Motor tract monitoring during insular glioma surgery

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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.


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.


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.

Abbreviations used in this paper:GBM = glioblastoma multiforme; LSA = lenticulostriate artery; MEP = motor evoked potential; MR = magnetic resonance; SSEP = somatosensory evoked potential; WHO = World Health Organization.

Article Information

Address reprint requests to: Georg Neuloh, M.D., Department of Neurosurgery, University of Bonn, D-53105 Bonn, Germany. email:

© AANS, except where prohibited by US copyright law.



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    Intraoperative MEP recordings (left) and pre- and postoperative T1-weighted MR images (upper and center right) obtained in a 39-year-old woman. The patient was symptomatic with a complex partial seizure, and a Yaşargil Type 5B insular GBM was resected. Only minor fluctuations of otherwise stable MEP amplitudes persisted throughout resection of the actual insular tumor portion. Postoperatively, there was no motor deficit and only a slight transient dysarthria. Diffusion weighted MR images (DWI, lower right) revealed ischemia in the caudate head and the dorsal subcortical insula lateral to the internal capsule (arrows).

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    Intraoperative MEP recordings (left) and pre- and postoperative MR images (right) obtained in a 21-year-old woman presenting with complex partial seizures. Perforating arteries (perforators) were exposed during resection of the dorsal-apical portion of an astrocytoma (WHO Grade II, Yaşargil Type 5A) close to the internal capsule. Resection was stopped when MEP deterioration occurred. There was no postoperative motor deficit.

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    Intraoperative MEP recordings (left) and pre- and postoperative MR images (upper and center right) obtained in a 40-year-old woman presenting with complex partial seizures. Significant instability of previously stable MEPs occurred during resection of the dorsal-apical aspect of an astrocytoma (WHO Grade II, Yaşargil Type 5A), and the LSAs were exposed along the medial tumor border at this point. Resection was abandoned, and there was a transient slight new hemiparesis that resolved until discharge. Postoperative diffusion weighted MR imaging (lower right) showed ischemia adjacent to the rostral and dorsal internal capsule (arrows).

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    Intraoperative MEP recordings (left) and pre- and postoperative MR images (right) obtained in a 53-year-old woman with symptoms of a slight hemiparesis. Deterioration and loss of MEP recordings occurred after resection of a recurrent Yaşargil Type 3B anaplastic astrocytoma was completed using a transsylvian approach. Intraoperative inspection revealed vasospasm of the M2 and M3 segments of the middle cerebral artery. After papaverine was applied, MEPs recovered abruptly within 6 minutes, and there was no new postoperative deficit.

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    Intraoperative MEP recordings (left) and pre- and postoperative MR images (upper and center right) obtained in a 29-year-old man presenting with complex partial seizures. Deterioration and then partial loss of MEPs was observed during dorsal resection of a Yaşargil Type 5B anaplastic oligoastrocytoma, and resection was abandoned. The MEPs did not fully recover, and there was a moderate postoperative hemiparesis that had resolved at 3-month follow up. Postoperative diffusion weighted MR images (lower right) showed pericapsular and coronal ischemic lesions (arrows).

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    Intraoperative MEP recordings (left) and pre- and postoperative MR images (upper and center right) obtained in a 43-year-old man presenting with complex partial seizures and organic psychosis. Previous resection and interstitial therapy for an early tumor recurrence performed elsewhere had led to tumor control for 6 years. An initially low-grade astrocytoma showed progressive, partially cystic growth and progression to malignancy. Dissection of scarred tumorous tissue from M1 and M2 segments was arduous. After emptying of the cysts via a frontobasal approach, MEPs deteriorated and vanished despite renewed positioning of the stimulation electrode. Subtotal resection was completed thereafter only in the noncritical frontal area. There was a dense new hemiplegia and aphasia. Postoperative diffusion weighted MR imaging (lower right) revealed capsular stroke (arrows). Within 3 months, the patient was ambulatory with assistance, but remained in a dependent state due to severe arm paresis and aphasia. ant. = anterior; perf. = perforated; subst. = substance.



