Cutaneous Silent Period Latency Research Articles

Single motor unit estimation of the cutaneous silent period in ALS

ObjectiveRecent evidence indicated that amyotrophic lateral sclerosis (ALS) also impairs spinal circuits, including those mediating cutaneous silent period (CSP). However, most studies utilised surface electromyography (sEMG), which needs more resolution to pinpoint changes at the single motoneuron level. We aimed to investigate CSP properties using single motor unit discharges in ALS. MethodsIn mild and severe ALS patients and controls, CSP was recorded in the first dorsal interosseus and analysed using the discharge rate method, which accurately shows the inhibitory postsynaptic potentials (IPSPs) profile. ResultsOur findings confirmed that the CSP latency was prolonged only in severe ALS patients. Moreover, the CSP duration was similar in each group, but late-stage ALS patients tend to have a longer CSP duration. The discharge rate method revealed a significantly longer duration (up to 150 ms) than the duration detected using sEMG. Strikingly, the motoneuron discharge rate – IPSP duration inverse relationship is lost in ALS patients, indicating a possible impairment in the motoneuron integrative properties. ConclusionsOur data support previous findings of prolonged latency, presented input–output modifications of motoneurons, and revealed the entire course of the CSP, representing a much stronger inhibitory event than previously thought. SignificanceMotoneuron integrative property modification assessed by CSP could be a new biomarker for ALS.

Neurophysiologic evaluation of patients with cervical spondylotic myelopathy

BackgroundCervical spondylotic myelopathy (CSM) is a neurodegenerative disease caused by repetitive spinal cord damage that has resulted in significant clinical morbidity. The clinical evaluation of signs and symptoms, as well as neuroimaging and several neurophysiological tests, are used to make the diagnosis.ObjectivesTo investigate changes in the cutaneous silent period (CuSP), cortical silent period (CoSP), and H-reflex in CSM patients, and to correlate these tests with the Japanese Orthopedic Association (JOA) score and Nurick’s grading, as well as to determine the diagnostic value of each of them.MethodsTwenty patients (14 males and 6 females) with CSM were clinically diagnosed and documented by magnetic resonance imaging (MRI), and they were paired with another 20 healthy volunteers (13 males and 7 females) as a control group. CuSP, CoSP, and H-reflex tests were performed on both groups.ResultsIn CSM patients, CuSP latency and duration are substantially longer and shorter in CSM patients, respectively. The degree of changes in CuSP latency is well correlated with the severity of the disease. Further, CoSP duration is significantly shortened. The H-reflex parameters did not differ significantly between the patient and control groups.ConclusionThe shortened CoSP’s duration and the prolonged CuSP's latency suggest malfunction of the inhibitory and excitatory circuits in the spinal cord. The CuSP is more sensitive and specific than the CoSP in the diagnosis of a patient with CSM.

Comparison of cutaneous silent period parameters in patients with primary Sjögren's syndrome with the healthy population and determination of ıts relationship with clinical parameters.

Small fiber neuropathy (SFN) is one of the main neurological manifestations in primary Sjögren's Syndrome (pSS). For the detection of SFN, cutaneous silent period (CSP) measurement is gaining popularity recently due to its non-invasiveness and practical application. Evaluating SFN involvement in patients with pSS using CSP and evaluating its relationship with clinical parameters. Patients with a diagnosis of pSS and healthy volunteers demographically homogeneous with the patient group were included in the study. The CSP responses were recorded over the abductor pollicis brevis muscle. The latency and duration values of the responses were obtained. In patient group, EULAR Sjögren's Syndrome Patient Reported Index (ESSPRI), Hospital Anxiety and Depression Scale (HADS), Short Form-36 (SF-36) questionnaire, Leeds Assessment of Neuropathic Symptoms and Signs (LANSS) and Central Sensitization Inventory (CSI) were applied for the evaluation of symptom severity, mood, quality of life, presence of neuropathic pain and central sensitization, respectively. The mean CSP latency was significantly longer in patient group compared to control group (p < 0.001). Mean CSP duration was also significantly shorter in patient group (p < 0.001). There were no significant differences in CSP parameters according to patients' neuropathic pain or central sensitization profile. There were significant correlations of CSP parameters (latency and duration, respectively) with ESSPRI dryness (ρ = 0.469, p = 0.004; ρ = -0.553, p < 0.001), fatigue (ρ = 0.42, p = 0.011; ρ = -0.505, p = 0.002), pain (ρ = 0.428, p = 0.009; ρ = -0.57, p < 0.001) subscores and mean ESSPRI score (ρ = 0.631, p < 0.001; ρ = -0.749, p < 0.001). When SF-36 subscores and CSP parameters were investigated, a significant correlation was found only between "bodily pain" subscore and CSP duration (ρ = -0.395, p = 0.017). In HADS, LANSS and CSI evaluations, a significant correlation was found only between HADS anxiety score and the CSP duration (ρ = 0.364, p = 0.02). As indicated by CSP measurement, SFN is more prominent in patients with pSS than in the healthy population. It is important to investigate the presence of SFN because of its correlation with the leading symptoms in the clinical spectrum of pSS.

