Somatosensory Evoked Potentials Findings Research Articles

Cerebrospinal Creatine Kinase BB Isoenzyme: A Biomarker for Predicting Outcome After Cardiac Arrest.

Cerebrospinal fluid creatine kinase BB isoenzyme (CSF CK-BB) after cardiac arrest (CA) has been shown to have a high positive predictive value for poor neurological outcome, but it has not been evaluated in the setting of targeted temperature management (TTM) and modern CA care. We aimed to evaluate CSF CK-BB as a prognostic biomarker after CA. We performed a retrospective cohort study of patients with CA admitted between 2010 and 2020 to a three-hospital health system who remained comatose and had CSF CK-BB assayed between 36 and 84h after CA. We examined the proportion of patients at hospital discharge who achieved favorable or intermediate neurological outcome, defined as Cerebral Performance Category score of 1-3, compared with those with poor outcome (Cerebral Performance Category score 4-5) for various CSF CK-BB thresholds. We also evaluated additive value of bilateral absence of somatosensory evoked potentials (SSEPs). Among 214 eligible patients, the mean age was 54.7 ± 4.8years, 72% of patients were male, 33% were nonwhite, 17% had shockable rhythm, 90% were out-of-hospital CA, and 83% received TTM. A total of 19 (9%) awakened. CSF CK-BB ≥ 230 U/L predicted a poor outcome at hospital discharge, with a specificity of 100% (95% confidence interval [CI] 82-100%) and sensitivity of 69% (95% CI 62-76%). When combined with bilaterally absent N20 response on SSEP, specificity remained 100% while sensitivity increased to 80% (95% CI 73-85%). Discordant CK-BB and SSEP findings were seen in 13 (9%) patients. Cerebrospinal fluid creatine kinase BB isoenzyme levels accurately predicted poor neurological outcome among CA survivors treated with TTM. The CSF CK-BB cutoff of 230 U/L optimizes sensitivity to 69% while maintaining a specificity of 100%. CSF CK-BB could be a useful addition to multimodal neurological prognostication after CA.

Pembrolizumab-associated Neuronopathy with Improved Lower Limb Somatosensory Evoked Potential After Intravenous Methylprednisolone Treatment: A Case Report.

Cases of neuronopathy associated with immune checkpoint inhibitors (ICIs) have rarely been reported. We herein report a case of ICI-associated neuronopathy. A 54-year-old man underwent chemotherapy for right maxillary sinus cancer. Two months after pembrolizumab treatment, diarrhea, worsening of abnormal sensations, and severe ataxia of the lower limbs were observed. Somatosensory evoked potentials (SEPs) with tibial nerve stimulation showed disappearance of the N21 waveform. A colonic biopsy suggested ICI-associated colitis. Based on these findings, the patient was diagnosed with ICI-associated neuronopathy. Clinical symptoms and SEP findings improved markedly after two courses of intravenous methylprednisolone.

Tibial nerve SEPs in diagnosing lumbar spinal stenosis: The utility of segmental evaluation using P15 and N21

