Transcranial direct current stimulation of the motor cortex induces distinct changes in thermal and mechanical sensory percepts

Objective

The aim of this single-blinded, complete crossover study was to evaluate the effects of tDCS on thermal and mechanical perception, as assessed by quantitative sensory testing (QST).

Methods

QST was performed upon the radial part of both hands of eight healthy subjects (3 female, 5 male, 25–41 years of age). These subjects were examined before and after cathodal, anodal or sham tDCS, applied in a random order. TDCS was administered for 15 min at a 1 mA current intensity, with the active electrode placed over the left primary motor cortex and the reference electrode above the right orbit.

Results

After cathodal tDCS, cold detection thresholds (CDT), mechanical detection thresholds (MDT), and mechanical pain thresholds (MPT) significantly increased in the contralateral hand, when compared to the baseline condition.

Conclusions

Cathodal tDCS temporarily reduced the sensitivity to A-fiber mediated somatosensory inputs.

Significance

Impairment of these somatosensory percepts suggests a short-term suppression of lemniscal or suprathalamic sensory pathways following motor cortex stimulation by cathodal tDCS.     

How should sensory function in the oropharynx be tested? Cold thermal testing; a comparison of the methods of levels and limits

Objective

Several studies indicate an upper airway peripheral neuropathy in obstructive sleep apnea syndrome (OSAS). The sensation of cold, as measured by cold detection thresholds (CDT), in the oropharynx has been shown to be compromised in patients with sleep apnea and, to a lesser extent, habitual snoring. To reveal whether this neuropathy is part of the pathogenetic process of OSAS, longitudinal studies of snorers are needed. The objective of the present study was to establish the test–retest repeatability for the two most commonly used thermal testing methods: the reaction time exclusive method of levels (MLE) and the method of limits (MLI).

Methods

Forty non-snoring subjects were tested at the soft palate and the lip at two separate occasions (mean interval 45 days) using a Medoc TSA – 2001 equipment with an intra-oral thermode.

Results

With MLE mean CDT’s were lower for both the lip and soft palate than with MLI. However, MLI showed a better test–retest repeatability (r = 2.2 vs. 2.6) for the soft palate.

Conclusions

MLI should be used in longitudinal studies. The performance of this method is also faster.

Significance

We have established a quick, safe and reliable method suitable for longitudinal studies of peripheral neuropathy in sleep apnea pathogenesis.     

Quantitative assessment of cutaneous thermal and vibration sensation and thermal pain detection thresholds in healthy children and adolescents

Quantitative sensory testing (QST) is a noninvasive, computer-assisted method for assessing function in peripheral small and large sensory fibers. In order to use QST for clinical neurological assessment in children, it is necessary: (1) to determine whether children can reliably perform these tests and (2) to characterize normal ranges in healthy children. Values of cold sensation, warm sensation, cold pain, heat pain, and vibration sensation detection thresholds were determined in the hand and foot with the method of limits (MLI) and method of levels (MLE) in 101 healthy children aged 6-17 years using a commercially available device. Both MLI and MLE were well-accepted by children, and there was good reproducibility between two sessions. The MLE takes longer to perform but produces lower thermal detection thresholds than the MLI. In the MLI, vibration and warm sensation showed higher thresholds in the foot than hand, whereas cold pain showed lower thresholds in the foot than hand. Based on these results, QST may be used to document and monitor the clinical course of sensory abnormalities in children with neurological disorders or neuropathic pain.     

Prevalence of silent myocardial ischemia in single and multiple lacunar infarcts and large vessel disease stroke

Background and purpose

The relationships between single (SLI) and multiple lacunar infarcts (MLI) and occult coronary artery disease (CAD) have not yet been sufficiently evaluated. We aimed to investigate the prevalence of silent CAD in patients with SLI, MLI and large vessel disease (LVD) stroke, and to identify factors associated with its presence.

Methods

We enrolled 125 patients who had suffered their first non-cardioembolic ischemic stroke but had no documented history of CAD. According to their pathologies, these patients were assigned to one of three groups: MLI (n = 21), SLI (n = 50) or LVD (n = 54). Asymptomatic CAD was detected by myocardial perfusion SPECT imaging.