AB0494 COMPARISON OF CUTANEOUS SILENT PERIOD PARAMETERS IN PATIENTS WITH PRIMARY SJÖGREN’S SYNDROME WITH THE HEALTHY POPULATION

BackgroundNeurological involvement has a great importance in the clinical spectrum of primary Sjögren’s syndrome (pSS) (1). The presence of small fiber neuropathy (SFN), which cannot be detected in routine electrophysiological examinations, causes the peripheral nervous system involvement to be underestimated in the course of the disease and causes pain-related symptoms in patients that cannot be explained by routine examinations (2). Various methods can be used in the detection of SFN, and cutaneous silent period (CSP) measurement is gaining popularity recently due to its non-invasiveness and practical application (3).ObjectivesEvaluating SFN involvement in patients with pSS using CSP and evaluating its relationship with clinical parameters.MethodsPatients with a diagnosis of pSS followed in the rheumatology outpatient clinic and healthy volunteers demographically homogeneous with the patient group were included in the study. The CSP responses were recorded over the abductor pollicis brevis muscle in the upper extremity of all participants. The latency and duration values of the responses were obtained. In patient group, EULAR Sjögren’s Syndrome Patient Reported Index (ESSPRI), Hospital Anxiety and Depression Scale (HADS), Short Form-36 (SF-36) questionnaire, Leeds Assessment of Neuropathic Symptoms and Signs (LANSS) and Central Sensitization Inventory (CSI) were applied for the evaluation of symptom severity, mood, quality of life, presence of neuropathic pain and central sensitization, respectively. Comparison of CSP parameters between patients with pSS and healthy volunteers was determined as the primary outcome measure. The secondary outcome measure was the relationship between CSP parameters and ESSPRI, HADS, SF-36, LANSS and CSI scores.ResultsA total of 36 patients and 36 healthy controls were included in the final analyses. There was no significant difference between the two groups in terms of demographic data. The mean CSP latency was significantly longer in patients with a mean of 78.18 (±7.51) when compared to controls with a mean of 67.91 (±6.41) (95% CI: 6.98- 13.55, p&lt;0.001). Mean CSP duration was also significantly shorter in patients with a mean of 33.40 (±6.93) (95% CI: 9.57 -15.31, p&lt;0.001). There were no significant differences in CSP parameters (latency and duration, respectively) according to patients’ neuropathic pain or central sensitization profile (p&gt;0.05 for all analyses). There were significant correlations of CSP parameters with ESSPRI dryness (r=0.469, p=0.004; r=-0.553, p&lt;0.001), fatigue (r=0.42, p=0.011; r=-0.505, p=0.002), pain (r=0.428, p=0.009; r=-0.57, p&lt;0.001) subscores and mean ESSPRI score (r=0.631, p&lt;0.001; r=-0.749, p&lt;0.001). Significant correlations were not found between CSP parameters and SF-36 scores, other than CSP duration and “pain” subscore (r=-0.395, p=0.017). When the other correlations were investigated there were no significant correlations other than CSP duration and the HADS anxiety score (r=-0.201, p=0.02).ConclusionAs an indicator of CSP measurement, SFN is more common in patients with pSS than in the healthy population. The association with important clinical symptoms of the disease course such as dryness, fatigue, pain and anxiety highlights the importance of detecting small fiber neuropathy.

