Is impulsivity in remitted bipolar disorder a stable trait? A meta-analytic review

Objective

To review scores on measures of impulsivity in remitted bipolar disorder.

Data source

We used keywords “impulsivity and bipolar” and “impulsivity and mania” to narrow down our search on Medline, EMBASE and Psychinfo to include those studies that had reported impulsivity scores using validated and reliable assessment measures in remitted bipolar disorder (both I and II). We searched all English language studies from 1990 to October 2012.

Study Selection

Nineteen reports met the inclusion criteria and were reviewed by two abstractors independently.

Data abstraction

We generated weighted mean differences (WMDs) from pooled data using RevManager 5.0 from Cochrane analysis.

Results

The Barratt Impulsivity Scale (BIS) 11 was the instrument most commonly used. Nineteen studies met the inclusion criteria, of which 2 were excluded due to incomplete data. A WMD of 12.8 was observed for BIS 11 total scores, 4.3 on the motor component, 4.1 on the cognitive and 7.6 on the non-planning components of the BIS 11 respectively.

Conclusion

Impulsivity is significantly higher in remitted bipolar patients than normal controls. Non-planning impulsivity is a key domain affected in bipolar disorder, which may represent a stable trait.     

Impulsivity in children and adolescents with mood disorders and unaffected offspring of bipolar parents

Objective

Increased impulsivity seems to be present across all phases of bipolar disorder (BD). Impulsivity may therefore represent an endophenotype for BD, if it is also found among normal individuals at high genetic risk for mood disorders. In this study, we assessed impulsivity across four different groups of children and adolescents: patients with BD, major depressive disorder (MDD) patients, unaffected offspring of bipolar parents (UO), and healthy controls (HC).

Subjects and Methods

52 patients with BD, 31 with MDD, 20 UO, and 45 HC completed the Barratt Impulsiveness Scale (BIS-11), an instrument designed to measure trait impulsivity.

Results

UO displayed significantly higher total BIS-11 impulsivity scores than HC (p = 0.02) but lower scores than BD patients (F = 27.12, p < 0.01). Multiple comparison analysis revealed higher BIS-11 total scores among BD patients when compared to HC (p < 0.01) and UO (p < 0.01). MDD patients had higher BIS-11 scores when compared to HC (p < 0.01). Differences between MDD patients and UO, as well as between MDD and BD patients, were not statistically significant.

Conclusion

Our findings suggest that trait impulsivity is increased among children and adolescents with mood disorders, as well as in unaffected individuals at high genetic risk for BD.     

Assessment of implicit self-esteem in bipolar manic and euthymic patients using the implicit association test

Objective

Although self-esteem is thought to be an important psychological factor in bipolar disorder, little is known about implicit and explicit self-esteem in manic patients. In this study, we investigated differences in implicit and explicit self-esteem among bipolar manic patients, bipolar euthymic patients, and healthy controls using the Implicit Association Test (IAT).

Methods

Participants included 19 manic patients, 27 euthymic patients, and 27 healthy controls. Participants completed a self-esteem scale to evaluate explicit self-esteem and performed the self-esteem IAT to evaluate implicit self-esteem.

Results

There were no differences among groups in explicit self-esteem. However, there were significant differences among groups in implicit self-esteem. Manic patients had higher IAT scores than euthymic patients and a trend toward higher IAT scores than healthy controls.

Conclusions

Our findings suggest that, on the latent level, a manic state is not simply the opposite of a depressed state. Furthermore, there may be a discontinuity of implicit self-esteem between manic and euthymic states. These unexpected results may be due to characteristics of the study participants or the methods used to assess implicit self-esteem. Nevertheless, they provide greater insights on the psychological status of manic patients.     

Age-grouped differences in bipolar mania

Objective

This review of published studies compares scores on individual items of mania rating scales that systematically recorded symptom severity in persons diagnosed with bipolar disorder to identify age-grouped differences.

Methods

An extensive literature search identified item scores from mania rating scales, with a particular emphasis on baseline Young Mania Rating Scale (YMRS) item scores in published double-blind, placebo-controlled studies of bipolar I manic disorder. These baseline YMRS item scores were assessed as a proportion of the total YMRS score and compared by age group. Additional YMRS item/total scores in subjects with bipolar spectrum disorders were added to expand the analysis.

