To study whether Heart Rate Variability (HRV) biofeedback training can improve abnormal head posture and painful symptomatology in patients with "cervical dystonia" not selected for DBS after extensive screening in a specialized unit but diagnosed " dysfunctional ".

Patients of the respiratory coherence group will receive HRV biofeedback training for 12 sessions during a 6 months-period. The hypothesis is that this kind of physiological noninvasive therapy increasing coherence respiratory, will reduce pain and patient's complain about their psychogenic abnormal head posture. Improvement of anxiety, depression and quality of life are expected.

Patients presenting with an isolated abnormal head posture, first diagnosed as cervical dystonia, demonstrated in fact, after neurological screening, to be of psychogenic origine. These patients are not candidate for functional surgery and, furthermore, usually refuse psychotherapy leading them to medical nomadism. This study proposes to evaluate the efficacy of an innovative intervention program based on Heart Rate Variability (HRV) biofeedback that promotes self-regulatory skills in dysfunctional movement disorders (DMD) patients in order to improve their condition and symptomatology.

Heart rate is under the control of efferent sympathetic and vagal activities directed to the sinus node, which are modulated by central brain stem (vasomotor and respiratory centers) and peripheral oscillators (oscillation in arterial pressure and respiratory movements). Spectral analysis of HRV is a reliable quantitative method for analyzing the modulatory effects of neural mechanisms on the sinus node. Several biofeedback protocols and assistive electronic technologies, such as proposed by SymbioCenter©, exist to enhance increase HRV and synchronize respiration with the heart rhythm. HRV biofeedback training appears to be an opportunity in the patient's management in order of preventing medical overconsuming. It is offering a safe and non-pharmacological alternative approach managed by a multidisciplinary team in a functional neurosurgery unit. It is expected that developing respiratory coherence in these patients will improve their painful symptomatology.

Inclusion criteria:

• Age 18 to 75
• Responding to somatoform disorder characteristics as described in ICD-10 (F45: "The onset of physical symptoms associated with an insistent medical quest, persisting despite repeated negative assessments and statements by physicians that the symptoms have no organic basis. If there is a genuine physical disorder, it does not account for the nature or severity of the symptoms, or the distress or concerns of the subject. The multidisciplinary team will determine whether or not the diagnosis of conversion disorder (disorder with functional neurological symptoms) of the DSMV (300.11) [ICD-10 equivalent: F44.4 "dissociative disorder with abnormal movements"] is associated with the diagnosis of conversion disorder (disorder with functional neurological symptoms) of the DSMV (300.11) [ICD-10 equivalent: F44.4 "dissociative disorder with abnormal movements"], selected by the multidisciplinary team after a phase 1 assessment.
• Patient benefiting from a social security scheme

Exclusion criteria:

• Simulation identified with obvious search for secondary benefit according to the ICD-10 classification ( Z76.5 Simulator: Person pretending to be ill (with obvious motivation"), or DSM-V(V65.2)
• Any other specific PAT-specific CEP (botulinum toxin, psychotherapy and/or relaxation provided by a professional (CBT, ACT, Mindfulness, etc.)) scheduled within 6 months, with the exception of the usual analgesics (Tier I or II)Presenting significant cognitive impairment (MoCa test ≤ 24/30),
• Absence foreseeable at least 30% of the sessions,
• Lack of informed consent.
• Pregnancy or planned pregnancy during the study period, Pregnant or breastfeeding women
• Major protected by law or patient under guardianship or curatorship
• Participation in other ongoing research