Osteochondromas of the cervical spine in atypical location.

In the current article we review the available English literature by pubmed search engine on the topic of osteochondromas and their location in the cervical spine. The focus is to investigate the location of the lesions in cervical spine and to analyze clinical presentations and symptoms of patients, the aetiology and histopathology examination of the masses. In addition we report a rare illustrative case of a 62 year-old man with an osteochondroma of the cervical spine. The mass developed at a very slow rate for many years and produced no clinical symptoms. The location of the extradural mass in the right atlanto-axial joint of C1 and C2 is extremely rare and was not been reported so far. After preoperative CT- and MRI-imaging the entire mass could be removed.

Persistent cerebrospinal fluid rhinorrhea by intrasphenoidal encephalocele.

The case of a 60-year-old man with a 6-month history of cerebrospinal fluid (CSF) rhinorrhea is presented. Computed tomography (CT) and magnetic resonance (MR) imaging revealed an intrasphenoidal mass extending through a bony defect of the roof of the left sphenoid sinus. Transnasal surgical repair was performed; intraoperatively the mass was identified as an intrasphenoidal encephalocele. The pathogenesis of this anomaly is analyzed, the clinical findings and the operative treatment are described, and the literature is reviewed.

Functional magnetic resonance imaging and cortical mapping in motor cortex tumor surgery: complementary methods.

Functional magnetic resonance imaging (fMRI) and direct electrocortical stimulation (DES) are the most commonly used means of analyzing the functional brain topography prior to surgery in the vicinity of Brodmann area 4. No consensus has been established in the literature about the significance of both procedures in reducing operative morbidity. The study presented here was conducted in 30 patients with tumors in the area of the primary motor cortex. Blood oxygen level dependent (BOLD) sequences were preoperatively established with a standardized paradigm. Intraoperatively motor mapping was performed with DES. The results of both methods were digitally matched with a frameless image-guidance system. Correlations between the results of fMRI and of DES were analyzed. Furthermore, the potential influences of the size, position, and histology of the lesions on the mapping results were analyzed and the motor outcome was evaluated. The mean deviation between the results of fMRI and of DES was 13.8 mm (range: 7-28 mm). This deviation was independent of the histology, size, or location of the corresponding lesion. The individual variability of the analysis threshold value for the evaluation of the BOLD sequences led to a considerable topographical inaccuracy. As complementary methods, fMRI contributes to estimating the operational risk, while DES is performed when the results of MRI and fMRI suggest an immediate proximity of the tumor to motor areas.

Debridement and spinal instrumentation as a single-stage procedure in bacterial spondylitis/spondylodiscitis.

OBJECT: The best surgical technique for patients with bacterial spinal infections is still discussed controversially. But recent publications suggest that titanium implants can be used safely in infectious sites in combination with debridement and antibiotic therapy. The purpose of this study is to provide further evidence in support of debridement and instrumentation as a single-stage procedure for spinal infection. METHODS: Twenty-four cases with cervical, thoracic, and lumbar spondylitis/spondylodiscitis were analyzed. In 17 cases, anterolateral stabilization was performed with titanium cages. No autologous or homologous bone grafts were used. Transpedicular screw/rod fixation following posterior debridement of the intervertebral space was performed in the other 7 cases. RESULTS: WBC and C-reactive protein levels decreased significantly after surgical debridement. Pain levels decreased from a preoperative median of 4 (on the Denis Pain Scale) to a postoperative median of 2. Twenty-two of the 24 patients were fully mobilized within 2 weeks after surgery. The Barthel Index improved from 60 (10-85) before surgery to 90 (65-100) after surgery. No recurrence of the initial infection was noticed during a mean follow-up period of 18 months. The fusion rate was 90.5%. The mortality rate was 1 out of 24 (4.2%). CONCLUSIONS: These findings support the position that debridement and instrumented fusion can be performed as a single-stage procedure without an increase in the recurrence rate or morbidity, compared with the use of autologous bone grafting or staged procedures. Same-stage instrumentation allows early postoperative mobilization of the patient, which is advantageous, especially for an increasingly elderly population and in patients with comorbidities.

