Correlation between EEG spectral power and cerebral perfusion in patients with acute ischemic stroke.

Dry electrode electroencephalography (EEG) has the potential to diagnose ischemic stroke in the acute phase. In the current study we determined the correlation between EEG spectral power and ischemic stroke size and location as determined by computed tomography perfusion (CTP). Dry electrode EEG recordings were performed in patients with acute ischemic stroke in the emergency room. CTP preceded the EEG recordings as part of standard imaging protocol. Infarct core volume, total hypoperfused volume and local cerebral blood flow (CBF) were estimated with CTP. Additionally, global and local EEG spectral power were determined. We used Spearman's correlation coefficients to evaluate the correlation between variables. We included 27 patients (median age 72 [IQR:69-80] years, 15/27 [56%] men). Median CTP-to-EEG time was 32 (range:8-138) minutes. Hypoperfused volumes were estimated for 12/27 (44%) patients. Infarct core volume correlated best with global delta power (ρ = 0.76, p < 0.01), total hypoperfused volume with global alpha power (ρ = -0.58, p = 0.05), and local CBF with local alpha power (ρ = 0.43, p < 0.01). We conclude that dry electrode EEG signals slow down with increasing hypoperfused volume, which could potentially be used to discriminate between small and large ischemic strokes.

EEG in a four-electrode frontotemporal montage reliably predicts outcome after cardiac arrest.

AIM: To increase efficiency of continuous EEG monitoring for prognostication of neurological outcome in patients after cardiac arrest, we investigated the reliability of EEG in a four-electrode frontotemporal (4-FT) montage, compared to our standard nine-electrode (9-EL) montage. METHODS: EEG recorded with Ag/AgCl cup-electrodes at 12 and/or 24 h after cardiac arrest of 153 patients was available from a previous study. 220 EEG epochs of 5 minutes were reexamined in a 4-FT montage according to the ACNS criteria. Background classification was compared to the available 9-EL classification using Cohens kappa. Reliability for prognostication was assessed in 151 EEG epochs at 24 h after CA using sensitivity and specificity for prediction of poor (cerebral performance categories (CPC) 3-5) and good (CPC 1-2) neurological outcome. RESULTS: Agreement for EEG background classification between the two montages was substantial with a kappa of 0.85 (95%-CI 0.81-0.90). Specificity for prediction of poor outcome was 100% (95%-CI 95-100) for both montages, sensitivity was 31% (95%-CI 21-43) for the 4-FT montage and 35% (95%-CI 24-47) for the 9-EL montage. Good outcome was predicted with 65% specificity (95%-CI 53-76) and 81% sensitivity (95%-CI 71-89) for the 4-FT montage, similar to the 9-EL montage. CONCLUSION: In this cohort, EEG background patterns determined in a four-electrode frontotemporal montage predict both poor and good outcome after CA with similar reliability. Our results may contribute to decreasing the workload of EEG monitoring in patients after CA without compromising reliability of outcome prediction. However, validation in a larger cohort is necessary, as is a multimodal approach.

Post-Irradiation Facial Neuromyotonia/Myokymia: A Hemifacial Spasm Mimic.

Background: Hemifacial spasm is diagnosed on a clinical base, with certain atypical features alerting the physician for mimics. Phenomenology shown: Hemifacial neuromyotonia/myokymia characterized by tonic hemifacial contraction followed by multifocal undulating hemifacial twitches. Educational value: These features are a red flag for (post-irradiation) facial neuromyotonia/myokymia which generally responds well to low dose carbamazepine.

The diagnostic value of clinical neurophysiology in hyperkinetic movement disorders: A systematic review.

INTRODUCTION: To guide the neurologist and neurophysiologist with interpretation and implementation of clinical neurophysiological examinations, we aim to provide a systematic review on evidence of electrophysiological features used to differentiate between hyperkinetic movement disorders. METHODS: A PRISMA systematic search and QUADAS quality evaluation has been performed in PubMed to identify diagnostic test accuracy studies comparing electromyography and accelerometer features. We included papers focusing on tremor, dystonia, myoclonus, chorea, tics and ataxia and their functional variant. The features were grouped as 1) basic features (e.g., amplitude, frequency), 2) the influence of tasks on basic features (e.g., entrainment, distraction), 3) advanced analyses of multiple signals, 4) and diagnostic tools combining features. RESULTS: Thirty-eight cross-sectional articles were included discussing tremor (n = 28), myoclonus (n = 5), dystonia (n = 5) and tics (n = 1). Fifteen were rated as 'high quality'. In tremor, the basic and task-related features showed great overlap between clinical tremor syndromes, apart from rubral and enhanced physiological tremor. Advanced signal analyses were best suited for essential, parkinsonian and functional tremor, and cortical, non-cortical and functional jerks. Combinations of electrodiagnostic features could identify essential, enhanced physiological and functional tremor. CONCLUSION: Studies into the diagnostic accuracy of electrophysiological examinations to differentiate between hyperkinetic movement disorders have predominantly been focused on clinical tremor syndromes. No single feature can differentiate between them all; however, a combination of analyses might improve diagnostic accuracy.