ObjectiveTo establish the utility of the additional evaluation of the P15 potential generated at the greater sciatic foramen in the tibial nerve somatosensory evoked potentials (SEPs) in diagnosing lumbar spinal stenosis (LSS). MethodsWe retrospectively reviewed tibial nerve SEP findings in patients having MRI-confirmed LSS at the cauda equina or conus/epiconus region. P15 and N21 potentials were recorded and the following findings were defined as localizing abnormalities: 1) normal P15 latency either with prolonged P15-N21 interval or with absent N21; 2) decreased ratio of the N21 amplitude to P15 amplitude. As non-localizing abnormalities, N21 and P38 latencies were also evaluated. Tibial nerve F-wave findings were also investigated. ResultsAccording to the entry criteria, 18 patients were included, 15 with cauda equina lesions and 3 with conus/epiconus lesions. Localizing abnormalities in SEPs were found in 67% of patients, achieving significantly higher sensitivity than delayed P38 latency (28%), and higher sensitivity than N21 abnormalities (39%), though this was not significant. Localizing abnormalities were observed even in 6 out of 11 patients lacking both sensory symptoms and signs. Tibial nerve F-wave was abnormal in 36% of 14 patients with F-wave examinations, whereas the localizing abnormalities in SEPs were found in 64% of the same patient population. P15 amplitude was depressed in 4 patients (22%), which may indicate the involvement of the dorsal root ganglion in LSS, although its latency was normal even for these patients. ConclusionsTibial nerve SEPs with the recording of P15 and N21 potentials achieved sufficiently high sensitivity in diagnosing LSS. They have the advantage over F-wave in that they can localize the lesion at the cauda equina or conus/epiconus level. SignificanceTibial nerve SEPs are promising in evaluating LSS, especially in documenting sensory tract involvement in cases lacking sensory symptoms/signs.

Correlation of urodynamic studies and somatosensory evoked potential and their prognostic value in children with closed spinal dysraphism

Somatosensory evoked potential (SSEP) and urodynamic studies (UD) are valuable tools for assessing patients with closed spinal dysraphism (CSD) before neurosurgical intervention. No studies have correlated their findings in this cohort and our aim is to study their correlation and prognostic value in pediatric patients with closed spinal dysraphism. Retrospective review of all patients referred to a multidisciplinary clinic in a tertiary pediatric surgical center over a 17 years period between April 2004 to September 2021 was performed. Inclusion criteria were <18 years old, diagnosed with CSD, with SSEP and UD done within 1 year of each other. Demographics data collected include age at presentation/at referral/at neurosurgical operation, gender, symptoms at presentation and intra-operative diagnoses. Pre-operative SSEP and UD findings were documented. Primary outcome was UD results in the group with normal and abnormal SSEP. Secondary outcome was urological and bowel function outcome in 4 groups of patients (Group A-both normal SSEP and UD, Group B- abnormal SSEP only, Group C - abnormal UD only and Group D-both abnormal SSEP and UD). A total of 45 patients were included for analysis. Mean follow up time was 118.9 months (24-216 months, SD 55.8 months). SSEP was normal in 20 patients and abnormal in 25 patients. Baseline demographics, preoperative symptoms and imaging were similar between 2 groups. Primary outcome Patients with abnormal SSEP were more likely to have abnormal UD results with a statistically significant difference (84% vs 40%, p<0.05). They have a significantly higher end-fill detrusor pressure (12% vs 0%, p<0.05), abnormal bladder compliance (20% vs 0%, p<0.05), abnormal cystometric capacity (48% vs 10%, p<0.05), poor emptying efficiency (24% vs 5%, p<0.05) and sphincter incompetence (8% vs 0%, p<0.05). Secondary outcome When compared to Groups A to C, patients in group D were more likely to be on anti-cholinergic (33.3% vs 4.3%, p<0.05), required clean intermittent catheterization (42.9% vs 4.3%, p<0.05) and had intravesical botulinum injection (19% vs 0%, p<0.05). All the patients who had augmentation cystoplasty were in this group as well. Bowel function in terms of regular enema use was also statistically significantly higher in this group (33.4% p<0.05). Pre-operative SSEP and UD results correlate well in patients with closed spinal dysraphism. Patients with abnormal SSEP and UD preoperatively have higher risk of urological deterioration over time. Close monitoring in this group is warranted.

A Biomarker for Benign Adult Familial Myoclonus Epilepsy: High-Frequency Activities in Giant Somatosensory Evoked Potentials.