Atypical location of a solitary intracranial chondroma without meningeal attachment.

The case of a 19-year-old female patient with a history of severe headache for several months is presented. Computed tomography (CT) as well as magnetic resonance imaging (MRI) revealed an intracranial, space-occupying mass with no meningeal attachment, located in the left frontal lobe. The entire tumour was removed, the pathological examination revealed a chondroma. The origin of this tumour is analysed, the clinical and histological findings are described and the literature is reviewed.

Multimodal protocol for awake craniotomy in language cortex tumour surgery.

BACKGROUND: Intra-operative neurophysiological language mapping has become an established procedure in patients operated on for tumours in the area of the language cortex. Awake cranial surgery has specific risks and patients are exposed to an increased physical and mental stress. The aim of the study was to establish an algorithm that enables tailoring the neurosurgical and anaesthetic techniques to the individual patient. METHOD: A total of 25 patients underwent awake craniotomy for intra-operative language mapping between 1999 and 2004. Following craniotomy under analgesia and sedation without rigid pin fixation of the head, cortical language mapping was performed in the fully co-operative patient. The results of functional magnetic resonance imaging and of cortical language mapping were incorporated into the 3D dataset for neuronavigation. Depending on the functional data and the individual operative risk tumour resection then proceeded either under conscious sedation with the option of subcortical language monitoring or under general anaesthesia. FINDINGS: After cortical language mapping patients are assigned to one of four groups: BACC (Berlin awake craniotomy criteria) I-IV. BACC I (9 patients): adequate functional data+operative risk not increased-->tumour resection in the awake patient; BACC II (4 patients): limited functional data+operative risk not increased-->tumour resection in the awake patient with the option of language monitoring as needed; BACC III (9 patients): adequate functional data+increased operative risk-->tumour resection under general anaesthesia using functional navigation; BACC IV (3 patients): limited functional data+increased operative risk-->tumour resection in the awake patient with the option of language monitoring as needed. We observed less adverse events in group BACC III. No permanent deterioration of language function occurred in this series. CONCLUSIONS: The multimodal protocol for awake craniotomy provides for tumour resection under general anaesthesia in selected patients using functional neuronavigation. Our experience with the algorithm suggests that it is a useful tool for preserving function in patients undergoing surgery of the language cortex while reducing the operative risk on an individual basis.

Motor nerve root monitoring during percutaneous transforaminal endoscopic sequestrectomy under general anesthesia for intra- and extraforaminal lumbar disc herniation.

INTRODUCTION: Percutaneous transforaminal endoscopic sequestrectomy (PTFES) for intra- and extraforaminal lumbar disc herniation (IHLD and EHLD) is usually performed under local anesthesia because the patient's full cooperation is necessary during surgery in order to reduce morbidity. This puts intraoperative stress on both the patient and the surgeon. The present study was performed to assess the safety and efficacy of performing PTFES under general anesthesia using a new protocol with continuous intraoperative neurophysiological monitoring (IOM). PATIENTS AND METHODS: Twenty-five patients with IHLD and/or EHLD were treated by PTFES under general anesthesia without neuromuscular blocking agents. Free-run electromyography (EMG) recordings from characteristic muscles were monitored for the nerve root exiting through the intervertebral foramen at the level of surgery as well as those immediately above and below this level. The recorded potentials were visualized and analyzed on the monitoring screen. Additionally, the EMG activity was played to the surgeon via loudspeakers. RESULTS: EMG-assisted endoscopic sequestrectomy was successfully completed in all 25 cases. Three patients showed complex repetitive discharge patterns already before the actual procedure, but these normalized upon removal of the sequester. Abnormal EMG changes in the form of intraoperative isolated spikes, phasic bursts, or tonic trains were recorded in 17 of the 25 cases. These occurred during placement of the endoscopic working channel in the area of the neuroforamen in 12 cases and during removal of the sequester in 6 cases. Spikes and bursts were evoked by direct contact with the nerve root or indirectly through traction or compression. Tonic discharge patterns, on the other hand, correlated with more severe mechanical stress caused for instance by compression or traction when the nerve root was fixed in the neuroforamen by the sequester. CONCLUSIONS: PTFES under general anesthesia is a safe and easy-to-perform technique for surgical management of intra- and/or extraforaminal lumbar disc herniation if combined with intraoperative neurophysiological monitoring. General anesthesia reduces intraoperative stress to a minimum, so that a larger number of patients may benefit from this minimally invasive procedure in future.

