It is believed that maximizing the removal of cancerous tumors enhances patient prognosis by extending both the time without disease progression and the overall survival period. The present study reviews methods for preserving motor function during glioma surgery near the eloquent cortex, along with electrophysiological monitoring for preserving motor function in brain tumor surgery performed deep within the brain. Integral to preserving motor function in brain tumor surgery is the monitoring of direct cortical motor evoked potentials (MEPs), transcranial MEPs, and subcortical MEPs.
The brainstem's structure exhibits a dense aggregation of essential cranial nerve nuclei and tracts. Surgical interventions in this anatomical location are, therefore, attended by significant risks. Celastrol in vitro To perform brainstem surgery effectively, a deep comprehension of anatomical principles is coupled with the critical need for electrophysiological monitoring. The facial colliculus, obex, striae medullares, and medial sulcus, prominent visual anatomical markers, lie on the floor of the 4th ventricle. Due to the potential for cranial nerve nuclei and nerve tracts to shift with a lesion, a precise understanding of their locations in the brainstem is crucial prior to any incision. The brainstem parenchyma's thinnest region, specifically due to lesions, defines the precise selection of the entry zone. The fourth ventricle floor's surgical access often relies on the suprafacial or infrafacial triangle as a cutting point. zoonotic infection Within this article, the electromyographic methodology for examining the external rectus, orbicularis oculi, orbicularis oris, and tongue muscles is discussed, featuring two illustrative cases involving pons and medulla cavernoma. A meticulous analysis of surgical needs in this manner may result in increased safety for such surgical procedures.
Extraocular motor nerve monitoring during skull base surgery ensures optimal outcomes by safeguarding cranial nerves. Several techniques exist for detecting cranial nerve function, ranging from electrooculography (EOG) for monitoring external eye movements, to electromyography (EMG), and the use of piezoelectric devices for sensing. Valuable and useful though it may be, challenges persist in the accurate monitoring of it during scans performed from within the tumor, potentially situated far from the cranial nerves. In this segment, we explored three distinct methods for tracking external eye movements: free-run EOG monitoring, trigger EMG monitoring, and piezoelectric sensor monitoring. For the correct performance of neurosurgical procedures, preserving extraocular motor nerves, the enhancement of these processes is indispensable.
Due to the progress in preserving neurological function during surgical procedures, intraoperative neurophysiological monitoring is now required and frequently utilized. Reports on the safety, efficiency, and consistency of intraoperative neurophysiological monitoring in children, especially newborns, are scarce. It is not until a child reaches two years of age that nerve pathway maturation is fully realized. It is frequently difficult to maintain a stable anesthetic level and hemodynamic status during procedures involving children. Further consideration is required when interpreting neurophysiological recordings in children, which differ significantly from those in adults.
Epilepsy surgeons frequently face the challenge of drug-resistant focal epilepsy, necessitating accurate diagnosis to pinpoint the epileptic foci and facilitate appropriate patient treatment. If noninvasive preoperative assessments fail to identify the location of seizure onset or eloquent cortical areas, invasive epileptic video-EEG monitoring utilizing intracranial electrodes becomes necessary. While electrocorticography utilizing subdural electrodes has long been employed to pinpoint epileptogenic regions, the use of stereo-electroencephalography in Japan has recently experienced a dramatic increase, owing to its less invasive approach and superior delineation of epileptogenic networks. Both surgical interventions are examined in this report, encompassing their underlying concepts, clinical indications, operational procedures, and contributions to the field of neuroscience.
Lesion management within the eloquent cortices during surgery requires preservation of brain functions. Intraoperative electrophysiological approaches are crucial for safeguarding the integrity of functional networks, for example, the motor and language areas. A recently developed intraoperative monitoring method, cortico-cortical evoked potentials (CCEPs), offers several key advantages, including a recording duration of approximately one to two minutes, eliminates the need for patient cooperation, and exhibits high levels of reproducibility and reliability in the collected data. Intraoperative CCEP studies recently highlighted the capability of CCEP to map out eloquent cortical regions and white matter tracts, including the dorsal language pathway, frontal aslant tract, supplementary motor area, and optic radiation. Subsequent studies are crucial to establish intraoperative electrophysiological monitoring procedures, even with general anesthesia in place.
