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Background We hypothesized that there may be adaptive changes in the central pathways in patients with dry eye. To delineate this issue, we aimed to analyze blink reflex (BR), prepulse inhibition (PPI) of BR, recovery excitability of BR (BR-RC), and somatosensory temporal discrimination threshold (STDT). Method We included 17 patients with dry eye between September 2018 and November 2018. We also formed a control group composed of 14 healthy subjects with similar age and gender. After clinical evaluation, we recorded BR, PPI of BR (with 50 and 100 ms intervals), BR-RC (300 and 500 ms intervals) and we determined STDT over second finger. Results None of the patients had any spasm activity. The disease duration was between 2 and 15 years. There was a R2-PPI deficit at each interval in the patient group compared to healthy subjects. The recovery ratios at 500 ms were higher in patients compared to healthy subjects. STDT was abnormally high in patients than healthy subjects (p = 0.000) despite the similar sensory threshold in both groups. Discussion Although the cohort in this study did not have any involuntary spasms, they exhibited inhibitory deficit, increased recovery excitability and abnormal STDT similar to that found in blepharospasm. Most of the patients in this cohort have been in follow-up for a long period and they did not develop any spasThus, we suggest patients with dry eye exhibit central adaptive changes.

Summary Objective: In our study, we aimed to investigate the relationship between the change in central sensory pathways and fine motor skills by examining patients with CTS. Methods A total of 37 patients with isolated CTS, 27 patients with diabetes mellitus (DM) and CTS, 21 patients with DM without CTS and 15 healthy controls were included in the study. None of them had polyneuropathy. Routine electrophysiological examination, sensory threshold (ST), somatosensory temporal discrimination threshold (STDT), nine-hole peg test (NHPT) were performed. Dropping objects from hand was questioned. Results The rate of dropping objects showed a trend to be higher in patients with CTS, with or without DM. In all participants who dropped objects, the duration of NHPT was found significantly higher. In CTS group with or without DM, second finger (2f) ST and STDT were higher than healthy individuals and cases with DM, the durations of NHPT was correlated with only 2f ST in all participants who dropped objects whereas there was no correlation with 2f STDT. When the isolated CTS and DM-diagnosed CTS groups were compared, only NHPT placement and total completion durations were longer in DM-diagnosed CTS and the other results were similar. Conclusions Similar to the literature, we showed that there was a maladaptive reorganization process in primary somatosensory cortex (S1), which was evaluated with 2f STDT in all of patient with CTS. But in our results, there is no relationship between the maladaptive reorganization process in S1 and impaired fine motor skills.

Objective Somatosensory blink reflex(SBR) is obtained after a peripheral sensory stimulation, generally after stimulating median nerve at wrist. Defensive peripersonal space (PPS) represent a safety zone for survival and this space is encoded by ventral intraparietal region and polysensory zone of postcentral gyrus, which modulate blink reflex. SBR response is enhanced if the hand is held close to the eye (in the peripersonal space). We aimed to investigate the modulation of SBR response in PPS. Methods We included 22 patients with episodic migraine, of whom 13 individuals were experiencing headache episode and 9 individuals were interictal period. We also included 14 healthy individuals. The three groups were similar in age and gender. SBR was recorded when the participants were sitting with their forearm resting on a pillow and also when their hands were in the peripersonal space surrounding face. Latency, amplitude and area-under the curve (AUC) were measured and compared between groups. Results In healthy volunteers and episodic migraine patients with headache, there was no significant difference between SBR latencies inside and outside PPS, however latency of SBR was short in PPS. However, in episodic migraine patients without headache there was no significant change in SBR latency, amplitude and area when the hand was in PPS compared to the hand on a pillow. Conclusion This results suggested that the modulation which was elicited by cortical areas encoding PPS, on the SBR is deteriorated in the interictal period of episodic migraine.