Benign adult familial myoclonus epilepsy (BAFME) is one of the diseases that cause cortical myoclonus (CM) with giant somatosensory evoked potentials (SEPs). There are no useful diagnostic biomarkers differentiating BAFME from other CM diseases. To establish reliable biomarkers including high-frequency oscillations (HFOs) with giant SEPs for the diagnosis of BAFME. This retrospective case study included 49 consecutive CM patients (16 BAFME and 33 other CM patients) who exhibited giant P25 or N35 SEPs. SEPs were processed by a band-pass filter of 400-1000 Hz to analyze HFOs. Clinical and SEP findings were compared between (1) BAFME and other CM groups and (2) patients with presence and absence of P25-HFOs (HFOs superimposed on giant P25). The diagnostic power of each factor for BAFME was calculated. All 16 BAFME patients showed SEP P25-HFOs with significantly higher occurrence (P < 0.0001) compared with that of other CM groups. The presence of P25-HFOs significantly correlated with a BAFME diagnosis (P < 0.0001) and high SEP P25 and N35 amplitudes (P=0.01 and P < 0.0001, respectively). BAFME was reliably diagnosed using P25-HFOs with high sensitivity (100%), specificity (87.9%), positive predictive value (80%), and negative predictive value (100%), demonstrating its superiority as a diagnostic factor compared to other factors. P25-HFOs with giant SEPs is a potential biomarker for BAFME diagnosis. P25-HFOs may reflect cortical hyperexcitability partly due to paroxysmal depolarizing shifts in epileptic neuronal activities and higher degrees of rhythmic tremulousness than those in ordinary CM. © 2021 International Parkinson and Movement Disorder Society.

Neurophysiological and neuroradiological multimodal approach for early poor outcome prediction after cardiac arrest

IntroductionPrognosticating outcome after cardiac arrest(CA) requires a multimodal approach. However, evidence regarding combinations of methods is limited. We evaluated whether the combination of electroencephalography(EEG), somatosensory evoked potentials(SEPs) and brain computed tomography(CT) could predict poor outcome. MethodsWe screened our database regarding patients successfully resuscitated after CA, for whom EEG, SEPs and brain CT were available within 24 h. EEG patterns were classified according to American Clinical Neurophysiological Society terminology; SEPs were graded accounting for the cortical responses of each hemisphere; and the grey matter/white matter(GM/WM) ratio was evaluated by brain CT. EEG patterns, SEP findings and GM/WM ratio (with a specificity of 100%) were, individually and in combination, related to poor outcome (death/unresponsive wakefulness state) at 6-month follow-up, using the cerebral performance categories(CPC). ResultsEEG, SEPs and brain CT were available in 183/273(67%) patients. Bilateral absent/absent-pathologic(AA/AP) cortical SEPs predicted a poor outcome with a sensitivity of 58.5%. A GM/WM ratio <1.21 predicted a poor outcome with a sensitivity of 50.4%. Isoelectric/burst-suppression EEG patterns predicted a poor outcome with a sensitivity of 43%. If at least one of these poor prognostic patterns was present, sensitivity for an ominous outcome increased to 71.5%. If, in the same subject, two poor prognostic patterns were simultaneously present, sensitivity was 48%. If all three poor prognostic patterns were present, sensitivity decreased by up to 23%. ConclusionIn this population, in which life-sustaining treatments were never suspended, the combination of EEG, SEPs and brain CT improved the sensitivity, maintaining the specificity of poor outcome prediction.

21. Brain computed tomography combined with somatosensory evoked potentials in the prediction of brain death after cardiac arrest

Brain Death (BD) in coma after cardiac arrest (CA) is difficult to predict. Basal ganglia Gray Matter/White Matter (GM/WM) ratio density and Somatosensory Evoked Potentials (SEPs) may differentiate patients evolving toward BD. We used SEPs and brain computed tomography (CT) within the first 24 h after the coma onset. We measured the basal ganglia level GM/WM ratio in a group of 73 comatose CA patients with bilateral absence (AA) of cortical SEPs, or monolateral absence and a pathological response in the other hemisphere (AP). Of the 73 patients included in the study, 22 (30%) evolved toward BD. The GW/WM ratio predicted the BD (ROC area = 0.68, p = 0.01). CT GM/WM ratio <1.07 had a sensitivity of 27%, a specificity of 96.2%, and a positive likelihood ratio of 6.91. In conclusion, SEPs and brain CT available within 24 h predict BD after CA. Severe SEP findings (SEP patterns AA, AP) identify a subset of patients in which BD can occur. Brain CT (GM/WM ratio in basal ganglia) predict an early evolution toward BD with a high specificity.

