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Abstract

Intraoperative neurophysiological monitoring (IONM) involves monitoring the functional integrity of critical brain regions and pathways as well as identifying and preserving functionally viable neural tissues (mapping) during surgery using electrophysiological techniques. Multimodality combines various neurophysiological techniques to optimise diagnostic effectiveness and to improve the outcomes of the surgeries. The present study is a case series with comprehensive and illustrative descriptions of the neurophysiological changes in five neuromonitored cases of cranial and spinal cord tumour surgeries conducted with a multimodal approach. The cases were monitored with somatosensory evoked potentials (SSEP), transcranial motor evoked potentials (TcMEP), and both free run and triggered electromyography (fEMG and tEMG). No false negative outcomes were identified in the cases studied as there was an association of absence of change in SSEP and TcMEP both, with no neurological deficit postoperatively. Two cases were identified as having true positive neuromonitoring alerts. No false positive alerts were found in any case. Multimodal monitoring using SSEP, TcMEP, and EMG (fEMG and tEMG) in cranial and spinal tumour surgeries can improve performance with fewer false-negative and false-positive results. Neuromonitoring approaches used in combination can provide reliable information regarding postoperative neurological outcomes.

Introduction

The delicate and elaborate organization of the brain and spinal cord contribute to the challenging nature of neurosurgical operations. Spine and cranial surgeries are often associated with substantial rates of postoperative complications; neurological deficits constitute a considerable proportion of these complications [1]. In the majority of neurosurgical procedures, the functional and normal brain will inevitably suffer damage while the abnormal tissues are being dissected or removed. These injuries could result from several techniques including cortical incisions, retraction of brain lobes or hemispheres, intraoperative bleeding and thermal injury due to electrocoagulation [2]. Postoperative neurological morbidity validates the importance of functional evaluation of the nervous system during surgical procedures. Curtailing perioperative risks and ensuring efficient monitoring may allow for the expansion of more aggressive surgical interventions, making more patients eligible for treatment. The intraoperative neuromonitoring (IONM) technique has become a vital component in many neurosurgeries. Although IONM has a long history, its application has only recently become widespread [3]. This technique primarily aims to prevent iatrogenic injuries and surgical insults to the nervous system and thus prevent secondary or postoperative neurological impairments. By conducting a continuous evaluation of the functional status of the nervous system in an anaesthetized patient during surgery, this procedure provides the surgical team with real-time information about the patient’s nervous system during an ongoing surgical manipulation. It has the potential to provide real-time feedback on critical neurological regions and pathways to the surgeon. In select circumstances, this feedback may prevent or mitigate neurological injury. As evidenced by a large multicenter study, spinal operations for deformity correction that incorporate the feedback of an experienced neurophysiology team can have as much as a 50% lower rate of neurological deficits [4].

A multimodal assessment helps in the evaluation of the functional status of sensory and motor pathways intra-operatively. Application of intraoperative neurophysiological monitoring via assessment of somatosensory evoked potential (SSEP), transcranial motor evoked potential (TcMEP) and electromyography of relevant nerve root myotomes to detect impending neurological injury has attained significance during the recent decades [5,6]. In spinal tumour surgeries, multimodal monitoring using SSEP and TcMEP has been reported to prevent surgically induced neurological complications [7]. The advantage of multimodal intraoperative neurophysiological monitoring (MIONM) is that it can make up for the shortcomings of each individual technique. It also appears to be reliable and useful for identifying perioperative neurological damage after spine surgery. The effectiveness of MIONM in spinal cord monitoring during spinal tumour resections is strongly supported by the literature [8,9]. Cerebellopontine (CP) angle tumour excision is a surgery which carries a considerable risk of facial nerve damage compared to other otological or parotid gland procedures. Facial nerve palsy is a devastating complication following CP angle tumour resections; this leads to functional as well as aesthetic deficits that can impair the patient's quality of life. In CP tumour surgeries, the technique provides the benefit of making information available to the surgical team regarding dynamic changes in the monitored structures and the possibility of cranial nerve localization using stimulation in the operating area. A previous similar study reports TcMEP along with EMG recordings as a useful method for monitoring the facial nerve during CP angle tumour surgeries [10].

The present study aims at evaluating neurophysiological changes that occurred during five different neuromonitored surgeries performed with a multimodality approach at our institution, along with a prospective evaluation for the development of new postoperative neurological deficits.

Materials & Methods

The neuromonitored surgeries were conducted in the operating room (neurosurgery and orthopaedic OTs) at All India Institute of Medical Sciences (AIIMS), Patna. Intraoperative neurophysiologic monitoring of each patient was performed on a 32-channel Xltek Protektor32 IOM system running EPWorks Software (Natus Neuro, Ontario, Canada) (Figure 1). The use of the IONM multimodalities to be tested was decided according to the location of the tumour in each patient. For SSEPs, the segmental level of the lesion determined the selection of the nerve to be stimulated. Median SSEPs were performed in order to monitor spinal cord surgery above the C6 level, ulnar nerve SSEPs for those involving the lower cervical...(More)

For more info please read, Multimodal Intraoperative Neurophysiological Monitoring in Cranial and Spinal Tumour Surgeries, by Cureus