21 cases (29%), and there was no new motor deficit except for transient paresis in nine of these cases (13%). Surgical measures could not prevent irreversible MEP deterioration in 11 cases (15%). Transient mild or moderate paresis occurred if complete MEP loss was avoided. Irreversible MEP loss in seven cases (10%) occurred after completion of resection in four of these seven cases, and was consistently an indicator of both a stroke within the deep motor pathways and permanent paresis, which remained severely disabling in three patients (4%). In contrast, permanently severe paresis occurred in two (18%) of 11 cases without useful MEP monitoring.

Conclusions

Continuous MEP monitoring is a valid indicator of motor pathway function during insular glioma surgery. This method indicates that remote ischemia, in this study the leading cause of impending motor deterioration, helps to avert definitive stroke of the motor pathways and permanent new paresis in the majority of cases. The rate of permanently severe new deficit appears to be greater in unmonitored cases.

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Konstantinos Gousias, Johannes Schramm and Matthias Simon

OBJECTIVE

Recent advances in radiotherapy and neuroimaging have called into question the traditional role of aggressive resections in patients with meningiomas. In the present study the authors reviewed their institutional experience with a policy based on maximal safe resections for meningiomas, and they analyzed the impact of the degree of resection on functional outcome and progression-free survival (PFS).

METHODS

The authors retrospectively analyzed 901 consecutive patients with primary meningiomas (716 WHO Grade I, 174 Grade II, and 11 Grade III) who underwent resections at the University Hospital of Bonn between 1996 and 2008. Clinical and treatment parameters as well as tumor characteristics were analyzed using standard statistical methods.

RESULTS

The median follow-up was 62 months. PFS rates at 5 and 10 years were 92.6% and 86.0%, respectively. Younger age, higher preoperative Karnofsky Performance Scale (KPS) score, and convexity tumor location, but not the degree of resection, were identified as independent predictors of a good functional outcome (defined as KPS Score 90–100). Independent predictors of PFS were degree of resection (Simpson Grade I vs II vs III vs IV), MIB-1 index (< 5% vs 5%–10% vs >10%), histological grade (WHO I vs II vs III), tumor size (≤ 6 vs > 6 cm), tumor multiplicity, and location. A Simpson Grade II rather than Grade I resection more than doubled the risk of recurrence at 10 years in the overall series (18.8% vs 8.5%). The impact of aggressive resections was much stronger in higher grade meningiomas.

CONCLUSIONS

A policy of maximal safe resections for meningiomas prolongs PFS and is not associated with increased morbidity.

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Axel Jung, Johannes Schramm, Kai Lehnerdt and Claus Herberhold

Object. Recurrent laryngeal nerve (RLN) palsy is a well-known complication of cervical spine surgery. Nearly all previous studies were performed without laryngoscopy in asymptomatic patients. This prospective study was undertaken to discern the true incidence of RLN palsy. Because not every RLN palsy is associated with hoarseness, the authors conducted a prospective study involving the use of pre- and postoperative laryngoscopy.

Methods. Prior to anterior cervical spine surgery preoperative indirect laryngoscopy was performed in 123 patients to evaluate the status of the vocal cords as a sign of function of the RLN. To assess postoperative status in 120 patients laryngoscopy was repeated, and in cases of vocal cord malfunction follow-up examination was conducted 3 months later.

In the group of 120 patients who attended follow-up examination, two (1.6%) had experienced a preoperative RLN palsy without hoarseness. Postoperatively the rate of clinically symptomatic RLN palsy was 8.3%, and the incidence of RLN palsy not associated with hoarseness (that is, clinically unapparent without laryngoscopy) was 15.9% (overall incidence 24.2%). At 3-month follow-up evaluation the rate had decreased to 2.5% in cases with hoarseness and 10.8% without hoarseness. Thus, the overall rate of early persisting RLN palsy was 11.3%.

Conclusions. Laryngoscopy revealed that the true incidence of initial and persisting RLN palsy after anterior cervical spine surgery was much higher than anticipated. Especially in cases without hoarseness this could be proven, but the initial incidence of hoarseness was higher than expected. Only one third of new RLN palsy cases could be detected without laryngoscopy. Resolution of hoarseness was approximately 70% in those with preoperative hoarseness. The true rate of RLN palsy underscores the necessity to reevaluate the surgery- and intubation-related techniques for anterior cervical spine surgery and to reassess the degree of presurgical patient counseling.

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Johannes Schramm, Karl Schaller, Jonas Esche and Azize Boström

OBJECTIVE

The objective of this study was to review the outcomes after microsurgical resection of cerebral arteriovenous malformations (AVMs) from a consecutive single-surgeon series. Clinical and imaging data were analyzed to address the following questions concerning AVM treatment in the post-ARUBA (A Randomized Trial of Unruptured Brain Arteriovenous Malformations) era. 1) Are the patients who present with unruptured or ruptured AVMs doing better at long-term follow-up? 2) Is the differentiation between Ponce Class A (Spetzler-Martin Grade I and II) patients versus Ponce Class B and C patients (Spetzler-Martin Grade III and IV) meaningful and applicable to surgical practice? 3) How did the ARUBA-eligible patients of this surgical series compare with the results reported in ARUBA?