Objective Hemifacial spasm (HFS) is characterized by spasms of facial muscles on one side of face. There are two hypothesis in the pathogenesis: a peripheral nerve hypothesis or hyperexcitability of the facial nucleus. Blink reflex (BR) excitability is increased in HFS. Here, we aimed to analyze the changes of BR-prepulse inhibition (PPI) which provides assessment of inhibitory control on facial circuitry. Patients and method We included 13 patients with HFS and 13 healthy subjects. Baseline BR, BR recovery at ISI of 300 ms and BR-PPI at ISI of 100 ms were performed on the right sides of healthy subjects and on the asymptomatic and symptomatic sides of patients. Latency, amplitude and area of R1 and R2 were measured in all tests and compared among two groups using Mann-Whitney U test and t-test for paired groups when appropriate. Results Baseline values of R1 and R2 were normal and similar among groups. The mean recovery of R2 area was the higher on both symptomatic side of HFS (77.5%) compared to asymptomatic side of HFS (46.5%) and compared to healthy subjects (27.2%, p = 0.007). All groups had inhibition during BR-PPI. However, PPI was low on both sides of HFS compared to healthy subjects (p = 0.010). There was no correlation between disease duration and recovery of BR or BR-PPI. Conclusions HFS patients in this study had increased recovery of BR indicating increased excitability of BR circuit which was bilateral but more prominent on the symptomatic side. Similarly, inhibitory control upon BR circuit was prominently reduced on bilateral sides in HFS group. Significance This study discloses the central changes in HFS.

Objective Blink reflex (BR) is obtained after different kinds of stimuli, such as trigeminal supraorbial branch stimulation (trigeminal BR, TBR) or median nerve stimulation at wrist (hand-evoked BR, HBR). Inhibition of TBR occurs when a preceding subthreshold stimulus is applied before trigeminal stimulation (prepulse inhibition, PPI). In healthy subjects, magnitude of HBR is increased and magnitude of PPI of TBR is decreased if the stimulated hand is positioned in the peripersonal space (PPS). Here, we aimed to investigate the changes of HBR and PPI of the TBR in PPS to understand alterations of cortical modulations of subcortical structures in cervical dystonia. Patients and method We recruited 23 consecutive patients with idiopathic CD and 21 healthy subjects. All participants had HBR and age and gender were similar between groups. HBR and PPI of the TBR were recorded while stimulated hand was in the extrapersonal space (far condition) and in the PPS (near condition). Baseline values were compared between patient with CD and healthy subjects. Further comparisons were done between far and near conditions. Results Magnitude of baseline HBR was bigger in patients with CD compared to healthy subjects. The magnitude further increased in healthy subjects whereas it was reduced in patients with CD. In healthy subjects, prepulse stimulation led to the reduced magnitude of R2 component of BR under far condition whereas the reduction was less evident under near condition. Although prepulse inhibition was low in patients with CD compared to healthy subjects, the reduction was more evident under near condition in patients with CD. Discussion Enhancement of HBR and attenuation of PPI of the TBR in the PPS is a normal phenomenon that provides evidence for top-down modulation of the neural circuitry underlying these reflexes. In CD, these normal alterations are lost which suggest abnormal modulation of higher-order centers.

Introduction The reports on tremor and different types of polyneuropathies have been increasing and it was suggested to be associated with cerebellar involvement in chronic inflammatory demyelinating polyneuropathy (CIDP). Apart from specific syndromes, the co-existence of polyneuropathy and myoclonus is exceptional. We previously observed cortical myoclonus in cases with inflammatory polyneuropathy who were referred for tremor analysis and aimed to analyze presence of myoclonus and its relation with clinical features in demyelinating polyneuropathies. Methods We prospectively included all patients with inflammatory polyneuropathy who were admitted between January 2017 and June 2017 and had tremor-like, regular or irregular involuntary movements on clinical examination. All patients underwent neurological examination and multichannel surface electromyography which included upper extremity muscles as well as lower extremity and facial or neck muscles in selected cases. We also recorded long latency reflexes and somatosensory evoked potentials (SEPs) to categorize myoclonus. Results We identified eight patients with demyelinating polyneuropathy who matched the inclusion criteria: four patients with CIDP, three patients with Guillain–Barre syndrome and one patient with Charcot-Marie-Tooth disease. The mean age was 50.5 ± 19.6 years (range: 26–81 years) and there were seven male patients. Seven out of eight patients had myoclonus, two of which were in the form of polyminimyoclonus. Others had myoclonus on both proximal and distal parts of upper extremities. Negative myoclonus was observed in four of them. Duration of myoclonus was between 30 and 100 ms. only one had duration of 200 ms. Most patients (five out of seven) had cortical myoclonus (with high-amplitude C reflex or SEPs). Conclusion Myoclonus in the patients with polyneuropathy was irregular tremor-like, however, the electrophysiological characteristics was similar to a cortical subtype. Therefore, it would be interesting to investigate a bigger cohort of inflammatory polyneuropathies for the presence and subtypes of myoclonus and to determine associated clinical features.

