Akiva Korn

Failed awake craniotomy: a retrospective analysis in 424 patients undergoing craniotomy for brain tumor

OBJECT Awake craniotomy for removal of intraaxial tumors within or adjacent to eloquent brain regions is a well-established procedure. However, awake craniotomy failures have not been well characterized. In the present study, the authors aimed to analyze and assess the incidence and causes for failed awake craniotomy. METHODS The database of awake craniotomies performed at Tel Aviv Medical Center between 2003 and 2010 was reviewed. Awake craniotomy was considered a failure if conversion to general anesthesia was required, or if adequate mapping or monitoring could not have been achieved. RESULTS Of 488 patients undergoing awake craniotomy, 424 were identified as having complete medical, operative, and anesthesiology records. The awake craniotomies performed in 27 (6.4%) of these 424 patients were considered failures. The main causes of failure were lack of intraoperative communication with the patient (n = 18 [4.2%]) and/or intraoperative seizures (n = 9 [2.1%]). Preoperative mixed dysphasia (p < 0.001) and treatment with phenytoin (p = 0.0019) were related to failure due to lack of communication. History of seizures (p = 0.03) and treatment with multiple antiepileptic drugs (p = 0.0012) were found to be related to failure due to intraoperative seizures. Compared with the successful awake craniotomy group, a significantly lower rate of gross-total resection was achieved (83% vs 54%, p = 0.008), there was a higher incidence of short-term speech deterioration postoperatively (6.1% vs 23.5%, p = 0.0017) as well as at 3 months postoperatively (2.3% vs 15.4%, p = 0.0002), and the hospitalization period was longer (4.9 ± 6.2 days vs 8.0 ± 10.1 days, p < 0.001). Significantly more major complications occurred in the failure group (4 [14.8%] of 27) than in the successful group (16 [4%] of 397) (p = 0.037). CONCLUSIONS Failures of awake craniotomy were associated with a lower incidence of gross-total resection and increased postoperative morbidity. The majority of awake craniotomy failures were preventable by adequate patient selection and avoiding side effects of drugs administered during surgery.

Efficacy of head repositioning in restoration of electrophysiological signals during cervical spine procedures.

Purpose: To evaluate the frequency of loss of neurophysiological potentials during head positioning, the usefulness of head repositioning to restore the potentials, and the effect on neurological outcome. Methods: We retrospectively reviewed consecutive cervical spine surgeries performed at the Israel Spine Center, Assuta Medical Center, during 2006 to 2013. Surgeries performed with neuromonitoring (transcranial-electric motor evoked potentials, somatosensory evoked potentials, electromyographic recordings) were included. Demographic data, medical history, findings at neurological examination and imaging, electrophysiological data recorded during surgery, and neurological outcomes were collected and analyzed. Results: Three hundred eighty-one patients met inclusion criteria. Loss of potentials detected in nine patients during patient positioning and repositioning was undertaken with the aim of restoring electrophysiological signals. In 5/9 patients, repositioning resulted in immediate reappearance of potentials; in 1/5, potentials were affected again during decompression. In 4/9, repositioning did not immediately restore electrophysiological signals; in ¼, potentials reappeared later during the decompression and in ¾, potentials had not recovered till the conclusion of surgery. There were new neurological deficits in 2/9, including one patient with loss of potential that was not restored with repositioning and the one in whom potential was restored but lost again during decompression. Conclusions: Intraoperative neuro monitoring is an efficient tool to alert the surgical team to potential neurological damage. Head reposition often restores the electrophysiological signals with possible prevention of impending sequelae.

Intra-operative multi-site stimulation: Expanding methodology for cortical brain mapping of language functions

Direct cortical stimulation (DCS) is considered the gold-standard for functional cortical mapping during awake surgery for brain tumor resection. DCS is performed by stimulating one local cortical area at a time. We present a feasibility study using an intra-operative technique aimed at improving our ability to map brain functions which rely on activity in distributed cortical regions. Following standard DCS, Multi-Site Stimulation (MSS) was performed in 15 patients by applying simultaneous cortical stimulations at multiple locations. Language functioning was chosen as a case-cognitive domain due to its relatively well-known cortical organization. MSS, performed at sites that did not produce disruption when applied in a single stimulation point, revealed additional language dysfunction in 73% of the patients. Functional regions identified by this technique were presumed to be significant to language circuitry and were spared during surgery. No new neurological deficits were observed in any of the patients following surgery. Though the neuro-electrical effects of MSS need further investigation, this feasibility study may provide a first step towards sophistication of intra-operative cortical mapping.

