Spheno-orbital meningiomas: interdisciplinary surgical approach, resectability and long-term results.

OBJECTIVE: To describe the interdisciplinary surgical approach in spheno-orbital meningiomas and to evaluate the operative results regarding resectability and functional outcome. PATIENTS AND METHODS: A series of 16 patients underwent surgical resection of spheno-orbital meningiomas followed by bony reconstruction. Four patients presented with a recurrent meningioma and had undergone surgical resection previously. Radical tumour removal was attempted in all cases, although no aggressive effort was made to remove tumour tissue infiltrating the cavernous sinus or soft tissues deep in the orbit to avoid severe functional disturbances. All patients but one were female (mean age 53 years). Mean follow-up period was 68 months (range 4-155 months). RESULTS: The leading symptom was proptosis in 14 patients, accompanied in 7 cases by progressive visual impairment. Surgical resection was thought to have been complete in 11 patients (69%) and incomplete in 5 (31%). Residual tumour was deliberately left when there was infiltration of the cavernous sinus (n = 4), the pterygopalatine fossa (n = 2) and/or the deep intraorbital soft tissues (n = 1). Tumour recurrence was observed in 9 patients, among whom were 6 patients with an initially "completely" resected meningioma. Eight patients underwent re-operation. Complete resection was achieved in 3 of these latter patients with an isolated exclusively intraorbital tumour manifestation. CONCLUSION: By means of combined skull base approaches, spheno-orbital meningiomas are grossly resected totally with a long-term survival free of recurrence and an acceptable quality of life. In some cases, deliberate subtotal tumour resection is useful to avoid severe neurological damage with sufficient tumour control and a valuable progression-free survival.

Observations on intraoperative somatosensory evoked potential (SEP) monitoring in the semi-sitting position.

BACKGROUND: Former case reports suggest that monitoring of median nerve somatosensory evoked potentials (M-SEP) is unreliable in patients operated in the semi-sitting position due to the occurrence of evoked potential changes unrelated to neurological damage. This study was designed to analyze these changes in greater detail and confirm that these changes are not caused by neurological damage. METHODS: M-SEP monitoring findings of 50 patients with surgery in the semi-sitting position were analyzed and compared with a group of 50 patients who underwent surgery in the supine position. M-SEP amplitudes and latencies at distinct steps of the monitoring procedure were used for further analysis. In 10 of the 50 semi-sitting patients, M-SEP were recorded additionally after surgery with the anesthetized patient in the supine position. RESULTS: Significant M-SEP changes occurred in the semi-sitting patients only. An amplitude loss of greater than 50% on at least one side was observed in 24 patients. The magnitude and the time course of the amplitude loss was considerably variable. A complete loss of the evoked potential was not observed in any case. In all 10 patients, M-SEP recovered completely when recorded in the supine position. CONCLUSIONS: In about half of the patients with M-SEP monitoring in the semi-sitting position, a significant amplitude loss occurs which is unrelated to neurological damage and presumably caused by subdural gas collections. There is no characteristic pattern of M-SEP changes which enables a differentiation of these 'artificial' alterations from true events. The only appropriate criterion to indicate an impending neurological damage in these patients seems to be a complete loss of the M-SEP potential.

The impact of neurophysiological intraoperative monitoring on surgical decisions: a critical analysis of 423 cases.

OBJECT: The aim of this observational clinical study was to analyze the impact of neurophysiological intraoperative monitoring (IOM) on the surgical procedure and to assess the benefits of such monitoring. METHODS: Data for 423 patients who underwent neurophysiological IOM with somatosensory evoked potentials and brainstem auditory evoked potentials during neurosurgical procedures were collected prospectively. The patients were classified into one of five groups according to the findings of IOM, the intervention following a monitoring alarm, and the patient's postoperative neurological condition. These groups were as follows: patients with true-positive findings with intervention (42 cases, 9.9%), those with true-positive findings without intervention (42 cases, 9.9%), those with false-positive findings (nine cases, 2.1%), those with false-negative findings (16 cases, 3.8%), and those with true-negative findings (314 cases, 74.2%). Different interventions followed an event identified with monitoring. These interventions were related to dissection in 17 cases, to perfusion pressure in 11, to a limitation of the surgical procedure in five, to vessel clipping in four, to vasospasm in three, and to retraction in one case. In one case the surgical procedure was abandoned. A critical analysis and cautious estimation of the interventions revealed that IOM was helpful in preventing a postoperative deficit in 5.2% of the monitored cases. CONCLUSIONS; For critical analysis of the benefits of IOM one must evaluate not only the findings of IOM and the patient's postoperative neurological condition but also the intraoperative findings and surgical interventions following a monitoring alarm. Evidence is presented that IOM is helpful in preventing a postoperative deficit.