[Sensor-based detection of skull positioning for image-guided cranial navigation under free head mobility]. / Sensorbasierte Schädelreferenzierung für die schnittbildgeführte Navigation unter freier Kopfbewegung.

PURPOSE: Although computer- and image-guided surgical procedures are an improvement of frame-guided stereotaxy, many navigation systems still require rigid fixation of the patient's head throughout the operation. This study describes the clinical application of a technical modification that enables cranial navigation with "free head mobility" using CT and MR images as well as the calculated 3-D reconstruction models. MATERIAL AND METHODS: A sensor-based electromagnetic neuronavigation system was expanded to allow the localization and position monitoring of several sensors within an electromagnetic field. One of these sensors was attached to a dental splint as an additional reference (DRF = dynamic reference frame). Thus, it was possible to determine the position of the sensor-guiding surgical instruments and to record the slightest movement of the cranium as well. This information was then used to continuously adapt the position of the imaging plane and the resultant calculated 3-D reconstructions to the actual position of the cranium. RESULTS: The clinical application of the DRF was tested for different neurosurgical procedures. They included image-guided biopsies and endoscopic interventions using MRI data, transnasal accesses to the base of the skull using CT data and surgical removal of multilocular metastases using data from both imaging modalities. Intracranial target reference points as well as those on the skull were found with a high accuracy to the initial measurement position after arbitrary movement of the patient's head. Thus, navigation was also possible without rigid fixation of the head because of the continuous adaptation of the imaging data on the change in position of the patient's head. CONCLUSION: Based on these first test results, a high clinical potential for DRF application in cranial navigation is to be expected. The aim of DRF is to dispense with the rigid fixation of the patient's head. This increases the application scope of image-guided navigation procedures to include, for example, any bioptic or endoscopic intervention, in which rigid pin fixation of the cranium is not required or desired. For all other procedures, continuous position monitoring by DRF ensures automatic correction of imaging data with mechanical alteration of the head position.

Prognostic value of improved intraoperative motor evoked potentials. A case report.

UNLABELLED: This unusual case involves intraoperative registration of improved motor evoked potentials accompanied by postoperative improvement of the motor status. CASE REPORT: A 51-year-old patient undergoing surgery for a right postcentral glioma was first submitted to phase reversal of somatosensory potentials for intraoperative localization of the central sulcus. During subsequent monopolar electric stimulation of the precentral gyrus, motor evoked potentials (MEPs) could not be recorded initially but only following extirpation of the tumor fraction in the central sulcus. The amplitudes of the registered potentials increased during the further clinical course. The preoperative arm-preponderant hemiparesis already improved on the first postoperative day. CONCLUSION: This intraoperative electrophysiological observation correlated with the postoperative neurological status, thus documenting functional recovery of the motor system through the intervention.

[Cost analysis of intraoperative neurophysiological monitoring (IOM)]. / Kostenanalyze des intraoperativen neurophysiologischen Monitorings (IOM).