The auditory startle response in relation to outcome in functional movement disorders.

BACKGROUND: The auditory startle reflex (ASR) is enlarged in patients with functional movement disorders (FMD). OBJECTIVES: To study whether the ASR relates to symptom reduction in FMD patients, who participated in a placebo controlled double blind treatment trial with Botulinum Neurotoxin (BoNT). METHODS: Response to treatment in the BoNT study was assessed using the Clinical Global Impression - Improvement scale (CGI-I). The electromyography (EMG) muscle activity of 7 muscles following 110 dB tones was measured in 14 FMD patients before and after one-year treatment and compared to 11 matched controls. The early and a late (behaviorally affected) component of the ASR and the sympathetic skin response (SSR) were assessed. RESULTS: 10 of 14 patients (71.4%) showed symptom improvement, which was believed to be mainly caused by placebo effects. The early total response probability of the ASR at baseline tended to be larger in patients compared to controls (p = 0.08), but normalized at follow-up (p = 0.84). The late total response probability was larger in patients vs. controls at baseline (p < 0.05), a trend that still was present at follow-up (p = 0.08). The SSR was higher in patients vs. controls at baseline (p < 0.01), and normalized at follow-up (p = 0.71). CONCLUSIONS: On a group level 71.4% of the patients showed clinical symptom improvement after treatment. The early part of the ASR, most likely reflecting anxiety and hyperarousal, normalized in line with the clinical improvement. Interestingly, the augmented late component of the ASR remained enlarged suggesting persistent altered behavioral processing in functional patients despite motor improvement.

Dystonic neck muscles show a shift in relative autospectral power during isometric contractions.

OBJECTIVE: To identify effects of a deviant motor drive in the autospectral power of dystonic muscles during voluntary contraction in cervical dystonia patients. METHODS: Submaximal (20%) isometric head-neck tasks were performed with the head fixed, measuring surface EMG of the sternocleidomastoid, splenius capitis and semispinalis capitis in CD patients and controls. Autospectral power of muscle activity, and head forces was analyzed using cumulative distribution functions (CDF). A downward shift between the theta/low alpha-band (3-10Hz) and the high alpha/beta-band (10-30Hz) was detected using the CDF10, defined as the cumulative power from 3 to 10Hz relative to power from 3 to 30Hz. RESULTS: CDF10 was increased in dystonic muscles compared to controls and patient muscles unaffected by dystonia, due to a 3-10Hz power increase and a 10-30Hz decrease. CDF10 also increased in patient head forces. CONCLUSIONS: Submaximal isometric contractions with the head fixed provided a well-defined test condition minimizing effects of reflexive feedback and tremor. We associate shifts in autospectral power with prokinetic sensorimotor control. SIGNIFICANCE: Analysis of autospectral power in isometric tasks with the head fixed is a promising approach in research and diagnostics of cervical dystonia.

Spectral EMG Changes in Cervical Dystonia Patients and the Influence of Botulinum Toxin Treatment.

Botulinum toxin (BoNT) injections in the dystonic muscles is the preferred treatment for Cervical Dystonia (CD), but the proper identification of the dystonic muscles remains a challenge. Previous studies showed decreased 8-14 Hz autospectral power in the electromyography (EMG) of splenius muscles in CD patients. Cumulative distribution functions (CDF's) of dystonic muscles showed increased CDF10 values, representing increased autospectral powers between 3 and 10 Hz, relative to power between 3 and 32 Hz. In this study, we evaluated both methods and investigated the effects of botulinum toxin. Intramuscular EMG recordings were obtained from the splenius, semispinalis, and sternocleidomastoid muscles during standardized isometric tasks in 4 BoNT-naïve CD patients, 12 BoNT-treated patients, and 8 healthy controls. BoNT-treated patients were measured 4-7 weeks after their last BoNT injections and again after 11-15 weeks. We found significantly decreased 8-14 Hz autospectral power in splenius muscles, but not in the semispinalis and sternocleidomastoid muscles of CD patients when compared to healthy controls. CDF10 analysis was superior in demonstrating subtle autospectral changes, and showed increased CDF10 values in all studied muscles of CD patients. These results did not change significantly after BoNT injections. Further studies are needed to investigate the origin of these autospectral changes in dystonia patients, and to assess their potential in muscle selection for BoNT treatment.

