[Associated EMG responses in Alzheimer's disease and in healthy subjects]

INTRODUCTION AND AIMS

Recently, the appearance of associated EMG responses in patients with probable Alzheimer s disease (AD) have been reported during the performance of cue stimuli recognition tasks using an oddball model. We present our work with AD patients and on the possibility of obtaining these responses in normal subjects by modifying the conditions under which the exploration is carried out.

PATIENTS AND METHODS

We review 38 cases of probable AD, mild and moderate in intensity, in which we explored reaction time by bilateral EMG recording in the extensor muscles of the hand. The same exploration was performed in 20 healthy subjects in basal conditions and again while a simple mathematical task was being performed.

RESULTS

In two of the 38 cases, both of moderate intensity, we observed associated EMG responses. On varying the conditions of exploration, 12 of the 20 normal subjects presented associated EMG responses.

CONCLUSION

Associated EMG responses are a neurophysiological phenomenon that can be observed in some patients with AD. In normal subjects, it is possible to trigger the appearance of associated EMG responses by reducing their capacity to concentrate on the task to be performed. During the performance of unilateral motor tasks, inhibition pathways are activated physiologically to prevent the mirror contraction of contralateral muscles, which can be affected by the lowered capacity to pay attention.

[Electromyographic diagnosis of 772 patients in the Móstoles Hospital]

INTRODUCTION AND OBJECTIVE

There are few references in the literature to demographic data of the disorders most frequently studied by electromyography. Our objective was to obtain a demographic description of the patients usually sent to us for electromyographic studies.

MATERIAL AND METHODS

Descriptive and analytical assessment was done of 914 electromyographic diagnoses seen in a sample of 722 patients sent to Mostoles Hospital, referral centre of Health District VIII of the Community of Madrid with an estimated population of 407,836 inhabitants, for conventional electroneurographic and electromyographic studies between May 1995 and February 1996. We recorded data regarding electromyographic diagnosis, localization, intensity, whether the study was for diagnostic purposes or follow-up, medical centre referring the patient, medical speciality sending the patient, clinical impression, age and sex.

RESULTS

The commonest pathology seen was carpal trapping of the median nerve, both in men and in women (three times more frequent in women). There was an estimated incidence of 136 cases per year per 100,000 women and 36 cases per year per 100,000 men (most frequent in patients aged 20-70, with a maximum frequency in those in their fifties). There was marked right sided predominance. The commonest pathology in men was polyneuropathy, with an estimated incidence of 80 cases per 100,000 men and 72 cases per 100,000 women. This was the commonest diagnosis in the patients aged over 70. Mononeuropathy of the legs was most commonly seen in men and in the first twenty years of life.