Introduction We hypothesized that prepulse inhibition (PPI) may be decreased in trigeminal neuralgia (TN) if it leads hyperactivity of trigeminal nucleus and tested our hypothesis in a group of patients with classical TN. Methods Consecutive nine patients with classical TN and 14 healthy subjects were enrolled in this study between January 2015 and August 2016. Diagnosis and classification were done according to the International Classification of Headache Disorders-3 (ICHD-3 beta version). Blink reflex and BR-PPI were recorded on both symptomatic and asymptomatic sides in patient group and on the right side in healthy subjects. Subthreshold conditioning stimulus was applied to the median nerve at second finger using an electrical stimulus at two different interstimulus intervals: 50 ms and 100 ms before the test stimulus to the supraorbital nerve. Results Standard BR recordings were normal in all groups. In healthy subjects, prepulse stimulus resulted in lower magnitude of BR-R2 ( p = 0.000 ) and longer R2 latencies ( p = 0.008 ) at ISIs of 50 ms and 100 ms in comparison to baseline recordings whereas no change after prepulse stimulation was observed on both symptomatic and asymptomatic sides of patients with TN. Conclusion Our study provided evidence for the reduced PPI and thus, sensory gating of brainstem in classical TN. This finding was bilateral and present even on the asymptomatic side.

Introduction Peripheral facial nerve palsy (PFP) is characterized by reduced motor performance on one side of face. The electrophysiological findings show smaller or delayed motor and facial reflex responses. It leads to a cortical reorganization and an imbalance in sensorimotor gating is also likely since sensory pathways innervating facial structures are intact and sensory inputs to face are transmitted smoothly. Herein, we aimed to analyze the alterations in sensorimotor gating at the level of brainstem after PFP. To examine sensorimotor gating, we used prepulse modulation (PPM) of blink reflex (BR). We also recorded recovery (RC) of BR to identify excitability changes in the facial nucleus. Methods We included 33 patients with PFP and 39 recordings in those patients. Six patients had serial recordings. Control group was composed of 16 healthy subjects with similar age and gender to the patient group (Table). Baseline BR, BR recovery at ISI of 300 ms and BR-PPM at ISI of 100 ms were performed on the right sides of healthy subjects and on both sides of patients. Severity of PFP was assessed according to clinical findings by House-Brackman scale and using electrophysiological methods. Patients with BR, facial motor response or electromyography findings indicating axon loss more than 85% were considered to have severe axon loss. Time lapse from the onset was categorized as early ( 15 days), middle (12–45 days) and late ( > 45 days). Results R1, R2 and R2c components of BR on symptomatic side were absent in 17, 9 and 13 recordings, respectively. When they were recorded, latencies were longer and magnitude was lower over symptomatic sides of patients compared to healthy subjects or asymptomatic sides of patients. Multivariate ANOVA showed significance at group level, at prepulse level and group x prepulse level. Mean magnitude of R1 was increased whereas mean R2 and R2c magnitude were reduced in all groups after prepulse stimulation (prepulse inhibition, PPI). Interestingly, suppression of R2 or R2c was lower on both sides of patient group compared to healthy subjects. There was no association between PPM% and categories according to time lapse or HBs. PPM% did not correlate with time lapse, either. Although R2-RC and R2C-RC were lower in healthy subjects compared to both sides of patients, the difference was not significant. When we conducted a multivariate analysis between BR-RC with fixed factor time lapse and HB, recovery rates were significantly lower in patients with lower HB scores. Conclusion Prepulse inhibition of R2 BR is reduced in patients with PFP. Filtering of facial sensory input at brainstem level is decreased leading to an increased transfer of trigeminal sensory inputs through brainstem. Although increased BR-RC correlated with disease severity, there was no correlation between reduced PPI-BR. Thus, reduced PPI is presumably related to monitor and to choose correct sequence of facial movements.

