Intraoperative Neurophysiologic Changes Research Articles

Combined Transoral Exoscope and OARM-Assisted Approach for Craniovertebral Junction Surgery. New Trends in an Old-Fashioned Approach.

The introduction of recent innovations in the field of intraoperative imaging and neuronavigation, such as the O-arm StealthStation, allows for obtaining crucial intraoperative data by performing safer and controlled surgical procedures. As part of the improvement of surgical visual magnification and wide expansion of surgical corridors, the 3D 4 K exoscope (EX) has nowadays become an interesting and useful tool. The transoral approach (TOA) is the historical gold-standard direct microsurgical route to ventral craniovertebral junction (CVJ). We herein report our experience, consisting of ten cases via TOA concerning the simultaneous application of an O-arm with a StealthStation navigation system (Medtronic, Memphis, TN) and an imaging system, along with the 3D 4 K exoscopes in the TOA, for the treatment of CVJ pathologies. No intraoperative neurophysiological changes or postoperative infections occurred, but neurological improvement was evident in all the patients. A complete decompression and a stable instrumentation and fusion of the CVJ were accomplished in all cases at the maximum follow-up time. With EX, the role of the surgeon becomes self-sufficient with better individual surgical freedom compared to endoscopic surgery and excellent 3D vision and magnification. O-arms offer absolutely reliable intraoperative support for more-effective CVJ decompression. Nevertheless, with O-arm-assisted neuronavigation, it can be difficult to navigate C1 lateral masses and C2 isthmi, and converting 3D into 2D real-time navigation can be quite complicated. Finally, the combination of an EX with an O-arm appears more time-consuming compared to the old-fashion one.

Do intra-operative neurophysiological changes during decompressive surgery for cervical myeloradiculopathy impact functional outcome? A prospective study

Do intra-operative neurophysiological changes during decompressive surgery for cervical myeloradiculopathy impact functional outcome? A prospective study

Intraoperative Auditory Brainstem Response Results Predict Delayed Sensorineural Hearing Loss After Middle Cranial Fossa Resection of Vestibular Schwannoma.

To identify intraoperative neurophysiologic measures predictive of delayed progressive sensorineural hearing loss in the operative ear after a middle fossa approach (MCF) for resection of vestibular schwannoma (VS). Retrospective review. Academic, tertiary referral center. Subjects with vestibular schwannoma who underwent a MCF microsurgical resection of VS were analyzed for individuals whose hearing was initially preserved but subsequently developed progressive sensorineural hearing loss in the operative ear. Thirty-seven patients were identified for whom audiologic and neurophysiologic data was available. Intraoperative neurophysiologic changes will correlate with delayed sensorineural hearing loss in the operative ear. Audiometric evaluations, intraoperative electrocochleography (ECoG), and auditory brainstem response (ABR) measures. Twenty-five subjects experienced stable hearing or hearing loss in the operative ear comparable to the contralateral ear. Twelve subjects suffered a significant increase in the hearing asymmetry between ears. Deterioration in the amplitude of wave V of the ABR persisting at the close of tumor resection correlated with delayed sensorineural hearing loss in the operative ear (p 0.02, 5% mean improvement in the stable hearing group, versus a 14% decline with progressive asymmetry), but changes in ECoG or other auditory brainstem response parameters (p > 0.05) were not predictive. Persisting amplitude reduction of wave V of the intraoperative ABR best correlates with delayed progressive sensorineural hearing loss in the operative ear. Neither persistent changes in ECoG, other ABR parameters, nor transient changes, correlated with delayed progressive sensorineural hearing loss in the operative ear.

Do Intraoperative Neurophysiological Changes During Decompressive Surgery for Cervical Myeloradiculopathy Affect Functional Outcome? A Prospective Study.