METHODS

Two hundred eighty-eight patients with cerebral AVMs underwent microsurgical resection between 1983 and 2012 performed by the same surgeon (J.S.). This is a prospective case collection study that represents a consecutive series. The results are based on prospectively collected, early-outcome data that were supplemented by retrospectively collected, follow-up data for 94% of those cases. The analyzed data included the initial presentation, Spetzler-Martin grade, obliteration rates, surgical and neurological complications, and frequency of pretreatment with embolization or radiosurgery. The total cohort was compared using “small-AVM,” Spetzler-Martin Grade I and II, and ARUBA-eligible AVM subgroups.

RESULTS

The initial presentation was hemorrhage in 50.0% and seizures in 43.1% of patients. The series included 53 Spetzler-Martin Grade I (18.4%), 114 Spetzler-Martin Grade II (39.6%), 90 Spetzler-Martin Grade III (31.3%), 28 Spetzler-Martin Grade IV (9.7%), and 3 Spetzler-Martin Grade V (1.0%) AVMs. There were 144 unruptured and 104 ARUBA-eligible cases. Preembolization was used in 39 cases (13.5%). The occlusion rates for the total series and small AVM subgroup were 99% and 98.7%, respectively. The mean follow-up duration was 64 months. Early neurological deterioration was seen in 39.2% of patients, of which 12.2% had permanent and 5.6% had permanent significant deficits, and the mortality rate was 1.7% (n = 5). Outcome was better for patients with AVMs smaller than 3 cm (permanent deficit in 7.8% and permanent significant deficit in 3.2% of patients) and Ponce Class A status (permanent deficit in 7.8% and significant deficit in 3.2% of patients). Unruptured AVMs showed slightly higher new deficit rates (but 0 instances of mortality) among all cases, and in the small AVM and Ponce Class A subgroups. Unruptured Spetzler-Martin Grade I and II lesions had the best outcome (1.8% permanent significant deficit), and ARUBA-eligible Spetzler-Martin Grade I and II lesions had a slightly higher rate of permanent significant deficits (3.2%).

CONCLUSIONS

Microsurgery has a very high cure rate. Focusing microsurgical AVM resection on unruptured lesions smaller than 3 cm or on Spetzler-Martin Grade I and II lesions is a good strategy for minimizing long-term morbidity. Well-selected microsurgical cases lead to better outcomes than with multimodal interventions, as in the ARUBA treatment arm, or conservative treatment alone. Long-term prospective data collection is valuable.

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Experimental spinal cord injury produced by slow, graded compression

Alterations of cortical and spinal evoked potentials

Johannes Schramm, Keizo Hashizume, Takanori Fukushima and Hiroshi Takahashi

✓ A new model of experimental spinal cord injury produced by slow, graded compression in cats is described. The extent of cord compression was evaluated by monitoring somatosensory evoked potentials (SEP's). The compression was exerted by means of a special screw-plate assembly with stepwise advancement of the compression plate at different time intervals and was completed when cortical SEP had disappeared. Every stage in the total course of gradual compression was expressed as a percentage of the total. Cortical and spinal SEP's were recorded at each increment. The SEP pattern was analyzed in terms of latency, amplitude, and wave form. It was noteworthy that SEP's were remarkably resistant to gradual compression. The amplitude of cortical SEP's began decreasing at a late stage of compression, usually at about 80% of total compression, and that of spinal SEP's some time earlier, at about 60% of total compression. They both then rapidly fell to zero. Cortical SEP's showed a slight increase in latency concurrent with the reduction of amplitude, while the latency of spinal SEP's was constant. Mid-thoracic SEP's showed considerable individual variation in wave form. Their changes were similar to those of cortical SEP. Thoracolumbar SEP's, recorded immediately rostral to the compression, showed little individual variation, and did not show flat recordings even with maximum compression. A small monophasic positive wave was present in all animals even after the cortical SEP's became flat. This “final potential” was assumed to be caused by electrotonic volume conduction from the activities of the dorsal white matter caudal to the compression site. The reversibility of SEP's after the release of compression was remarkable. Both cortical and spinal SEP's could show complete recovery even when histological examination demonstrated hemorrhagic necrosis. The present data show no linear correlation between SEP changes and degree of compression. There are no changes with slight or moderate degree of compression. Alterations of SEP's in slow compression models should suggest the presence of a severe degree of compression.

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Johannes Schramm, Rolf Krause, Taku Shigeno and Mario Brock

✓ Averaged somatosensory evoked potentials from the epidural space in response to sciatic nerve stimulation were recorded in bipolar and common reference mode in cats following various types of injury. An investigation was conducted on the development and properties of the spinal evoked response recorded from the center of the injury site, designated here as the “spinal cord evoked injury potential.” Typically it is a two-peak monophasic positive potential, approximately 40 msec in duration, with a slight negative afterwave. With increasing distance from the site of injury, its amplitude rapidly decreases, whereas latency remains constant. The common reference recording technique resulted in an earlier and better demonstration of the evoked injury potential, especially when it was transitory or incomplete. When impairment of conduction developed gradually, the evoked injury potential developed gradually too. In serial recordings along the spinal cord axis, the transition from a normal triphasic to a monophasic evoked injury potential allowed a precise localization of the lesion.

These data suggest that the diagnostic value of intraoperative spinal cord monitoring may be increased by adopting a technique that incorporates several epidural recordings with a common reference recording technique. The spinal cord evoked injury potential seems to be a more sensitive indicator of spinal cord injury than the cortical evoked potential. The findings are discussed in the light of the presently developing spinal cord monitoring techniques.