Introduction Long latency reflexes (LLRs) are medium to late latency responses which are obtained over a muscle after a peripheral stimulation. In epilepsy, presence and amplitudes are supposed to be higher due to increased cortical excitability. We aimed to analyze LLRs in juvenile myoclonic epilepsy (JME) and progressive myoclonic epilepsy (PME), to determine the frequency of three subtypes and to analyze whether parameters regarding LLRs may be used in differentiating these two disorders. Our hypothesis was cortical excitability and amplitudes and frequency of LLRs would be higher in PME. Methods We included 30 patients with JME, 18 patients with PME and 28 healthy subjects. LLRs were recorded over abductor policis brevis muscle after stimulating median nerve at wrist during rest and active movement. Latencies and amplitudes of segmental reflex and LLRs, presence of LLR I, II, and III, the ratio of segmental reflex amplitude and LLR amplitude were compared among three groups. ROC curves were formed for LLR I amplitude and amplitude ratio to evaluate ‘cut-off’ values in differentiating PME and JME. Results C reflex was detected in only PME group and LLR I presence during active movement was the highest in PME group (57.9%, p = 0,001). Although LLR I amplitude was also the highest in PME group, ratio was higher in JME group since amplitude of segmental reflex was also higher in patients with PME. Both parameters were higher in PME and JME groups compared to healthy subjects (LLR I amplitude: p = 0.005 and ratio: p = 0.011, Kruskal–Wallis test). LLR I amplitude was able to differentiate patients with epilepsy and healthy subjects with an accuracy of 57–82% (p = 0.008) whereas ratio was able to recognize patients with an accuracy of 60–86% (p = 0.003). Ratio above 1.05 had the sensitivity and specificity of 77.8% and 71%, respectively in diagnosing patients with PME or JME. Conclusion Presence of C reflex and higher LLR I amplitudes suggest the presence of exaggerated cortical response to peripheral stimuli in PME. However, cortical excitability measured by LLR I amplitude is high in both JME and PME and hence does not provide differentiation of these two disorders.

Background Startle reflex (SR) is a generalized defense reaction which is elicited by unexpected stimuli. To elicit SR, auditory and electrical stimulations are used in electrophysiological investigations. Somatosensory startle reflex (SS-SR) is recently described in healthy volunteers after median and tibial stimulation. Studies in patients with brainstem lesions showed importance of upper brainstem in development of SS-SR. Here, we aim to investigate SS-SR systematically in various movement disorders to address its characteristics in comparison to ASR. Methods We have examined ASR and SS-SR in patients with dystonia ( n = 12), multiple system atrophy ( n = 8), corticobasal degeneration ( n = 5), restless legs syndrome ( n = 14), progressive supranuclear palsy ( n = 11), essential tremor ( n = 18) and idiopathic PD (n = 16) and healthy volunteers ( n = 35) under the same conditions. ASR and SS-SR were recorded over orbicularis oculi (o.oc), sternocleidomastoid (SCM), and biceps brachii (BB) after bilateral auditory and median nerve electrical stimulations, respectively. Results The pattern and probability rates over each three muscle of ASR were similar in MSA, RLS, ET, PD and healthy individuals. Probability rates of responses over each muscle and total ASR probability were the highest in dystonia group whereas they were the lowest in CBD and PSP ( p o.oc = 0.016, p scm = 0.036, p bb = 0.000, p total = 0.009). Onset latencies of O.oc responses were also longer in CBD and PSP groups ( p = 0.001). Presence of SSR was also the highest in dystonia and lowest in PSP group similar to ASR. Latency of O.oc response was longest in CBD group. Pattern of SS-SR was similar to healthy individuals in all disease groups except dystonia and MSA in which BB responses were more common than SCM responses. Conclusions The findings of ASR parallel the previous findings. Dystonia patients are known to have exaggerated ASRs. The decreased response in PSP was previously suggested as a support to show extent of pathology. Findings regarding SS-SR also parallel ASR. SS-SR is also exaggerated in dystonia. Different pattern of response appears to be a reflection of overflow phenomenon. However, development of withdrawal reaction is a possibility. Shorter onset latencies in dystonia group probably also reflect increased excitability. Absence of SS-SR or longer latencies in PSP reflects impairment of its pathway which supports the opinion that it may share pathway with ASR and its generator is possibly in the upper brainstem.