Electrophysiological findings in patients with restless legs syndrome

BackgroundRestless legs syndrome (RLS) manifests as an urge to move the body to relieve the discomfortable sensations, primarily when resting, sitting, laying down, or sleeping. Diagnosis of RLS relies on clinical criteria, and the immobilization test was the only instrumental tool with equivocal results. ObjectivesTo assess different electrophysiological findings in patients with RLS, and compare the diagnostic values of these parameters in the diagnosis of RLS. Methods30 patients with primary RLS and 30 controls who were matched for age and gender were studied. Participant's demographics, laboratory findings, and electrophysiological test, namely nerve conduction studies (NCS), cutaneous silent period (CSP), H reflex and sympathetic skin response (SSR), F-wave latency, amplitude, F-wave duration (FWD), and the ratio between FWD and duration of the corresponding compound muscle action potential (FWD/CMAPD) were analyzed. ResultsNone of the patients showed altered NCS data. FWD of upper (12.37 ± 2.77 ms) and lower limb (21.71 ± 5.24 ms) were significantly longer in patients. Also, FWD/CMAP duration of the upper (1.03 ± 0.2) and lower limb (2.02 ± 0.55) was longer in patients. Likewise, they exhibited delayed CSP latency from TA (110.62 ± 13.73 ms) and APB (77.35 ± 12.16 ms) whereas the CSP duration from TA and APB was decreased (37.36 ± 11.59 ms; 42.55 ± 7.97 ms, respectively). The SSR latency was not different, and right-sided H reflex amplitude (5.07 ± 3.98 mV) and H/M ratio (0.65 ± 1.81) were significantly increased in the patient group. ConclusionThe data suggest that there may be a dysfunction of the inhibitory/excitatory circuits at a spinal level; and no pathology in the peripheral nerves. The unilateral difference of H reflex amplitude and H/M ratio may suggest asymmetrical central inhibitory dysfunction. Further prospective studies with larger cohorts are now needed to evaluate the pathophysiology of RLS with different neurophysiological assessment tools.

Metabolic syndrome and anthropometric indices in CTS hands: an electrophysiological study.

This study aims to evaluate the effect of metabolic syndrome (MetS) and anthropometric indices on carpal tunnel syndrome (CTS). Forty-three healthy controls and 41 CTS patients were enrolled. Complaints of patients were assessed by Boston Questionnaire (BQ). MetS components were investigated. Wrist circumference, wrist depth, wrist width, palm width, and palm length were measured. Routine nerve conduction studies of median and ulnar nerves as well as the "sensitive" comparison tests were performed. Cutaneous silent period (CuSP) was studied by stimulating both second and fifth digital nerves while recording over thenar muscles. The vast majority of the participants were female and right-handed. CTS was bilateral in 61% of patients. Data of 109 hands were analyzed. MetS was more frequent in CTS patients. BQ scores were not related to MetS. Waist circumference, serum TG, and fasting glucose levels were higher in CTS patients. CTS hands with MetS had lower median CMAP amplitudes and increased sensory thresholds. Sensory thresholds were increased with both median and ulnar nerve stimulations suggesting a wider spread of peripheral nerve excitability changes in MetS presence. CuSPs were recorded from all 109 hands. CuSP latencies and durations were similar between controls and CTS patients. Wrist ratio was the only anthropometric index that was a statistically significant predictor for CTS development. MetS was more prevalent in CTS patients. Some clinical and electrophysiological features (mainly sensory thresholds) may worsen in presence of MetS, but not the wrist ratio.

Electrodiagnostic study in patients with fibromyalgia: Implication for central sensitization

Background: Fibromyalgia is a syndrome characterized by chronic pain, depression, fatigue, and sleep disturbance. Different hypotheses have emerged about its pathogenesis, but central sensitization, which plays an important role in the development of neuropathic pain, is considered to be the main mechanism. We aim to compare patients with fibromyalgia and healthy controls with different electrodiagnostic testing, and if present, to corroborate whether there is any relationship between electrodiagnostic measures. Also, we sought to test the diagnostic value of some of these measures. Methods: A case-control study of thirty-one patients with fibromyalgia with a duration of illness ranging from 5 months to 10 years were recruited for the study. Full medical history, clinical neurological examination, and electrodiagnostic tests of the upper and lower extremity including nerve conduction studies, needle electromyography, sympathetic skin response, cutaneous silent period and muscle fiber conduction velocity. Results: Sympathetic skin response latency and cutaneous silent period latency were not different between the patients and the control group. Cutaneous silent period duration was prolonged and the muscle fiber conduction velocity is faster in the subjects with fibromyalgia. The latter measures have similar diagnostic value. Sex has no significant impact on electrodiagnostic measures and the latter not correlated with patients' age. Conclusion: A central sensitization and concomitant deregulation of the efferent higher motor centers might be implicated in the pathogenic mechanism of fibromyalgia.