Enhanced stability of somatosensory evoked potentials attained in the median nerve by using temporal electrodes for intraoperative recording in patients in the semisitting position.

OBJECT: Findings published in case reports indicate that monitoring of median nerve somatosensory evoked potentials (MN-SSEPs) is unreliable in patients who undergo surgery while in the semisitting position due to the occurrence of changes in the potentials that are unrelated to neurological damage. The present study was designed to test the hypothesis that in these patients MN-SSEPs are more stable when recording electrodes are placed over the temporal region. METHODS: In 30 patients who underwent surgery in the semisitting position, MN-SSEPs were recorded intraoperatively by using electrodes placed over the temporal region as well as those placed at conventional recording sites. The authors analyzed MN-SSEP amplitudes and latencies at different recording sites and at distinct steps of the monitoring procedure. In 10 of the 30 patients a clinically significant attenuation (> 50%) of MN-SSEP amplitude was observed at conventional recording sites and this was obviously not related to neurological damage. In contrast, no significant changes were observed in MN-SSEPs recorded from electrodes located over the temporal region. CONCLUSIONS: In patients who undergo surgery in the semisitting position, the use of additional recording electrodes placed over the temporal region makes intraoperative MN-SSEP monitoring less prone to false-positive alarms and thus enhances the reliability of intraoperative MN-SSEP monitoring.

Favourable outcome after biopsy and decompression of a holocord intramedullary spinal cord astrocytoma in a newborn.

A 4-month-old male infant presented with hydrocephalus as the initial clinical symptom due to a holocord intramedullary low-grade astrocytoma. This case illustrates a possible alternative treatment to radical surgery with a benign long-term course over a 4.5 year follow-up period.

Visual evoked potentials for intraoperative neurophysiologic monitoring using total intravenous anesthesia.

Conflicting reports on the usefulness of intraoperative monitoring of visual function by means of visual evoked potentials (VEPs) initiated this study. In 32 patients without visual problems, VEPs were recorded to evaluate the reliability for intraoperative monitoring with total intravenous anesthesia. All patients underwent noncranial surgery. Using a standard technique, VEPs were recorded preoperatively in the awake patients and after induction of anesthesia during surgery. A total of 1436 intraoperative traces were recorded and analyzed. A minor prolongation of the P100 latency of 8% and a more pronounced attenuation of the P100-N145 amplitude of 60% were observed in the anesthetized patients. In most of the anesthetized patients, a stable recording of VEPs was not obtainable. In 4 patients (12.5%), clearly identifiable VEP peaks were detected in more than 90% of the traces recorded intraoperatively. In 88% of the patients, reproducible VEPs were obtained in less than 75% of the intraoperative traces only. We concluded that with standard recording techniques and total intravenous anesthesia, intraoperative VEP monitoring in surgically anesthetized patients is not reliable.

VEGF plasma levels in non-ruptured intracranial aneurysms.

Aneurysm growth appears to be associated with an increased risk of rupture. Therefore, it may be of interest to identify mechanisms contributing to aneurysm growth. Angiogenic factors, particularly vascular endothelial growth factor (VEGF), appear to play an important role in the pathogenesis and growth of cerebrovascular malformations. We aimed to study systemic VEGF levels as a potential systemic marker in patients with non-ruptured intracranial aneurysms compared with healthy controls. Mean VEGF plasma concentrations were found to be increased in patients with non-ruptured intracranial aneurysms compared with healthy controls (85.2 pg/ml versus 44.1 pg/ml). This difference did not reach significance in the analyzed study cohort (p=0.05) but only when the analysis was restricted to male patients (p=0.04). Female patients and controls demonstrated significantly increased VEGF plasma levels only on correlation with age but not with the presence of aneurysms. Neither the presence of multiple aneurysms nor aneurysm location were correlated with VEGF levels. Although overall VEGF plasma difference was not statistically significant, we found significantly increased levels in male patients. Furthermore, we identified a distinct group of female patients with intracranial aneurysms who presented excessively increased VEGF plasma levels to an amount that was not observed in the controls. Further studies may clarify the relationship of aneurysm growth and VEGF.