Continuous mapping of the corticospinal tracts in intramedullary spinal cord tumor surgery using an electrified ultrasonic aspirator

Intramedullary spinal cord tumors (IMSCTs) represent a rare entity, accounting for 4%-10% of all central nervous system tumors. Microsurgical resection of IMSCTs is currently considered the primary treatment modality. Intraoperative neurophysiological monitoring (IONM) has been shown to aid in maximizing tumor resection and minimizing neurological morbidity, consequently improving patient outcome. The gold standard for IONM to date is multimodality monitoring, consisting of both somatosensory evoked potentials, as well as muscle-based transcranial electric motor evoked potentials (tcMEPs). Monitoring of tcMEPs is optimal when combining transcranial electrically stimulated muscle tcMEPs with D-wave monitoring. Despite continuous monitoring of these modalities, when classic monitoring techniques are used, there can be an inherent delay in time between actual structural or vascular-based injury to the corticospinal tracts (CSTs) and its revelation. Often, tcMEP stimulation is precluded by the surgeons preference that the patient not twitch, especially at the most crucial times during resection. In addition, D-wave monitoring may require a few seconds of averaging until updating, and can be somewhat indiscriminate to laterality. Therefore, a method that will provide immediate information regarding the vulnerability of the CSTs is still needed. The authors performed a retrospective series review of resection of IMSCTs using the tip of an ultrasonic aspirator for continuous proximity mapping of the motor fibers within the spinal cord, along with classic muscle-based tcMEP and D-wave monitoring. The authors present their preliminary experience with 6 patients who underwent resection of an IMSCT using the tip of an ultrasonic aspirator for continuous proximity mapping of the motor fibers within the spinal cord, together with classic muscle-based tcMEP and D-wave monitoring. This fusion of technologies can potentially assist in optimizing resection while preserving neurological function in these challenging surgeries.

Subcortical Mapping Using an Electrified Cavitron UltraSonic Aspirator in Pediatric Supratentorial Surgery

BACKGROUND Intraoperative electrophysiology is increasingly used for various lesion resections, both in adult and pediatric brain surgery. Subcortical mapping is often used in adult surgery when lesions lie in proximity to the corticospinal tract (CST). We describe a novel technique of continuous subcortical mapping using an electrified Cavitron UltraSonic Aspirator (CUSA) in children with supratentorial lesions. METHODS We evaluated the method of subcortical mapping using a CUSA as a stimulation probe. Included in this study were children (<18 years of age) with supratentorial lesions in proximity to the CST in which the CUSA stimulator was applied. Data were collected retrospectively. RESULTS Eleven children were included. Lesions were located in the thalamus (3), basal-ganglia (2), lateral ventricle (1), and convexity (5). Lesions included low-grade gliomas (6), arteriovenous malformation (1), cavernoma (1), cortical dysplasia (1), ependymoma grade II (1), and high-grade glioma (1). Seven patients had positive mapping responses to CUSA-based stimulation at various stimulation intensities. These responses led to a more limited resection in 5 cases. There were no complications related to the mapping technique. CONCLUSION Continuous CUSA-based subcortical stimulation is a feasible mapping technique for assessing proximity to the CST during resection of supratentorial lesions in children. Future studies should be performed to better correlate the current threshold for eliciting a motor response with the distance from the CST, as well as the effect of age on this technique.

Electrophysiological monitoring during preoperative angiography to guide decisions regarding permanent occlusion of major radicular arteries in patients undergoing total en bloc spondylectomy.

OBJECTIVE Preoperative embolization is performed before spine tumor surgery when significant intraoperative hemorrhage is anticipated. Occlusion of radicular and segmental arteries may result in spinal ischemia. The goal of this study was to check whether neurophysiological monitoring during preoperative angiography in patients scheduled for total en bloc spondylectomy (TES) of spine tumors improves the safety of vessel occlusion. METHODS This was a case series study of patients who underwent tumor embolization under somatosensory evoked potential (SSEP) and motor evoked potential (MEP) monitoring in preparation for TES in treating spine tumors. The angiography findings, the embolized vessels, and the results are presented. RESULTS Five patients whose ages ranged from 33 to 75 years and who had thoracic spine tumors are reported. Four patients suffered from primary tumor and 1 patient had a metastatic tumor. Radicular arteries at the tumor level, 1 level above, and 1 level below were permanently occluded when SSEPs and MEPs were preserved during temporary occlusion. No complications were encountered during or after the angiography procedure and embolization. CONCLUSIONS Temporary occlusion with electrophysiological monitoring during preoperative angiography may improve the safety of permanent radicular artery occlusion, including the artery of Adamkiewicz in patients undergoing TES for the treatment of spine tumors.

