Intraoperative motor and somatosensory evoked potential monitoring during surgical clipping of ruptured and unruptured intracranial aneurysms: a comparative study

OBJECTIVE The current study investigated the correlation between intraoperative motor evoked potential (MEP) and somatosensory evoked potential (SSEP) monitoring and both short-term and long-term motor outcomes in aneurysm patients treated with surgical clipping. Moreover, the authors provide a relatively optimal neurophysiological predictor of postoperative motor deficits (PMDs) in patients with ruptured and unruptured aneurysms. METHODS A total of 1017 patients (216 with ruptured aneurysms and 801 with unruptured aneurysms) were included. Patient demographic characteristics, clinical features, intraoperative monitoring data, and follow-up data were retrospectively reviewed. The efficacy of using changes in MEP/SSEP to predict PMDs was assessed using binary logistic regression analysis. Subsequently, receiver operating characteristic curve analysis was performed to determine the optimal critical value for duration of MEP/SSEP deterioration. RESULTS Both intraoperative MEP and SSEP monitoring were significantly effective for predicting short-term (p < 0.001 for both) and long-term (p < 0.001 for both) PMDs in aneurysm patients. The critical values for predicting short-term PMDs were amplitude decrease rates of 57.30% for MEP (p < 0.001 and area under the curve [AUC] 0.732) and 64.10% for SSEP (p < 0.001 and AUC 0.653). In patients with an unruptured aneurysm, the optimal critical values for predicting short-term PMDs were durations of deterioration of 17 minutes for MEP (p < 0.001 and AUC 0.768) and 21 minutes for SSEP (p < 0.001 and AUC 0.843). In patients with a ruptured aneurysm, the optimal critical values for predicting short-term PMDs were durations of deterioration of 12.5 minutes for MEP (p = 0.028 and AUC 0.706) and 11 minutes for SSEP (p = 0.043 and AUC 0.813). CONCLUSIONS The authors found that both intraoperative MEP and SSEP monitoring are useful for predicting short-term and long-term PMDs in patients with unruptured and ruptured aneurysms. The optimal intraoperative neuromonitoring method for predicting PMDs varies depending on whether the aneurysm has ruptured or not.

Electrophysiological characteristics and anatomical differentiation of epileptic and non-epileptic myoclonus

Background Electrophysiological techniques have been used for discriminating myoclonus from other hyperkinetic movement disorders and for classifying the myoclonus subtype. This study was carried out on patients with different subtypes of myoclonus to determine the electrophysiological characteristics and the anatomical classification of myoclonus of different etiologies. This study included 20 patients with different subtypes of myoclonus compared with 30 control participants. Electrophysiological study was carried out for all patients by somatosensory evoked potential (SSEP) and electroencephalography (EEG) while the control group underwent SSEP. SSEP was evaluated in patients and control groups by stimulation of right and left median nerves. Results This study included 50 cases with myoclonus of different causes with mean age of 39.3 ± 15.7 and consisted of 23 males and 27 females. Twenty-nine (58%) of the patients were epileptics, while 21 (42%) were non-epileptics. Cases were classified anatomically into ten cases with cortical myoclonus (20%), 12 cases with subcortical myoclonus (24%), and 28 cases with cortical–subcortical myoclonus (56%). There was a significant difference regarding the presence of EEG findings in epileptic myoclonic and non-epileptic myoclonic groups (P = 0.005). Also, there were significant differences regarding P24 amplitude, N33 amplitude, P24–N33 peak-to-peak complex amplitude regarding all types of myoclonus. Primary myoclonic epilepsy (PME) demonstrated significant giant response, juvenile myoclonic epilepsy (JME) demonstrated no enhancement compared to controls, while secondary myoclonus demonstrated lower giant response compared to PME. Conclusion Somatosensory evoked potential and electroencephalography are important for the diagnosis and anatomical sub-classification of myoclonus and so may help in decision-making regarding to the subsequent management.

The Vagus Nerve Somatosensory-evoked Potential in Neural Disorders: Systematic Review and Illustrative Vignettes

Objective. To review the scientific publications reporting vagal nerve somatosensory-evoked potential (VSEP) findings from individuals with brain disorders, and present novel physiological explanations on the VSEP origin. Methods. We did a systematic review on the papers reporting VSEP findings from individuals with brain disorders and their controls. We evaluated papers published from 2003 to date indexed in PubMed, Web of Science, and Scielo databases. We extracted the following information: number of patients and controls, type of neural disorder, age, gender, stimulating/recording and grounding electrodes as well as stimulus side, intensity, duration, frequency, and polarity. Information about physiological parameters, neurobiological variables, and correlation studies was also reviewed. Representative vignettes were included to add support to our conclusions. Results. The VSEP was studied in 297 patients with neural disorders such as Parkinson’s disease (PD), Alzheimer’s disease, vascular dementia, mild cognitive impairment, subjective memory impairment, major depression, and multiple sclerosis. Scalp responses marked as the VSEP showed high variability, low validity, and poor reproducibility. VSEP latencies and amplitudes did not correlate with disease duration, unified PD rating scale score, or heart function in PD patients nor with cerebrospinal fluid β amyloid, phosphor-τ, and cognitive tests from patients with mental disorders. Vignettes demonstrated that the VSEP was volume conduction propagating from muscles surrounding the scalp recording electrodes. Conclusion. The VSEP is not a brain-evoked potential of neural origin but muscle activity induced by electrical stimulation of the tragus region of the ear. This review and illustrative vignettes argue against assessing the parasympathetic system using the so-called VSEP.