- Email: [email protected]
33. Intraoperative visual evoked potential monitoring and its pitfalls
Society Proceedings / Clinical Neurophysiology 125 (2014) e13–e24
analyses the occurrence of intraoperative changes in MEP and SEP with regard to lesion location and postoperative neurological outcome. Materials and methods: 210 patients (49 13 years, 109 female) undergoing surgeries within the vicinity of the cerebello-pontine angle (77), cerebellum (59), brainstem (40), skull base tumours (26) and others (5) were analysed. Results: 171/210 (81.4%) surgeries were uneventful for long-tract monitoring. 9/39 SEP and MEP-alterations (23%) were transient and without neurological long-term sequelae. Permanent deterioration was seen in 19/39 patients (49%), of which 4 were related to tumour dissection and followed by slight permanent neurological deficit. 11 patients (28%) encountered losses of at least one modality, which were related to surgical microdissection within the vicinity of the brainstem in 9 patients. 4/9 patients suffered a severe long-term deficit. Overall, positive predictive value for long tract neuromonitoring was 0.394, negative predictive value 0.994, sensitivity 0.934 and specificity 0.886. 28/39 (71%) SEP- and MEP-alterations occurred in 66 brainstem respective skull base tumours compared to 11/39 (29%) alterations in all other 144 locations. Tumour location and alterations in intraoperative neuromonitoring significantly correlated with patient outcome (p < 0.001, chi-square test). Conclusion: In summary, long tract monitoring with SEPs and MEPs in infratentorial surgeries has a high sensitivity and negative predictive value indicating postoperative neurological status. It is recommended especially in those surgeries where microdissection within the vicinity of the brainstem might lead to injury of perforating vessels and subsequent perfusion deficit within the brainstem. doi:10.1016/j.clinph.2013.12.034
32. Intraoperative pathoelectrophysiologic response during SDR and correlation with cognitive improvement—Tali Biron, Akiva Korn, Liana Beni-Adani (Sourasky Ichilov Medical Center, Israel) Introduction: Selective dorsal rhizotomy (SDR) is commonly guided by an intraoperative pathoelectrophysiologic response (IPR) to electrical stimulation of posterior rootlets. The rootlets guided partial transection leads to reduced spasticity postoperatively. Prior studies have shown a statistically significant correlation between the extent of IPR and the preoperative degree of lower extremity GMFM (gross motor function measure) as well as postoperative improvement. Studies have also shown cognitive function (CF) improvement in patients who have undergone SDR, yet it is unknown whether this is a direct or indirect effect of the spasticity reduction. No study has investigated the correlation between IPR and cognitive function.The goal of this study was to answer the question: is there a direct correlation between the extent of IPR and postoperative CF improvement?. Material and methods: 11 children with baseline GMFCS 3–5 underwent SDR directed by IPR (5 female, 6 male, age range 3– 10 years).IPR severity was classified according to a Modified Phillips & Parks scale (1–6). The CF included communication skills, speech, eye contact, and caregiver’s evaluation. CF Data was stratified by a 3 degree scale (normal, abnormal, absent). The change in each function was scored on a 5 degree score, ( 2)–(+2). Intraoperatively, rootlets displaying any degree of IPR were transected unless motor sphincter innervation was evident. The degree and extent of IPR and transaction were correlated with cognitive parameters. Results: 177 IPR rootlets were transected. 91% of patients showed CF improvement after SDR. At this time, no specific direct correlation was found between IPR and CF improvement, including specific CF components: eye contact, speech, communication and caregiver’s evaluation. This could be due to small sample size and nearly global CF improvement.
