Brain Plasticity and Emotion Recognition in Patients With Facial Palsy Before & After Surgical Rehabilitation: MEG Study

Facial palsy (of one hemiface) affects the sensorimotor representation of the face of the patients, and possibly also their mental representation of emotional facial expressions. Patients with severe facial palsy can benefit from surgical rehabilitation, allowing them to recover the motor and expressive function of the face. Three surgical techniques are performed to rehabilitate facial palsy: Facio-facial anastomosis (AFF), Hypoglosso-facial anastomosis (AHF), and Lengthening temporalis myoplasty (LTM). Prinicipal objective is to study brain plasticity and facial emotion recognition in patients with facial palsy before and after surgical rehabilitation. For this, the investigators will use magnetoencephalography (MEG), which is a non-invasive brain imaging method with high temporal and good spatial resolution.

• First objective is to characterize the brain plasticity at a global level, independently of the surgical technique used. The investigators will use simple motor tasks consisting in performing different facial movements and a control index flexion task to examine the cortical plasticity associated with the restauration of the motor and expressive function of the face in patients with facial palsy.
• Second objective is to examine if the brain magnetic responses associated with the recognition of emotional faces are modified in the paralyzed patients. The investigators will study the brain responses to angry, sad, happy, and neutral faces in a simple emotion recognition task.

Twenty patients with facial palsy will be included in the study. They will undergo two visits, during which MEG will be recorded in two types of tasks: motor task and emotion recognition task (see below). One visit will take place before surgery. The second visit will take place after the surgical intervention and the face motor rehabilitation, 3 to 18 months after the 1st visit.

MOTOR TASK: The motor task will comprise 5 types of simple movements: eye blinks, smiling, tongue protraction, teeth greeting, index flexion. These movements will be performed repetitively - at a pace of about 1 movement every 2 second - in separate, randomly alternating, blocks of 24 movements of each type, for a total of 120 movements of each type.

EMOTION RECOGNITION TASK: A total of 320 faces will be presented to the patients. The faces will be distributed in 5 blocks of 16 different faces (8 male, 8 female), displaying each of 4 emotional expressions: happiness, anger, sadness, and neutral expression. Occasional suprised target faces will be added. The patient's task will be to report the occurrence of those faces by pressing a button in his/her dominant hand. The stimuli will be presented in random order in each block.

The investogators will analyze neuromagnetic activities at the sensor and source levels during the motor tasks (primary objective) and in response to the faces (secondary objective).

Inclusion criteria

• No history of psychiatric illness
• Severe facial palsy (V or VI grade on House and Brackman scale)
• No evolutive neurologic pathology beside the lesion of the VIIth nerve
• Signature of informed consent
• Being a member of, or beneficiary of, a social security scheme

Exclusion criteria

• Evolutive neurological disease outside the lesion of the VIIth nerve
• General pathology leading to neuropathy
• Person unable to express his/her consent
• Adult under a legal protection measure
• Adult deprived of liberty by judicial or administrative decision.
• Adult participating in another research protocol involving the human person or subjected to a period of exclusion from another research
• Claustrophobia
• Implants or metallic objects (including eyeglasses) that are susceptible to pertrubate the MEG signal
• Treatment with known action on the central nervous system (Excessive recreational use of psychotropic drugs, ongoing benzodiazepine therapy)
• For the patients who will undergo a complementary structural MRI for MEG source localisation, additional exclusion criteria are the contraindications to MRI (including: pacemaker or neurosensitive stimulator or implanted defibrillator, anevrism or vascular malformation of the brain, cochlear implants, ferromagnetic objects or prosthesis in the eyes or brain, mechanical heart valve prosthesis, permanent eye makeup; pregnant or nursing women)