SHORT REPORT The onset of amyotrophic lateral sclerosis

Two patients in whom both the neurological examination and electromyography (EMG) were normal prior to the onset of amyotrophic lateral sclerosis (ALS) are reported. In each patient, the onset of ALS some 18 months later was clearly defined clinically and confirmed by subsequent EMG studies. These unique observations show that ALS commences at a defined time, and that there is early generalisation with an initial phase of rapid progression. T he onset of sporadic amyotrophic lateral sclerosis (ALS) is usually uncertain, although patients often believe that they can define it. There are very few clinical observa-tions relevant to this issue, which is important in under-standing the dynamics of progression in the disease.1 2 Here we describe two patients who were observed clinically and by electromyography (EMG) before and shortly after the onset and then during the course of the disease. All EMG studies were performed by the same neurophysiologist (MC). Our observations show that sporadic ALS, like familial ALS,3 seems to have a relatively abrupt onset