Results

Silent CAD was detected in 40 patients (32% of the total); of those that experienced CAD, 15 (30%) were from the SLI group, 7 (33%) had MLI, and 18 (33%) had an LVD stroke. Differences between the groups were not significant. During a median follow-up of 48 months, the overall stroke recurrence was 8.8%; the stroke recurrence rates for each subgroup were 6% in patients with SLI, 7% in LVD and 19% in MLI. Mortality was higher in patients from the MLI and LVD groups (26% and 14%, respectively) than in those from the SLI group (6%; p = 0.02). We found no relationships between the various risk factors and silent CAD.

Conclusions

In this exploratory study, SPECT imaging results revealed that the prevalence of abnormal myocardial perfusion was similar in patients with either single or multiple lacunar infarcts and those that had experienced large vessel disease stroke.     

Vestibular evoked myogenic potentials and habituation to seasickness

Objective

Seasickness may impose severe limitations on the performance of ships’ crew. Cervical vestibular evoked myogenic potentials (cVEMP) assess the function of the saccule, the organ responsible for monitoring vertical linear acceleration, which has been found to be the most provocative motion stimulus in the evolution of motion sickness. We used the cVEMP test in a prospective evaluation of susceptibility and habituation to seasickness.

Methods

Forty-six naval recruits underwent the cVEMP test before exposure to sea conditions. After 6 months’ sailing experience, participants completed a questionnaire evaluating their initial and current seasickness severity. Based on their most recent experience, subjects were divided into three groups: non-vomiting non-habituating (NV-NH), vomiting (V), and non-vomiting habituating (NV-H).

Results

Statistically significant lower thresholds for cVEMP were found in subjects who habituated to sea conditions (NV-H), compared with those remaining severely susceptible (V) (77.0 dB HL vs. 84.9 dB HL; p < 0.01).

Conclusions

The ability to produce the cVEMP at lower thresholds represents a broader dynamic range, in which the reflex can respond to a wider array of stimuli amplitudes.

Significance

The present study demonstrates the potential of the cVEMP test for predicting future habituation to seasickness.     

Assessment of the performances of AcuStar HIT and the combination with heparin-induced multiple electrode aggregometry: A retrospective study

Background

Early diagnosis of immune heparin-induced thrombocytopenia (HIT) is challenging. HemosIL® AcuStar HIT and heparin-induced multiple electrode aggregometry (HIMEA) were recently proposed as rapid diagnostic methods.

Objectives

We conducted a study to assess performances of AcuStar HIT-IgG (PF4-H) and AcuStar HIT-Ab (PF4-H). The secondary objective was to compare the performances of the combination of Acustar HIT and HIMEA with standardised clinical diagnosis.

Methods

Sera of 104 suspected HIT patients were retrospectively tested with AcuStar HIT. HIMEA was performed on available sera (n = 81). The clinical diagnosis was established by analysing in a standardized manner the patient’s medical records. These tests were also compared with PF4-Enhanced®, LTA, and SRA in subsets of patients. Thresholds were determined using ROC curve analysis with clinical outcome as reference.

Results

Using the recommended thresholds (1.00 AU), the negative predictive value (NPV) of HIT-IgG and HIT-Ab were 100.0% (95% CI: 95.9%-100.0% and 95.7%-100.0%). The positive predictive value (PPV) were 64.3% (95% CI: 35.1%-87.2.2%) and 45.0% (95% CI: 23.2%-68.6%), respectively. Using our thresholds (HIT-IgG: 2.89 AU, HIT-Ab: 9.41 AU), NPV of HIT-IgG and HIT-Ab were 100.0% (95% CI: 96.0%-100.0% and 96.1%-100.0%). PPV were 75.0% (95% CI: 42.7%-94.5%) and 81.8% (95% CI: 48.3%-97.7%), respectively. Of the 79 patients with a medium-high pretest probability score, 67 were negative using HIT-IgG (PF4-H) test at our thresholds. HIMEA was performed on HIT-IgG positive patients. Using this combination, only one patient on 79 was incorrectly diagnosed.