Elaborate mapping of the posterior visual pathway in awake craniotomy

OBJECTIVE Resection of intraaxial tumors adjacent to the optic radiation (OR) may be associated with postoperative visual field (VF) deficits. Intraoperative navigation using MRI-based tractography and electrophysiological monitoring of the visual pathways may allow maximal resection while preserving visual function. In this study, the authors evaluated the value of visual pathway mapping in a series of patients undergoing awake craniotomy for tumor resection. METHODS A retrospective analysis of prospectively collected data was conducted in 18 patients who underwent an awake craniotomy for resection of intraaxial tumors involving or adjacent to the OR. Preoperative MRI-based tractography was used for intraoperative navigation, and intraoperative acquisition of 3D ultrasonography images was performed for real-time imaging and correction of brain shift. Goggles with light-emitting diodes were used as a standard visual stimulus. Direct cortical visual evoked potential (VEP) recording, subcortical recordings from the OR, and subcortical stimulation of the OR were used intraoperatively to assess visual function and proximity of the lesion to the OR. VFs were assessed pre- and postoperatively. RESULTS Baseline cortical VEP recordings were available for 14 patients (77.7%). No association was found between preoperative VF status and baseline presence of cortical VEPs (p = 0.27). Five of the 14 patients (35.7%) who underwent subcortical stimulation of the OR reported seeing phosphenes in the corresponding contralateral VF. There was a positive correlation (r = 0.899, p = 0.04) between the subcortical threshold stimulation intensity (3-11.5 mA) and the distance from the OR. Subcortical recordings from the OR demonstrated a typical VEP waveform in 10 of the 13 evaluated patients (76.9%). These waveforms were present only when recordings were obtained within 10 mm of the OR (p = 0.04). Seven patients (38.9%) had postoperative VF deterioration, and it was associated with a length of < 8 mm between the tumor and the OR (p = 0.05). CONCLUSIONS Intraoperative electrophysiological monitoring of the visual pathways is feasible but may be of limited value in preserving the functional integrity of the posterior visual pathways. Subcortical stimulation of the OR may identify the location of the OR when done in proximity to the pathways, but such proximity may be associated with increased risk of postoperative worsening of the VF deficit.

Massive hematomyelia following intramedullary spinal cord tumor surgery

Dear Editor, We would like to present an interesting case of postoperative hematomyelia following resection of an intramedullary spinal cord tumor (IMSCT) and discuss its clinical implications. Hematomyelia is a relatively rare phenomenon. Hematomyelia is mostly associated with traumatic insult, spinal vascular malformations such as intramedullary cavernous malformations [3, 10], or anticoagulation therapy [1, 9]. Clinical presentation varies from acute onset of spinal neurological deficits, accompanied by severe back or radicular pain, to chronic, slowly progressing neurological decline. A slow clinical course is usually associated with better prognosis [7]. Hematomyelia is a known presenting sign of spinal cord tumors [8]. It is also a rarely described complication of IMSCT surgery [2, 5]. Our patient was a 32-year-old male with a history of lung sarcoidosis presented with progressive sensorymotor disturbances of the lower limbs. MRI demonstrated multifocal pial lesions with a large intramedullary lesion at T6-7. Following rapid worsening of motor functions, he was operated upon. A subtotal resection of the lesion was performed. Pathology was consistent with low-grade glial tumor with pilocytic features. Following the first surgery, weakness on the right side improved. Eighteen months after surgery, a further decline in motor function was noticed. MRI demonstrated marked growth of the remnant tumor with homogenous enhancement and subependymal spread evident up to C6-7. The patient experienced rapid motor deterioration and underwent a second operation. A very generous subtotal re-resection was performed. Throughout the surgery, MEP and SSEP potentials monitoring remained uneventful. At the conclusion of surgery, the spinal cord was free of pressure with absolute hemostasis, and displayed pulsation and free CSF flow. Immediately following surgery the patient felt well, with evident motor improvement. However, on postoperative day 2 the patient attempted to get up from his bed unassisted and collapsed. A family member lifted the patient back to his bed. A few hours later the patient began suffering from severe back pain. In the following hours, the patient developed almost complete quadriplegia with minimal distal left hand movements. An emergency MRI revealed massive hematomyelia from the tumor site at T7 ascending all the way up to the foramen magnum (Fig. 1). A decision not to operate was made. The patient was intubated and transferred to the NICU. He underwent a tracheostomy, and over the next few weeks regained motor function in the upper limbs. The patient remains paraplegic however. B. Shofty : J. Roth :A. Korn : S. Constantini (*) Department of Pediatric Neurosurgery, Tel-Aviv Medical Center, 6th Weizman St., Tel-Aviv, Israel e-mail: sconsts@netvision.net.il