Is brain computed tomography combined with somatosensory evoked potentials useful in the prediction of brain death after cardiac arrest?

Brain death (BD) in coma after cardiac arrest (CA) is difficult to predict. Basal ganglia gray matter/white matter (GM/WM) ratio density and somatosensory evoked potentials (SEPs) may differentiate patients evolving toward BD. We used SEPs and brain computed tomography (CT) after coma onset, within the first 24hours. Of the 160 patients included in the study, 22 (14%) evolved toward BD. SEP patterns predicted BD (ROC area=0.82, P<0.0001). The combination of SEP patterns, bilaterally absent (AA) and absent on one hemisphere and pathological on the other (AP), predicted BD with a sensitivity of 100% and a specificity of 62.3%, with a positive likelihood ratio of 2.65. The GM/WM ratio predicted BD (ROC area=0.68, P=0.01). A GM/WM ratio <1.07 had a sensitivity of 30.4%, a specificity of 94.9%, and a positive likelihood ratio of 6.27. The combination of SEP and CT findings did not increase the prediction of BD. SEPs and brain CT within 24hours predicted BD after CA. Severe SEP findings (SEP patterns: AA, AP) identified a subset of patients in whom BD could occur. Brain CT (GM/WM ratio in basal ganglia) predicted an early evolution toward BD with high specificity but lower sensitivity.

ID 36 – Somatosensory evoked potentials in juvenile myoclonic epilepsy with tremor and essential tremor

Objective Many clinicians may encounter juvenile myoclonic epilepsy (JME) patients complaining of tremor. The etiology and generators of this tremor are not clear. We aimed to evaluate if there were differences or similarities between JME tremor and ET by using somatosensory evoked potentials (SEP). Methods We analyzed the median SEPs of 14 patients with JME complaining of hand tremor, 14 patients with ET, and 14 healthy volunteers. Tremors were also assessed by accelerometric recordings. Results The N20-P25 and P25-N35 amplitudes were significantly higher in the JME group as compared to other groups. In three siblings in the JME group “giant SEPs” were observed. Moreover left N20, P25 latencies were significantly longer in ET group. Tremor frequencies of both groups showed some overlap but ET had a distinctive pattern whereas JME patients had mild interrupting myoclonus. Ten JME patients were using VPA, but their tremor had started earlier. Conclusions The SEP amplitudes of two patient groups are different even though they have the tremor as a common symptom. Our findings might be interpreted as there are two different pathophysiological mechanisms associated with this similar symptom in JME and ET patients. Key message Same complaint, different SEP findings.

Tibial somatosensory evoked potential can prognosticate for ambulatory function in subacute hemiplegic stroke

Early prediction of expected recovery in stroke can help in planning appropriate medical and rehabilitation interventions. Recovery of ambulation is one of the essential endpoints in stroke rehabilitation. However, the correlation of somatosensory evoked potentials (SSEP) with clinical parameters and their predictive significance are not clearly defined. We aimed to examine the association between tibial nerve SSEP and ambulatory outcomes in subacute hemiplegic stroke patients. We reviewed medical records for hemiplegic patients with first-ever stroke who received inpatient rehabilitation from January 2009 to May 2013. We excluded patients with diabetes mellitus, quadriplegia, bilateral lesions, brainstem lesions, those aged over 80years, and those with severe musculoskeletal problems. Tibial nerve SSEP were performed when they were transferred to the rehabilitation department. SSEP findings were divided into three groups; normal, abnormal and absent response. Berg balance scale and functional ambulation category (FAC) at discharge were compared with initial tibial SSEP findings using one-way analysis of variance. Thirty-one hemiplegic patients were included. Berg balance scale and FAC were significantly different according to the SSEP (P<0.001). Post hoc analysis showed a significant difference between normal and absent response in Berg balance scale (P<0.001) and FAC (P<0.001), and between abnormal and absent response in Berg balance scale (P=0.012) and FAC (P=0.019). Functional outcomes of the normal response group were better than the abnormal response group, but there was no statistical significance. These findings suggest that initial tibial nerve SSEP may be a useful biomarker for prognosticating functional outcomes in hemiplegic patients.