Conclusion

Acustar HIT showed good performances to exclude the diagnosis of HIT. Combination with HIMEA improves PPV.     

Rapid exclusion of the diagnosis of immune HIT by AcuStar HIT and heparin-induced multiple electrode aggregometry

Background

Accurate diagnosis of heparin-induced thrombocytopenia (HIT) is essential but remains challenging. We have previously demonstrated, in a retrospective study, the usefulness of the combination of the 4Ts score, AcuStar HIT and heparin-induced multiple electrode aggregometry (HIMEA) with optimized thresholds.

Objectives

We aimed at exploring prospectively the performances of our optimized diagnostic algorithm on suspected HIT patients. The secondary objective is to evaluate performances of AcuStar HIT-Ab (PF4-H) in comparison with the clinical outcome.

Methods

116 inpatients with clinically suspected immune HIT were included. Our optimized diagnostic algorithm was applied to each patient. Sensitivity, specificity, negative predictive value (NPV), positive predictive value (PPV) of the overall diagnostic strategy as well as AcuStar HIT-Ab (at manufacturer’s thresholds and at our thresholds) were calculated using clinical diagnosis as the reference.

Results

Among 116 patients, 2 patients had clinically-diagnosed HIT. These 2 patients were positive on AcuStar HIT-Ab, AcuStar HIT-IgG and HIMEA. Using our optimized algorithm, all patients were correctly diagnosed. AcuStar HIT-Ab at our cut-off (> 9.41 U/mL) and at manufacturer’s cut-off (> 1.00 U/mL) showed both a sensitivity of 100.0% and a specificity of 99.1% and 90.4%, respectively.

Conclusion

The combination of the 4Ts score, the HemosIL® AcuStar HIT and HIMEA with optimized thresholds may be useful for the rapid and accurate exclusion of the diagnosis of immune HIT.     

Corticospinal excitability during walking in humans with absent and partial body weight support

Objective

To establish changes in corticospinal excitability with absent and partial body weight support (BWS), and determine test–retest reliability of motor evoked potentials (MEPs) recordings during stepping in healthy humans.

Methods

The tibialis anterior (TA) and soleus MEPs during stepping at 0 and at 25 BWS were recorded in two experimental sessions in the same subjects. Transcranial magnetic stimulation was delivered randomly across the step cycle at 1.2 × TA MEP resting threshold. The non-stimulated associated electromyogram (EMG) was subtracted from the TA and soleus MEPs at identical time windows and bins of the step cycle, and the resultant values were normalized to the maximal homologous EMG activity during stepping. The relationship between MEPs and background EMG activity was determined for each BWS level and session tested.

Results

The TA MEPs were facilitated at heel contact, progressively decreased during the stance phase, and facilitated throughout the swing phase of the step cycle. In contrast, the soleus MEPs were progressively increased at early-stance, depressed at the stance-to-swing transition, and remained depressed throughout the swing phase. The TA and soleus MEPs were modulated in a similar pattern across sessions at 0 and at 25 BWS, and were linearly related to the associated background EMG activity.

Conclusions

These results provide evidence that reduced body weight loading does not alter the strength of corticospinal excitability, and that MEPs can be reliably recorded at different sessions during stepping in healthy humans.

Significance

A rehabilitation strategy to restore gait in neurological disorders utilizes BWS during stepping on a motorized treadmill. Based on our findings, the strength of corticospinal drive will not be affected negatively during stepping under conditions of partial body loading.     

Clinical usefulness of the Spanish version of the Mississippi Aphasia Screening Test (MASTsp): validation in stroke patients

Objective

Clinical validation of the Spanish version of the Mississippi Aphasia Screening Test (MASTsp) as a screening test for language disorders in patients who have suffered a stroke.

Material and methods

A total of 29 patients who had suffered a stroke and had aphasia after a left hemispheric lesion were evaluated with the MASTsp, the Boston Diagnostic Aphasia Examination and the Token Test at baseline and after six months of rehabilitation. Two expert speech-therapists evaluated twelve aphasic patients to determine the inter-observer reliability. This sample was assessed twice in the same week to analyse the reproducibility of the test (test-retest reliability). Aphasic patients were compared with a matched sample of non-aphasic patients with vascular lesions in the right hemisphere (n =29) and a group of healthy subjects (n=60) stratified by age and educational level.

