Foot Dystonia Treatment by Botulinum Toxin Injections in Parkinson Disease : Efficiency of Injections Made in Extrinsic Muscle (Flexor Digitorum Longus Muscle) Compared to Intrinsic Muscle (Flexor Digitorum Brevis or Quadratus Plantae Muscles)

Foot dystonia is frequently observed in patients suffering from Parkinson'disease. It is characterized by an abnormal involuntary movement which is very uncomfortable (difficult to walk) and painful for the patient.

Botulinum toxin injections seem to be efficient to treat this dystonia. However studies on this topic are few and very imprecise (many muscle injected, especially the Flexor digitorum longus, different doses used, heterogeneous population with many types of dystonia included, open studies).

Study progress :

After an inclusion visit, patients are randomized in one of the 3 following groups :

* First group (PL : placebo) :

  * J0 : Patient will receive 1 injection of placebo in the Flexor digitorum longus and 1 injection of placebo in the Flexor digitorum brevis or in the quadratus plantae
  * J+1month : First evaluation
  * J+3 months : Patient will receive again 1 injection of placebo in the Flexor digitorum longus and 1 injection of placebo in the Flexor digitorum brevis or in the quadratus plantae
  * J+4 months : Last evaluation
* Second group (ME : Extrinsic muscle)

  * J0 : Patient will receive 1 injection of Botulinum toxin (100U) in the Flexor digitorum longus and 1 injection of placebo in the Flexor digitorum brevis or in the quadratus plantae
  * J+1 month : First evaluation
  * J+3 months : Patient will receive again 1 injection of Botulinum toxin (100U) in the Flexor digitorum longus and 1 injection of placebo in the Flexor digitorum brevis or in the quadratus plantae
  * J+4 months : Last evaluation
* Third group (MI : Intrinsic muscle)

  * J0 : Patient will receive 1 injection of placebo in the Flexor digitorum longus and 1 injection of Botulinum toxin (100U) in the Flexor digitorum brevis or in the quadratus plantae
  * J+1 month : First evaluations
  * J+3 months : Patient will receive again 1 injection of placebo in the Flexor digitorum longus and 1 injection of Botulinum toxin (100U) in the Flexor digitorum brevis or in the quadratus plantae
  * J+4 months : Last evaluations

During injections (J0 and J+3M), we will measure the pain induced by injections (EVA) For each evaluation (J+1M and J+4M), following evaluations will be made: clinical improvement (CGI), dystonia evaluation (duration and severity, Burke scale), pain (EVA) and quality of life (PDQ39).

Eligibility Criteria:
Inclusion Criteria:

* Age : 30-75 years
* Patient with an idiopathic Parkinson's disease according to the criteria of the "Parkinson's Disease Society Brain Bank"
* Patient with unilateral tiptoe dystonia. Dystonia must be present more than 1h /day and induce difficulties to walk (severity index ≥ 3 (1 : light, 2 : moderate, 3 : severe, 4 : very severe)).
* Patients never treated with botulinum toxin or already treated for more than 6 months.
* Affiliation to social security
* Agreement of patients

Exclusion Criteria:

* Patients suffering of an atypical Parkinson syndrome
* Patient with a bilateral tiptoe dystonia
* Patients with contraindication to the botulinum toxin use
* Women without efficient contraception
* Person who participate to an other study