Prolonged central sensory conduction time in patients with chronic arsenic exposure

BackgroundMany patients from Toroku, Japan, who have chronic arsenic exposure demonstrate whole-body sensory disturbance that is slightly more pronounced in the extremities. Although previous research in this population showed a mild peripheral neuropathy, it is unknown whether these patients have central nervous system impairment. To investigate the lesion sites underlying sensory disturbance related to chronic arsenic poisoning, we analyzed somatosensory evoked potentials (SEP). MethodsClinical features, nerve conduction study results, and median and/or tibial SEP were analyzed in patients with chronic arsenic exposure (total, 13 patients; median & tibial, 4; median, 5; tibial, 4) retrospectively. The SEP findings in patients were compared with those in normal controls. ResultsThe median SEP results indicated a conduction delay between the proximal brachial plexus and the primary sensory cortex, and tibial SEP findings indicated a delay between the dorsal gray matter of the lumbosacral cord and the primary sensory cortex. ConclusionThis is the first study to identify an impairment of the central somatosensory pathway in patients with chronic arsenic exposure. Sensory disturbance in these patients is related not only to peripheral neuropathy but also to impairment of the central nervous system.

Somatosensory evoked potential findings in ankylosing spondylitis.

Somatosensory evoked potential (SSEP) abnormalities were reported in patients with ankylosing spondylitis (AS). This study aimed to investigate SSEP abnormalities and its relation with clinical findings in AS patients. The study included 26 patients with AS and 17 age-matched health volunteers (Control for SSEP). Median nerve SSEP findings were normal in all AS cases. However, delayed latency and/or very low amplitude of tibial nerve SSEP was found in 20 (76.9%) AS patients. There were significant correlations between tibial SSEP latency and disease duration (R=0.433 to 0.635). There was also an inverse correlation between tibial SSEP amplitude and disease duration (R=-0.429, p=0.047). Serum estradiol level, hip total bone mineral density, The Bath Ankylosing Spondylitis Functional Index (BASFI) score and Beck depression score were significantly lower in AS patients with SSEP abnormalities (37.3±10.8 pg/mL, 0.916±0.123 g/cm(2), 35.0±27.9, 12.8±8.4, respectively) than in AS patients without SSEP abnormalities (53.7±12.3 pg/mL, 1.103±0.197 g/cm(2), 64.8±15.5, 24.8±10.1, respectively). Significant inverse correlations between SSEP latencies and dehydroepiandrosterone sulphate (DHEAS) levels were found (R=-0.400 to -0.713). There were also significant inverse correlation between SSEP latencies and DHEAS/oestrogen index (R=-0.596 to -0.868), and between SSEP latencies and DHEAS/Progesterone index (R=-0.467 to -0.685). As a conclusion, this study indicates that tibial nerve SSEP abnormalities are common in patients with AS and there are significant correlations between clinical findings of AS and SSEP abnormalities.