Startle responses in functional jerky movement disorders are increased but have a normal pattern.

BACKGROUND: Exaggerated startle reactions have been frequently described in patients with functional movement disorders (FMD). Long onset latencies and inconsistent recruitment pattern are thought to be a hallmark in these patients. The auditory startle reflex has not been systematically assessed though. OBJECTIVES: Assessing the frequency and pattern of the early and late component of the auditory startle response in patients with functional jerky movement disorders. METHODS: A case-control design was used to study 17 patients with functional jerky movement disorders and 15 healthy gender- and age-matched control subjects. The auditory startle reflex was elicited by 108 dB loud tones and assessed with electromyography in multiple muscles. RESULTS: Response probability of the early and the late response were significantly enlarged in patients with FMD. The early response showed a normal muscle recruitment pattern whereas the late response revealed a more variable pattern compared to controls. The early and late responses showed normal habituation in both groups. Remarkably, a high response rate of the abdominal muscle was noted especially in patients suffering from abdominal jerks. CONCLUSIONS: This study shows enlarged, but normally patterned early startle responses in FMD. The high response frequency of the late responses found in these patients reflects a behavioral component. Hypersensitivity to external stimuli, often noted in FMD is supported by high response probabilities of both components of the auditory startle response.

Ataxia, dystonia and myoclonus in adult patients with Niemann-Pick type C.

BACKGROUND: Niemann-Pick type C (NP-C) is a rare autosomal recessive progressive neurodegenerative disorder caused by mutations in the NP-C 1 or 2 gene. Besides visceral symptoms, presentation in adolescent and adult onset variants is often with neurological symptoms. The most frequently reported presenting symptoms of NP-C in adulthood are psychiatric symptoms (38 %), cognitive decline (23 %) and ataxia (20 %). Myoclonus can be present, but its value in early diagnosis and the evolving clinical phenotype in NP-C is unclear. In this paper we present eight Dutch cases of NP-C of whom five with myoclonus. METHODS: Eight patients with genetically confirmed NP-C were recruited from two Dutch University Medical Centers. A structured interview and neuropsychological tests (for working and verbal memory, attention and emotion recognition) were performed. Movement disorders were assessed using a standardized video protocol. Quality of life was evaluated by questionnaires (Rand-36, SIP-68, HAQ). In four of the five patients with myoclonic jerks simultaneous EEG with EMG was performed. RESULTS: A movement disorder was the initial neurological symptom in six patients: three with myoclonus and three with ataxia. Two others presented with psychosis. Four experienced cognitive deficits early in the course of the disease. Patients showed cognitive deficits in all investigated domains. Five patients showed myoclonic jerks, including negative myoclonus. In all registered patients EEG-EMG coherence analysis and/or back-averaging proved a cortical origin of myoclonus. Patients with more severe movement disorders experienced significantly more physical disabilities. CONCLUSIONS: Presenting neurological symptoms of NP-C include movement disorders, psychosis and cognitive deficits. At current neurological examination movement disorders were seen in all patients. The incidence of myoclonus in our cohort was considerably higher (63 %) than in previous publications and it was the presenting symptom in 38 %. A cortical origin of myoclonus was demonstrated. Our data suggest that myoclonus may be overlooked in patients with NP-C. All patients scored significantly lower on physical domains of HRQoL. Symptomatic treatment of movement disorders may improve physical functioning and subsequently HRQoL.

Determinants of disability in cervical dystonia.

