Corticomotor facilitation in vegetative state: results of a pilot study

Abstract

Objective: To investigate whether corticomotor facilitation induced by transcranial magnetic stimulation (TMS-CF) could evoke a simple purposeful motor behavior in patients with a diagnosis of vegetative state.

Design: Cross-sectional survey.

Setting: Post-coma and rehabilitation care unit.

Participants: Patients (N=6) with a diagnosis of vegetative state.

Interventions: A cascade of consecutive motor-evoked potentials (MEPs) was elicited under 3 different conditions: in the first condition, patients were at rest (Rest); in the second, they were asked to open and close the right hand (Execution); in the third, the examiner modeled a movement of abduction of the thumb in front of the patient who was encouraged in advance to imitate the action (Observation to Imitate).

Main outcome measures: Changes in MEP values from the abductor pollicis brevis muscle and improvement in scores on the Coma Recovery Scale-Revised.

Results: TMS-CF alone or combined with verbal instructions did not yield any change; only the combination with imitation caused changes in MEPs (shorter latency and increased amplitude) associated with behavioral improvement in 4 patients.

Conclusions: Encouraging observation to imitate may favor the transformation of some perceived actions into motor images and performances, probably depending on the activation of mirror motor neurons. In our opinion, combining visual input with TMS-CF might have reinforced the coupling between movement planning and execution, promoting the recovery of elementary motor activities in some patients. The proposed protocol may contribute to unmasking signs of preserved consciousness in patients with latent capacities for recovery.

Keywords: APB; Brain injuries; CRS-R; Coma Recovery Scale-Revised; MCS; MEP; Minimally conscious state; Rehabilitation; TMS; TMS-CF; Transcranial magnetic stimulation; VS; Vegetative state; abductor pollicis brevis; minimally conscious state; motor-evoked potential; transcranial magnetic stimulation; transcranial magnetic stimulation corticomotor facilitation; vegetative state.