Role of EMG evaluation in muscle hyperactivity - Spanish Research

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Abstract from J Neurol. 2004 Mar;251(3):251-60. s

Role of EMG evaluation in muscle hyperactivity syndromes.

Valls-Sole J, Montero J.

Unitat d'EMG, Servei de Neurologia, Hospital Clinic, Villarroel, 170,

08036, Barcelona, Spain

Muscle hyperactivity can be a clinical feature on its own or, more

commonly, an observation on electromyography (EMG) examinations.

Whatever manifestation it takes,muscle hyperactivity always means

enhanced excitability of muscle, axons or neurons. Clinical findings may

be variable, ranging from fasciculations to muscle cramps. Even though

clinical examination may lead in most instances to suggest the diagnosis

of the underlying disease, EMG studies are necessary to identify the

type of abnormal discharges and suggest the site of their suspected

origin. Although in clinical studies, the action potential showing

abnormal muscle hyperactivity is practically always recorded from muscle

fibers, the site in which the impulse has arisen will determine its

shape and firing patterns. In this review, we describe the EMG

characteristics observed in syndromes featuring muscle hyperactivity and

the pathophysiology underlying the abnormal firing of muscle fibers.