Results

Preadolescents with bipolar disorder had significantly higher YMRS item scores than adolescents on aggression, irritability, and motor activity. Young Mania Rating Scale baseline item scores relative to the YMRS total score revealed that adolescents diagnosed with bipolar I mania scored comparatively higher than did adults on YMRS aggression and irritability items, whereas adults with bipolar I manic disorder scored comparatively higher on the grandiosity and sexual interest items. Age-grouped findings from subjects diagnosed with bipolar I, II, and Not Otherwise Specified (NOS) disorders yielded similar age-grouped results.

Conclusion

In age-grouped YMRS item assessments of bipolar mania, anger dyscontrol was most prominent for youth, whereas disordered thought content was paramount for adults.     

Temperament and character traits in patients with bipolar disorder and associations with attempted suicide

Objective

This study was intended to investigate temperament and character traits in bipolar disorder patients with or without a history of attempted suicide.

Methods

One hundred nineteen patients diagnosed with euthymic bipolar disorder based on Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision, and with no accompanying Axis I and II comorbidity, and 103 healthy controls were included. Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Axis I and II disorders were used to exclude Axis I and II comorbidity. Temperament and character traits of bipolar patients with a history attempted suicide (25.2%, n = 30) or without (74.8%, n = 89) and of the healthy volunteers were determined using the Temperament and Character Inventory. The association between current suicide ideation and temperament and character traits was also examined.

Results

Bipolar patients with or without a history of attempted suicide had higher harm avoidance (HA) scores compared with the healthy controls. Persistence scores of bipolar patients with no history of attempted suicide were lower than those of the healthy controls. Self-directedness (SD) scores of the bipolar patients with a history of attempted suicide were lower than those of patients with no such history. Self-transcendence scores of bipolar patients with no history of attempted suicide were lower than those of both the healthy controls and of those patients with a history of attempted suicide. A positive correlation was determined between current suicidal ideation scale scores and HA, and a negative correlation between SD and cooperativeness was determined.

Conclusions

High harm avoidance may be a temperament trait specific to bipolar disorder patients. However, it may not be correlated with attempted suicide in such patients. These may have low persistence, high SD and low self-transcendence temperament and character traits that protect against attempted suicide. Harm avoidance, SD, and cooperativeness may be correlated with current suicidal ideation.     

Validation of the Italian version Inventory of Complicated Grief (ICG): A study comparing CG patients versus bipolar disorder,PTSD and healthy controls

Background

A minority (9%–20%) of bereaved individuals experience symptoms of persistent intense grief associated with significant distress and impairment. This recently identified distinct post-loss syndrome has been variously named complicated grief, prolonged grief disorder, traumatic grief and persistent complex bereavement disorder. The Inventory of Complicated Grief (ICG) is a self-report instrument used to reliably identify this syndrome. We undertook a study to: 1) validate the Italian version of the ICG; 2) examine its performance in a clinical of bereaved individuals with complicated grief, post-traumatic stress disorder, bipolar disorder and healthy controls.

Methods

Study participants included 171 bereaved individuals clinically diagnosed with complicated grief (n=64); post-traumatic stress disorder (n=72); bipolar disorder (n=35) and 58 bereaved healthy controls. Assessments included the Structured Clinical Interview for DSM-IV Axis I disorders (SCID-I/P) and the Italian version of the ICG.

Results

The mean total ICG score was significantly different among the study groups [F(3.228) = 94.19, p < .001]. Post-hoc Games–Howell comparisons indicated significantly higher scores in complicated grief patients with respect to the other three groups and significantly lower scores in healthy controls compared to all other participants. The scale demonstrated a high level of internal consistency: Cronbach’s alpha value for the whole sample was 0.947. Factor analyses demonstrated a single-factor solution.

Conclusions

This study provides evidence of the validation of the Italian version of the ICG, tested in a large and well-characterized clinical help-seeking population. These data further support the existence of a unique grief-related syndrome different from bipolar and post-traumatic stress disorders.     

The loudness dependence of the auditory evoked potential (LDAEP) in schizophrenia,bipolar disorder,major depressive disorder,anxiety disorder,and healthy controls

Background

Serotonergic dysfunction in schizophrenia, bipolar disorder, major depressive disorder, anxiety disorder, and healthy controls was evaluated by measuring the activity of the loudness dependence of the auditory evoked potential (LDAEP).

