$460 Thursday, November 10, 2005 Poster Abstracts

investigate peripheral nerve function, data pertaining to the validity of this technique in the central nervous system is lacking. The aim of this study was to determine the ability of threshold tracking TMS to assess cortical excitability. Method: Motor evoked potentials were generated in 20 healthy controls using a 90 mat circular coil connected to a BiStim 200 dual pulse magnetic stimulator. Surface electrode recordings were obtained from the abductor pollicis brevis muscle. An MEP amplitude of 0 .2mV (peak-to-peak) was tracked by the conditioned test stimulus. Results: There were two distinct phases of early cortical inhibition (ECD, as represented by an increase in conditioning test st imulus intensity required to maintain a constant output of 0.2 mV, peaking at interstimuhis intervals (ISI) of 1 ms (7.8% increase) and 3 ms (11.2% increase). In addition, ECI occurred up to an ISI of 5 ms. Interestingly, this was not followed by significant facilitation. Late inhibition occurred at ISI of 50-300 ms, peaking at 150 ms (24.2% increase). Conclusion: Threshold tracking TMS proved successful in healthy controls. Studies are underway to assess the utility of this technique as a diagnostic tool and as a marker of disease progression of neuro- degenerative diseases, specifically amyotrophic lateral sclerosis.

1415 Abnormal sitlgle-fibre E M G study in a patient with ant i -GQlb Negative Miller Fisher Syndrome

Chan, YC ~. ZNational University Hospital, Singapore, Singapore

Background: Miller Fisher syndrome (MFS) is strongly associated with a raised an t i -GQlb level. Recent studies have provided evidence that at t t i-GQlb antibodies can mediate pathophysiological changes at the motor nerve terminal and patients with ophthalmoplegia and raised an t i -GQlb antibodies have increased jitter on single-fibre E M G (SFEMG) studies. Case report: We report a patient who presented with clinical features of MFS but had negative test for G Q l b antibodies. S F E M G done at initial presentation showed increased jitter while a repeat test done upon clinical recovery was normal. Discussion: Our case illustrates that increased jitter on S F E M G testing is non-specific for neuromuscular junction disorders and also raises the possibility that there may be other pathogenic antibodies acting at the site of the neuronmscular junct ion in MFS.

1416 Electrodiagnosis and Puffer Fish poisoning

Nguyen Huu, C ~, Le T u Quoc, T ~. 1University Training Center for Health Care Professionals, Ho Chi Mint city, Vietnam; 2ChoRay Hospital, Ho Chi Minh city, Iqetnam

A ease report: There were 5 persons in a family in a coastal province of central Vietnanr affected by puffer fish poisoning. All patients developed acute flaccid paralysis and respiratory failure. Four of them died several hours after consuming the fish. Only one patient survived and was admitted to our hospital with intubation and mechanical ventilation. In the first day after poisoning, there were no compound nmscle action potentials (CMAP) and sensory nerve action potentials (SNAP) obtained on electrodiagtrostic studies, indicating that the toxin has had a complete blocking effect on motor and sensory nerve conduction but not on the neuromuscular synapse. The insertional potentials were normal when needle E M G was perforated. EEG was normal with positive Berger's reaction. Clinical examination showed that the patient appeared to be in a deep coma. The patient was taken off the respirator 3 days later and then completely recovered without any sequelae. The patient assured us that he was conscious during the first day, when E E G and E M G were performed. Electrodiagnostic examination 5 days after the poisoning showed nearly normal amplitudes of C M A P and SNAP with normal motor and sensory conduction velocities. There is no abnormality on needle E M G exanfination, suggesting axonal sparing.

Conclusion: Our s tudy results suggest that in patients with puffer fish poisoning the toxin (tetradotoxin) has a complete conduction block effect on nerves but not on the neuromuscular sylrapse, and it is pro- bable that the toxin has no effect on the central nervous system.

1417 Integrative properties of Neurouluscular Synapses in hmnans

Delelis, V ~, Ulkatan, S a. Zlnstitute for Neurology and Neurosurgery, St. Luk-e's Roosevelt Hospital, New York., USA

Background: Integrative properties of h u m a n neuronmscular synapses have not been very well studied in clinical neurophysiology. Method: In three patients intraoperatively and one healthy subject (in a two separate trials) we stimulated medial nerve at the wrist, facial nerve at the exit of stylomastoid foramen, and tibial nerve at the ankle using near the threshold constant current intensity o f the stimuli duration of 500 ~zs. The recordings of the compound muscle action potential (CMAP) were done from opponens pollicis, orbicularis otis and hallucis brevis nmscles. Stimulation and recordings in the healthy subjects was done with percutaneous electrodes while in the patients, recordings was done with a needle electrodes. Results: In healthy subjects as well as patients, near the threshold current intensity of applied single st imulus over the nerve did not elicit CMAP in the appropriate nmscle. When a nunrber of near the threshold stimuli were increased to the two, five, seven, or nine stinmli and packed in a short train with inter st imulus intervals of 2 ms, this resulted in the successful eliciting of C M A P amplitude of 100 to 200 #V. Conclusion: We concluded that described phenomenon is due to the integrative action of neuronmscalar sytrapses capable to summate the trains of sub threshold intensity stinmli and generate CMAP.

1418 Median Motor Terminal Latency Index in diagnosis of Carpal Tunnel Syndrome

Erdeuloglu, AK ~, Varlibas, A a. 1 University of Kirikkale, Medical School, Department of Neurology, Turkey

Objective: To investigate the diagnostic contribution of median ter- minal latency index (MTLI) in early carpal tunnel syndrome (CTS). Patients and Method: Twenty-nine patients with CTS and forty-three controls were included into the study. Age of patients with CTS diagnosis were ranged between 29 and 56 years (mean: 43.1 ± 7.6), controls 25 and 65 years (mean: 44.1 ± 10.9). hr electrophysiological study, median motor and sensorial latency, velocity and anrplitudes were measured. Terminal latency index of control and c r s patients were assessed according to electrophysiological parameters of median nerve. Results: In CTS patients, mean median motor velocity was 52.2 ± 6.2 m/sc, median distal latency 5.1 ± 1.2 m sc, anrplitudes 8.7 ± 3.7 m V and MTLI 0.27 ± 0.04. Mean median motor and sensorial velocity, distal latency and amplitudes, and M T L I were statistically different between CTS and control groups (p < 0.01). In CTS patients, median ten-ninal latency index was prolonged slightly in eight patients, mild in 15 and severe in six. As MTLI was found to be normal limits in 36 control patients, there was slight prolongation of median terminal latency index in seven. In CTS group, M T L I was found to be slightly prolonged in eight and mild in nine of C [S patients which median motor latency and velocity were within normal limits. Conclusion: Terminal latency index has supplementary diagnostic contribution for early CTS patients.

1419 The Electrophysiologie profiles of patients diagnosed with Hansen's Disease seen in a Tertiary Hospital