Small fiber neuropathy and related factors in patients with systemic lupus erythematosus; the results of cutaneous silent period and skin biopsy

IntroductionEvaluating small nerve fibers in patients with systemic lupus erythematosus (SLE) using cutaneous silent period (CSP) and skin biopsy and assesssing the relationship between clinical signs, autoantibodies and neuropathic pain score.Objective – methodsFifty one SLE patients and 46 healthy volunteers were included in this study. Nerve conduction studies and CSP were performed both on upper and lower limbs in subjects. Skin biopsy was performed and the number of epidermal nerve density and IL-6 staining were evaluated.ResultsIn SLE patients, CSP latencies were significantly prolonged both in lower and upper limbs and lower and upper extremity CSP durations were significantly shorter when compared to controls (p < 0.001). The number of epidermal nerve was significantly lower in SLE patients when compared to healthy controls (p < 0.001).ConclusionWe detected marked small nerve fiber damage in both lower and upper limbs in SLE patients using CSP. Decreased epidermal nerve density also supports this finding.

The effect of vitamin D replacement on spinal inhibitory pathways in women with chronic widespread pain

Vitamin D replacement helps in pain reduction in patients with chronic widespread pain (CWP). But the current literature lack studies that investigate its mechanism. Cutaneous silent period (CSP) is the electrophysiologic analog of the spinal inhibitory pathways and an objective method to document their involvement. This study aims to show if vitamin D replacement has an effect on the spinal inhibitory pathways through CSP parameters. Female patients who have CWP with vitamin D deficiency were included. Patients received an 8-week replacement therapy of vitamin D. Patients’ pain were evaluated using the visual analog scale (VAS) and Leeds assessment of neuropathic symptoms and signs pain scale (LANSS). Quality of life with Nottingham Health Profile (NHP) and CSP parameters were also recorded before and after treatment. A total of 51 patients were included in the final analyses. The mean age of the patients was 44.3 ± 12.7 (minimum 18-maximum 65). Mean symptom duration was 13.1 ± 6.7 (minimum3-maximum 24) months. Patients' mean BMI was 21.6 ± 3.9 (minimum 18.0 maximum 29.1). Patients' median VAS and LANSS scores decreased significantly (p < 0.01) and NHP scores improved significantly in all subsets (p < 0.01). Vitamin D replacement did not significantly change CSP latency and duration (p = 0.06 and p = 0.12).Vitamin D replacement does not seem to work via modifying the spinal inhibitory pathways that are involved in the formation of the cutaneous silent period. This is the first study to objectively investigate the effect of vitamin D replacement on central sensitization mechanisms.

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

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). 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. 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). 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.

Use of cutaneous silent period parameters as a diagnostic indicator in patients with restless legs syndrome-a study in south Indian population

Objective: The objectives of this study were to investigate cutaneous-silent- period (CSP) parameters- CSP latency and CSP duration in patients with ‘Restless legs Syndrome’ and compare it with that of normal healthy controls. Methods: Thirty patients diagnosed with restless legs syndrome were included in this study. The cutaneous silent period was evoked by electrical stimulation of sural nerve whereby both CSP parameters CSP latency and CSP duration were recorded and analyzed. Results: The mean latencies of CSP among the thirty RLS patients were 101.95±12.12 while the control group showed 96.23± 9.16. There is a statistically significant high average latency in RLS patients (101.95± 12.12) than control group (96.23± 9.16) with p value=0.044. This study also showed the average CSP duration to be high in RLS patients (42.25± 11.12), when compared to the control group – 36.75± 8.35 (p value=0.035). Conclusion: While RLS is a common sensorimotor disorder, the diagnosis of RLS is purely clinical and there are no objective tests for the diagnosis. Unfortunately, the awareness is poor among the lay population, general practitioners and even specialists in the Indian subcontinent. The authors feel that the CSP test can be used as an objective method supporting the diagnosis of RLS. Furthermore, we believe that this paper will help create awareness in addition to encouraging more research in this arena from medical personnel in India.