e23
Conclusion: Cognitive improvement after SDR is a common and consistent finding that needs to be further investigated. Presently, IPR cannot be shown to be a marker for CF changes post-SDR. doi:10.1016/j.clinph.2013.12.035
Speaker abstracts – Incorporated into speaker presentations 33. Intraoperative visual evoked potential monitoring and its pitfalls—Kunihiko Kodama, Tetsuya Goto, Kazuhiro Hongo (Department of Neurosurgery, Shinshu University, School of Medicine, Japan) Introduction: Visual evoked potentials (VEP) have been installed as a method for intraoperative visual function monitoring. However, there have been few reports regarding pitfalls of intraoperative VEP monitoring. To clarify this, relationships between intraoperative VEP waveform changes and postoperative visual function were analysed retrospectively. Material and methods: Intraoperative VEP monitoring was performed in 123 surgeries, including three intraorbital, 96 parasellar and 24 cortical lesions in Shinshu University Hospital. Red flash light was provided to each eye independently. Supramaximal stimulation was found before starting surgical procedure and control VEP amplitude was measured. Decrease by 50% of control VEP amplitude was defined as a warning sign and reported to surgeons. The surgical procedure was ceased on the surgeon’s decisions. Intraoperative VEP monitoring and postoperative visual function were analysed. Results: In 238 out of 246 eyes (97%), steady VEP monitoring was recorded. Transient VEP decrease was observed in 18 sides, but visual function was preserved. A permanent VEP decrease was seen in 18 sides, which resulted in visual impairment in 10 sides, and no visual aggravation in 8 sides postoperatively. The VEP amplitude was preserved greater than 50% in 200 of 202 sides, and visual function was preserved. In a patient with tuberculum sellae meningioma, visual acuity aggravated though VEP was maintained at 77% of control amplitude. In one side, visual acuity improved but minor visual field defect was encountered postoperatively, though VEP was unchanged throughout the surgery. Conclusions: Intraoperative VEP monitoring predicts postoperative visual function: a 50% decrease of VEP amplitude can detect postoperative visual aggravation with a sensitivity of 99%. Pitfalls for intraoperative VEP monitoring are: (1) preoperative severe visual dysfunction, low amplitude of control VEP may interfere with intraoperative VEP monitoring in this method. (2) Visual field defect without decrease in the visual acuity may not be predicted by VEP monitoring. Attention should be paid to these pitfalls for reliable intraoperative VEP monitoring. doi:10.1016/j.clinph.2013.12.036
34. Mechanism of therapeutic benefit with dorsal column stimulation using a computational model of the spinal cord—Jay Shils a, Kris Carlson b, Longzhi Mei b, Jeffrey Arle b,c (a The Lahey Clinic and Tufts University Medical School, United States, b Beth Israel Deaconess Medical Center, United States, c Harvard University, United States) Objective: Dorsal column stimulation (DCS) is a widely used therapy to treat refractory neuropathic pain of the trunk and limbs. The mechanisms by which such stimulation achieves pain relief, however, have yet to be fully elucidated and may even be contrary to one of the standard theories of pain, ‘ ~gate control theory’ (‘ ~gate
analyses the occurrence of intraoperative changes in MEP and SEP with regard to lesion location and postoperative neurological outcome. Materials and methods: 210 patients (49 13 years, 109 female) undergoing surgeries within the vicinity of the cerebello-pontine angle (77), cerebellum (59), brainstem (40), skull base tumours (26) and others (5) were analysed. Results: 171/210 (81.4%) surgeries were uneventful for long-tract monitoring. 9/39 SEP and MEP-alterations (23%) were transient and without neurological long-term sequelae. Permanent deterioration was seen in 19/39 patients (49%), of which 4 were related to tumour dissection and followed by slight permanent neurological deficit. 11 patients (28%) encountered losses of at least one modality, which were related to surgical microdissection within the vicinity of the brainstem in 9 patients. 4/9 patients suffered a severe long-term deficit. Overall, positive predictive value for long tract neuromonitoring was 0.394, negative predictive value 0.994, sensitivity 0.934 and specificity 0.886. 28/39 (71%) SEP- and MEP-alterations occurred in 66 brainstem respective skull base tumours compared to 11/39 (29%) alterations in all other 144 locations. Tumour location and alterations in intraoperative neuromonitoring significantly correlated with patient outcome (p < 0.001, chi-square test). Conclusion: In summary, long tract monitoring with SEPs and MEPs in infratentorial surgeries has a high sensitivity and negative predictive value indicating postoperative neurological status. It is recommended especially in those surgeries where microdissection within the vicinity of the brainstem might lead to injury of perforating vessels and subsequent perfusion deficit within the brainstem. doi:10.1016/j.clinph.2013.12.034
32. Intraoperative pathoelectrophysiologic response during SDR and correlation with cognitive improvement—Tali Biron, Akiva Korn, Liana Beni-Adani (Sourasky Ichilov Medical Center, Israel) Introduction: Selective dorsal rhizotomy (SDR) is commonly guided by an intraoperative pathoelectrophysiologic response (IPR) to electrical stimulation of posterior rootlets. The rootlets guided partial transection leads to reduced spasticity postoperatively. Prior studies have shown a statistically significant correlation between the extent of IPR and the preoperative degree of lower extremity GMFM (gross motor function measure) as well as postoperative improvement. Studies have also shown cognitive function (CF) improvement in patients who have undergone SDR, yet it is unknown whether this is a direct or indirect effect of the spasticity reduction. No study has investigated the correlation between IPR and cognitive function.The goal of this study was to answer the question: is there a direct correlation between the extent of IPR and postoperative CF improvement?. Material and methods: 11 children with baseline GMFCS 3–5 underwent SDR directed by IPR (5 female, 6 male, age range 3– 10 years).IPR severity was classified according to a Modified Phillips & Parks scale (1–6). The CF included communication skills, speech, eye contact, and caregiver’s evaluation. CF Data was stratified by a 3 degree scale (normal, abnormal, absent). The change in each function was scored on a 5 degree score, ( 2)–(+2). Intraoperatively, rootlets displaying any degree of IPR were transected unless motor sphincter innervation was evident. The degree and extent of IPR and transaction were correlated with cognitive parameters. Results: 177 IPR rootlets were transected. 91% of patients showed CF improvement after SDR. At this time, no specific direct correlation was found between IPR and CF improvement, including specific CF components: eye contact, speech, communication and caregiver’s evaluation. This could be due to small sample size and nearly global CF improvement.
