Objective: To  investigate the link between sleep and cortical plasticity in cervical dystonia (CD).

Background: CD is the most frequent type of dystonia. Although still debated, a growing body of literature suggests that an alteration of brain plasticity may play a key role in the pathophysiology of CD. Since sleep is known to be implicated in the regulation of cortical plasticity, sleep disturbance and changes in cortical plasticity in CD may both reflect some common brainstem basic neural circuit defect.

Method: CD patients and age-matched healthy subjects (HS) underwent two repetitive transcranial magnetic stimulation (rTMS) sessions (potentiation and a depotentiation protocol), within a 12 hours interval (evening and morning session). The amplitude of the motor evoked potentials (MEPs) recorded at baseline and after each protocol were compared.

Results: As expected, HS showed changes of MEP amplitude in accordance to the potentiation/depotentiation protocols. Potentiation indeed, was more evident in the evening session, whereas in the morning there was a prominent depotentiation. We observed a similar response after the potentiation protocol in CD patients. On the contrary, after the depotentiation protocol, CD patients had a paradoxical hyperpotentiation that was even stronger in the morning session.

Conclusion: This finding seems to point in the direction of a hypersynaptic plasticity in CD patients and are thus consistent with the hypothesized alteration of cortical activity in the pathophysiology of CD. Furthermore, sleep seems to play a role in the rTMS-mediated response in CD patients that will needs to be further investigated.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/cortical-homeostatic-plasticity-alteration-in-cervical-dystonia/