Methods

The 357 subjects who were evaluated comprised 55 normal controls, 123 patients with major depressive disorder, 37 with bipolar disorder, 46 with schizophrenia, 37 with panic disorder (PD), 31 with generalized anxiety disorder (GAD), and 28 with post-traumatic stress disorder (PTSD).

Results

LDAEP was significantly stronger in healthy controls than in patients with either bipolar disorder (p = 0.025) or schizophrenia (p = 0.008), and significantly stronger in patients with major depressive disorder than in those with bipolar disorder (p = 0.01) or schizophrenia (p = 0.03). LDAEP did not differ significantly between patients with major depressive disorder and healthy control subjects (p = 0.667), or between healthy control subjects and patients with anxiety disorder, including PD (p = 0.469), GAD (p = 0.664), and PTSD (p = 0.167).

Conclusion

The findings of the present study reveal that patients with major psychiatric disorders exhibit different strengths of LDAEP according to their serotonin-related pathology. Studies controlled for psychotropic medication, menstruation cycle, and smoking are needed.     

Coping profiles in bipolar disorder

Objective

As coping responses have the capacity to distinctly influence the illness course in affective disorders, they form targets for psychological intervention. Beneficial effects have been reported for interventions incorporating adaptive coping in bipolar disorder. Identification of differential coping preferences in bipolar disorder sub-types has etiological and clinical implications. As most studies to date have focused exclusively on bipolar I disorder, the current study examines coping profiles in those with a bipolar I or II disorder, contrasted with unipolar depressive and healthy controls.

Methods

Groups were derived on the basis of agreement between clinician and DSM-IV diagnoses. Participants (94 bipolar I, 114 bipolar II, 109 unipolar recurrent depression, 100 healthy controls) completed coping style measures including the Brief Cope, Responses to Positive Affect questionnaire, Response Styles Questionnaire, the Coping Inventory for Prodromes of Mania, and the Cognitive Emotion Regulation Questionnaire.

Results

Bipolar (I and II) participants were more likely than unipolar participants to ruminate about positive affect, and engage in risk taking when faced with negative affect. Medication status and current mood symptoms influenced risk-taking scores in the bipolar sub-sets, however rumination about positive affect appeared to represent a trait-like response in those with a bipolar II disorder. Behavioral coping strategies differentiated bipolar sub-types, with bipolar II participants being less likely to seek support when faced with stress, and less likely to engage in strategies to down-regulate hypomania.

Conclusion

Coping style differences were observed between bipolar sub-types. Further consideration of such differentiating characteristics should serve to direct the focus towards specific targets for clinical intervention, reflecting nuances integral to the differing conditions.     

Cognitive endophenotypes in OCD: A study of unaffected siblings of probands with familial OCD

Background

Impairments in executive functions and non-verbal memory are considered potential endophenotype markers of obsessive–compulsive disorder (OCD). For the neuropsychological deficits to be considered endophenotypes, they should be demonstrable in unaffected family members.

Aim

To compare the neuropsychological performance in unaffected siblings of probands with familial OCD with that of individually matched healthy controls.

Methods

Twenty-five unaffected siblings of OCD probands with familial OCD, and 25 individually matched healthy controls were assessed with tests of attention, executive function, memory and intelligence.

Results

Unaffected siblings showed significant deficits in tests of decision making and behavioural reversal i.e., the Iowa Gambling Task (IGT) and the Delayed Alternation Test (DAT) respectively, but performed adequately in other tests.

Conclusions

Our study suggests that the deficits in decision making and behavioural reversal could be potential endophenotypes in OCD. These deficits are consistent with the proposed neurobiological model of OCD involving the orbitofrontal cortex. Future studies could couple cognitive and imaging strategies to identify neurocognitive endophenotypes in homogenous samples of OCD.     

Brain GABA levels in patients with bipolar disorder

Purpose

A growing body of research supports an important role for GABA in the pathophysiology of bipolar and other mood disorders. The purpose of the current study was to directly examine brain GABA levels in a clinical sample of bipolar patients.

General methods

We used magnetic resonance spectroscopy (MRS) to examine whole brain and regional GABA, glutamate and glutamine in 13 patients with bipolar disorder compared to a matched group of 11 healthy controls.

Findings

There were no significant differences in GABA, glutamate or glutamine between patients and controls.

