Caffeine and cortical excitability, as measured with paired-pulse transcranial magnetic stimulation.

INTRODUCTION/AIMS: The transcranial magnetic stimulation tests of short-interval intracortical inhibition (SICI) by both conventional amplitude measurements (A-SICI) and threshold-tracking (T-SICI) are important methods to investigate intracortical inhibitory circuits, and T-SICI has been proposed to aid the diagnosis of amyotrophic lateral sclerosis. Beverages containing caffeine are widely consumed, and caffeine has been reported to affect cortical excitability. The aim of this study was to determine whether these SICI tests are affected by caffeine. METHODS: Twenty-four healthy subjects (13 females, 11 males, aged from 19 to 31, mean: 26.2 ± 2.4 years) were studied in a single fixed-dose randomized double-blind placebo-controlled cross-over trial of 200 mg caffeine or placebo ingested as chewing gum. A-SICI and T-SICI, using parallel tracking (T-SICIp), were performed before and after chewing gum. RESULTS: There was no significant change in SICI parameters after placebo in A-SICI (p > .10) or T-SICIp (p > .30), and no significant effect of caffeine was found on A-SICI (p > .10) or T-SICIp (p > .50) for any of the interstimulus intervals. DISCUSSION: There is no need for caffeine abstention before measurements of SICI by either the T-SICI or A-SICI measurements.

Visual temporal discrimination is impaired in patients with migraine without aura.

BACKGROUND AND OBJECTIVE: Dysfunctional sensory processing is described in migraine. This study aimed to evaluate visual perception in patients with migraine without aura using the visual temporal discrimination (VTD) test. METHODS: A total of 45 participants were enrolled in this prospective exploratory study. In all, 15 patients had migraine without aura and 15 healthy volunteers were analyzed in the study. The VTD threshold (VTDT) was measured using light-emitting diode lights to perceive two separate visual stimuli as clearly distinct. VTD was tested during the attack and the interictal period. The disease duration, attack side, visual analog scale for pain, accompanying symptoms, and allodynia were recorded during the attack. RESULTS: The VTDT of each visual field in both attack (mean [SD] 102.3 [38.4] ms for the right visual field and 106.3 [52.2] ms for the left) and the interictal periods (mean [SD] 75.2 [27.9] ms for the right and 78.2 [27.9] ms for the left) were significantly higher than in the control group (mean [SD] 45.3 [9.9] ms for the right and 48.2 [11.9] ms for the left) (p < 0.001, p < 0.001, p = 0.003, p < 0.001, respectively). The ipsilateral threshold during the attack was significantly prolonged compared to the interictal period (mean [SD] 143.8 [53.8] vs. 78 [19.6] ms, p = 0.025) and the contralateral threshold during the attack (mean [SD] 143.8 [53.8] vs. 71.9 [14.1] ms, p = 0.025). The ipsilateral threshold was significantly correlated with the visual analog score (r = 0.894, p < 0.001) and frequency of the attacks (r = 0.696, p = 0.004), but not correlated with photophobia. CONCLUSION: The VTDTs are prolonged both ictally and interictally in patients with migraine without aura attacks. Ipsilateral threshold prolongation is more pronounced during lateralized migraine attacks. The results suggest dysfunctional visual perception is not limited to the migraine attack period, and a defective sensory processing/modulation in the visual pathways may involve the superior colliculus.

Evaluation of Auditory Temporal Discrimination Thresholds in Migraine Patients.