Berger MS: Functional mapping-guided resection of low-grade gliomas. Clin Neurosurg 42:4374521995


Berger MSRostomily RC: Low grade gliomas: functional mapping resection strategies, extent of resection, and outcome. J Neurooncol 34:851011997


Berman JIBerger MSMukherjee PHenry RG: Diffusion-tensor imaging-guided tracking of fibers of the pyramidal tract combined with intraoperative cortical stimulation mapping in patients with gliomas. J Neurosurg 101:66722004


Cedzich CTaniguchi MSchafer SSchramm J: Somatosensory evoked potential phase reversal and direct motor cortex stimulation during surgery in and around the central region. Neurosurgery 38:9629701996


Deletis V: Intraoperative monitoring of the functional integrity of the motor pathways. Adv Neurol 63:2012141993


Deletis VKothbauer KIntraoperative neurophysiology of the corticospinal tract. Staalberg ESharma HSOlsson Y: Spinal Cord Monitoring WienSpringer1998. 421444


Duffau HBauchet LLehericy SCapelle L: Functional compensation of the left dominant insula for language. Neuroreport 12:215921632001


Duffau HCapelle L: Preferential brain locations of low-grade gliomas. Cancer 100:262226262004


Duffau HCapelle LDenvil DSichez NGatignol PLopes M: Functional recovery after surgical resection of low grade gliomas in eloquent brain: hypothesis of brain compensation. J Neurol Neurosurg Psychiatry 74:9019072003


Duffau HCapelle LLopes MBitar ASichez JPvan Effenterre R: Medically intractable epilepsy from insular low-grade gliomas: improvement after an extended lesionectomy. Acta Neurochir (Wien) 144:5635722002


Duffau HCapelle LLopes MFaillot TSichez JPFohanno D: The insular lobe: physiopathological and surgical considerations. Neurosurgery 47:8018112000


Duffau HKarachi CGatignol PCapelle L: Transient Foix-Chavany-Marie syndrome after surgical resection of a right insulo-opercular low-grade glioma: case report. Neurosurgery 53:4264312003


Duffau HTaillandier LGatignol PCapelle L: The insular lobe and brain plasticity: lessons from tumor surgery. Clin Neurol Neurosurg 108:5435482006


Ebel HEbel MSchillinger GKlimek MSobesky JKlug N: Surgery of intrinsic cerebral neoplasms in eloquent areas under local anesthesia. Minim Invasive Neurosurg 43:1921962000


Ebeling UKothbauer K: Circumscribed low grade astrocytomas in the dominant opercular and insular region: a pilot study. Acta Neurochir (Wien) 132:66741995


Guenot MIsnard JSindou M: Surgical anatomy of the insula. Adv Tech Stand Neurosurg 29:2652882004


Hentschel SJLang FF: Surgical resection of intrinsic insular tumors. Neurosurgery 57:1761832005


Holland NR: Subcortical strokes from intracranial aneurysm surgery: implications for intraoperative neuromonitoring. J Clin Neurophysiol 15:4394461998


Horiuchi KSuzuki KSasaki TMatsumoto MSakuma JKonno Y: Intraoperative monitoring of blood flow insufficiency during surgery of middle cerebral artery aneurysms. J Neurosurg 103:2752832005


Kombos TSuess OCiklatekerlio OBrock M: Monitoring of intraoperative motor evoked potentials to increase the safety of surgery in and around the motor cortex. J Neurosurg 95:6086142001


Kreth FWSchatz CRFaist MOstertag CB: Tumors of the insula. J Neurosurg 86:9109111997. (Letter)


Krieger DAdams HPAlbert Fvon Haken MHacke W: Pure motor hemiparesis with stable somatosensory evoked potential monitoring during aneurysm surgery: case report. Neurosurgery 31:1451501992


Lang FFOlansen NEDeMonte FGokaslan ZLHolland ECKalhorn C: Surgical resection of intrinsic insular tumors: complication avoidance. J Neurosurg 95:6386502001


Mehrkens JHKreth FWMuacevic AOstertag CB: Long term course of WHO grade II astrocytomas of the Insula of Reil after I-125 interstitial irradiation. J Neurol 251:145514642004