Background Pain is a disturbing non-motor feature of Parkinson's disease(PD), with a reported prevalence of 40–50%. We aimed to understand the differences in nociceptive flexion reflex (NFR) in PH patients with/without pain. Methods We included 22 PD patients (9 patients without pain, 13 patients with pain) and 28 age-and-gender matched controls (13 subjects reported no pain, 15 controls with pain). NFR was recorded while lying supine. Stimulation with 20ms train of four 0.5ms electrical pulses was given to sole of the foot, recordings were done over anterior tibialis (AT) and long head of biceps femoris (BFLH). Results The latency of NFR recorded over AT was similar between patients with PD and controls with pain, but BFLH latency was shorter in PD group (100.0 ± 42.2 ms vs 108.4 ± 32.8ms, p > 0,05). The NFR amplitude in PD patients with pain was higher compared to patients without pain and healthy subjects. Conclusion Our study showed that parameters of NFR differ between PD patients with and without pain and controls. The higher amplitudes and shorter latencies may suggest that pain may have a facilitatory role in the manifestation of NFR.

Objective Prepulse inhibition (PPI) is a neurophysiological method in which inhibition of a reflex response occurs when a preceding stimulus is applied. It is generally created by digital somatosensory stimulation. R2 magnitude gets reduced using certain interstimulus intervals (ISIs) whereas short ISI leads to facilitation of R1. We aimed to analyze the changes of BR-PPI using digital somatosensory stimulation and mixed nerve stimulation at wrist. Patients and method We included 18 healthy subjects (38.8 ± 10.9 years, 12 women) and performed BR investigations after unconditioned and conditioned supraorbital electrical stimuli. For conditioned stimuli, we applied two different preceding subthreshold somatosensory stimuli: i. stimulation of second finger, ii. stimulation of median nerve at wrist. Three different ISIs (50, 100, 300 ms) were used for each type of stimulation. Presence and extent of alteration after each conditioning stimulus were compared. Results R2 area significantly reduced after each conditioning stimulus at each ISI. R2 latency was longer at ISIs of 100 and 300 ms whereas R1 magnitude was higher at all ISIs. However, the increase in R1 magnitude was more pronounced at ISIs of 50 and 100 ms. Conclusions Our results clearly show that both digital somatosensory and mixed nerve stimulations lead to inhibition of R2 area and facilitation of R1 magnitude. Therefore, both stimulations and both techniques are comparable.

Background Somatosensory startle reflex (SSSR) was recently studied in healthy subjects. Following corticospinal tract lesions caused by stroke or spinal cord injury (SCI), auditory startle reflex (ASR) has been reported to enhance due to reorganization of circuits rostral and caudal to the lesion. To further understand changes in SSSR and ASR, we investigated both responses in patients with spinal cord injury (SCI) and stroke. Methods We examined characteristics of ASR and SSSR in 14 SCI and 40 stroke patients (16 brainstem and 24 cerebral hemispheric infarctions) and 39 age and gender matched healthy subjects. ASR was obtained after eight auditory stimuli and SSSR was elicited after median nerve stimulation at the wrist. Surface electromyographic recordings were obtained from orbicularis oculi (O.oc), sternocleidomastoid (SCM), biceps brachii (BB) and abductor pollicis brevis (APB) muscles. Results Total ASR probabilities at distal muscles were significantly higher in patients with SCI and in stroke patients especially with brainstem infarctions. Similarly SSSR rates were increased in both patient groups compared to controls (for APB p Conclusions In conclusion, we have found that SSR and ASR were enhanced in stroke and SCI and this enhancement was more prominent in distal muscles. Secondly, the properties of ASr and SSSR differed according to the lesion site.