INTRODUCTION: Although vestibular migraine is well defined, the effects of migraine on the auditory system have not been clearly identified yet. The aim of this study was to determine the effect of migraine on the auditory system. METHODS: Migraine patients without hearing loss were included in the study. Group 1 consisted of patients with migraine pain, group 2 consisted of patients with migraine in the interictal period, and group 3 consisted of healthy volunteers with similar demographic characteristics to groups 1 and 2. Random gap detection test was applied to all 3 groups. Additionally, group 2 and group 3 patients were evaluated with the auditory cortical potentials and the mismatch negativity test. RESULTS: There was a statistically significant difference between the 3 groups in the random gap detection test. There was no statistically significant difference in auditory cortical potentials between group 2 and group 3; however, a statistically significant difference was found between the groups in terms of mismatch negativity test latency. CONCLUSION: An auditory pathway may be affected in migraine patients, although hearing tests are normal. This interaction continues between attacks, being more evident during the pain period. Therefore, disorders of hearing or speech perception in migraine patients should be evaluated by further audiological tests.

Mirror neuron activity depending on the content and stage of the observed action: a TMS study.

Background/aim: The firing rate of the mirror neuron system in monkeys decreases systematically with more repetitions. The aim of this study is to investigate whether the activity of the mirror neuron system varies based on the observed movement and the contents of the action, as well as whether there is inhibition in the mirror neuron system when humans observe repeated actions. If inhibition is present, the second question of the study is whether it is related to the organization of the observed action. Materials and methods: Fourteen healthy volunteers participated in the study. Transcranial magnetic stimulation was applied to the left primary motor cortex and motor evoked potentials (MEPs) were recorded from the right first dorsal interosseous and abductor pollicis brevis muscles while the participants were watching videos specially prepared for the study. Results: There were no significant changes in MEP amplitudes compared to baseline MEPs while observing aimless action. However, while participants watched the repeated action video, the mean MEP amplitude increased at the beginning of the movement, but neither facilitation nor inhibition was detected when the participants watched the phase of grasping the object of the action compared to the baseline MEP amplitude. On the other hand, while participants were watching different activities, an increased MEP amplitude was observed at the beginning of the movement and in the grasping of the object of the action. Additionally, there was no significant reduction in MEP amplitude during any movement stages while observing the repeated action video. Conclusion: The findings of this study suggest that the activation of the mirror neuron system in humans depends on the content and stages of the observed movement. Additionally, there was no inhibition or systematic reduction in MEP amplitudes while watching a repeated action.

Cerebellar Transcranial Direct Current Stimulation Does Not Alter Somatosensory Temporal Discrimination Threshold.

This study aimed to explore the role of the cerebellum on the somatosensory temporal discrimination (STD) process. Twenty healthy volunteers were enrolled in the study. Each participant was included in three different transcranial direct current stimulation (tDCS) sessions as anodal, cathodal, and sham sessions in randomised order. Anodal and cathodal cerebellar tDCS (cTDCS) were given for 20 min at an intensity of 2 mA. The results of the study indicate no effect of cTDCS on STD. Although the study results show that cTDCS does not affect STD, because of the restricted sample size of the study, it is useful and necessary to investigate this relationship more in depth in a larger healthy subject population using different cTDCS methodologies.

Estimating the motor unit number of the flexor carpi ulnaris muscle with MScanFit MUNE.

INTRODUCTION/AIMS: MScanFit motor unit number estimation (MUNE) is a promising method for motor unit estimation and is reported to have good reliability in distal and small muscles. In this study, we investigated the reliability of MScanFit MUNE in a proximal forearm muscle, the flexor carpi ulnaris. METHODS: Twenty healthy volunteers were included in this study, and 15 participants were re-evaluated in a second session. The ulnar nerve was stimulated at the elbow and a compound muscle action potential (CMAP) scan from the flexor carpi ulnaris (FCU) muscle was recorded from each arm. CMAP, MUNE, and other motor unit parameters were obtained. Reproducibility was evaluated using intraclass correlation coefficients (ICCs). RESULTS: The average MUNE from 40 FCU muscles was 90.9 (standard deviation: 16.4). MScanFit MUNE and CMAP were not significantly different between the dominant and non-dominant sides. The ICC indicated good reliability between sessions for each side (0.81 and 0.8, respectively). DISCUSSION: Our results indicate that MScanFit MUNE is a feasible method with good reproducibility for MUNE of the FCU muscle.