Somatosensory Evoked Potentials Help Prevent Positioning‐Related Brachial Plexus Injury during Skull Base Surgery

Evaluate the use of somatosensory evoked potentials (SSEP) monitoring to detect positioning-related brachial plexus injury during skull base surgery. Prospective cohort observational study. University Hospital. Patients undergoing skull base surgery had a focused neurologic exam of the brachial plexus performed before and after surgery. Under stable anesthesia, brachial plexus SSEP values were obtained before and after surgical positioning. Significant SSEP changes required a readjustment of arm or neck positions. SSEPs were assessed every 30 minutes. If changes were noted, position was readjusted and SSEPs were reassessed until surgical completion. Demographic data, neurologic exams, SSEP latency, and amplitude values were recorded. Persistent changes were correlated with postoperative neurologic findings. Sixty-five patients, 15 to 77 years old, were studied. Six patients (9.2%) developed SSEP amplitude changes after positioning (average amplitude decrease 72.8%). One patient had a significant latency increase. The sensitivity of SSEP for detection of injury was 57%, while specificity was 94.7%. The average body mass index (BMI) of patients with normal and abnormal SSEPs was 28.7 ± 5.6 versus 29.2 ± 8.0, respectively. Average BMI of patients with postoperative symptoms regardless of SSEP findings was 33.8 ± 4.3. Two patients who had persistent SSEP changes after positioning had BMIs of 40.1 and 31.2 kg/m(2), respectively. Improvement in neurologic findings occurred in all patients after surgery. This study demonstrates that upper extremity nerve stress can be detected in real time using SSEP and may be of value in protecting patients from nerve injury undergoing lateral skull base surgery.

Craniocervical decompression in patients with mucopolysaccharidosis VI: development of a scoring system to determine indication and outcome of surgery

To analyse diagnostic value of somato-sensory evoked potentials (SEP), magnetic resonance imaging (MRI), and clinical neurological examination in the decision for decompression surgery in mucopolysaccharidosis (MPS) VI patients with craniocervical cord compression (CCJ). We retrospectively analysed neurological examination, SEP of the median nerve and MRI outcomes from 31 MPS VI patients. Individual scores for each test (based on severity of findings) and a sum of scores of all three procedures (CCJ score) were evaluated for their potential to measure the need for and improvement after surgery. Differences between rapidly and slowly progressive patients were also evaluated. Fourteen patients (45 %) aged 4-34 years underwent decompression surgery. Median age at first operation was lower in rapidly than in slowly progressive patients (12 vs. 24 years; P = 0.008). Neurological and SEP findings but not MRI results differed significantly between non-operated and operated patients (P < 0.001, P = 0.003 and P = 0.08, respectively). A significant relationship was found between MRI and clinical neurological examination (P < 0.001) and between SEP and clinical neurological examination (P = 0.01) but not between MRI and SEP (P = 0.06). The CCJ score discriminated between operated and non-operated patients (4-9 points vs. 0-3 points; P < 0.001) and decreased in 61.5 % of patients after surgery. CCJ is common in rapidly and slowly progressive MPS VI patients. The CCJ score is an objective and transparent tool for assessing pathology of the CCJ, the need for surgery, and improvement after surgery.

Potenciales evocados auditivos del tronco cerebral y somatosensoriales en los pacientes con malformación de Chiari

Chiari malformations (CM) include a series of congenital anomalies involving the descent of the cerebellar tonsils below the foramen magnum, which may be associated with compression in the brainstem, upper spinal cord, and cranial nerves, consequently altering the responses of brainstem auditory evoked potentials (BAEP) and somatosensory evoked potentials (SSEP). However, only a small number of authors have described the indications of these tests in CM, and study groups to date have been small and heterogeneous. To review the results of BAEPs and SSEPs in published studies of patients with Chiari type 1 malformation (CM-1) or Chiari type 2 malformation (CM-2) as well as the indications of both tests in the diagnosis, treatment, and monitoring of both diseases, especially CM-1. We present a review article analyzing data from all published studies in Medline starting in 1966, located through PubMed, using combinations of the following keywords: 'Chiari malformation', 'Arnold-Chiari malformation', 'Chiari type 1 malformation', 'Arnold-Chiari type 1 malformation', 'evoked potentials', 'brainstem auditory evoked potentials' and 'somatosensory evoked potentials' as well as records of patients with CM-1 from the neurosurgery and neurophysiology departments at the Hospital Universitari Vall d'Hebron. Common findings of SSEP are a reduction in cortical amplitude from the posterior tibial nerve, a reduction or absence of cervical median nerve potential, and an increased N13-N20 interval. In BAEP, the most frequent findings are an increased I-V interval and a peripheral or cochlear auditory disturbance.