Background Our current understanding of brainstem reflex physiology comes chiefly from the classic anatomical–functional correlation studies that traced the central circuits underlying brainstem reflexes and establishing reflex abnormalities as markers for specific areas of lesion. Our aim is to investigate the correlation between the brainstem reflex abnormalities and lesion localization in three different diseases with brainstem lesions. Methods Masseter inhibitory and blink reflexes were studied in 21 multiple sclerosis, 15 stroke and 17 Behcet’s disease patients with brainstem lesions on brain magnetic resonance imagings. The reflex responses were compared with those of 20 healthy subjects of comparable age. SPSS for Windows 11.5 package was employed for statistical processing. Results Latency abnormalities of the blink and the masseter inhibitory reflexes were the most prominent in MS group. No significant differences were found in duration and degree of suppression among the groups in MIR responses. The highest abnormality percentages in MS group were in R1component of blink reflex (% 71, 4) and S2 component of masseter inhibitory reflex (% 90, 5). And also R1 of BR and S2 of MRI were the most abnormal responses in the all groups compared to other parameters. Conclusions Distinct reflex abnormalities indicate lesions at specific sites. A number of lesions suspected on clinical data may be confirmed by reflex findings only and not by imaging studies. Reflex testing can be utilized to demonstrate multiple lesions and evaluate dissemination of central nervous involvement in patients with brainstem lesions. Increased abnormality percentage in MS group may be explained by the fact that supratentoriel lesions affect brainstem reflex responses. Since lesions in Behcet’s disease are localised in mesencephalon commonly, superior to MIR and BR circuits, the abnormality in this group is much less relatively.

Background Juvenile myoclonic epilepsy (JME) which is among idiopathic generalized epilepsies presents with myoclonus and/or generalized tonic–clonic seizures during puberty. Electrophysiological studies showed findings at several levels including cortex, thalamus and spinal cord in JME. Given these information, we aimed to analyze electrophysiological findings at the level of brainstem using blink reflex (BR) and blink reflex recovery cycle (BR-RC). Methods Eighteen JME patients and age and sex matched 18 healthy volunteers are included in the study. BR and BR-RC with interstimulus intervals of 200 ms and 400 ms were recorded over orbicularis oculi on the nondominant side under the same conditions. Results JME patients had longer onset latencies ( p = 0.046) and higher amplitudes ( p = 0.022) of R2 component of BR. Recovery of responses after double stimulation with interstimulus interval of 400 ms was higher in JME patients ( p = 0.040). Use of valproate did not have an impact on reflex responses. Conclusion Our results support increased excitability of BR pathway in JME without relevant pathological findings regarding BR.

Aim Following the electrical stimulation of mixed nerve during voluntary muscle contraction, temporarily suppressed EMG activation called mixt nerve silent period (MNSP). MNSP is interrupted by several bursts; first one is segmental reflex (SR) and others known as a long-loop reflexes(LLR). Vibration has been shown suppress the segmental H-reflex amplitude by increasing Ia afferent discharge. In this study, our aim was to provide insight into SR characteristics and the effects of vibration on other parameters. Method Eleven healthy volunteer (5 women, 33.36 ± 5.35 years) included the study. Vibration was applied for 2 min at 100 Hz with repositioning amplitude of 1 mm on right forearm. Median nerve stimulated at wrist during thumb abduction and MNSP recorded at baseline, during and after the vibration application. Latencies of SR, LLR and MNSP and amplitudes of SR and LLR compared for each session. Results Average SR and LLR amplitudes, MNSP durations before, during and after vibration were found as (1093.36 ± 606.16/877.22 ± 390.37/863.0 ± 604.51), (561.17 ± 353.8/1363.92 ± 1242.78/1100.0 ± 901.65) and (108.6 ± 12.41/113.55 ± 21.35/100.47 ± 18.03) respectively. MNSP durations, SR and LLR latencies were not significantly different between sessions. While SR amplitude tended to decrease, LLRA tended to increase. Conclusion Present study demonstrated that short-therm vibration is not effective on MNSP parameters. Our results may support that SR share similar characteristics with HR.