Fusion of the cerebellar hemispheres ventral to the brainstem: a rare hindbrain-related malformation.

INTRODUCTION: New variations of cerebellar malformations are being increasingly recognized using modern neuroimaging techniques. Until now only dorsal cerebellar fusion syndromes, such as the rhombencephalosynapsis and its variations have been recognized. CASE REPORT: We report on a 17-month-old male infant presenting with an exceptional hindbrain related malformation characterized by midline fusion of the cerebellar hemispheres ventral to the brainstem and causing symptoms due to brainstem compression. DISCUSSION AND CONCLUSION: A more detailed understanding of the cerebellar embryogenesis is required to unravel the underlying mechanisms leading to this type of cerebellar malformation, which cannot easily be integrated into the common classification systems. Both the morphological features and the clinical presentation are different from those of other cerebellar structural abnormalities. If this type of congenital malformation is detected more frequently in the future, it seems reasonable that it should be added to the list of cerebellar malformations as a distinct type.

Vascular endothelial growth factor plasma levels are significantly elevated in patients with cerebral arteriovenous malformations.

BACKGROUND: Since growth and de novo generation of cerebrovascular malformations were demonstrated, a strictly congenital model cannot be further supported as unique factor in the pathogenesis of cerebral arteriovenous malformations (AVMs). Vascular endothelial growth factor (VEGF) has previously been demonstrated to be highly expressed in AVMs by immunohistochemical methods. However, systemic VEGF levels have not been analysed previously. This study aimed to investigate VEGF plasma concentrations as a possible plasma marker for neovascularization in patients with cerebral AVMs compared to healthy controls. METHODS: The study included 17 patients with cerebral AVMs and 40 healthy controls. VEGF plasma concentrations were measured by a specific enzyme immuno-assay. RESULTS: VEGF plasma concentrations were significantly higher in patients with cerebral AVMs (mean 140.9 pg/ml, SD 148.5 pg/ml and median 63.0 pg/ml) compared to a healthy control group (mean 44.7 pg/ml, SD 36.4 pg/ml and median 35.0 pg/ml), p = 0.0003. CONCLUSIONS: Our findings suggest that VEGF plasma concentrations might play a role in the pathogenesis of cerebral AVMs. Further studies are necessary and would contribute to an improved understanding of the pathogenesis of cerebral AVMs.

Functional magnetic resonance imaging in anesthetized patients: a relevant step toward real-time intraoperative functional neuroimaging.

OBJECTIVE: The introduction of intraoperative 1.5-T magnetic resonance imaging may provide up-to-date functional information in the surgical environment. However, feasible passive paradigms that allow the examination of anesthetized patients will be a precondition for intraoperative functional magnetic resonance imaging (fMRI). The aim of this study is to evaluate the feasibility of a recently developed passive fMRI paradigm for functional neuroimaging in anesthetized patients. METHODS: We investigated four anesthetized patients with intracranial pathological conditions not related to the sensorimotor cortex. All patients had been anesthetized with standard total intravenous anesthesia for more than 24 hours before the fMRI scan. Anesthesia and monitoring were sustained during the scanning procedure. A simultaneous electrical stimulation of the median and tibial nerves was applied to elicit a cortical activation using a custom-designed magnetoelectrically shielded conductor. Statistical evaluation using Statistical Parametric Mapping software (Wellcome Department of Imaging Neuroscience, University College, London, England) and the Talairach Daemon Client (Version 1.1; Research Imaging Center, University of Texas Health Science Center, San Antonio, TX) followed. RESULTS: Three of four patients showed a good activation of the sensorimotor cortex under anesthesia. In one patient, no significant activation was observed, presumably as a result of increased body impedance because of severe edema. Standard dosages of the narcotics did not influence the cortical response; however, stimulation intensity had to be increased compared with awake patients. We did not detect relevant interferences with magnetic resonance imaging arising from the technical setup. CONCLUSION: The method presented proved to be a feasible paradigm for fMRI evaluation of the sensorimotor cortex in anesthetized patients and thus forms a relevant step toward real intraoperative functional neuroimaging.

Brain perfusion following single seizures.