Cutaneous silent period in myofascial pain syndrome.

An increased response to painful stimuli without spontaneous pain suggests a role of central hyperexcitability of pain pathways in the pathogenesis of myofascial pain syndrome (MPS). In this study we aimed to test the hypothesis that spinal pain pathways are affected in MPS. We used cutaneous silent period (CSP) parameters to demonstrate the hyperexcitability of spinal pain pathways in MPS. Twenty-nine patients diagnosed with MPS and 30 healthy volunteers were included in the study. The CSP recordings were performed in the right upper and left lower extremities. In both upper and lower extremities, patients had prolonged CSP latencies (P = 0.034 and P = 0.049 respectively) and shortened CSP durations (P = 0.009 and P = 0.008, respectively). Delayed and shortened CSP in MPS patients implies dysfunction in the inhibitory mechanism of the spinal/supraspinal pain pathways, suggesting central sensitization in the pathogenesis of MPS and supporting our research hypothesis. Muscle Nerve 57: E24-E28, 2018.

42. The effects of THC on Cutaneous Silent Period

The analgesic effects of cannabinoids are mediated through the activity on the endogenous cannabinoid system. (−)-trans-Δ 9 -tetrahydrocannabinol (THC) is the principal psychoactive constituent of cannabis and it shows a partial agonist activity on cannabinoid receptors, in particular CB1 receptor, mainly expressed by neurons of the central and peripheral nervous system. Several studies demonstrate the effects of THC on pain perception. The aim of this study was to evaluate the effects of THC in 13 healthy volunteers (HV) through the analysis of Cutaneous Silent Period (CSP), a nociceptive spinal inhibitory reflex, considered a defense response, specific for the human upper limbs. CSP parameters have been recorded from the abductor digiti minimi (ADM) before and after an hour from the administration of a cannabis-based preparation. We recorded the same parameters before and after the administration of placebo in the same volunteers. The results showed that the CSP latency and amplitude left unchanged in HV after the drug administration at the dose commonly used to suppress nociceptive reflexes in humans. These differential effects of a narcotic-analgesic drug provide evidence that the Cutaneous Silent Period is not a THC-sensitive nociceptive reflex.

Lengthened Cutaneous Silent Period in Fibromyalgia Suggesting Central Sensitization as a Pathogenesis.

The pathogenesis of fibromyalgia (FM) has not been clearly elucidated, but central sensitization, which plays an important role in the development of neuropathic pain, is considered to be the main mechanism. The cutaneous silent period (CSP), which is a spinal reflex mediated by A-delta cutaneous afferents, is useful for the evaluation of sensorimotor integration at the spinal and supraspinal levels. To understand the pathophysiology of FM, we compared CSP patterns between patients with FM and normal healthy subjects. Twenty-four patients with FM diagnosed in accordance with the 1990 American College of Rheumatology classification system and 24 age- and sex-matched healthy volunteers were recruited. The CSP was measured from the abductor pollicis brevis muscle. Demographic data, number of tender points, and visual analog scale and FM impact questionnaire scores were collected. The measured CSP and clinical parameters of the patient and control groups were compared. In addition, possible correlations between the CSP parameters and the other clinical characteristics were analyzed. Mean CSP latencies did not differ between patients (55.50 ± 10.97 ms) and healthy controls (60.23 ± 11.87 ms; p = 0.158), although the mean CSP duration was significantly longer in patients (73.75 ± 15.67 ms) than in controls (63.50 ± 14.05 ms; p = 0.021). CSP variables did not correlate with any clinical variables. The significantly longer CSP duration in FM patients suggests central dysregulation at the spinal and supraspinal levels, rather than peripheral small fiber dysfunction.