Correlation between transcranial motor and somatosensory-evoked potential findings in cervical myelopathy or radiculopathy during cervical spine surgery

Background: The correlation between electrophysiological recordings, MR images, and physical findings in cervical stenosis and cervical myelopathy are still open to debate. The goal of this study was to determine sensitivity of motor-evoked potential (MEP) and somatosensory-evoked potential (SSEP) in detecting cervical myelopathy and its correlates with the MRI findings in patients undergoing cervical spine surgeries.Method: Transcranial motor-evoked potentials (TcMEPs) and SSEPs were performed intraoperatively in 100 patients. The ‘baseline’ recordings of TcMEPs and SSEPs were correlated with patient’s physical findings as well as the MR images.Results: Posterior tibial and median nerves’ scalp SSEP latencies were increased in myelopathic patients compared to the radiculopathy group. MEPs recorded from distal muscles such as abductor pollicis brevis and adductor hallucis (AH) muscles were more likely to be absent in myelopathic patients compared with the patients with only radiculopathy. The myelopathic patients were more likely to have no response (NR) for the lower extremity SSEP test compared with radiculopathy patients.Conclusion: MEP shows more sensitivity toward detecting myelopathy which is correlated well with abnormal MR images.

The impact of subdural air collection on intraoperative motor and somatosensory evoked potentials: fact or myth?

Surgery in the semi-sitting position is susceptible to changes in motor (MEP) and somatosensory evoked potentials (SEPs), which are not related to neurological impairment. These changes have been suggested to be caused by the insulating effect of subdural air collection. This study sought to investigate the correlation of MEP and SEP final-to-baseline amplitude ratios to postoperative volumetry of frontoparietal subdural air collection. Median nerve SEP and hand MEP findings of 47 patients operated on in the semi-sitting position were compared with 7 patients operated on in the supine position. Computed tomography was routinely performed on the 1st postoperative day in all patients, and subdural air volumetry was calculated. Final-to-baseline MEP and SEP amplitude ratios were calculated and correlated to subdural air volumetry. SEP changed in 12 patients, and MEP changed in 7 patients. Postoperative subdural air collections were significantly different between the groups (semi-sitting group, mean 31.2 cm(3); supine group, mean 2 cm3; p = 0.000). For the SEP ratios, a moderate negative correlation with subdural volumetry was found in the semi-sitting group (p = 0.044). Conversely, there was no correlation in the subset of patients with SEP attenuation (p = 0.846). As concerns the MEP ratios, no correlation was demonstrated in any group (semi-sitting, p = 0.967; supine, p = 0.193). Although SEP amplitude reductions were associated with large subdural air collections, this was not observed in the subset of patients with SEP attenuation and for the MEP monitoring, suggesting other pathophysiological mechanisms, such as brain shift, for the artificial amplitude reduction.

Electrophysiological characterisation in hereditary spastic paraplegia type 5

Objective To assess in SPG5 hereditary spastic paraparesis (HSP) the involvement of the central (CNS) and the peripheral (PNS) nervous system by a multimodal electrophysiological approach. Methods Four patients belonging to three HSP families, with a molecular diagnosis of SPG5, underwent electrophysiological evaluation including electromyography (EMG) and nerve conduction study (NCS), motor-evoked potentials (MEPs) by transcranial magnetic stimulation (TMS) and somatosensory evoked potentials (SEPs) at upper and lower limbs, visual (VEPs) and brainstem auditory evoked potentials (BAEPs). In one patient, electrophysiological evaluation was performed twice at the age of 12 and 31 years. Results EMG and NCS were normal. MEPs and SEPs were abnormal in all patients along the central pathway for upper and/or lower limbs. VEPs revealed a damage of visual pathway and BAEPs showed the involvement of auditory pathway within the brainstem. In the patient who underwent electrophysiological follow-up, MEP and SEP findings were unmodified, whereas VEPs showed no reproducible responses. Conclusions We report an extensive electrophysiological evaluation of SPG5 and we confirm that the SPG5 phenotype may be broader than pure presentation. Significance Electrophysiological evaluation, showing diffuse CNS involvement with PNS sparing, could be very useful to address the molecular diagnosis and to follow-up a hypothetical treatment.