BACKGROUND: Cervical dystonia (CD) is characterized by involuntary muscle contractions causing abnormal postures and/or twisting movements of the head and neck. These motor symptoms can have a major impact on disability. Treatment with botulinum toxin injections aims to reduce motor symptoms, and therefore disability. Despite motor improvements, many patients still experience difficulties with performing daily life activities. To optimize treatment, other factors that determine disability should be identified. OBJECTIVE: To explore and identify clinical characteristics that relate to disability in CD. METHODS: Data on disability, severity of dystonia, anxiety, depression, pain and quality of life of 96 CD patients was analyzed with a principal component analysis (PCA). Multiple regression analysis was performed to determine which components derived from the PCA explain most of the variance in disability. RESULTS: PCA revealed five components (disability, psychiatric features, pain, physical function and severity of dystonia), explaining 74.4% of the variance in disability. Multivariate association between disability and the other components was statistically significant (R2 change 0.433, F change (4-86) = 22.39, p = .000). Psychiatric features had the largest contribution to disability (standardized beta = 0.555, p = 0.000) followed by pain (standardized beta = 0.232 p = 0.004). Physical functioning (standardized beta = 0.059 p = 0.507) and severity of dystonia (standardized beta = -0.001 p = 0.991) had no significant contribution. CONCLUSIONS: In CD patients, psychiatric features and pain are important determinants of disability. Interventions to reduce psychiatric problems and pain should have a more prominent role in the treatment of CD patients in order to improve disability levels.

Improved identification of dystonic cervical muscles via abnormal muscle activity during isometric contractions.

BACKGROUND: The preferred treatment for cervical dystonia (CD) is injection of botulinum toxin in the dystonic muscles. Unfortunately, in the absence of reliable diagnostic methods it can be difficult to discriminate dystonic muscles from healthy muscles acting in compensation. We investigated if dystonic muscle activation patterns could be identified in cervical dystonia patients during a harmonized isometric contraction task. Furthermore, we investigated whether dystonia worsens at higher levels of voluntary contraction, which might further improve the identification of dystonic muscle activity. METHODS: An isometric device was used to investigate muscle activation during voluntary contraction tasks in 10 controls and 10 CD patients. Surface electromyography (EMG) of the sternocleidomastoidus, splenius capitis, and semispinalis capitis muscles was evaluated during a rest task and when performing submaximal (20%) and maximal voluntary contractions for eight head transversal force directions and for head twist. Two measures were developed to identify dystonic activation: 1) Muscle activity in the contraction direction in which the contribution of the muscle was lowest (Minimum EMG), and 2) the average muscle activity over all contraction directions (Total Mean EMG). RESULTS: Patients showed increased dystonic activity in the rest task and during submaximal contractions relative to controls, but not during maximal contractions. Increases in Minimum EMG indicated an inability of patients to deactivate dystonic muscles counteracting the task. Increases in Total Mean EMG indicated dystonic activity in all task directions. During maximal contractions these effects were absent in dystonic muscles. Dystonia is therefore found not to worsen at higher levels of isometric voluntary contraction. The activity of dystonic muscles modulated with different loading directions similar to controls. Using Minimum EMG 54% of the muscles clinically diagnosed as dystonic and 91% of non-dystonic muscles were predicted correctly. CONCLUSIONS: Dystonic muscle activity was found in cervical dystonia patients during submaximal contractions in all task directions using a harmonized isometric task, but no differences were found during maximal contractions. With some adaptation this method may prove useful to identify dystonic muscles.

EMG coherence and spectral analysis in cervical dystonia: discriminative tools to identify dystonic muscles?

OBJECTIVE: Botulinum toxin injections in the dystonic muscles are the preferred treatment for cervical dystonia (CD), but proper selection of the dystonic muscles remains a challenge. We investigated the use of EMG coherence and autospectral analysis as discriminative tools to identify dystonic muscles in CD patients. METHODS: We compared the occurrence of 8-14 Hz autospectral peaks and 4-7 Hz intermuscular coherences between 10 CD patients and 10 healthy controls. Secondly, we compared the muscles with significant 4-7 Hz coherences with the muscles that were selected clinically for botulinum toxin treatment. RESULTS: Autospectral peaks between 8 and 14 Hz were significantly more often absent in the splenius capitis (SPL) muscles of CD patients compared to controls (p<0.01). Contrary to previous findings, there was no significant difference in the occurrence of 4-7 Hz intermuscular coherences between patients and controls and the diagnostic accuracy of coherence analysis to identify the clinically dystonic muscles was low. CONCLUSION: Intermuscular EMG coherence analysis cannot reliably discriminate patients from controls. Autospectral changes in the SPL muscles are a more discriminative feature of CD. In patients, coherence analysis does not seem to be a reliable method to identify dystonic muscles. The clinical relevance and the origin of the autospectral changes need further study.

Cervical dystonia: improved treatment response to botulinum toxin after referral to a tertiary centre and the use of polymyography.