Cutaneous silent period recordings in demyelinating and axonal polyneuropathies

ObjectiveTo investigate the cutaneous silent period (CSP), a spinal inhibitory reflex mainly mediated by A-delta fibres, in demyelinating and axonal polyneuropathy (PNP) and evaluate whether CSP parameters differ between patients with and without neuropathic pain. MethodsEighty-four patients with demyelinating PNP, 178 patients with axonal PNP and 265 controls underwent clinical examination, DN4 questionnaire, standard nerve conduction study, motor-root stimulation and CSP recordings from abductor digiti minimi. We calculated the afferent conduction time of CSP (a-CSP time) with the formula: CSP latency−root motor evoked potential latency. ResultsIn the demyelinating PNP group the a-CSP time was significantly longer; in the axonal PNP group, CSP duration was shorter than the demyelinating group (p=0.010) and controls (p=0.001). CSP parameters were not different between patients with and without neuropathic pain. ConclusionsThe abnormality of a-CSP time in the demyelinating PNP group suggests the crucial role of A-delta fibres in the mechanism of CSP; the shorter CSP duration in the axonal PNP group supports the strong influence of the number of axons on this parameter.Our study suggests that neuropathic pain could be related to pathophysiological mechanisms differing from mere A-delta fibre loss. SignificanceCSP evaluation is effective in detecting A-delta fibre dysfunction in axonal as well as demyelinating PNP.

Small fiber neuropathy associated with hyperlipidemia: utility of cutaneous silent periods and autonomic tests.

Background. Established electrophysiological methods have limited clinical utility in the diagnosis of small fiber neuropathy. The cutaneous silent period (CSP) may be useful as a method for the evaluation of smaller and unmyelinated fiber dysfunctions. Hyperlipidemia is a very rare cause of small fiber neuropathy. In this study, hyperlipidemia and small fiber neuropathy in symptomatic patients with normal nerve conduction studies were evaluated with autonomic tests and cutaneous silent periods. Methods. Twenty-five patients with clinically suspected small fiber neuropathy and 23 healthy volunteers were included. CSP latency and duration, as well as CSP latency difference of the upper and lower extremities, were examined. Two tests were used to assess the autonomic nervous system, namely, the R-R interval variation test in basal and profound breath conditions and the sympathetic skin response. Results. Twenty-five patients with clinically suspected small fiber neuropathy and normal nerve conduction studies were compared with 23 controls. In the upper extremities, patients had prolonged CSP latencies (P = 0.034) and shortened CSP durations (P = 0.039), whereas in the lower extremities, patients had shortened CSP durations (P = 0.001). The expiration-to-inspiration ratios were also reduced in patients groups. There was no significant difference between sympathetic skin response latencies and amplitude of the case and control groups. Conclusion. Our findings indicate that CSP may become a useful technique for the assessment of small fiber neuropathy in hyperlipidemic patients.

Influence of limb temperature on cutaneous silent periods

ObjectiveThe cutaneous silent period (CSP) is a spinal inhibitory reflex mediated by small-diameter afferents (A-delta fibers) and large-diameter efferents (alpha motoneurons). The effect of limb temperature on CSPs has so far not been assessed. MethodsIn 27 healthy volunteers (11 males; age 22–58years) we recorded median nerve motor and sensory action potentials, median nerve F-wave and CSPs induced by noxious digit II stimulation in thenar muscles in a baseline condition at room temperature, and after randomly submersing the forearm in 42°C warm or 15°C cold water for 20min each. ResultsIn cold limbs, distal and proximal motor and sensory latencies as well as F-wave latencies were prolonged. Motor and sensory nerve conduction velocities were reduced. Compound motor and sensory nerve action potential amplitudes did not differ significantly from baseline. CSP onset and end latencies were more delayed than distal and proximal median nerve motor and sensory latencies, whereas CSP duration was not affected. In warm limbs, opposite but smaller changes were seen in nerve conduction studies and CSPs. ConclusionThe observed CSP shift “en bloc” towards longer latencies without affecting CSP duration during limb cooling concurs with slower conduction velocity in both afferent and efferent fibers. Disparate conduction slowing in afferents and efferents, however, suggests that nociceptive EMG suppression is mediated by fibers of different size in the afferent than in the efferent arm, indirectly supporting the contribution of A-delta fibers as the main afferent input. SignificanceLimb temperature should be taken into account when testing CSPs in the clinical setting, as different limb temperatures affect CSP latencies more than large-diameter fiber conduction function.