Results

The MASTsp showed a good convergent validity, interobserver validity, test-retest reliability and a moderate sensitivity to detect changes over time. A diagnostic cut-off <90 on the MASTsp total test score is proposed.

Conclusions

The MASTsp is a valid tool for the detection and monitoring of language problems in patients with stroke.     

After-discharges and seizures during pediatric extra-operative electrical cortical stimulation functional brain mapping: Incidence,thresholds, and determinants

Objective

This study examined the incidence, thresholds, and determinants of electrical cortical stimulation (ECS)-induced after-discharges (ADs) and seizures.

Behavioral techniques for attenuating the expression of fear associations in an animal model of anxiety

Background and objectives

Recent data indicate that extinguished fear often returns when the testing conditions differ from those of treatment. Several manipulations including extensive extinction training, extinction in multiple contexts, and spacing the extinction trials and sessions reduce the return of fear. Moreover, extensive extinction and extinction in multiple contexts summate in reducing return of fear, and the spacing of the extinction trials and the spacing of extinction sessions summate in reducing return of fear. Here we evaluated whether these techniques also attenuate the context specificity of latent inhibition, and whether they summate to further decrease fear responding at test.

Methods

In two experiments, with rats as subjects in a lick suppression preparation, we assessed the effects of massive CS preexposure, CS preexposure in multiple contexts, and of spacing the CS-preexposure trials and sessions, in reducing the context specificity of latent inhibition.

Results

Fear responding was attenuated by all four manipulations. Moreover, extensive CS preexposure in multiple contexts, and conjoint spacing of the CS-preexposure trials and sessions, were more effective in reducing the context specificity of latent inhibition than each manipulation alone.

Limitations

Our experimental designs evaluated degrees of context specificity of latent inhibition but omitted groups in which latent inhibition was assessed without a context shift away from the context of latent inhibition treatment. This precluded us from drawing conclusions concerning absolute (as opposed to relative) levels of recovery from latent inhibition.

Conclusions

Techniques effective in decreasing the return of conditioned fear following extinction are also effective in decreasing the context specificity of latent inhibition in an animal model of anxiety. Fear and anxiety disorders might be prevented in anxious human participants with the same techniques used here, but that is still an empirical question.     

Efficacy of body exposure as treatment component for patients with eating disorders

Background and objectives

Body exposure and cognitive restructuring are well known interventions in cognitive-behavioral therapies for patients with eating disorders. Though promising, little is known about the impact of body exposure on body dissatisfaction, overvaluation of weight and shape and other aspects of eating disorder psychopathology. Thus, the aim of the two studies presented here is to evaluate the efficacy of mirror exposure and video exposure on body dissatisfaction, weight and shape concerns and other aspects of eating disorder psychopathology.

Method study 1

Fourteen women diagnosed with Eating Disorders Not Otherwise Specified (EDNOS; DSM-IV-TR) were treated in repeated mirror exposure sessions. Assessments were carried out before (baseline) and after body exposure.

Results study 1

Measures of body dissatisfaction, shape concerns and eating disorder psychopathology were significantly improved at the post treatment assessment.

Method study 2

Thirteen women with Bulimia Nervosa (BN; DSM-IV-TR) received repeated mirror and video exposure sessions. Measures were assessed before (baseline) and after body exposure.

Results study 2

Body image dissatisfaction was significantly improved at post treatment assessment.

Limitations

These preliminary results are based on subjective data from two small clinical samples. Comparisons between the studies are limited by design variations.

Conclusions

The studies provide evidence that body exposure is a promising technique for treatment of body dissatisfaction in EDNOS and BN. Moreover, in EDNOS shape concern and aspects of eating disorder psychopathology were improved after body exposure. Reasons for the lack of change in shape and weight concern as well as in eating disorder psychopathology in BN are discussed.     