Feasibility and reliability of MScanFit motor unit number estimation in peroneus longus muscle.

INTRODUCTION/AIMS: Motor unit number estimation (MUNE) methods may be valuable to detect motor involvement earlier than compound muscle action potential (CMAP) amplitude. The most recent MUNE method, MScanFit, has been shown to have advantages compared with previously described methods. However, MScanFit has only been applied in a few lower extremity muscles. In this study we examined the feasibility and reliability of MScanFit in peroneus longus muscle. METHODS: Twenty healthy controls (16 males and 4 females; mean age, 36.05 ± 2.58 years) were examined twice within a 1- to 2-week interval. Fibular nerve was stimulated at the knee and CMAP scans were recorded from peroneus longus muscle. From this, MScanFit MUNE and size parameters were calculated, as was the CMAP amplitude. The reliability was examined using coefficient of variation (CV) and intraclass correlation coefficient (ICC). MUNE was correlated with CMAP amplitude using linear regression analysis. RESULTS: The CV between sessions was higher for CMAP amplitude (11.63 ± 1.88%) than MScanFit MUNE (3.13 ± 0.78%). Among the size parameters, mean unit amplitude (µV) showed the lowest CV (11.46 ± 1.77%). Using ICC, CMAP amplitude exhibited good reliability (0.787), whereas that of MScanFit MUNE was excellent (0.902). Reliability was good for all size parameters. There was no significant correlation between MScanFit MUNE and CMAP amplitude (R = 0.25, P > .05). DISCUSSION: MScanFit MUNE is feasible in the peroneus longus muscle, with high test-retest reliability in healthy subjects. Studies in patients are needed to examine the sensitivity of this muscle in disease.

Short latency afferent inhibition: comparison between threshold-tracking and conventional amplitude recording methods.

Short-latency afferent inhibition (SAI), which is conventionally measured as a reduction in motor evoked potential amplitude (A-SAI), is of clinical interest as a potential biomarker for cognitive impairment. Since threshold-tracking has some advantages for clinical studies of short-interval cortical inhibition, we have compared A-SAI with a threshold-tracking alternative method (T-SAI). In the T-SAI method, inhibition was calculated by tracking the required TMS intensity for the targeted MEP amplitude (200 uV) both for the test (TMS only) and paired (TMS and peripheral stimulation) stimuli. A-SAI and T-SAI were recorded from 31 healthy subjects using ten stimuli at each of 12 inter-stimulus intervals, once in the morning and again in the afternoon. There were no differences between morning and afternoon recordings. When A-SAI was normalized by log conversion it was closely related to T-SAI. Between subjects, variability was similar for the two techniques, but within-subject variability was significantly smaller for normalized A-SAI. Conventional amplitude measurements appear more sensitive for detecting changes within-subjects, such as in interventional studies, but threshold-tracking may be as sensitive as detecting abnormal SAI in a patient.

Cortical plasticity causes useless hand syndrome in multiple sclerosis: a neurophysiological study in a rare case.

BACKGROUND: Useless Hand Syndrome (UHS) is a rare clinical manifestation of an upper cervical cord lesion, which is most commonly associated with multiple sclerosis (MS). The pathophysiological mechanism underlying UHS remains unclear. CASE: We report a 25-year-old woman, who described numbness in her left upper extremity. Cervical magnetic resonance imaging revealed a posterior upper cervical cord lesion. There was no cortical lesion that could explain the clinical findings. We measured (1) short-latency afferent inhibition (SAI) by obtaining motor evoked potentials as an indicator of sensorimotor integration and (2) somatosensorial temporal discrimination threshold (STDT) to display central somatosensory pathway function. In the right cerebral hemisphere, we found an excessive increase in STDT and no inhibition in the SAI paradigm. CONCLUSIONS: These findings indicate that impairment of sensorimotor integration and central processing of sensory stimuli cause useless hand syndrome.

