RESUMO
We assessed 26 patients with cervical dystonia, in whom botulinum toxin (BT) injections had failed, before selective peripheral denervation. We decided to base the decision which muscle should be denervated on both clinical information and EMG data and focussed on the following features: activity at onset or during 'dystonic spasms' (according to the concept of the 'leading' dystonic muscle), paradoxical activity during voluntary head movements causing restriction of head movements opposite the side of head turn or tilt and activity when symptoms deteriorated during walking. To identify these muscles we developed a new recording system that integrates simultaneous video-taping and polymyography (video EMG) by means of a digital counter, driven by the recording software (resolution 0.1 s), that was fixed in view of the video camera. This system time-locked clinical signs with relevant EMG activity thus allowing demonstration of the above features. These were found in 68% of dystonic muscles with each of them being present in approximately 40%. Video EMG allows an integrated approach to identify overactive neck muscles in patients with cervical dystonia taking into account both relevant clinical findings and EMG data.