RATIONALE: Cervical dystonia is the most common form of (primary) dystonia. The first line of treatment for cervical dystonia is intramuscular injections with botulinum toxin. To optimise the response to botulinum toxin proper muscles selection is required. Pre-treatment polymyographic EMG in addition to clinical evaluation is hypothesised to be a good tool to improve muscle selection and treatment outcome. OBJECTIVE: To determine the efficacy of botulinum toxin treatment after adjacent polymyographic EMG in cervical dystonia patients referred to our tertiary referral centre with an unsatisfactory response to botulinum toxin treatment elsewhere. METHODS: We performed a retrospective analysis of 40 consecutive second opinion cervical dystonia patients. Standard polymyographic EMG was performed before treatment. We retrieved the Tsui scores and subjective evaluations from the first visit, after 12 weeks and after one year of treatment. In addition, we assessed the final outcome of treatment in our centre based on the records and asked the patients for their personal opinion about the effect of referral to our centre on their treatment response. RESULTS: After one year of treatment there was a significant improvement on both the Tsui scores (p < 0.01) and the subjective treatment evaluation (p < 0.001.) On their last visit 60% of the patients still continued treatment with a reasonable to good response. CONCLUSION: A substantial amount of CD patients with an unsatisfactory response to botulinum toxin improved after polymyography and subsequent treatment with botulinum toxin in a tertiary referral centre.

The long-term follow-up of treatment with corticosteroid injections in patients with carpal tunnel syndrome. When are multiple injections indicated?

The objective of this prospective study was to investigate the long-term effect of one or more local corticosteroid injections in patients with carpal tunnel syndrome and whether a good response can be predicted. Follow-up visits took place at 3 weeks, 6 months, and 1 year after the first corticosteroid injection. Thirty of the 120 patients (25%) had a good outcome with a single injection, 11 additional patients (9%) needed a second injection, and five patients (4%) needed a third injection to reach a good outcome after 1 year. Of patients with an initial good treatment response, 28 (52%) had a good outcome after 1 year compared with 18 (27 %) who had an initially moderate or no response to treatment. One-third of patients with carpal tunnel syndrome had a long-term beneficial effect from corticosteroid injection, especially when they had a good initial response.

How to tackle tremor - systematic review of the literature and diagnostic work-up.

BACKGROUND: Tremor is the most prevalent movement disorder in clinical practice. It is defined as involuntary, rhythmic, oscillatory movements. The diagnostic process of patients with tremor can be laborious and challenging, and a clear, systematic overview of available diagnostic techniques is lacking. Tremor can be a symptom of many diseases, but can also represent a distinct disease entity. OBJECTIVE: The objective of this review is to give a clear, systematic and step-wise overview of the diagnostic work-up of a patient with tremor. The clinical relevance and value of available laboratory tests in patients with tremor will be explored. METHODS: We systematically searched through EMBASE. The retrieved articles were supplemented by articles containing relevant data or provided important background information. Studies that were included investigated the value and/or usability of diagnostic tests for tremor. RESULTS: In most patients, history and clinical examination by an experienced movement disorders neurologist are sufficient to establish a correct diagnosis, and further ancillary examinations will not be needed. Ancillary investigation should always be guided by tremor type(s) present and other associated signs and symptoms. The main ancillary examination techniques currently are electromyography and SPECT imaging. Unfortunately, many techniques have not been studied in large prospective, diagnostic studies to be able to determine important variables like sensitivity and specificity. CONCLUSION: When encountering a patient with tremor, history, and careful clinical examination should guide the diagnostic process. Adherence to the diagnostic work-up provided in this review will help the diagnostic process of these patients.

Muscle selection for treatment of cervical dystonia with botulinum toxin--a systematic review.

RATIONALE: Cervical dystonia, also called spasmodic torticollis, is the most common form of (primary) dystonia. Intramuscular injections with botulinum toxin are the first line of treatment for cervical dystonia. To optimise the treatment response to botulinum toxin correct muscles should be selected. Clinical evaluation is important for muscle selection but the value of additional tests to identify dystonic muscles remains unclear. OBJECTIVE: To evaluate all relevant literature regarding the best approach to select dystonic muscles for treatment with botulinum toxin. METHODS: We conducted a systematic review of studies that had investigated methods of selecting muscles for treatment with botulinum toxin. In addition, we compared all prospective botulinum toxin trials using either clinical evaluation or polymyographic electromyography for muscle selection. RESULTS: Forty relevant studies were included and polymyographic electromyography recordings were most often employed. In several studies, polymyographic electromyography revealed a different pattern of muscle involvement compared to that found during clinical evaluation. In one randomized controlled trial polymyographic electromyography significantly improved the outcome of botulinum toxin treatment. A limited number of studies used positron emission tomography -computed tomography imaging or frequency analysis of the electromyography signal to identify dystonic muscles but their effect on the outcome of treatment has never been studied. CONCLUSION: Polymyographic electromyography may improve the outcome of botulinum toxin treatment in cervical dystonia, but evidence is limited and larger studies are needed.