PURPOSE: The aim of this study was to assess the regional relative interictal and postictal perfusion changes in temporal and parietal lobe epilepsy. METHODS: We investigated interictal and postictal magnet resonance perfusion changes in five patients with temporal lobe epilepsy either with hippocampal sclerosis (n = 3) or without (n = 2), and in one patient with extratemporal (parietal lobe) epilepsy. T(2)*-weighted single-shot echo-planar images were acquired after bolus application of 0.2 mmol/kg gadolinium-diethylene triamine pentaacetic acid (GD-DTPA) at baseline and after intervals of 2-12 min, 15-23 min, 28-50 min, 63-72 min, and 180-240 min. The bolus-peak ratio was calculated in regions of interest in the hippocampus (HIP), parahippocampal gyrus (PHG), thalamus (THA), cortex (COR), and white matter (WM), yielding relative perfusion changes. RESULTS: Interictally, we found relative hyperperfusion of the ictogenic side in five of six patients in the HIP. Postictally, the perfusion decreased in the HIP by 25-39% as compared to baseline, whereas the PHG showed a reverse pattern. In the late postictal phase, perfusion increased in the HIP again and decreased in the PHG. In the THA, the inter- and postictal changes were small (5-19%). COR and WM showed equivocal results. CONCLUSION: Postictal relative hypoperfusion in the HIP appears to be associated with the cessation of neuronal ictal discharge, whereas postictal hyperperfusion in the PHG lags behind and may reflect increased metabolism to restore the interictal state of neuronal excitability.

Early seizures following non-penetrating traumatic brain injury in adults: risk factors and clinical significance.

BACKGROUND: In the literature dissenting data are obtained about risk factors for early post-traumatic seizures and their impact on outcome. This study was conducted to obtain more information about the clinical significance of early seizures and their possible impact on the treatment of traumatic brain injury. METHODS AND RESULTS: A consecutive series of 1868 adult patients with head injury were analysed retrospectively. Demographic data of the patients, characteristics of the injury, and findings on CT scan were recorded. Risk factors for early post-traumatic seizures were identified using univariate statistics. A multivariate logistic regression was performed to look for interaction of different variables. The impact of early post-traumatic seizures on outcome was examined in an analogous way. Chronic alcohol abuse, subdural haematoma and brain contusion were identified as independent risk factors for early post-traumatic seizures. A significant association of early post-traumatic seizures with an unfavourable outcome was observed, but this effect was small compared to other variables. CONCLUSIONS: Early post-traumatic seizures appear to be an acute reaction of the brain to cortical damage with little independent impact on the management of head injury.

Intramedullary spinal cord cavernous malformations: clinical features and risk of hemorrhage.

The aim of this study was to review the natural history of symptomatic intramedullary spinal cord (IMSC) cavernous malformations in order to analyze the underlying mechanisms leading to symptoms and determine the potential risk of lesional hemorrhage. Between January 1990 and June 2001, ten consecutive patients with IMSC cavernous malformations were treated surgically in our institution. Age ranged from 17 to 73 years (mean 34.5). All patients became symptomatic due to one or more hemorrhages leading to neurological deficits of different severity, with a more aggressive course for upper cervical lesions. Pre- and postoperative patient condition was classified according to the Frankel scale. Four patients experienced one hemorrhage, four patients two, one patient three, and another one five repeated hemorrhages. The annual retrospective hemorrhage rate for symptomatic IMSC cavernous malformations was 4.5% per patient/year, with a prospective rehemorrhage risk of 66% per patient/year. The postoperative condition was improved in four patients and unchanged in six, and none grew worse. Detailed analysis of history and clinical course in all patients revealed an acute onset of symptoms with subsequent neurological deterioration after each bleeding episode. Based on the significant risk of rehemorrhage and the gratifying functional results, surgery is indicated for symptomatic IMSC cavernous malformations.

Reconstruction of the laminar roof with miniplates for a posterior approach in intraspinal surgery: technical considerations and critical evaluation of follow-up results.