Study Design:Prospective cohort.Objective:To investigate whether intraoperative neuromonitoring (IONM) positive changes affect functional outcome after surgical intervention for myeloradiculopathy secondary to cervical compressive pathology (cervical compressive myelopathy).Methods:Twenty-eight patients who underwent cervical spine surgery with IONM for compressive myeloradiculopathy were enrolled. During surgery motor-evoked potential (MEP) and somatosensory evoked potential (SSEP) at baseline and before and after decompression were documented. A decrease in latency >10% or an increase in amplitude >50% was regarded as a “positive changes.” Patients were divided into subgroups based on IONM changes: group A (those with positive changes) and group B (those with no change or deterioration). Nurick grade and modified Japanese Orthopaedic Association (mJOA) score were evaluated before and after surgery.Results:Nine patients (32.1%) showed improvement in MEP. The mean preoperative Nurick grade and mJOA score of group A and B were (2.55 ± 0.83 and 11.11 ± 1.65) and (2.47 ± 0.7 and 11.32 ± 1.24), respectively. The mean postoperative Nurick grade of groups A and B at 6 months was 1.55 ± 0.74 and 1.63 ± 0.46, respectively, and this difference was not significant. The mean postoperative mJOA score of groups A and B at 6 months was 14.3 ± 1.03 and 12.9 ± 0.98, respectively, and this difference was statistically significant (P = .011). Spearman correlation coefficient showed significant positive correlation between the IONM change and the mJOA score at 6 months postoperatively (r = 0.47; P = .01).Conclusion:Our study shows that impact of positive changes in MEP during IONM reflect in functional improvement at 6 months postoperatively in cervical compressive myelopathy patients.

Combined transoral exoscope and OArm-assisted approach for craniovertebral junction surgery: Light and shadows in single-center experience with improving technologies.

Background:The introduction of recent innovations in the field of intraoperative imaging and neuronavigation, such as OArm Stealth Station, allows to obtain crucial intraoperative data by performing safer and controlled surgical procedures. As part of the improvement of surgical visual magnification and wide expansion of surgical corridors, the 3D-4K exoscope (EX) represents nowadays an interesting and useful tool. Transoral approach (TOA) represents the historical gold standard direct microsurgical route to ventral craniovertebral junction (CVJ).Methods:We herein report a preliminary experience on 6 cases of 33 patients operated by TOA concerning the simultaneous application of OArm with Stealth Navigation system (Medtronic, Memphis, TN) and imaging system along with the 3D-4K EXs in TOA for the treatment of CVJ pathologies.Results:Neither intraoperative neurophysiological changes nor postoperative infections occurred, but a neurological improvement was evident in all the patients. A complete decompression along with stable instrumentation and fusion of the CVJ was accomplished in all cases at the maximum follow-up (mean: 16.8 months).Conclusions:With EX, the role of surgeon become self-sufficient with a better individual surgical freedom compared to endoscopic surgery and excellent 3D vision and magnification. OArm allows an absolutely reliable intraoperative support for a more effective CVJ decompression. Nevertheless, with OArm-assisted neuronavigation, it can be difficult to navigate C1 lateral masses and C2 isthmi, and to convert 3D into 2D real-time navigation, it can become quite complicate. Finally, the association of EX and OArm appears more time consuming compared to the old fashion one.

Accuracy of robot-assisted pedicle screw insertion in adolescent idiopathic scoliosis: is triggered electromyographic pedicle screw stimulation necessary?

Screw malpositioning is an identifiable cause of intraoperative neurophysiologic changes. Although triggered screw electromyography (t-EMG) has been found to exhibit high sensitivity for identifying malpositioned screws, no previous study has assessed the utility of combining t-EMG with robotic-assisted pedicle screw placement for identifying malpositioned screws. We sought to evaluate the utility of t-EMG used in combination with robotic-assisted pedicle screw placement for identifying malpositioned screws in patients with adolescent idiopathic scoliosis (AIS). Patients undergoing robotic-assisted posterior spinal fusion with pedicle screw fixation for AIS underwent retrospective review from a single surgeons prospectively collected database. Preoperative demographic data and curve characteristics were recorded. Computed tomography (CT) scans were reviewed, measuring pedicle width and classifying pedicle morphology using the channel classification system. Pedicle data was compared against intra-operative t-EMG data, with a minimal threshold of 8 mA used for screw removal and screw path examination and the rate of screw re-direction recorded. All pedicle screws were verified using image intensification. Forty-nine patients (11 males, 38 females, average age 14.49 years) with an average curve magnitude of 51 degrees and placement of 844 pedicle screws to attain an average curve correction of 67.7%. The incidence of an absent pedicle (type C or D morphology) was 2%. Overall, 24 screws (2.8%) were identified with an abnormal t-EMG threshold. All screws were found to have an intact medial wall upon probing and were reinserted without re-direction. No patient or curve characteristic was predictive of abnormal t-EMG amplitude but smaller pedicles correlated with smaller amplitudes. With precise pre-operative planning, robotic-assisted pedicle screw placement has shown to be a safe and effective method in treating AIS patients as shown by the lack of medial pedicle breach and malpositioned screws. We found no evidence to support combined use of t-EMG for identifying medially malpositioned screws.