Early diagnosis of amyotrophic lateral sclerosis by threshold tracking and conventional transcranial magnetic stimulation.

BACKGROUND AND PURPOSE: Short-interval intracortical inhibition by threshold tracking (T-SICI) has been proposed as a diagnostic tool for amyotrophic lateral sclerosis (ALS) but has not been compared directly with conventional amplitude measurements (A-SICI). This study compared A-SICI and T-SICI for sensitivity and clinical usefulness as biomarkers for ALS. METHODS: In all, 104 consecutive patients referred with suspicion of ALS were prospectively included and were subsequently divided into 62 patients with motor neuron disease (MND) and 42 patient controls (ALS mimics) by clinical follow-up. T-SICI and A-SICI recorded in the first dorsal interosseus muscle (index test) were compared with recordings from 53 age-matched healthy controls. The reference standard was the Awaji criteria. Clinical scorings, conventional nerve conduction studies and electromyography were also performed on the patients. RESULTS: Motor neuron disease patients had significantly reduced T-SICI and A-SICI compared with the healthy and patient control groups, which were similar. Sensitivity and specificity for discriminating MND patients from patient controls were high (areas under the receiver operating characteristic curves 0.762 and 0.810 for T-SICI and A-SICI respectively at 1-3.5 ms). Paradoxically, T-SICI was most reduced in MND patients with the fewest upper motor neuron (UMN) signs (Spearman ρ = 0.565, p = 4.3 × 10-6 ). CONCLUSIONS: Amplitude-based measure of cortical inhibition and T-SICI are both sensitive measures for the detection of cortical involvement in MND patients and may help early diagnosis of ALS, with T-SICI most abnormal before UMN signs have developed. The gradation in T-SICI from pathological facilitation in patients with minimal UMN signs to inhibition in those with the most UMN signs may be due to progressive degeneration of the subset of UMNs experiencing facilitation.

A new parameter to discriminate amyotrophic lateral sclerosis patients from healthy participants by motor cortical excitability changes.

INTRODUCTION: We sought a combination of abnormalities to define a more sensitive measure of cortical excitability in amyotrophic lateral sclerosis (ALS). METHODS: The automatic threshold tracking method was employed to assess the resting motor threshold, intracortical facilitation (ICF), short-interval intracortical inhibition (SICI), and short-interval intracortical faciilitation (SICF) in patients and controls. RESULTS: SICF at interstimulus intervals (ISI) between 1 and 1.8 ms and 2 and 3 ms as well as average SICI and SICI at ISIs of 1 and 2.5 ms were significantly reduced in ALS. The SICI curve was altered, displaying a solitary peak. Discriminant analysis revealed that the combination of SICI 2.5 ms and the mean SICF between 1 and 1.8 ms ISIs was the most sensitive parameter to distinguish patients with ALS from healthy participants. DISCUSSION: Along with the reduced SICI and its altered shape, connectivity between motor cortical circuits is changed in ALS. Combination with SICF increases the diagnostic utility of SICI in ALS.

Impaired short- and long-latency afferent inhibition in amyotrophic lateral sclerosis.

INTRODUCTION: To test the hypothesis of impaired cholinergic activity in amyotrophic lateral sclerosis (ALS), we studied short- and long-latency afferent inhibition (SAI and LAI). METHODS: The ulnar nerve was stimulated at the wrist preceding transcranial magnetic stimulation (TMS), 21 ms for SAI and 200 ms for LAI, in 21 patients and 17 control subjects. Short-interval intracortical inhibition (SICI) and cognitive function was assessed in ALS patients using automatic threshold tracking and the Montreal Cognitive Assessment (MoCA). RESULTS: The SAI paradigm resulted in inhibition in all control subjects, whereas inhibition was observed in 13 of 21 (62%) patients. Mean SAI and LAI values were significantly reduced in ALS. No significant correlation existed between afferent inhibition and other neurophysiological data. The MoCA was normal in all but 1 patient. DISCUSSION: LAI and SAI are both impaired in ALS, probably unrelated to increased cortical excitability or cognitive dysfunction. Muscle Nerve 59:699-704, 2019.

