P4.9 Electromyographic changes in the course of adhesive arachnoiditis a case report

14th ECCN / 4th ICTMS/DCS Objectives: (a) To outline the timing of the neurophysiological abnormalities induced by botulinum toxin A; (b) to investigate the neurophysiological findings; (c) to assess the correlation between neurophysiological and morphological findings. Materials and Methods: Ten healthy volunteers were inoculated with 15 UI botulin toxin type A in extensor brevis digitorum (EDB) muscle. The peroneal nerve was stimulated at the ankle and the cMAP was recorded at rest, at 3 and 20 Hz. At the same time an EMG and SFEMG analysis was conducted on the EDB muscle. The study was performed at baseline, then weekly for the first 4 weeks, then every two weeks for the following 8 weeks. Results: A week after the inoculation all the subjects showed a small cMAP amplitude, with a recovery beginning on week 4 and partially resolved by the end of the observation period. Absence of decremental response at slow rate repetitive nerve stimulation (RNS) and absence of facilitation at high rate RNS were observed in all the subjects. The EMG examination demonstrated scanty fibrillations and low amplitude, short duration motor unit potentials since the first week. Abnormal jitter and blocking were showed by SFEMG from the week 2 and these abnormalities were more prominent on week 8, combined with denervation/reinnervation findings. Conclusions: The low cMAP amplitude is the main early finding in case of botulism; the absence of facilitation is always present, and it is probably related to the structural synaptic blockage. Subsequently, jitter abnormalities appear together with the denervation/reinnervation changes, suggesting that they are related to the sprouting of the nerve terminal and the formation of new neuromuscular junctions. P4.8 Should medial and lateral antebrachial cutaneous nerves still be considered “unusual”? Normative values and a methodological proposal to improve technical feasibility A. Comanducci1 , M. Borsi1 , L. Caremani1 , R. Carrai1 , F. Pinto1 , A. Amantini1 , A. Grippo1 1 Unit of Clinical Neurophysiology, Department of Neurological Sciences, University of Florence, Italy Introduction: Electrodiagnostic study of the Lateral and Medial Antebrachial Cutaneous nerves (LABCN, MABCN) may be clinically useful to evaluate several conditions as brachial plexopathies. Nevertheless these nerves are not routinely tested especially because their recording is very sensitive to artifacts and limited by a large number of technical pitfalls. Furthermore literature data are conflicting in technical execution and are lacking in describing how to overcome artifacts. Objectives: (a) To describe main technical pitfalls encountered; (b) to provide normative values; (c) to investigate the effects of age, sex, height and body mass index (BMI); (d) to compare results with a standard sensory nerve of upper limb. Methods: We studied 50 healthy subjects (age range 20 88): antidromic LABCN and MABCN conduction studies were performed with stimulation and recording sites identified according anatomic landmarks instead of using fixed distances. We used simultaneous recording in order to prevent potential costimulation artifacts. Antidromic ulnar nerve conduction study was also performed. Results: LABCN and MABCN sensory action potentials (SAPs) were obtained respectively in 97% and 93% of subjects. Mean values were: LABCN onset-to-peak amplitude 20.9 mV, conduction velocity 60 m/s; MABCN onset-to-peak amplitude 11.7 mV, conduction velocity 61 m/s. We defined also the lower limits for conduction velocity (2.5 SD); the lower limits for amplitude (5th percentiles) and the upper limit for interside asymmetry (95th ). Among the factors investigated the increase of BMI was significantly correlated with an amplitude reduction of LABCN, MABCN and Ulnar Nerve SAPs. Conclusions: LABCN and MABCN are not commonly tested. We showed a technical reliability and feasibility in recording these nerves similar to standard upper limb nerves. In our opinion, a rigorous approach could allow their wider inclusion in normative data of neurophysiology laboratories and finally increase their use in clinical practice.