Normalization of the auditory startle reflex after symptom reduction in children with anxiety disorders.

BACKGROUND: In an earlier study the Auditory Startle Response (ASR) of anxiety disordered (AD) children proved to be enlarged. This study examines in a controlled design to what extent this increase is responsive to symptom reduction during Cognitive Behavioral Therapy (CBT) METHODS: The activity of 6 muscles following 104 dB tones in 20 patients (M = 12,7 years; SD = 2.5) and 25 matched controls was measured with an electromyogram (EMG). In addition, the sympathetic skin response was investigated. Response to treatment was investigated with the Anxiety Disorder Interview Schedule for Children (ADIS-C) and the Spence Children's Anxiety Scale (SCAS). RESULTS: Treatment responders (n = 12) showed a significant ASR decrease over time, whereas non-responders (n = 8) showed a significant ASR increase or no significant ASR difference. In controls, the ASR was not significantly different at follow up compared to baseline. The sympathetic skin response was stable in controls and treatment responders but significantly increased over time in treatment non-responders. Linear regression suggested that one of the ASR pre-treatment parameters (multiple muscle EMG magnitude) predicts treatment response. CONCLUSIONS: The ASR decreases in AD children when anxiety symptoms diminish. In addition, the ASR may be useful in predicting response to CBT in AD children.

Increased saccadic rate during smooth pursuit eye movements in patients at Ultra High Risk for developing a psychosis.

Abnormalities in eye tracking are consistently observed in schizophrenia patients and their relatives and have been proposed as an endophenotype of the disease. The aim of this study was to investigate the performance of patients at Ultra High Risk (UHR) for developing psychosis on a task of smooth pursuit eye movement (SPEM). Forty-six UHR patients and twenty-eight age and education matched controls were assessed with a task of SPEM and psychiatric questionnaires. Our results showed that both the corrective and non-corrective saccadic rates during pursuit were higher in the UHR group. There were however no differences in smooth pursuit gain between the two groups. The saccadic rate was related to positive UHR symptoms. Our findings indicate that abnormalities in SPEM are already present in UHR patients, prior to a first psychotic episode. These abnormalities occur only in the saccadic system.

Somatosensory evoked potentials during mild hypothermia after cardiopulmonary resuscitation.

OBJECTIVE: In patients who remain in a coma after cardiopulmonary resuscitation (CPR), the bilateral absence of cortical N20 responses of median nerve somatosensory evoked potentials (SSEP) 24 hours after admission invariably correlates with a poor neurologic outcome. Nowadays, CPR patients are treated with mild hypothermia, with simultaneously administered sedative drugs, hampering clinical neurologic assessment. We investigated whether SSEP performed during hypothermia can reliably predict a poor neurologic outcome. METHODS: Between July 2006 and April 2008, this multicenter prospective cohort study included adult comatose patients admitted after CPR and treated with induced mild hypothermia (32-34 degrees C). SSEP was performed during hypothermia, and in patients who remained comatose after rewarming, a second SSEP was performed. Neurologic outcome was assessed 30 days after admission with the Glasgow Outcome Scale. RESULTS: Seventy-seven consecutive patients were included in 2 hospitals. In 13 patients (17%), the cortical N20 response during hypothermia was bilaterally absent. In 9 of these 13 patients in whom SSEP could be repeated during normothermia, the N20 response was also absent, yielding a positive predictive value of 1.00 (95% confidence interval [CI] 0.70-1.00). All 13 patients with absent SSEP during hypothermia had a poor neurologic outcome, yielding a positive predictive value of 1.00 (95% CI 0.77-1.00). CONCLUSIONS: The results of this pilot study show that bilaterally absent cortical N20 responses of median nerve somatosensory evoked potentials performed during mild hypothermia after resuscitation can predict a poor neurologic outcome. We started a larger multicenter prospective cohort study to confirm these results.