Reduced Short-Latency Afferent Inhibition Indicates Impaired Sensorimotor Integrity During Migraine Attacks.

BACKGROUND AND OBJECTIVE: Migraine attacks disrupt sensory information processing and may also disturb sensorimotor integration. This prospective pilot study aimed to assess the sensorimotor integration and inhibitory circuitry in the sensorimotor cortex using short-latency afferent inhibition (SAI) paradigm in migraine. METHODS: Twenty-five migraine without aura patients (10 interictal, 5 preictal, 10 ictal) and 16 healthy controls were enrolled. SAI was elicited by combining the right median nerve electrical stimulation and left motor cortical magnetic stimulation at the 21-millisecond interval. Mean motor evoked potential (MEP) amplitude ratio, recorded from right abductor pollicis muscle after single and conditioned stimulations, was calculated as SAI. RESULTS: Average MEP inhibition ratio after single and conditioned stimuli in healthy controls was not significantly different from interictal patients (45.1% ± 20.3% vs 44.5% ± 14.75% [P = .93]). However, SAI was significantly reduced during preictal/prodromal (-14.6% ± 42.8% [P = .002]) and ictal/headache (-7.4% ± 31.1% [P = .0001]) periods of migraine compared to healthy controls. CONCLUSION: Pronounced decrease in SAI during preictal and ictal periods in migraine was shown for the first time. Instead of inhibition to a conditioned stimulus, facilitation in the sensorimotor cortex was detected both ictally and preictally. Preictal SAI results suggest the presence of increased excitability state several hours prior to the headache phase. This phenomenon could be related to the cortical hyperresponsivity to sensory stimuli and cognitive disturbances accompanying migraine attacks as SAI is modulated by cholinergic activity.

Anticipatory effect of execution on observation: an approach using ExoPinch finger robot

Background/aim: This study aims to explore the mirror neuron system (MNS) involvement using mu (8­12 Hz)/beta (15­25 Hz) band suppression in an action observation-execution paradigm. Materials and methods: Electrophysiological (EEG) data from 16 electrodes were recorded while 8 participants observed video clips of a hand squeezing a spring. Specifically, the effect of anticipated execution on observation was studied. For this purpose, a fully actuated finger exoskeleton robot was utilized to synchronize observation and execution and to control the execution condition for the partici-pants. Anticipatory effect was created with a randomized robot accompany session. Results: The results showed that the observational condition (with or without anticipation) interacted with hemisphere at central chan-nels near somatosensory cortex. Additionally, we explored the response of MNS on the kinetics features of visual stimuli (hard or soft spring). Conclusion: he results showed an interaction effect of kinetics features and hemisphere at frontal channels corresponding nearly to the ventral premotor cortex area of the brain. The activation of mirror neurons in this area plays a crucial role in observational learning. Based on our results, we propose that specific type of visual stimuli can be combined with the functional abilities of the MNS in the ac-tion observation based treatment of hand motor dysfunction of stroke patients to have a positive additional impact.

Spinal excitability changes do not influence the mechanisms of split-hand syndrome in amyotrophic lateral sclerosis.

INTRODUCTION: We studied spinal excitability and its relation to motor unit action potential (MUAP) changes in the thenar and hypothenar muscles in patients with amyotrophic lateral sclerosis (ALS). METHODS: Quantitative MUAP and peak ratio interference analyses were performed, and cutaneous silent period (CutSP) was measured in the abductor digiti minimi (ADM) and first dorsal interosseous (FDI) muscles of patients with ALS and controls. RESULTS: Patients with ALS revealed more prominently increased duration (P = 0.002), number of phases (P = 0.02), size index (P = 0.02), and thickness (P = 0.02) in ADM than in FDI. The number of small segments was significantly decreased in ADM (P = 0.036) compared with controls. CutSP latency was prolonged in both ADM and FDI in ALS (P < 0.05). DISCUSSION: Although the reinnervation capacity was notably higher in the ADM of patients with ALS, the lack of a significant difference in CutSP measurements between ADM and FDI argues against spinal excitability changes in the development of split-hand syndrome. Muscle Nerve 58: 503-508, 2018.