Modulation of visual evoked potentials by high-frequency repetitive transcranial magnetic stimulation in migraineurs

Objective

High-frequency repetitive transcranial magnetic stimulation (rTMS) modulates cortical excitability. We investigated its effect on visual evoked potentials (VEPs) in migraine.

Methods

Thirty-two headache-free controls (CO), 25 interictal (MINT) and 7 preictal migraineurs (MPRE) remained after exclusions. VEPs to 8′ and 65′ checks were averaged in six blocks of 100 single responses. VEPs were recorded before, directly after and 25 min after 10 Hz rTMS. The study was blinded for diagnosis during recording and for diagnosis and block number during analysis. First block amplitudes and habituation (linear amplitude change over blocks) were analysed with repeated measures ANOVA.

Results

With 65′ checks, N70-P100 habituation was reduced in MINT compared to CO after rTMS (p = 0.013). With 8′ checks, habituation was reduced in MPRE compared to MINT and CO after rTMS (p < 0.016). No effects of rTMS on first block amplitudes were found.

Conclusion

RTMS reduced habituation only in migraineurs, indicating increased responsivity to rTMS. The magnocellular visual subsystem may be affected interictally, while the parvocellular system may only be affected preictally.

Significance

Migraineurs may have increased responsiveness to rTMS because of a cortical dysfunction that changes before a migraine attack.     

Aptitude–Treatment interaction effects in psychooncological interventions

Objective

To examine aptitude–treatment interaction (ATI) effects in cancer patients receiving psychooncological interventions (POIs).

Method

N= 36 cancer patients were treated with POI. Hierarchical linear regression was used to test two interaction effects between patient baseline characteristics (aptitudes) and process analyses of therapy sessions (treatment) on change in mental health during POI.

Results

Patients with high emotional distress did best when their therapy reduced arousal, and patients with lower emotional distress benefited most if therapists emphasized arousal induction. The interaction between the coping style of the patient (internalizing vs. externalizing) and the focus of the treatment (emotion vs. behavior) did not predict POI outcomes.

Conclusions

The ATI effect of patient's distress and therapist's arousal induction/reduction may help therapists to make differential treatment decisions in POI. Tailoring treatments to cancer patients based on their personal characteristics may enhance the effectiveness of POI.     

Enhancing plasticity through repeated rTMS sessions: The benefits of a night of sleep

Objective

Previous work has demonstrated that corticospinal facilitation from 20 Hz repetitive transcranial magnetic stimulation (rTMS) was greater during a second rTMS session 24 h after the first. We sought to determine whether such metaplasticity is dependent on a particular phase of the normal sleep–wake/circadian cycle.

Methods

Twenty healthy participants received two sessions of 20 Hz rTMS over the hand motor cortex (M1) spaced 12 h apart, either over-day or overnight.

Results

Baseline corticospinal excitability did not differ by group or session. The time-of-day of Session 1 did not influence the relative increase in excitability following rTMS. However, the increase in excitability from the second rTMS session was 2-fold greater in the overnight group.

Conclusions

When a night with sleep follows rTMS to M1, the capacity to induce subsequent plasticity in M1 is enhanced, suggesting sleep–wake and/or circadian-dependent modulation of processes of metaplasticity.

Significance

TMS treatment of neuropsychiatric disorders entails repeated sessions of rTMS. Our findings suggest that the timing of sessions relative to the sleep–wake/circadian cycle may be a critical factor in the cumulative effect of treatment. Future studies using this paradigm may provide mechanistic insights into human metaplasticity, leading to refined strategies to enhance non-invasive stimulation therapies.     

Pseudo-subarachnoid hemorrhage: A potential imaging pitfall associated with spontaneous intracranial hypotension

Objective

(1) To determine the frequency of CT mimics of subarachnoid hemorrhage (SAH) in a large cohort of subjects with spontaneous intracranial hypotension (SIH). (2) To emphasize the distinctive radiologic features of SIH.

Patients and methods

CT scans of 95 subjects with SIH were retrieved and reviewed to search for findings of pseudo-SAH (CT mimics of SAH in the absence of blood).