Thalamic infarction disrupts spinothalamocortical projection to the mid-cingulate cortex and supplementary motor area

Thalamic infarction presenting with heat anesthesia is rare. A 62-year-old man developed acute heat anesthesia and deep sensory disturbance in the right half of his body, but sensation for cold and pain was preserved. The resolution of these symptoms was accompanied by the gradual development of central dysesthesia. Magnetic resonance imaging (MRI) and computed tomography (CT) findings showed a small infarction in the left thalamic principal somatosensory nucleus (ventral caudal) and pulvinar. Single-photon emission CT showed hypoperfusion in the mid-cingulate cortex (mid-CC) and supplementary motor area (SMA), however, the primary and secondary somatosensory cortices were spared. Somatosensory-evoked potential findings were normal. The disruption of spinothalamocortical projection to the mid-CC and SMA is attributable to the development of central dysesthesia in the present case.

Analysis of motor and somatosensory evoked potentials during thoracic and thoracoabdominal aortic aneurysm repair

Use of motor evoked potentials (MEP) and somatosensory evoked potentials (SSEP) monitoring during thoracic and thoracoabdominal aortic surgery is controversial. This study evaluated the intraoperative use of SSEP and MEP during thoracoabdominal repair and assessed their role in decreasing the risk of spinal cord ischemia and paralysis. We conducted paired SSEP and MEP monitoring to assess agreement between the methods and their ability to predict neurologic outcome in 233 patients. Changes in SSEP and MEP monitoring were classified as no change, reversible change, or irreversible change during the intraoperative period and by the conclusion of surgery. Agreement between the methods was computed using the Cohen kappa statistic. Sensitivity, specificity, and positive and negative predictive values were computed for each method on the immediate and delayed neurologic deficit. Immediate neurologic deficit, determined immediately upon awakening from anesthesia and confirmed by a neurologist, occurred in eight of 233 (3.4%) patients. For any change (reversible plus irreversible), agreement between MEP and SSEP was relatively low (kappa = 0.53), despite being highly statistically significant (P < .001). MEP tended to overestimate SSEP for immediate neurologic deficit, demonstrating a 53% false-positive rate, compared with a 33% false-positive rate for SSEP (specificity ratio, 1.42; P < .0001). With irreversible change, agreement between the methods was 90% (kappa = 0.896, P < .0001). Only irreversible change was significantly associated with neurologic outcome (odds ratio, 21.9; P < .00001 for SSEP; 60.8, P < .0001 for MEP), but sensitivity and positive predictive values were low (37% and 33% for SSEP; 22% and 45% for MEP, respectively). Reversible changes in neurophysiologic monitoring were not significantly associated with immediate neurologic deficit. Negative predictive values for all negative evoked potential findings were >98% for immediate deficit. No evoked potential variables were associated with delayed deficit. SSEP and MEP monitoring were highly correlated only when intraoperative changes were irreversible. Reversible changes were not significantly associated with immediate neurologic deficit. Irreversible changes were significantly associated with immediate neurologic deficit, and the findings were identical for SSEP and MEP in this variable, indicating that the more complex MEP measures do not add further information to that obtained from SSEP. Normal SSEP and MEP findings had a strong negative predictive value, indicating that patients without signal loss are unlikely to awake with neurologic deficit.