Аннотация:Cervical dystonia (CD), the most common form of focal dystonia is characterized by
abnormal head posture combined with jerky or tremulous movements. The
mechanistic underpinning of this common disorder remains unclear. One of the
theories suggests increased activity through cortico-striato-pallidal “direct” and
“indirect” pathway as a cause of dystonia. Reduced pallidal output, changes in firing
pattern and long-lasting inhibition induced by cortical stimulation was previously
described. The aim of our study was to characterize evoked single-unit activity in
response to voluntary movement of affected (dystonic) neck muscles and compare it
with unaffected (clinically normal) hand movement. We used microelectrode
recording from 12 CD subjects undergoing deep brain stimulation (DBS) surgery
under local anesthesia. We analyzed 45 neck and 21 hand movement sensitive
neurons, recorded from GPi and GPe. Comparison of single-unit response with
electromyography (EMG) revealed either lead or lag in neural response. Some
neurons responded by short-term phasic activation (or inhibition) as a rule initiating
movement and other cells characterized by long-term tonic responses. Some
neurons responded with both lead and lag excitatory-inhibitory components
accompanied by low frequency (1-5 Hz) oscillations. Comparison between hand and
neck movement showed several differences. About 50% of neck sensitive cells
responded with prolonged inhibition while most hand movements responded by
excitation. Wherein in contrast to hand responses, all neck responses had an
exponential decay with comparable to EMG decay time constant. Such decay in
neuronal response was characterized by the time constant comparable to the one
explained by previously described abnormal head neural integrator controlling head
position.