Conclusions

Further research is needed to better characterize the GABAergic and glutamatergic effects of pharmacotherapy, anxiety comorbidity and clinical state in bipolar disorder.     

Autobiographical memory and its association with neuropsychological function in bipolar disorder

Objective

The aim of this study was to investigate the overgeneralization of autobiographical memory (AM) in bipolar disorder (BD) and assess its association with multiple cognitive domains.

Method

Twenty-eight clinically stable bipolar I patients and an equal number of age- and gender-matched healthy controls (HC) were included. All participants were examined using the autobiographical memory test (AMT) and the neuropsychological battery including the general intelligence, attention, verbal memory, verbal fluency, visual memory, and executive functions domain. Demographic, clinical, and test variables were compared between BD and HC groups. Correlation analyses of AMT scores with cognitive functions were performed within each group, controlling for demographic and clinical variables.

Results

Total and negative scores of AMT were significantly lower in BD patients compared to HC individuals. AMT scores were significantly correlated with WAIS similarities, WCST perseverative errors, and WCST categories completed in BD, whereas AMT scores were correlated with verbal memory and verbal fluency in HC.

Conclusion

Our findings suggest that overgeneral AM is a characteristic of BD and is related to executive function. Future studies should investigate the benefit of additional treatment focusing on overgeneral AM in BD.     

Motor inhibition and cognitive flexibility in pathologic skin picking

Background

Individuals with pathologic skin picking (PSP) often report significant difficulty resisting the urges and drive to engage in picking behavior. Studies have shown significant inhibitory deficiencies (i.e. increased impulsivity) in subjects with other putative obsessive–compulsive spectrum disorders, such as trichotillomania, using objective tests. This study sought to assess motor inhibitory control and aspects of cognitive flexibility in a sample of individuals with PSP.

Method

Twenty subjects with PSP (mean age 33.1 ± 14.3 years; 85% female) and 20 healthy controls (mean age 31.6 ± 9.1 years; 85% female) underwent cognitive assessments using the Stop-signal and Intra-dimensional/Extra-dimensional (ID/ED) set-shift tasks. Groups were matched for age, gender, and education.

Results

PSP was associated with significantly impaired stop-signal reaction times but intact ID/ED cognitive flexibility compared to controls. Measures of disease severity in the PSP subjects did not covary significantly with stop-signal performance.

Conclusion

The finding of impaired inhibitory control but intact set-shift cognitive flexibility draws remarkable parallels with findings in trichotillomania but differs from obsessive compulsive disorder. These findings have important implications for understanding potential neurobiological dysfunction in PSP, how the disorder should be classified, and suggest new potential treatment directions.     

Metacognitions and emotional schemas: a new cognitive perspective for the distinction between unipolar and bipolar depression

Introduction

Clinicians need to make the differential diagnosis of unipolar and bipolar depression to guide their treatment choices. Looking at the differences observed in the metacognitions, and the emotional schemas, might help with this differentiation, and might provide information about the distinct psychotherapeutical targets.

Methods

Three groups of subjects (166 unipolar depressed, 140 bipolar depressed, and 151 healthy controls) were asked to fill out the Metacognitions Questionnaire–30 (MCQ-30), and the Leahy Emotional Schema Scale (LESS). The clinicians diagnosed the volunteers according to the criteria of DSM-IV-TR with a structured clinical interview (MINI), and rated the moods of the subjects with the Montgomery Asberg Depression Rating Scale (MADRS), and the Young Mania Rating Scale (YMRS). Statistical analyses were undertaken to identify the group differences on the MCQ-30, and the LESS.

Results

The bipolar and unipolar depressed patients' scores on the MCQ-30 were significantly different from the healthy controls, but not from each other. On the LESS dimensions of guilt, duration, blame, validation, and acceptance of feelings, all three groups significantly differed from each other. There were no statistically different results on the LESS dimensions of comprehensibility, consensus, and expression. The mood disordered groups scored significantly different than the healthy controls on the LESS dimensions of simplistic view of emotions, numbness, rationality, rumination, higher values, and control.

Conclusions

These results suggest that the metacognitive model of unipolar depression might be extrapolated for patients with bipolar depression. These results are also compatible to a great extent with the emotional schema theory of depression.     