Do intra-operative neurophysiological changes predict functional outcome following decompressive surgery for lumbar spinal stenosis? A prospective study.

To analyse the relation between immediate intraoperative neurophysiological changes during decompression and clinical outcome in a series of patients with lumbar spinal stenosis (LSS) undergoing surgery. Twenty-four patients with neurogenic intermittent claudication (NIC) due to LSS undergoing decompressive surgery were prospectively studied. Intra operative trans-cranial motor evoked potentials (tcMEPs) were recorded before and immediately after surgical decompression. Lower limb normalised tcMEP improvement was used as primary neurophysiological outcome. Clinical outcome was assessed using the Zurich Claudication Questionnaire (ZCQ) self-assessment score, before surgery (baseline) and at an average of 8 and 29 months post-operatively. We found a moderate positive correlation between tcMEP changes and ZCQ at early follow-up (R=0.36). At late follow-up no correlation was found between intra-operative tcMEP and ZCQ changes. Dichotomizing the data showed a statistically significant relationship between tcMEP improvement and better functional outcome at early follow-up (P=0.013) but not at later follow-up (P=1). Our findings suggest that intra-operative neurophysiological improvement during decompressive surgery may predict a better clinical outcome at early follow-up although this is not applicable to late follow-up possibly due to the observed erosion of functional improvement with time.

P166 - Accuracy of Robot-Assisted Pedicle Screw Insertion in Adolescent Idiopathic Scoliosis: Is Triggered Electromyographic Pedicle Screw Stimulation Necessary?

BACKGROUND CONTEXT: Screw malpositioning is an identifiable cause of intraoperative neurophysiologic changes. Although triggered electromyography (t-EMG) has been found to exhibit high sensitivity for identifying malpositioned screws, no previous study has assessed the utility of combining t-EMG with robotic-assisted pedicle screw placement for identifying malpositioned screws.

Intraoperative Neurophysiological Changes Induced by Thoracic Pedicle Screws Intentionally Placed Within the Spinal Canal: An Experimental Study in Pigs

Study DesignExperimental study, ObjectivesTo document and analyze the neurophysiological changes during spinal cord monitoring when thoracic pedicle screws are intentionally placed within the spinal canal. Summary of Background DataAlthough the rate of misplaced screws is relatively high, few patients have neurological impairment. This suggests that a significant degree of medullary displacement and/or compression is necessary to produce neurophysiological changes. MethodsThe spinal cord of 3 experimental pigs was surgically exposed at 3 different levels (T11, T9, and T6). Two pedicle screws were placed within the spinal canal at each vertebral level under direct vision. One was placed on the lateral edge of the dural sac, causing only a slight cord displacement; a second screw was placed in the middle of the spinal canal, producing marked displacement of the neural structures. During the procedure, neurophysiological monitoring of the spinal cord was performed. ResultsNo neurophysiological changes were observed in any screws placed at the lateral edge of the dural sac for 20 minutes after screw placement. When the screws were placed in the center of the spinal canal, neurophysiological changes occurred with a mean latency of 10.1 ± 2.1 minutes, and at 11.6 ± 1.9 minutes there was complete loss of the spinal cord evoked potentials in all cases. After these centered screws were removed, evoked potentials began to recover, with a latency of 9.7 ± 3.0 minutes in 7 of 9 cases. ConclusionsNeurophysiological monitoring of the spinal cord does not detect moderate compression even 20 minutes after neural compression. Only thoracic pedicle screws provoking marked displacement of the spinal cord were able to cause delayed neurophysiological changes leading to loss of spinal cord evoked potentials, which in 22% of cases did not recover after the pedicle screw was removed.