STUDY DESIGN: A retrospective clinical follow-up study of patients who underwent intraspinal surgery with reconstruction of the laminar roof using titanium miniplates. OBJECTIVE: To evaluate the surgical technique of laminar roof reconstruction and to analyze follow-up results with regard to bony healing of the laminae and the development of spinal deformities. SUMMARY AND BACKGROUND DATA: The reconstruction of the laminar roof was initially proposed to overcome adverse effects associated with extensive cervical laminectomy in children. Because technical evolutions such as the use of an air drill and miniplates have facilitated the procedure, it has gained more widespread use as a posterior approach for intraspinal surgery. Thus, with a sufficient number of patients treated and a longer period of follow up, it seems reasonable to critically evaluate the technique and its suitability as a standard approach for intraspinal surgery. METHODS: The surgical procedures of 79 patient who underwent intraspinal surgery with osteotomy and reconstruction of a total of 323 spinal laminae using an air drill and miniplates were analyzed. In 59 patients, data of a complete clinical and radiologic follow-up examination were evaluated. Plain radiographs and computed tomography scans were analyzed for bony healing of the laminae and spinal alignment. RESULTS: Minor complications such as cerebrospinal fluid collections and disturbed wound healing occurred within normal ranges. The was no case of dural, nerve root, or spinal cord injury attributable to laminotomy or laminar reconstruction. Eight (14.3%) patients complained of moderate to severe local pain at the time of follow-up examination and 8 patients stated impaired mobility of their spine at the surgical site. Bony healing was confirmed radiologically in 86.1% of the laminae. In 12 patients, a preexisting spinal deformity worsened after surgery and five patients demonstrated a new spinal malalignment. No patient required additional surgery because of progressive spinal deformity. Intramedullary location of the lesion and cervical location of surgery were significantly associated with the development of spinal malalignment, whereas incomplete bony healing of the laminae was not. CONCLUSIONS: The reconstruction of the laminar roof using the technique described is safe, well suitable to serve as a standard posterior approach to intraspinal pathologies, and offers distinct advantages over laminectomy. However, some patients, particularly those with intramedullary cervical lesions, could develop spinal malalignment after surgery despite reconstruction of the laminar roof and sufficient bony healing of the laminae.

A novel passive functional MRI paradigm for preoperative identification of the somatosensory cortex.

The purpose of this study was to assess the feasibility of a novel passive functional magnetic resonance imaging (fMRI) paradigm for activation analysis of the somatosensory cortex utilizing a specifically designed conductor for electrical stimulation of the median and tibial nerves. Thirteen healthy volunteers underwent electrical stimulation of these nerves with defined frequencies and intensities in a block-designed fashion. Electrical stimuli were applied by two custom-designed magnetoelectrically protected coaxial leads, taking into account the technical difficulties of the application of electrical current in the fMRI environment. Activation effects were analysed in real-time mode and validated by statistical parametric mapping. The shielded conductors suppressed electromagnetically derived artefacts nearly completely. The measurements revealed maximum cortical activation when applying a stimulation frequency of 3 Hz and an intensity of 3 mA above motor threshold. Simultaneous stimulation of both the median and tibial nerves enhanced identification of the central region significantly. A standardized setup for the clinical environment was evolved. With this passive paradigm, the identification of the somatosensory cortex was possible in all evaluated cases. The presented technical setup and paradigm is a reliable and fast method for preoperative identification of the somatosensory cortex and may represent a feasible paradigm for generation of pre- and intraoperative fMRI in functionally disabled patients.

Presurgical evaluation of epilepsy by brain diffusion: MR-detected effects of flumazenil on the epileptogenic focus.

PURPOSE: After focal status epilepticus, focal alterations of the apparent diffusion coefficient (ADC) have been demonstrated in the epileptogenic zone by using diffusion-weighted magnetic resonance (MR)imaging (DWI). Effects of flumazenil on an epileptogenic focus have been demonstrated by EEG recordings, but not by functional MRI. We hypothesized that dynamic spatiotemporal alterations of brain diffusion of the epileptogenic focus after application of flumazenil will be detectable by DWI and correlate with the epileptogenic zone. METHODS: Twelve adult patients considered for epilepsy surgery with medically intractable temporal lobe epilepsy (TLE; n = 7), extratemporal lobe epilepsy (ETE; n = 2), and TLE+ETE (n = 3) were prospectively examined with DWI interictally (serving as baseline) and 10 min after application of 1 mg flumazenil i.v. RESULTS: The baseline interictal ADC was significantly elevated in the hippocampus on the ictogenic side in the patients with TLE (p = 0.002) as compared with healthy volunteers. The following changes of the mean ADC were seen in different regions of interest (ROIs) after injection of flumazenil: decreases in the hippocampus on the seizure-onset side by 14.8% (p = 0.005); decreases in the parahippocampal gyrus on both sides by 6.8% (epileptogenic side; p = 0.044) or 7.9% (nonepileptogenic side; NS), respectively; decreases in the cortex on the nonictogenic side by 7.9% (p = 0.047); and no significant changes of the ADC in the other ROIs. CONCLUSIONS: ADC decreases measured after application of flumazenil were seen in the seizure-onset zone as revealed by EEG and structural MRI and are an indicator of focus localization in patients with TLE.