Background Sleep bruxism (SB) is a stereotyped movement disorder characterized by grinding or clenching of the teeth during sleep. Neurophysiologic methods offer approaches to study the excitability in SB by recording the motor potentials evoked by masseter muscles and masseter inhibitory reflex (MIR). Auditory startle reaction (ASR) has been found to be increased in restless leg syndrome but it has not been studied in SB. We aimed to show the hyperexcitability in the central jaw motor pathways in patients with SB by studying MIR and ASR responses. Methods 10 patients (mean age 48,4 ± 10,2 years; 8 male and 2 female) and 20 healthy subjects (mean age 34,4 ± 11,2 years; 6 male and 14 female) were enrolled in the study. The EMG activity was recorded from two masseter muscles by surface electrodes. The duration and latency of early and late silent periods and suppression ratios obtained from patient and control groups were compared. ASR was recorded from o. oculi, masseter, sternocleidomastoid, biceps brachii and tibialis anterior muscles and probability and latencies were evaluated. SPSS for Windows 11.5 package was employed. Results The differences in silent period onset latencies between patients and normal subjects were not significant but durations of early and late silent periods were shorter in SB group. Conclusions These results may indicate a reduced capacity for inhibition by the circuits responsible for the late period in SB and this increased excitability in central motor pathways could derive from an impaired modulation of subcortical structures especially brainstem inhibitory circuits and not from altered cortical mechanisms. Since ASR did not differ between the control and patient groups, it can be possible to say that there’s no abnormality in brainstem and reticulospinal circuits in SB patients.

Introduction Neurons firing during observation of movement are termed as mirror neurons which are suggested to play role in performing skilled movement and praxis functions. In monkeys, function of mirror neurons was reported to be preparation for movement. In humans, motor evoked potential (MEP) amplitudes get increased during observation of movement similar to performance of the same act ( Fadiga et al., 1995 ). Based on the previous work which showed presence of apraxia in Parkinson’s disease (PD) ( Uluduz et al., 2010 ), we aimed to examine praxis function in PD using electrophysiological parameters in comparison to clinical examination battery. Patients and methods Three PD patients with apraxia and four PD patients without apraxia were included in the study. Presence of apraxia was determined using Mayo Clinic apraxia assessment test which was validated for Turkish population. Detailed neurological and cognitive examinations were performed. MEPs were recorded over dominant abductor policis brevis (APB) muscle after stimulation over C3′/C4′ area using circular coil in 2 states: 1. resting, and 2. observation. Resting motor threshold, motor amplitudes and latencies during resting and observation, and change ratios of amplitudes and latencies were compared between patients with and without apraxia. Results Resting motor thresholds as well as resting and observation latencies were lower, and resting and observation amplitudes were higher in the nonapraxia group ( Table 1 ). However, none of them reached statistical significance. Latencies got shortened and amplitudes increased during observation significantly in the nonapraxia group compared to apraxia group. Discussion Cognitive symptoms are one of the nonmotor symptoms which are as frequent as motor symptoms in PD and recent studies showed development of isolated memory, visuo-spatial or executive deficits even in the early stages of disease. However, praxis functions are less commonly investigated in PD. Electrophysiological studies suggested that mirror neurons possibly exist in humans as MEP amplitudes gets increased during observation of movement similar to performance of the same act. We also observed a similar increase in nonapraxia PD patients. We think that absence of this pattern also provides additional support for apraxia in early stage PD.