Differential effect of baclofen on cortical and spinal inhibitory circuits

ObjectiveThe cutaneous silent period (SP) is a spinal inhibitory reflex, which suppresses activity in spinal motor nuclei. Transcranial magnetic stimulation (TMS) elicits a cortical SP, which represents GABAB receptor-mediated inhibition of cortical excitability. Baclofen as a strong GABAB agonist effectively reduces muscle hypertonia, however, it is not known whether intrathecal baclofen (ITB) may modulate spinal inhibitory circuits. MethodsWe evaluated clinical and neurophysiological effects of ITB in ten patients with severe spasticity due to spinal cord injury (n=9) and chronic progressive multiple sclerosis (n=1). Neurophysiological assessment included H reflex and cutaneous and cortical SPs, before and 15, 30, 60, 90, 120, and 180min after ITB bolus administration. ResultsITB suppressed soleus H reflex as early as 15min after lumbar bolus injection; MAS scores declined after 1h. Cortical SP end latency and duration increased progressively with a significant maximum 3h following ITB bolus, whereas cutaneous SP latency and duration did not change significantly. ConclusionThe present findings suggest that baclofen does not affect the cutaneous SP, but prolongs the cortical SP. SignificanceThe spinal inhibitory circuitry of the cutaneous SP is not modulated by GABAB receptor-mediated activity, in contrast to the cortical inhibitory circuitry of the cortical SP, which is subject to powerful GABAB control.

Effect of Alpha-Lipoic Acid on Cutaneous-Silent-Period Parameters in Patients with Type 2 Diabetes Mellitus (P01.201)

Objective: The aim of this study was to investigate cutaneous-silent-period (CSP) parameters in patients with type 2 diabetes mellitus (DM) and examine the effects of Alpha-lipoic acid (ALA) treatment on CSP which, to our knowledge, have not been investigated till date in the literature. Background Small myelinated (A-d) and unmyelinated (C) somatic sensory fibers are initially affected and may be the earliest exhibited sign of neuropathy in glucose dysmetabolism. Cutaneous silent period (CSP) is an inhibitory spinal reflex and its afferents consist of A-d nerve fibers. Design/Methods: A total of 17 patients with DM and 25 healthy volunteers were studied. CSP latency and duration in the upper and lower extremities were examined in the two groups. In DM patients, the variables were examined before and after ALA treatment. Results: Upper-extremity CSP latency {79,50 (59,50-89,50) ms} was longer in patients, compared with controls {73,75 (56,00-85,25) ms} (p=0,007). Lower-extremity CSP latency was longer {112,75 (78,25-152,75) ms} in patients, compared with controls {96,25 (80,00-113,00) ms} (p Conclusions: The results suggest that ALA treatment may improve small-fibre neuropathy (SFN) in DM patients. CSP may be used as a measure of ALA treatment effectiveness. Disclosure: Dr. Yucel has nothing to disclose. Dr. Oz has nothing to disclose. Dr. Akgun has nothing to disclose. Dr. Taslipinar has nothing to disclose. Dr. Erdogan has nothing to disclose. Dr. Yasar has nothing to disclose. Dr. Ulas has nothing to disclose. Dr. Odabasi has nothing to disclose.

Effect of pramipexole on cutaneous-silent-period parameters in patients with restless legs syndrome

Objective The aim of this study was to investigate cutaneous-silent-period (CSP) parameters in patients with restless legs syndrome (RLS) and examine the effects of treatment on CSP which, to our knowledge, have not been investigated till date. Methods A total of 25 patients with RLS and 25 healthy volunteers were studied. CSP latency and duration in the upper and lower extremities were examined in the two groups. In RLS patients, the variables were examined before and after pramipexole treatment. Results Lower-extremity CSP latency was longer (106.22 ± 11.69 ms vs. 91.67 ± 8.53 ms; p < 0.001) and CSP duration was shorter (35.50 ± 10.91 ms vs. 49.47 ± 6.43 ms; p < 0.001) in patients, compared with controls. In the patient group, CSP durations in the upper (40.88 ± 7.95 ms vs. 46.84 ± 10.22 ms; p = 0.006) and lower extremities (35.50 ± 10.91 ms vs. 44.91 ± 6.43 ms; p = 0.005) were prolonged after treatment, compared with pre-treatment values. Conclusions Small-fibre neuropathy may exist in RLS. In addition, we suggest that pramipexole may regulate cortical and spinal inhibitory mechanisms. Significance The use of CSP may aid in the diagnosis of RLS and may be used as a measure of treatment effectiveness.