Analysis of mirror neuron system activation during action observation alone and action observation with motor imagery tasks.

This study aimed to explore the relationship between action observation (AO)-related corticomotor excitability changes and phases of observed action and to explore the effects of pure AO and concurrent AO and motor imagery (MI) state on corticomotor excitability using TMS. It was also investigated whether the mirror neuron system activity is muscle-specific. Fourteen healthy volunteers were enrolled in the study. EMG recordings were taken from the right first dorsal interosseous and the abductor digiti minimi muscles. There was a significant main effect of TMS timing (after the beginning of the movement, at the beginning of motor output state, and during black screen) on the mean motor evoked potential (MEP) amplitude. Mean MEP amplitudes for AO combined with MI were significantly higher than pure AO session. There was a significant interaction between session and TMS timing. There was no significant main effect of muscle on MEP amplitude. The results indicate that corticomotor excitability is modulated by different phases of the observed motor movement and this modulation is not muscle-specific. Simultaneous MI and AO enhance corticomotor excitability significantly compared to pure AO.

Brainstem reflex excitability changes in patients with amyotrophic lateral sclerosis.

INTRODUCTION: In this study we explored brainstem reflex excitability changes, blink reflex recovery cycles (BRRCs), and masseter inhibitory reflexes (MIRs) in patients with amyotrophic lateral sclerosis (ALS). METHODS: Fourteen ALS patients and 14 healthy control subjects were recruited. The BRRC was examined at interstimulus intervals (ISIs) of 100, 200, 300, 400, 500, and 600 ms. The latencies and durations of silent period 1 (SP1) and silent period 2 (SP2) of the MIR were measured. RESULTS: Decreased R2 area suppression was prominent in the ALS group at ISIs of 200, 300, and 400 ms (P < 0.02), whereas no significant differences between groups at 100, 500, and 600 ms ISIs (P > 0.05) were observed. SP2 duration was significantly prolonged in the ALS group compared with controls (P = 0.01). CONCLUSIONS: Brainstem inhibitory and excitatory interneuronal activity is altered in ALS, possibly brought about by physiological and morphological changes at the cortical or bulbar levels. Muscle Nerve 56: 925-929, 2017.

Somatosensory temporal discrimination remains intact in tension-type headache whereas it is disrupted in migraine attacks.

Background and objective Somatosensory temporal discrimination was recently reported as prolonged during migraine attacks, which is consistent with disrupted sensorial perception in migraine. However, knowledge about central sensory processing in tension-type headache is still lacking. This prospective, controlled study aimed to investigate somatosensory temporal discrimination thresholds in tension-type headache. Methods The study included 10 tension-type headache patients, 10 migraine patients and 10 healthy volunteers without headache. Somatosensory temporal discrimination thresholds were evaluated during the headache attacks of tension-type headache and migraine patients. Results Somatosensory temporal discrimination thresholds of tension-type headache patients (39.0 ± 5.5 ms for the right hand and 40.6 ± 4.6 ms for the left hand) were significantly lower than those of episodic migraine patients (137.1 ± 35.8 ms for the right hand and 118.4 ± 34.3 ms for the left hand, p < 0.0001 and p < 0.0001 respectively), and comparable to those of healthy volunteers (38.6 ± 5.3 ms for the right hand and 38.3 ± 7.2 ms for the left hand, p = 0.79 and p = 0.45 respectively). Conclusion Central sensory processing, as tested by somatosensory temporal discrimination, was remarkably disrupted during the headache attacks in migraineurs, whereas it remained intact in the tension-type headache patients.