e23
Conclusion: Cognitive improvement after SDR is a common and consistent finding that needs to be further investigated. Presently, IPR cannot be shown to be a marker for CF changes post-SDR. doi:10.1016/j.clinph.2013.12.035
Speaker abstracts – Incorporated into speaker presentations 33. Intraoperative visual evoked potential monitoring and its pitfalls—Kunihiko Kodama, Tetsuya Goto, Kazuhiro Hongo (Department of Neurosurgery, Shinshu University, School of Medicine, Japan) Introduction: Visual evoked potentials (VEP) have been installed as a method for intraoperative visual function monitoring. However, there have been few reports regarding pitfalls of intraoperative VEP monitoring. To clarify this, relationships between intraoperative VEP waveform changes and postoperative visual function were analysed retrospectively. Material and methods: Intraoperative VEP monitoring was performed in 123 surgeries, including three intraorbital, 96 parasellar and 24 cortical lesions in Shinshu University Hospital. Red flash light was provided to each eye independently. Supramaximal stimulation was found before starting surgical procedure and control VEP amplitude was measured. Decrease by 50% of control VEP amplitude was defined as a warning sign and reported to surgeons. The surgical procedure was ceased on the surgeon’s decisions. Intraoperative VEP monitoring and postoperative visual function were analysed. Results: In 238 out of 246 eyes (97%), steady VEP monitoring was recorded. Transient VEP decrease was observed in 18 sides, but visual function was preserved. A permanent VEP decrease was seen in 18 sides, which resulted in visual impairment in 10 sides, and no visual aggravation in 8 sides postoperatively. The VEP amplitude was preserved greater than 50% in 200 of 202 sides, and visual function was preserved. In a patient with tuberculum sellae meningioma, visual acuity aggravated though VEP was maintained at 77% of control amplitude. In one side, visual acuity improved but minor visual field defect was encountered postoperatively, though VEP was unchanged throughout the surgery. Conclusions: Intraoperative VEP monitoring predicts postoperative visual function: a 50% decrease of VEP amplitude can detect postoperative visual aggravation with a sensitivity of 99%. Pitfalls for intraoperative VEP monitoring are: (1) preoperative severe visual dysfunction, low amplitude of control VEP may interfere with intraoperative VEP monitoring in this method. (2) Visual field defect without decrease in the visual acuity may not be predicted by VEP monitoring. Attention should be paid to these pitfalls for reliable intraoperative VEP monitoring. doi:10.1016/j.clinph.2013.12.036
34. Mechanism of therapeutic benefit with dorsal column stimulation using a computational model of the spinal cord—Jay Shils a, Kris Carlson b, Longzhi Mei b, Jeffrey Arle b,c (a The Lahey Clinic and Tufts University Medical School, United States, b Beth Israel Deaconess Medical Center, United States, c Harvard University, United States) Objective: Dorsal column stimulation (DCS) is a widely used therapy to treat refractory neuropathic pain of the trunk and limbs. The mechanisms by which such stimulation achieves pain relief, however, have yet to be fully elucidated and may even be contrary to one of the standard theories of pain, ‘ ~gate control theory’ (‘ ~gate