INTRODUCTION: A number of studies demonstrate that a significant reduction of postoperative neurological deficits can be achieved by applying intraoperative neurophysiological monitoring (IOM) methods. A cost analysis of IOM is imperative considering the strained financial situation in the public health services. MATERIAL AND METHODS: The calculation model presented here comprises two cost components: material and personnel. The material costs comprise consumer goods and depreciation of capital goods. The computation base was 200 IOM cases per year. Consumer goods were calculated for each IOM procedure respectively. The following constellation served as a basis for calculating personnel costs: (a) a medical technician (salary level BAT Vc) for one hour per case; (b) a resident (BAT IIa) for the entire duration of the measurement, and (c) a senior resident (BAT Ia) only for supervision. RESULTS: An IOM device consisting of an 8-channel preamplifier, an electrical and acoustic stimulator and special software costs 66,467 euros on the average. With an annual depreciation of 20%, the costs are 13,293 euros per year. This amounts to 66.46 euros per case for the capital goods. For reusable materials a sum of 0.75 euro; per case was calculated. Disposable materials were calculate for each procedure respectively. Total costs of 228.02 euro; per case were,s a sum of 0.75 euros per case was calculated. Disposable materials were calculate for each procedure respectively. Total costs of 228.02 euros per case were, calculated for surgery on the peripheral nervous system. They amount to 196.40 euros per case for spinal interventions and to 347.63 euros per case for more complex spinal operations. Operations in the cerebellopontine angle and brain stem cost 376.63 euros and 397.33 euros per case respectively. IOM costs amount to 328.03 euros per case for surgical management of an intracranial aneurysm and to 537.15 euros per case for functional interventions. Expenses run up to 833.63 euros per case for operations near the motor cortex and to 117.65 euros per case for intraoperative speech monitoring. DISCUSSION: Costs for inpatient medical rehabilitation have increased considerably in recent years. In view of the financial situation, it is necessary to reduce postoperative morbidity and the costs it involves. IOM leads to a reduction of morbidity. The costs for IOM calculated here justify its routine application in view of the legal and socioeconomic consequences of surgery-related neurological deficits.

Intracranial image-guided neurosurgery: experience with a new electromagnetic navigation system.

BACKGROUND: The aim of image-guided neurosurgery is to accurately project computed tomography (CT) or magnetic resonance imaging (MRI) data into the operative field for defining anatomical landmarks, pathological structures and tumour margins. To achieve this end, different image-guided and computer-assisted, so-called "neuronavigation" systems have been developed in order to offer the neurosurgeon precise spatial information. METHOD: The present study reports on the experience gained with a prototype of the NEN-NeuroGuard neuronavigation system (Nicolet Biomedical, Madison, WI, USA). It utilises a pulsed DC electromagnetic field for determining the location in space of surgical instruments to which miniaturised sensors are attached. The system was evaluated in respect to its usefulness, ease of integration into standard neurosurgical procedures, reliability and accuracy. FINDINGS: The NEN-system was used with success in 24 intracranial procedures for lesions including both gliomas and cerebral metastases. It allowed real-time display of surgical manoeuvres on pre-operative CT or MR images without a stereotactic frame or a robotic arm. The mean registration error associated with MRI was 1.3 mm (RMS error) and 1.5 mm (RMS error) with CT-data. The average intra-operative target-localising error was 3.2 mm (+/- 1.5 mm SD). Thus, the equipment was of great help in planning and performing skin incisions and craniotomies as well as in reaching deep-seated lesions with a minimum of trauma. INTERPRETATION: The NEN-NeuroGuard system is a very user-friendly and reliable tool for image-guided neurosurgery. It does not have the limitations of a conventional stereotactic frame. Due to its electromagnetic technology it avoids the "line-of-sight" problem often met by optical navigation systems since its sensors remain active even when situated deep inside the skull or hidden, for example, by drapes or by the surgical microscope.

Monitoring of intraoperative motor evoked potentials to increase the safety of surgery in and around the motor cortex.