The reliability of intraoperative auditory brainstem response (ABR) monitoring in evaluating cochlear function has been well-established. Surgical interventions involving microvascular decompression for hemifacial spasm, trigeminal neuralgia, or glossopharyngeal neuralgia demand mandatory intraoperative ABR recordings. A cerebellopontine tumor, despite preserving effective hearing, necessitates auditory brainstem response (ABR) monitoring throughout surgical procedures to maintain hearing capacity. The ABR wave V's prolonged latency and subsequent amplitude decrease are indicators of potential postoperative hearing loss. In the event of intraoperative ABR abnormalities during surgery, the surgeon must alleviate the cerebellar retraction on the cochlear nerve and passively wait for the ABR to return to a normal state.
To address the challenge of anterior skull base and parasellar tumors involving the optic pathways in neurosurgery, intraoperative visual evoked potentials (VEPs) have become a critical tool for preventing postoperative visual complications. A light-emitting diode thin pad photo-stimulation apparatus, including a stimulator (Unique Medical, Japan), was used in our procedure. Simultaneous to the data collection, we monitored the electroretinogram (ERG) to account for any potential technical problems. One way to define VEP is as the amplitude range encompassed by the maximum positive wave occurring at 100 milliseconds (P100) and the preceding negative deflection labeled N75. Biotinidase defect To ensure reliable intraoperative visual evoked potential (VEP) monitoring, the reproducibility of the VEP signal must be established, especially in patients with pre-existing severe visual impairment and a demonstrably reduced amplitude during the procedure. Furthermore, it is crucial to diminish the amplitude by fifty percent. Surgical protocols should be adjusted or interrupted when these situations arise. The link between the absolute intraoperative VEP measurement and postoperative visual outcome has not been conclusively demonstrated. In the existing intraoperative VEP system, peripheral visual field defects, even mild ones, are not discernible. Nevertheless, intraoperative VEP, complemented by ERG monitoring, provides surgeons with a real-time alert system to help them prevent postoperative vision loss. A thorough comprehension of the principles, characteristics, disadvantages, and constraints of intraoperative VEP monitoring is fundamental to its effective and reliable utilization.
The basic clinical technique of measuring somatosensory evoked potentials (SEPs) is essential for functional mapping and monitoring of brain and spinal cord responses during surgery. Considering that a single stimulus' evoked potential is weaker than the encompassing electrical activity (including background brain activity and electromagnetic noise), the average response from multiple controlled stimuli, taken across synchronized trials, is needed to extract the resulting waveform. Analyzing SEPs involves considering their polarity, the time delay from stimulus initiation, and the amplitude change from the baseline for each wave component. In monitoring, the amplitude is the key, in mapping, polarity is the key. A waveform amplitude that is 50% lower than the control waveform suggests a potential significant impact on the sensory pathway, whereas a polarity reversal, characterized by cortical sensory evoked potential distribution, frequently implies a central sulcus localization.
Motor evoked potentials (MEPs) are a prevalent method used in intraoperative neurophysiological monitoring. The procedure includes direct cortical stimulation of MEPs (dMEPs), acting upon the primary motor cortex of the frontal lobe, as identified by short-latency somatosensory evoked potentials; it also includes transcranial MEPs (tcMEPs), employing high-current or high-voltage transcranial stimulation with scalp-installed cork-screw electrodes. dMEP is a technique employed during brain tumor operations close to the motor zone. Spinal and cerebral aneurysm surgeries frequently leverage the simplicity, safety, and wide application of tcMEP. The relationship between the enhancement of sensitivity and specificity in compound muscle action potentials (CMAPs) after normalizing peripheral nerve stimulation within motor evoked potentials (MEPs) to account for muscle relaxants is presently unknown. Despite this, tcMEP's potential in decompression procedures for compressive spinal and nerve ailments might predict the recovery of postoperative neurological symptoms correlated with a normalization of CMAP values. Using CMAP normalization is a method to prevent the anesthetic fade phenomenon. The 70%-80% amplitude decrease in intraoperative motor evoked potentials (MEPs) precedes postoperative motor paralysis, necessitating the implementation of site-specific alarm systems.
The early years of the 21st century have seen the steady proliferation of intraoperative monitoring techniques in both Japan and internationally, bringing about descriptions of motor, visual, and cortical evoked potentials.