Neuromonitoring changes in pediatric spinal deformity surgery: a single-institution experience

Intraoperative monitoring of the spinal cord has become the standard of care during surgery for pediatric spinal deformity correction. The use of both somatosensory and motor evoked potentials has dramatically increased the sensitivity and specificity of detecting intraoperative neurophysiological changes to the spinal cord, which assists in the intraoperative decision-making process. The authors report on a large, single-center experience with neuromonitoring changes and outline the surgical management of patients who experience significant neuromonitoring changes during spinal deformity correction surgery. The authors conducted a retrospective review of all cases involving pediatric patients who underwent spinal deformity correction surgery at Shriners Hospital for Children, Philadelphia, between January 2007 and March 2010. Five hundred nineteen consecutive cases were reviewed in which neuromonitoring was used, with 47 cases being identified as having significant changes in somatosensory evoked potentials, motor evoked potentials, or both. These cases were reviewed for patient demographic data and surgical characteristics. The incidence of significant neuromonitoring changes was 9.1% (47 of 519 cases), including 6 cases of abnormal Stagnara wake-up tests, of which 4 had corroborated postoperative neurological deficits (8.5% of 47 cases, 0.8% of 519). In response to neuromonitoring changes, wake-up tests were performed in 37 (79%) of 47 cases, hardware was adjusted in 15 (32%), anesthesiology interventions were reported in 5 (11%), hardware was removed in 5 (11%), the patient was successfully repositioned in 3 (6%), and the procedure was aborted in 13 (28%). In 1 of the 4 patients with new postoperative deficits, the deficit had fully resolved by the last follow-up; the other 3 patients had persistent neurological impairment as of the most recent follow-up examination. The authors observed a sensitivity of 100% for intraoperative neuromonitoring. Due to the profound risks associated with spinal deformity surgery, intraoperative neurophysiological monitoring is an integral tool to warn of impending spinal cord injury. Intraoperative neuromonitoring appears to provide a safe and useful warning mechanism to minimize spinal cord injury that may arise during scoliosis correction surgery in pediatric patients.

Predictors of Outcome in Patients with Spinal Cord Ischemia after Open Aortic Repair

Spinal cord ischemia is a potentially devastating complication of thoracic aortic surgery. However, predictors of outcome have not been well characterized. The study objective was to generate a prognostic score that accurately stratifies patient outcomes, aiding in future management and planning. A retrospective review of 224 consecutive open thoracic aortic surgeries identified patients with spinal cord ischemia, defined as changes on intraoperative somatosensory evoked potentials (SSEP) and/or paraparesis/paraplegia postoperatively. The outcome of interest was poor outcome, defined as death or discharge with a lower extremity motor score ≤40, indicating impaired ambulation. Demographic and clinical characteristics were tested in univariate analyses and significant factors were incorporated in multivariate modeling to determine independent predictors of poor outcome. Seventy-five patients were identified with spinal cord ischemia, of which 43(57 %) had poor outcomes including 28(37 %) that died prior to discharge. Factors associated with poor outcome in univariate analysis included absent lumbar CSF drain (p = 0.03), surgical repair that crossed the diaphragm (p = 0.002), permanent intraoperative SSEP change (p = 0.02), postoperative renal failure (p = 0.004), paraplegia (p = 0.001), and concomitant stroke (p = 0.04). In multivariable analysis, surgical repair crossing the diaphragm (OR 4.8, CI 1.4-16.7, p = 0.02), paraplegia (OR 4.5, CI 1.4-14.0, p = 0.01), and renal failure (OR 6.1, CI 1.7-21.2, p = 0.005) were independently associated with poor outcome. Patients with transient intraoperative neurophysiologic changes were least likely to have poor outcome when compared to patients with no or permanent SSEP changes, and those not monitored (p = 0.03). Development of spinal cord ischemia with thoracic aortic repair often leads to death or disability. Characteristics known at the time of event can accurately predict the likelihood of poor outcome.

