Utilidad de la electromiografía de esfínter anal en el diagnóstico diferencial de la atrofia multisistémica

Introduction. Multiple system atrophy (MSA) is a neurodegenerative disease; dysautonomia are the cardinal symptoms and its associates with cerebellar syndrome (MSA-C) or parkinsonism (MSA-PK). Differential diagnosis of MSA-PK with other parkinsonism is difficult; it's required an ideal diagnosis test. The degeneration of Onuf 's nucleus, exclusively in MSA, might suggest that presence of denervation of the anal sphincter may be taken into account as diagnostic criteria for AMS. Objetive. To establish the clinical utility of anal sphincter electromyography (AS-EMG) in the differential diagnosis of AMS with other parkinsonian syndromes. Materials and Methods. A systematic review wasdone, which included 17 studies that analyzed the results of AS-EMG in patients with MSA. Of these, 11 studies were analytical and compared patients with MSA and other parkinsonisms, the remaining studies were descriptive. Results. The duration of motor unit potentials (MUP) is significantly higher in patients with MSA compared with other parkinsonism with a cut-off value superior 13 ms; the operating characteristics of this parameter are potentially useful. Only one study found significant differences in the percentage of polyphasic MUP, which had a clinically useful sensitivity and specificity when the cut off is greater than 60%. The other studies reported no statistically significant differences between parkinsonism. Conclusions. The available literature points to the potential usefulness of EMG-EA in the differential diagnosis of parkinsonism other AMS, but more studies need to be conducted to address the existing methodological limitations.