OBJECT: The repetitive application of high-frequency anodal monopolar stimulation during surgery in or near the motor cortex allows a qualitative and quantitative evaluation of motor evoked potentials (MEPs). Using this method, motor pathways and motor function can be continuously monitored during surgery. METHODS: In this prospective study, 70 patients underwent MEP monitoring during surgery performed in the central region. All procedures were performed after general anesthesia had been induced without the aid of muscle relaxants. The motor pathways were monitored during the entire surgical procedure by repetitive high-frequency anodal monopolar stimulation (frequency 400-500 Hz; train 7-10 pulses; impulse duration 0.2-0.7 msec; and stimulation intensity 16.9 +/- 7.76 mA). The MEPs were continuously evaluated to assess their latency, potential duration, and amplitude. Recorded alterations in these parameters were subsequently correlated with surgical maneuvers and with postoperative neurological deterioration. The monitoring parameters (latency, potential duration, and amplitude) had a broad interindividual range of variation. A correlation between individual intraoperative changes in the potentials and surgical maneuvers or postoperative neurological deterioration was observed in eight cases. A spontaneous shift in latency greater than 15% or a sudden reduction in the amplitude of the potential greater than 80% was considered a warning criterion. In all cases in which there was an irreversible change in latency or a complete loss of potentials were observed, there was postoperative neurological deterioration. CONCLUSIONS: Improved surgical safety can be achieved using intraoperative neurophysiological monitoring procedures. Repetitive stimulation of the motor cortex proved to be a reliable method for monitoring subcortical motor pathways. Changes in MEP latency and MEP amplitude served as warning criteria during surgery and possessed prognostic value.

Lumbar disc herniation in patients up to 25 years of age.

Retrospective analysis of 165 patients (105 males, 60 females) with a mean age of 21.2 years (range 14 to 25 years) of 6933 surgically treated patients from January 1987 to May 1999 focused on age and sex distribution, body mass, familial predisposition, trauma, histology, and clinical course. The incidence of herniated lumbar discs was 2.3% in patients aged up to 25 years. A valid family history was obtained in 121 patients and a positive history was found in 82 of these patients (67.8%). The patients had a higher body mass index compared to a group of individuals with a similar age structure. Radiography demonstrated bony changes in 124 patients (75.2%), primarily attributable to postural deformities such as scoliosis. The condition of the bony structures seems to be more important than the condition of the disc tissue in the occurrence of this disease in young patients.

Can continuous intraoperative facial electromyography predict facial nerve function following cerebellopontine angle surgery?

Intraoperative cranial nerve monitoring has significantly improved the preservation of facial nerve function following surgery in the cerebellopontine angle (CPA). Facial electromyography (EMG) was performed in 60 patients during CPA surgery. Pairs of needle electrodes were placed subdermally in the orbicularis oris and orbicularis oculi muscles. The duration of facial EMG activity was noted. Facial EMG potentials occurring in response to mechanical or metabolic irritation of the corresponding nerve were made audible by a loudspeaker. Immediate (4-7 days after tumor excision) and late (6 months after surgery) facial nerve function was assessed on a modified House-Brackmann scale. Late facial nerve function was good (House-Brackmann 1-2) in 29 of 60 patients, fair (House-Brackmann 3-4) in 14, and poor (House-Brackmann 5-6) in 17. Postmanipulation facial EMG activity exceeding 5 minutes in 15 patients was associated with poor late function in five, fair function in six, and good function in four cases. Postmanipulation facial EMG activity of 2-5 minutes in 30 patients was associated with good late facial nerve function in 20, fair in eight, and poor in two. The loss of facial EMG activity observed in 10 patients was always followed by poor function. Facial nerve function was preserved postoperatively in all five patients in whom facial EMG activity lasted less than 2 minutes. Facial EMG is a sensitive method for identifying the facial nerve during surgery in the CPA. EMG bursts are a very reliable indicator of intraoperative facial nerve manipulation, but the duration of these bursts do not necessarily correlate with short- or long-term facial nerve function despite the fact that burst duration reflects the severity of mechanical aggression to the facial nerve.

Subdural air limits the elicitation of compound muscle action potentials by high-frequency transcranial electrical stimulation.

High-frequency transcranial electrical stimulation was performed in 8 patients undergoing surgery in the sitting position. Following the opening of the dura of the posterior fossa changes in compound muscle action potentials were observed. These changes were not attributable to surgical manoeuvres at the brain stem or spinal cord, or to anaesthetic changes. In all these cases intraoperative fluoroscopy of the skull revealed a subdural air collection underneath the stimulation electrodes. Such a subdural air collection, not infrequent in patients operated on in the sitting position, limits the application of high-frequency transcranial electrical stimulation as a monitoring technique. It remains unclear if this effect is due to the increasing distance between scalp and cortex and the insulating effect of subdural air, or due to displacement of the motor cortex. The practical importance of this report is derived from the increasing application of intraoperative motor pathway monitoring.

