P261 Cortical excitability changes in the earliest stages of amyotrophic lateral sclerosis (ALS)

Abstract

Objectives To reveal CE changes in the earliest stages of ALS. Methods The prospective analysis of CE tested with TMS was done with 11 patients at the earliest stage of ALS when the diagnosis was considered as “possible ALS” according to the Awaji and El Escorial criteria. The “possible ALS” was established in 3 patients with signs of frontotemporal dementia and 4 patients had bulbar onset. In all patients, the resting motor threshold (RMT) was checked with the motor evoked potential (MEP) recorded bilateral from abductor pollicis brevis (ABP) and tibialis anterior (TA) muscles. There was no subjective weakness in target muscles but the normal or increased tendon reflexes. After 1.8–2.2 years of the follow up period, the diagnosis of ALS corresponded all the criteria of reliable disease with upper and lower motor neuron involvement. Results In the early stages of possible ALS the RMT registered from the upper and lower extremities was normal: APB 40 ± 5%, TA 65 ± 7%. The paradoxical “normality” did not correlate to clinical features provided evidence of upper motor neuron involvement.The MEP amplitude was normal. After 1.8–2.2 years, in all cases, the RMT increased or MEP was absent. Conclusions In the earliest stages of ALS the level of RMT doesn’t differ from measurements in normal individuals, and can’t be used as the parameter of suggesting CE changes. Significance The question of what one mean by early stages of ALS is the most vulnerable issue in investigations of CE in motor neuron disease.