Voluntary movement reverses the effect of cathodal transcranial direct current stimulation (tDCS) on corticomotor excitability.

Motor cortex activity level is a critical part of the effect of transcranial direct current stimulation (tDCS) on corticomotor excitability. Based on homeostatic plasticity, the state of the stimulated cortical area influences the direction of neuroplastic changes induced by stimuli. Owing to homeostatic plasticity, cathodal tDCS (c-tDCS) would likely have a pronounced inhibitory effect on corticomotor excitability during a motor task, compared with the resting state. To test this hypothesis, we detected motor evoked potential (MEP) amplitude changes before and during c-tDCS with voluntary movement. Twelve healthy right-handed volunteers (9 males, 27-48 years) were enrolled in the study. Subjects performed little finger abduction motor task. Passive (APB) and active (ADM) muscles were studied. MEP amplitudes were measured during resting (baseline) and movement stages, and subsequently with the contralateral M1 modulated by c-tDCS. c-tDCS caused reduced baseline MEP amplitude in the ADM (p < 0.05) and APB (p < 0.001) muscles. Sham stimulation had no effect on the baseline MEP amplitudes. MEP amplitude ratio (MEP amplitude triggered by movement/baseline MEP amplitude) was higher during c-tDCS than before c-tDCS (p < 0.01). Our results suggested that during voluntary contraction, c-tDCS has an opposite effect on corticospinal excitability compared with resting state modulation effect. This contrast effect could be related to modulation of movement preparation and execution.

Somatosensory temporal discrimination is prolonged during migraine attacks.

BACKGROUND AND OBJECTIVE: Symptoms and signs of sensorial disturbances are characteristic features of a migraine headache. Somatosensory temporal discrimination measures the temporal threshold to perceive two separate somaesthetic stimuli as clearly distinct. This study aimed to evaluate somaesthetic perception in migraine patients by measuring the somatosensory temporal discrimination thresholds. METHODS: The study included 12 migraine patients without aura and 12 volunteers without headache. Somatosensory temporal discrimination threshold (STDT) values were measured in the face (V3) and hands (C7) during a lateralized headache attack and the headache-free interictal period. The disease duration, pain intensity, phonophobia, photophobia, nausea, vomiting, and brush allodynia were also recorded during the migraine attack. RESULTS: STDT values were within normal limits and not different between the control group and the interictal period in migraine patients. Compared to the headache-free period, STDT values during the attack were significantly prolonged in the contralateral hand (C7) (155.7 ± 84.2 vs 40.6 ± 16.1 ms [P < .001]), ipsilateral hand (C7) (88.6 ± 51.3 vs 31.4 ± 14.2 ms [P < 0.001]), contralateral face (V3) (65.5 ± 35.4 vs 37.6 ± 22.2 ms [P = .006]) and ipsilateral face (V3) (104.1 ± 44.5 vs 37.5 ± 21.4 ms [P < 0.001]) according to the lateralization of the headache. Ictal STDT values of the contralateral hand and ipsilateral face were significantly increased compared to that of the ipsilateral hand and contralateral face (155.7 ± 84.2 ms vs 88.6 ± 5.1.3 ms [P = .001], 104.1 ± 44.5 ms vs 65.5 ± 35.4 ms [P = 0.001]). No allodynia was detected in the areas that were tested for somatosensory temporal discrimination. The visual analog scale scores were correlated with the somatosensory temporal discrimination thresholds of the contralateral hand (r = 0.602, P = .038), whereas no correlation was detected between the somatosensory temporal discrimination thresholds and disease duration, brush allodynia in the forehead, phonophobia, photophobia, nausea and vomiting. CONCLUSION: The study demonstrates for the first time that somatosensory temporal discrimination thresholds are elevated during migraine attacks. A transient disruption of the central processing of somaesthetic stimuli during the lateralized migraine attack may provide additional information to understand the mechanisms of the cognitive and sensory perception impairment associated with migraine headache and may have diagnostic value.