Abstracts of Poster Presentations / Clinical Neurophysiology 125, Supplement 1 (2014) S1–S339 S269 Figure 2. The relationship between muscle strength and transcranial stimulation mo- tor evoked potential. Conclusions: There is the positive relation between the MEP amplitude and the muscle strength. So, the fixed quantity evaluation method using the statistical technique makes TCS-MEP reliable. And TCS-MEP may enhance us to remove tumors in central nervous system and at the same time preserve motor functions. Moreover this relation between MEP and muscle strength is useful for understanding the motor control system. P850 Electrophysiological pattern in GLUT1 deficiency syndrome (A275T mutation) C. Giliberto 1 , V. Sofia 1 , R. Barone 2 , R. Guerrini 3 , M. Zappia 1 1 University of Catania, Department G.F. Ingrassia, Section of Neurosciences, Catania, Italy; 2 University of Catania, Pediatric Neurology, Department of Pediatrics, Catania, Italy; 3 University of Florence, Pediatric Neurology, Unit and Laboratories, Children’s Hospital A. Meyer, Florence, Italy Question: Glucose transporter type 1 deficiency syndrome (GLUT1DS) is characterized by impaired glucose transport across the blood-brain barrier due to SLC2A1-gene mutation. GLUT1DS infancy onset shows epileptic encephalopathy, ataxia and microcephaly although paroxysmal exercise- induced dyskinesia and epilepsy may also be observed. Exercise and recovery-induced modifications of GLUT4 and GLUT1 expression in human muscle have been reported.We describe clinical and electromyographyc correlates of a GLUT1DS patient with adult-onset of exercise-induced dystonia. Patients and methods: A 19 year old male with mild mental retardation presented with a two-year history of episodic stiffness in his calves and feet and painless flexion of the toes followed by leg weakness triggered by exertion and starvation and alleviated by rest and eating. His father had experienced exercise-induced leg dystonia at younger age. A heterozygous missense of mutation (c.823G>A; p.A275T) of SLC2A1 gene was found in the proband and his father.The proband underwent an electromyographyc study after voluntary contraction (5 minutes) to investigate muscle mem- brane excitability with the evaluation of compound muscle action potential (CMAP) amplitude. Results: The test disclosed significant decrement of CMAP amplitude up to -42% (n.v.≤-20%) after 40 minutes from exercise with respect to the pre-exercise CMAP amplitude (baseline). The same test repeated after carbohydrate-rich food intake showed a significant improvement of CMAP from baseline (-26%). Conclusions: The electrophysiological study after exercise showed a reduc- tion of CMAP amplitude in this patient with GLUT1DS (A275T mutation). Our data suggest a possible involvement of muscle membrane excitability in GLUT1DS. P851 Tracking the spatiotemporal profile of cortical and peripheral motor axon hyperexcitability in amyotrophic lateral sclerosis E. Bakola 1 , P. Kokotis 1 , R. Carr 2 , M. Schmelz 2 , M. Rentzos 1 , T. Zambelis 1 , N. Karandreas 1 1 University of Athens, Medical School, Department of Neurology, Athens, Greece; 2 University of Heidelberg, Mannheim Medical School, Department of Anesthesiology, Mannheim, Germany Question: Recent studies using magnetic and electrical excitability tracking tools have confirmed early hyperexcitability in ALS. This study sets out to use excitability testing to examine directly the spatiotemporal profile of cortical and peripheral hyperexcitability in ALS patients simultaneously, to associate these parameters to the clinical course of the disease and to compare them with healthy controls. Methods: Nineteen patients with first-diagnosed definite ALS (group A), four patients with advanced disease (group B) and ten control healthy vol- unteers (group C) were included in the study. Multiple axonal excitability properties (threshold electrotonus, strength-duration time constant, recov- ery cycle, current-threshold relationship) and TMS investigations including measurement of resting motor threshold (RMT) and motor evoked potential (MEP) were measured. Results: In group A there were greater changes in depolarizing threshold electrotonus (TD) compared with group B (t-test p<0.03). No differences in recovery cycle, strength-duration time constant, current-threshold re- lationship were noted between the three groups. Regarding the cortical excitability parameters, there was a significant decrease in the slope of MEP amplitude to TMS intensity in group B with the advanced disease in comparison to controls (Mann-Whitney U test p<0.05). ANCOVA showed strong correlation between TD and slope of cortical excitability (p<0.01) after correcting for the status of the disease (groups A,B,C). Conclusions: These are preliminary results of an ongoing study trying to understand the changes in axonal and cortical excitability in first-diagnosed and advanced disease in order to provide insight into the pathophysiologi- cal basis of the disease and furthermore provide useful information for the best treatment approach in the future. References: [1] Bae JS, et al. The puzzling case of hyperexcitability in amyotrophic lateral sclerosis. J Clin Neurol 2013 Apr;9(2):65-74. [2] Khedr EM, et al. Cortical excitability of amyotrophic lateral sclero- sis: transcranial magnetic stimulation study. Neurophysiol Clin 2011 May;41(2):73-9. [3] Shibuta Y, et al. Increased variability of axonal excitability in amy- otrophic lateral sclerosis. Clin Neurophysiol 2013 May 29. P852 Temporal profile of the effects of regional anesthesia on the cutaneous silent period of foot muscles I. Araujo Mota 1,2 , X. Sala-Blanch 2 , J.B. Fernandes 2 , M. Neves Cardoso 2,3 , J. Valls-Solé 2 1 Federal University of Paraiba, Joao Pessoa, Brazil; 2 Hospital Clinic University of Barcelona, Barcelona, Spain; 3 Hospital Santo António, Serviço de Neurofisiologia, Porto - Portugal, Portugal Question: It is commonly accepted that cutaneous silent period (CuSP) is mediated by small fibers but median size or large afferents may also contribute. We examined the effects of blocking pain afferents by regional anesthesia on the silent period latency and duration in foot muscles. Methods: We studied 10 patients with indication for surgical treatment of hallux valgus before and after ultrasound-guided popliteal sciatic nerve block (US-SPB). CuSP was obtained from the extensor digitorum brevis muscle to high intensity electrical stimuli applied to the big toe with ring electrodes. We also obtained the sympathetic skin response (SSR) from both feet to the same electrical stimulus and the skin temperature variation using an infrared thermometer. We evaluated motor fibers through the analysis of F waves. Results: The SSR showed an early block of the efferent sudomotor fibers (mean of 4.5 m), which was almost immediately followed by a decrease in CuSP duration and a delay in CuSP onset latency. At the same time there was also an increase in temperature in the ipsilateral leg and a decrease in the contralateral one. The CuSP end latency remained unaltered up to