Intra-operative mapping of the motor cortex during surgery in and around the motor cortex.

The intra-operative use of neurophysiological techniques allows reliable identification of the sensorimotor region, and constitutes a prerequisite for its anatomical and functional preservation. The present prospective study combines monopolar cortical stimulation (MCS) with the recording of phase reversal of somatosensory evoked potentials (SEP-PR) in a protocol for the intra-operative mapping of the motor cortex. Functional mapping of the motor cortex by SEP-PR and MCS was performed in 70 patients during surgery in and around the motor cortex. The central sulcus was identified by SEP-PR. Cortical motor mapping was then performed by monopolar anodal (400 Hz) stimulation. Motor responses were recorded by needle electrodes placed in the muscles of the contralateral extremities. Surgery was performed under general anaesthesia without muscle relaxants. Intra-operative localization of the central sulcus by SEP-PR was possible in 68 patients (97.14%). Motor evoked potentials (MEP) were elicited following MCS in 67 cases (95.7%). In 3 cases no MEP was recorded, not even after maximal stimulation intensity, the central sulcus being localized by SEP-PR only. On the other hand, MCS allowed localizing the motor cortex in the 2 cases with no recordable SEP-PR. Thus, combining SEP-PR and MCS allowed intra-operative localization of the sensorimotor cortex in 100% of the cases.

A new cortical electrode for neuronavigation-guided intraoperative neurophysiological monitoring: technical note.

Intraoperative neurophysiological mapping and monitoring of eloquent brain areas can be combined with image-guided localisation to enhance the safety and efficacy of surgical procedures in the motor cortex. We designed a new type of cortical electrode which can be repeatedly placed on the cortical surface and allows accurate and reproducible stimulation by means of a navigation pointer. The newly designed device consists of a monopolar electrode contact for direct cortical stimulation, housed in a holder which allows placement, easy removal, and precise repeated placement of a surgical navigation pointer. It can be used for navigation-guided, high-frequency anodal monopolar cortical stimulation (MCS) for the mapping of eloquent cortex, and for monitoring of motor pathways. While the cortex is stimulated, compound muscle action potentials (CMAP) are recorded from muscles of the contralateral extremities and are assessed both qualitatively and quantitatively. When the device is used in combination with intraoperative navigation, the stimulation sites may optionally be registered or displayed on the system monitor. This allows repeated pinpointing and obviates the need for strip or grid electrodes in the operative field; although such electrodes may be useful for continuous monitoring, they often are in the surgeon's way. In addition, the primary and supplementary motor cortex can be mapped by determining the location of the sites of stimulation on surface-projected images of the cerebral cortex.

Demonstration of cerebral plasticity by intra-operative neurophysiological monitoring: report of an uncommon case.

It has been postulated long ago that "eloquent" areas shift their location in patients with arteriovenous malformations (AVM). Obviously the "motor region" in not located in the precentral gyrus in a patient with an AVM in the "motor region". We report on the case of a 15-year old boy with an AVM in the left sensorimotor cortex, in whom intra-operative mapping showed an inexcitability of the precentral gyrus, while stimulation of the cortex anterior to the primary motor cortex elicited motor responses. This indicates that motor function was translocated from the primary to the supplementary motor cortex. Surgery was performed under general anaesthesia. Neurophysiological monitoring was performed throughout surgery. The central sulcus was identified by phase reversal of the somatosensory evoked potentials. The motor cortex was mapped by direct high-frequency (500 Hz) monopolar anodal stimulation. In the patient herein reported, stimulation of the "anatomically" defined primary motor cortex induced no motor response, as expected. Motor response was elicited only by stimulation of the cortex anterior to the precentral gyrus. There was no postoperative deterioration of motor function. These observations indicate that the precentral gyrus was functionally "useless". The motor region was relocated into more rostral areas in the supplementary motor cortex. This translocation of function in the presence of an AVM indicates cerebral plasticity.