Mehrkens JHNoachtar SWinkler PAKreth FW: In response to: H. Duffau, L. Capelle, M. Lopes, A. Bitar, J.P. Sichez, R. Van Effenterre: Medically intractable epilepsy from insular low-grade gliomas: improvement after extended lesionectomy. Acta Neurochir (2002) 144:563–573. Acta Neurochir (Wien) 145:87902003


Neuloh GPechstein UCedzich CSchramm J: Motor evoked potential monitoring with supratentorial surgery. Neurosurgery 54:106110622004


Neuloh GSchramm J: Monitoring of motor evoked potentials compared with somatosensory evoked potentials and microvascular Doppler ultrasonography in cerebral aneurysm surgery. J Neurosurg 100:3893992004


Neuloh GSchramm J: Motor evoked potential monitoring for the surgery of brain tumors and vascular malformations. Adv Tech Stand Neurosurg 29:1712282004


Pechstein UCedzich CNadstawek JSchramm J: Transcranial high-frequency repetitive electrical stimulation for recording myogenic motor evoked potentials with the patient under general anesthesia. Neurosurgery 39:3353441996


Quiñones-Hinojosa AAlam MLyon RYingling CDLawton MT: Transcranial motor evoked potentials during basilar artery aneurysm surgery: technique application for 30 consecutive patients. Neurosurgery 54:9169242004


Sala FLanteri P: Brain surgery in motor areas: the invaluable assistance of intraoperative neurophysiological monitoring. J Neurosurg Sci 47:79882003


Schatz CRKreth FWFaist MWarnke PCVolk BOstertag CB: Interstitial 125-iodine radiosurgery of low-grade gliomas of the insula of Reil. Acta Neurochir (Wien) 130:80891994


Shankar ARajshekhar V: Radiological and clinical outcome following stereotactic biopsy and radiotherapy for low-grade insular astrocytomas. Neurol India 51:5035062003


Suzuki KKodama NSasaki TMatsumoto MKonno YSakuma J: Intraoperative monitoring of blood flow insufficiency in the anterior choroidal artery during aneurysm surgery. J Neurosurg 98:5075142003


Szelenyi ABueno de Camargo AFlamm EDeletis V: Neuro-physiological criteria for intraoperative prediction of pure motor hemiplegia during aneurysm surgery. Case report. J Neurosurg 99:5755782003


Szelenyi AKothbauer Kde Camargo ABLanger DFlamm ESDeletis V: Motor evoked potential monitoring during cerebral aneurysm surgery: technical aspects and comparison of transcranial and direct cortical stimulation. Neurosurgery 57:3313382005


Taniguchi MCedzich CSchramm J: Modification of cortical stimulation for motor evoked potentials under general anesthesia: technical description. Neurosurgery 32:2192261993


Ture UYaşargil DCAl-Mefty OYaşargil MG: Topographic anatomy of the insular region. J Neurosurg 90:7207331999


Ture UYaşargil MGAl-Mefty OYaşargil DC: Arteries of the insula. J Neurosurg 92:6766872000


Van Roost DThees CBrenke COppel FWinkler PASchramm J: Pseudohypoxic brain swelling: a newly defined complication after uneventful brain surgery, probably related to suction drainage. Neurosurgery 53:131513272003


Vanaclocha VSaiz-Sapena NGarcia-Casasola C: Surgical treatment of insular gliomas. Acta Neurochir (Wien) 139:112611341997


Varnavas GGGrand W: The insular cortex: morphological and vascular anatomic characteristics. Neurosurgery 44:1271381999


Yaşargil DC: Microneurosurgery 4A:StuttgartThieme1994


Yaşargil MGReeves JD: Tumours of the limbic and paralimbic system. Acta Neurochir (Wien) 116:1471491992


Zentner JMeyer BStangl ASchramm J: Intrinsic tumors of the insula: a prospective surgical study of 30 patients. J Neurosurg 85:2632711996


Zhou HHKelly PJ: Transcranial electrical motor evoked potential monitoring for brain tumor resection. Neurosurgery 48:107510812001


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