Intraoperative Disc Herniation During Posterior Spinal Fusion for Correction of Scheuermannʼs Kyphosis

A retrospective case report. To report a previously unpublished complication associated with surgical correction of Scheuermann's kyphosis (SK). Recently, a review of a large Scoliosis Research Society database reported a 1.9% risk of neurologic injury during surgical correction of SK. Typically, changes in neurophysiological monitoring are attributed to hypoperfusion of the spinal cord during deformity correction and can be treated by elevating the mean arterial blood pressure or by decreasing the amount of correction. However, other reversible etiologies of neurologic compromise theoretically exist as well. SK is associated with degenerative changes in the intervertebral disc, and an intraoperative neural compromise could be due to disc herniations during application of powerful deformity corrective forces. The patient's medical history, physical examination, and diagnostic studies were retrospectively reviewed. We encountered a previously unreported complication of intraoperative disc herniation causing neural compromise during deformity correction of SK. A 17-year-old patient developed a T10-T11 herniated nucleus pulposus during posterior spinal fusion for SK. We postulate that abnormal intervertebral disc degeneration associated with SK and significant pressure on the middle spinal column during application of the cantilever correction maneuver contributed to the disc herniation, which resulted in acute unilateral leg pain and weakness. To our knowledge, no reported case of this phenomenon has been documented in the literature. Surgeons should consider acute disc herniation as a possible etiology for intraoperative neurophysiologic changes.

39. Characterization of Intraoperative Neurophysiologic Changes Due to Vascular Compression during Anterior Lumbar Surgery

BACKGROUND CONTEXT: The anterior retroperitoneal approach is often used to gain access to the anterior lumbar spine. During this approach, dissection and retraction of the aorta and iliac vessels may be required. Occult intraoperative vascular insufficiency may lead to catastrophic complications and thus early detection is critical to satisfactory patient outcomes. Intraopertive neurophysiologic monitoring (IONM) using posterior tibial nerve somatosensory evoked potentials (PTN SSEP) is an accepted technique for monitoring neural pathways during spinal procedures.

Neurophysiologic monitoring to assure delivery of retrograde cerebral perfusion

Background: Patients undergoing complex aortic procedures performed with deep hypothermia and circulatory arrest have a significant risk of an adverse neurologic event when the arrest period is prolonged. Retrograde cerebral perfusion appears to improve cerebral protection, although collapsed cortical veins or functional jugular venous valves may restrict flow at the frequently recommended maximum pressure of 25 mm Hg. Therefore, the purpose of this study was to demonstrate the benefit of multimodality neurophysiologic monitoring in assuring delivery of retrograde cerebral perfusion. Methods: Electroencephalography, cerebral blood flow velocity, and regional cerebral venous oxygen saturation were used to quantify the intraoperative neurophysiologic changes accompanying retrograde cerebral perfusion. The magnitude of changes was compared with those previously observed during arrest without retrograde cerebral perfusion. Results: Thirty patients underwent complex aortic procedures necessitating circulatory arrest, 22 with retrograde cerebral perfusion. The mean retrograde perfusion pressure of 40 mm Hg (30 to 49 mm Hg, 95% confidence interval) and flow rate of 1.2 L/min (0.9 to 1.6 L/min) necessary to achieve documented retrograde cerebral perfusion was much higher than previously recommended. During both retrograde cerebral perfusion and rewarming, cerebral oximetric monitoring guided adjustments in perfusion parameters to limit the rate of desaturation to 0.4% per minute (0.3% to 0.6%). With retrograde cerebral perfusion there was a rapid (1) recovery of electroencephalographic activity during rewarming (21 minutes [range 16 to 26 minutes]) and (2) return of consciousness after the operation (81% [58% to 95%, 95% confidence interval] awake by 12 hours). There was no transcranial Doppler evidence of cerebral edema with retrograde cerebral perfusion. Two neurologic complications occurred in the 22 patients managed with retrograde cerebral perfusion and one in the eight patients managed with arrest only. Conclusions: Multimodality neurologic monitoring assured optimal brain cooling and bihemispheric delivery of retrograde cerebral perfusion. Necessary retrograde pressure and flow were often higher than values previously reported. Avoidance of profound cerebral venous oxygen desaturation during retrograde cerebral perfusion and rewarming was associated with rapid recovery of neurologic function. (J Thorac Cardiovasc Surg 1997;113:748-57)