The ALDH2 and 5-HT2A genes interacted in bipolar-I but not bipolar-II disorder

Objective

Clarifying the similarities and differences between the two most common subtypes of bipolar disorder, bipolar-I and bipolar-II, is essential for improving our understanding of them. Because the serotonergic system has been implicated in the pathogenesis of bipolar disorder, it may be important to investigate genes such as the aldehyde dehydrogenase 2 (ALDH2) and serotonin 2A receptor genes, which are involved in metabolizing serotonin and encoding serotonin receptors. We examined the association of the ALDH2 and 5-HT2A-A1438G polymorphisms with bipolar I and II and possible interactions between these genes.

Methods

One thousand forty-nine participants were recruited: 249 with bipolar-I, 456 with bipolar-II, and 344 healthy controls. The genotypes of the ALDH2 and 5HT2A-A1438G polymorphisms were determined using polymerase chain reactions plus restriction fragment length polymorphism analysis.

Results

Logistic regression analysis showed a significant effect of the ALDH2 and the 5-HT2A-A1438G polymorphisms, and a significant interaction effect for the A/G genotypes of the 5-HT2A-A1438G polymorphism and the ALDH2*1*1 genotypes (p = 0.004) discriminated between bipolar-I patients and controls without bipolar disorder. These polymorphisms, however, were not associated with bipolar-II disorder.

Limitations

The significant differences of age and gender between patients and controls limit the comparison, although statistical adjustments were made for them.

Conclusion

Our findings provide initial evidence that the ALDH2 and 5-HT2A genes interact in bipolar-I but not in bipolar-II disorder. Our findings suggest a unique genetic distinction between bipolar-I and bipolar-II.     

Childhood trauma and dissociation in tertiary care patients with migraine and tension type headache: A controlled study

Objective

The aims of this study were: i) to compare the severity of somatoform and psychoform dissociation and childhood trauma among migraine patients, tension-type headache patients (TTH), and healthy controls; and, ii) to identify any relationships between headache characteristics and dissociative symptoms and traumatic childhood experiences among tertiary care patients with headache.

Methods

The study sample consisted of 79 patients with migraine, 49 patients with TTH and 40 healthy controls. They completed the socio-demographic form, Childhood Trauma Questionnaire (CTQ), Dissociative Experiences Scale (DES), and the Somatoform Dissociation Questionnaire (SDQ).

Results

The average score for childhood emotional abuse was significantly higher in the TTH and migraine patients than in healthy controls; mean scores for emotional neglect and physical abuse were higher in TTH patients than healthy controls; and the total CTQ score was higher in TTH patients than in either migraine patients or healthy controls. Average DES scores were significantly higher in TTH patients versus migraine patients and controls; and SDQ scores were higher in both headache groups than in controls. Headache duration and severity were found to be significantly related to childhood abuse scores among migraine but not TTH patients.

Conclusion

Our findings support the evidence of a relationship between childhood trauma and migraines, and suggest that childhood traumatic events are common and deleteriously effect migraine characteristics. Also our study suggests that childhood trauma may have a role in TTH. Significant differences in the DES and SDQ scores between groups may be explained by the differences in childhood trauma experiences.     

Dimensions affectives et impulsives dans le trouble bipolaire et le trouble de la personnalité borderline

Background

Studies have shown that patients with borderline personality disorder are often misdiagnosed to have bipolar disorder and conversely. Indeed, a number of characteristics common to both disorders could explain this problem: emotional instability as well as impulsivity represent confounding factors and contribute to the risk of misdiagnosis. However, it appears that these characteristics manifest themselves in different ways according to the pathology. The aim of the study is to show differences between affective lability, emotional intensity and impulsivity dimensions. The clinical aim is to refine bipolar disorder and borderline personality disorder diagnosis, to improve psychological care for these patients in the long-term.

Preattentive dysfunction in bipolar disorder: A MEG study using auditory mismatch negativity

Background

Neuropsychological studies have demonstrated that cognitive dysfunction represents pathophysiological mechanisms underlying bipolar disorder. However, information processing deficits in bipolar disorder have not often been examined electrophysiologically. Here, we examined preattentive processing and sensory information processing using mismatch field (MMNm) and P1m components, respectively, using magnetoencephalography.

Methods

Ten patients with bipolar disorder and 20 healthy volunteers participated in the study. The participants were presented with auditory stimuli sequences comprising standard and deviant stimuli. MMNm was elicited in response to changes in duration and frequency of pure-tone stimuli and a vowel across-category change.