Results

Pseudo-SAH radiologic findings (increased attenuation in the basilar cisterns, sylvian fissures, or along the tentorium) were detected on CT scans of 10 of the 95 SIH subjects. However, on MRI scans, these subjects exhibited the typical SIH abnormalities (diffuse pachymeningeal enhancement and brain sagging with obliteration of basilar cisterns).

Conclusions

In the emergency room, SIH should be considered in the differential diagnosis between SAH and pseudo-SAH. Although SIH and SAH can share some radiologic features, SIH has distinctive MRI and CT findings. Their recognition should obviate the need for more invasive procedures (e.g., cerebral angiography) to definitely rule out SAH and an aneurismal source of bleeding.     

Impact of pulse duration in single pulse TMS

Objective

The intensity of transcranial magnetic stimulation (TMS) is typically adjusted by changing the amplitude of the induced electrical field, while its duration is fixed. Here we examined the influence of two different pulse durations on several physiological parameters of primary motor cortex excitability obtained using single pulse TMS.

Methods

A Magstim Bistim² stimulator was used to produce TMS pulses of two distinct durations. For either pulse duration we measured, in healthy volunteers, resting and active motor thresholds, recruitment curves of motor evoked potentials in relaxed and contracting hand muscles as well as contralateral (cSP) and ipsilateral (iSP) cortical silent periods.

Results

Motor thresholds decreased by 20% using a 1.4 times longer TMS pulse compared to the standard pulse, while there was no significant effect on threshold adjusted measurements of cortical excitability. The longer pulse duration reduced pulse-to-pulse variability in cSP.

Conclusions

The strength of a TMS pulse can be adjusted both by amplitude or pulse duration. TMS pulse duration does not affect threshold-adjusted single pulse measures of motor cortex excitability.

Significance

Using longer TMS pulses might be an alternative in subjects with very high motor threshold. Pulse duration might not be relevant as long as TMS intensity is threshold-adapted. This is important when comparing studies performed with different stimulator types.     

Estudios normativos españoles en población adulta joven (proyecto NEURONORMA jóvenes): normas para las pruebas Visual Object and Space Perception Battery y Judgment of Line Orientation

Introduction

The Visual Object and Space Perception Battery (VOSP) and Judgment of Line Orientation tests (JLO) are used in clinical practice to assess visuoperceptual and visuospatial abilities.

Objective

In this study, as part of the Spanish normative studies project in young adults (NEURONORMA young adults), we present normative data for a short version of the VOSP test and for the JLO test.

Material and methods

The sample consisted of 179 participants who are cognitively normal and range in age from 18 to 49 years. Tables are provided to convert raw scores to scaled scores. Education- and sex-adjusted scores were obtained by applying linear regression techniques.

Results

Our results show that education and sex only affect scores on the JLO test, and that age has no effect.

Conclusions

The normative data obtained will be extremely useful in the clinical evaluation of young Spanish adults.     

Differential CT features of acute lentiform subdural hematoma and epidural hematoma

Objectives

Acute subdural hematoma (SDH) normally appears as a panhemispheric collection of blood with a crescent configuration. However, a number of SDH show lentiform appearances, mimicking acute epidural hematoma (EDH). In this study, we reported our experiences with this special disease entity. Radiological features that aided in the accurate localization of the hematoma were also addressed.

Patients and methods

From among 51 acute SDH cases who were surgically treated between July 2007 and April 2008, five cases whose SDH had a localized convex appearance were enrolled. Surgical records and CT images were retrospectively reviewed. Important CT features that could differentiate lentiform SDH from EDH were especially analyzed.

Results

Subdural adhesions were major causes of localized SDH in four out of five patients, all of whom had previous neurosurgical interventions or radiotherapy. Though those hematomas appeared as biconvex on CT scans, four differential features could be identified in favor of SDH. These included a crescentic tail, an obtuse angle at the margin of the hematoma, a dural line above the hematoma and a direct connection to the underlying intracerebral hematomas.

Conclusions

Biconvex localized SDH might be misinterpreted as acute EDH if the diagnosis is based on the shape of the hematoma alone. This study emphasized that a detailed evaluation of surgical histories and CT features are mandatory in differentiating lentiform SDH and EDH.