S73 P4.9 Electromyographic changes in the course of adhesive arachnoiditis a case report K. Tomczykiewicz1 , J. Staszewski1 , M. Sadowska1 , E. Skrobowska2 Clinic of Neurology, Military Medical Institute, Warsaw, Poland, 2 Department of Radiology, Military Medical Institute, Warsaw, Poland

1

Adhesive arachnoiditis (AA) is a rare, chronic, insidious condition that causes debilitating, intractable pain and a range of other neurological problems including progressive paraplegia. It is usually linked with previous lumbar operation procedures, myelography, trauma or anesthetic medications given to subarachoid space. The diagnostic role and characteristics of EMG in such cases is not well known. We present a case report of a 45 years-old woman, with acute, severe form of AA. Progressive, massive flaccid paraplegia began a few days after the L4/5 discectomy. The first MRI examination of the lumbar spine was normal, but EMG revealed symptoms of a severe breakage of the Th11 to S2 radices. Repeated MRI showed complete opacification of the thecal sac, extending over cervical to lumbar level. The patient functional disability improved after implementation of systemic steroid treatment and rehabilitation. EMG examination is an important tool in patients with AA because it provides functional assessment of severity and extension of the neuronal damage. It can also be useful in the evaluation of short- and long-term prognosis. The complete EMG examinations performed before and after steroid treatment and rehabilitation as well as MRI examinations will be presented. P4.10 Paired pulse TMS for the assessment of fatigue in hereditary and acquired neuropathies H. Tesfaghebriel1 , S. Ferrari1 , R. Fazio1 , V. Di Stefano1 , L. De Toni Franceschini1 , R. Guerriero1 , S. Previtali1 , S. Amadio1 , G. Comi1 , U. Del Carro1 1 Department of Neurology, Neurorehabilitation and Neurophysiology INSPE San Raffaele Institute, Milan, Italy Objective: To investigate relationships between motor cortex excitability changes and feeling of fatigue in patients with peripheral neuropathy. Methods: Two groups of patients with chronic sensory-motor neuropathy, either acquired (12 patients) or hereditary (16), entered the study. Before and after each fatiguing exercise they underwent intracortical inhibition test (IIT), by means of paired-pulse transcranial magnetic stimulation (TMS). We evaluated motor evoked potentials (MEP) amplitude, motor threshold and an index of IIT expressed as percentage of unconditioned MEP (MEP/R) at different interstimulus intervals (1, 3, 15 e 20 ms). Results: Patients with hereditary neuropathies displayed significant increases of motor cortex excitability after effort, which differed from normal curve in that hyperexcitability was quantitatively more evident. Most striking differences were found, however, in the acquired neuropathies group, where an unexpected hyperexcitability of motor cortex at basal IIT, before any fatiguing test, was observed; adaptation to fatigue was characterised by a paradoxical increase on intracortical inhibition. Conclusion: Sustained motor efforts disrupt normal excitatory/inhibitory balance of motor cortex, leading to a hyperexcitability of motor system, which is also observed in hereditary neuropathies, even though at a higher excitability level. Notably, in patients with acquired neuropathies, motor cortex hyperexcitability is found in basal condition, probably as a consequence of a reduced inhibitory peripheral feed-back. The exhaustion of cortical functional reserve in basal conditions could easily explain the failure of mechanisms allowing the motor cortex to compensate fatigue through the increase of motor excitability level seen in normal subjects. P4.11 Near-nerve neurography of plantar digital nerves in healthy subjects B. Falck1 , S. Laaksonen2 , K. Nyrhinen2 , L. Puksa3 Department of Clinical Neurophysiology, University Hospital, Uppsala, Sweden, 2 Department of Clinical Neurophysiology, University Hospital, Turku, Finland, 3 Department of Neurology, University Hospital, Tartu, Estonia

1

Introduction: Plantar digital nerves can be studied in patients with suspected Morton’s metatarsalgia, tarsal tunnel syndrome and other neuropathies in the foot. We have used the method since 1983. The