Results

The magnetic global field power of MMNm in the right hemisphere under the pure-tone condition was significantly delayed in patients with bipolar disorder compared to healthy volunteers, and that of P1m did not differ between the two groups. The MMNm dipole in the left hemisphere was located inferior in patients with bipolar disorder than in healthy volunteers. This finding did not correlate with clinical symptoms.

Conclusions

Information processing at the preattentive level is impaired in patients with bipolar disorder irrespective of clinical symptoms, and this dysfunction is not due to sensory level dysfunction. The quality of preattentive information processing impairment is different between patients with bipolar disorder and patients with major depressive disorder, as shown by the MMNm latency and power differences.     

Subcortical brain volumes relate to neurocognition in schizophrenia and bipolar disorder and healthy controls

Background

Similar patterns of subcortical brain abnormalities and neurocognitive dysfunction have been demonstrated in schizophrenia and bipolar disorder, with more extensive findings in schizophrenia. It is unknown whether relationships between subcortical volumes and neurocognitive performance are similar or different between schizophrenia and bipolar disorder.

Methods

MRI scans and neuropsychological test performance were obtained from 117 schizophrenia or 121 bipolar spectrum disorder patients and 192 healthy control subjects. Using the FreeSurfer software, volumes of 18 selected subcortical structures were automatically segmented and analyzed for relationships with results from 7 neurocognitive tests.

Results

In schizophrenia, larger left ventricular volumes were related to poorer motor speed, and bilateral putamen volumes were related to poorer verbal learning, executive functioning and working memory performance. In bipolar disorder, larger left ventricular volumes were related to poorer motor speed and executive functioning. The relationship between left putamen volume and working memory was specific to schizophrenia. The relationships between left inferior lateral ventricles and motor speed and between right putamen volumes and executive functioning were similar in schizophrenia and bipolar disorder, and different from healthy controls. The results remained significant after corrections for use of antipsychotic medication. Significant structure-function relationships were also found when all subjects were combined into one group.

Conclusion

The present findings suggest that there are differences as well as similarities in subcortical structure/function relationships between patients with schizophrenia or bipolar disorder and healthy individuals. The observed differences further suggest that ventricular and putamen volume sizes may reflect severity of cognitive dysfunction in these disorders.     

SCN8A as a novel candidate gene associated with bipolar disorder in the Han Chinese population

Background

Bipolar disorder (BPD) is a common, severe and recurrent psychiatric disorder. It has been suggested that BPD patients have a higher risk of suicide than patients with any other psychiatric illnesses. A recent study found that suicide attempt was associated with the SCN8A gene, which has been mapped close to one of the BPD susceptibility loci. Thus, SCN8A is likely to be a candidate gene for BPD.

Methods

In this study, three SNPs (rs1601012, rs303810, rs60637) were analyzed in 506 bipolar patients and 507 controls of Han origin.

Results

We found that two individual SNPs showed statistically significant differences between cases and controls in both allele and genotype distribution, but only rs303810 was still significant in allele distribution (p = 0.0164) after correction. No obvious linkage disequilibrium or haplotypes were observed among these SNPs.

Conclusion

Our results indicate that SCN8A may be a potential susceptibility gene for bipolar disorder in the Han Chinese population.     

The latency distribution of motor evoked potentials in patients with multiple sclerosis

Objective

To compare the individual latency distributions of motor evoked potentials (MEP) in patients with multiple sclerosis (MS) to the previously reported results in healthy subjects (Firmin et al., 2011).

Methods

We applied the previously reported method to measure the distribution of MEP latencies to 16 patients with MS. The method is based on transcranial magnetic stimulation and consists of a combination of the triple stimulation technique with a method originally developed to measure conduction velocity distributions in peripheral nerves.

Results

MEP latency distributions in MS typically showed two peaks. The individual MEP latency distributions were significantly wider in patients with MS than in healthy subjects. The mean triple stimulation delay extension at the 75% quantile, a proxy for MEP latency distribution width, was 7.3 ms in healthy subjects and 10.7 ms in patients with MS.

Conclusions

In patients with MS, slow portions of the central motor pathway contribute more to the MEP than in healthy subjects. The bimodal distribution found in healthy subjects is preserved in MS.

Significance

Our method to measure the distribution of MEP latencies is suitable to detect alterations in the relative contribution of corticospinal tract portions with long MEP latencies to motor conduction.