Abnormal Movements, Cerebellum and Sensorimotor : Oculomotor Study
Abnormal Movements, Cerebellum and Sensorimotor : Oculomotor Study
Dystonia is a movement disorder characterized by involuntary, sustained, often repetitive
 muscle contractions of opposite muscles that lead to abnormal twisting movements or odd
 postures. Essential tremor is a slowly progressive neurologic disorder characterized by the
 appearance of a tremor during the voluntary movement. The pathophysiology of dystonia or
 essential tremor is not fully elucidated. Dystonia and essential tremor are associated with
 dysfunction of the sensorimotor basal ganglia-cortical network and involvement of the
 cerebellum and cerebellar pathways has also been recently suggested.

 The investigators propose to study 30 patients having a primary dystonia (15 DYT11
 genetically documented), 15 patients having an essential tremor without deep brain
 stimulation and 15 patients having an essential tremor with deep brain stimulation.A group of
 30 healthy volunteers will be recruited and tested according to the same modalities. They
 will be paired in sex and age. 30 patients having a Parkinson disease will be also tested.

 Eye position will be sampled with a video-based monocular eye tracker (SMI, Germany) before
 and immediately after an adaptation task. Saccade adaptation is evaluated as the percentage
 change in the mean saccade amplitude between pre-test and post-test.

 Expected results:

 -  no or fewer alteration of the performance to the adaptation task in the Parkinson group
 than in the Essential Tremor group/ dystonia group.

 -  abnormal reactive saccade backward adaptation in the Dystonia group and Essential Tremor
 group, providing further neurophysiological evidence of cerebellar dysfunction.
Dystonia is a movement disorder characterized by involuntary, sustained, often repetitive
 muscle contractions of opposite muscles that lead to abnormal twisting movements or odd
 postures. Essential tremor is a slowly progressive neurologic disorder characterized by the
 appearance of a tremor during the voluntary movement. High frequency stimulation of the
 ventral intermedius nucleus (Vim) of the thalamus, relay for the cerebellar output, is
 successfully used for the treatment of severe essential tremor. It occasionally induces
 adverse event such as balance disorders or cerebellar symptoms. The pathophysiology of
 dystonia or essential tremor is not fully elucidated. Dystonia and essential tremor are
 associated with dysfunction of the sensorimotor basal ganglia-cortical network and
 involvement of the cerebellum and cerebellar pathways has also been recently suggested. It
 seems that dystonia and essential tremor could be the result of basal ganglia or cerebellar
 dysfunction, or from dysfunction of structures controlled at the same time by the cerebellum
 and the basal ganglia.

 methodology: We propose to study 30 patients having a primary dystonia (15 DYT11 genetically
 documented), 15 patients having an essential tremor without deep brain stimulation and 15
 patients having an essential tremor with deep brain stimulation.

 A group of 30 healthy volunteers will be recruited and tested according to the same
 modalities. They will be paired in sex and age. 30 patients having a Parkinson disease will
 be also tested.

 The subjects will be seated in darkness facing a screen located 60 cm before their eyes,
 their chin on a chin strap and their forehead placed against a frontal support. Eye position
 is sampled at 500 Hz with a video-based monocular eye tracker (SMI, Germany). Each recording
 session start with a calibration test in which the subjects looked at nine consecutive
 targets covering the entire visual field, as used during the oculomotor paradigms: four
 experimental conditions: a visually guided saccade task, a pre-test, a backward adaptation
 task, and a post-test. The pre-test and post-test (40 trials each) are performed before and
 immediately after the backward adaptation task, in the same conditions, except that the
 target was extinguished when the velocity threshold (150°/s for 10 ms) is reached, instead of
 jumping to a new location. This avoided any post-saccadic visual feedback that would
 counteract the adaptive mechanism. Saccade adaptation is evaluated as the percentage change
 in the mean saccade amplitude between the pre-test and post-test.

 Expected results:

 -  no or fewer alteration of the performance to the adaptation task in the Parkinson group
 than in the Essential Tremor group/ dystonia group.

 -  abnormal reactive saccade backward adaptation in the Dystonia group and Essential Tremor
 group, providing further neurophysiological evidence of cerebellar dysfunction.
Inclusion criteria:

 -  Age ≥18 years

 -  -normal cognitive functions (>24y)

 -  Normal clinical examination of ocular mobility, visualization of the target

 -  No drug potentially able to modify and to influence the data: anti-depressants,
 neuroleptics, anti-emetics, amphetamines, anti myoclonic/dystonic drugs, alcohol,
 dopaminergic drug, antiepileptic.

 -  Dystonia or essential tremor or Parkinson: diagnostic made by a neurologist

 -  For DYT11: mutation in SGCE gene.

 -  For dystonia: No secondary dystonia

 -  For Parkinson : UPDRS<28

 -  No other neurological disorder

 For the patient having deep brain stimulation:

 -  Duration of stimulation> 6 months

 -  Cerebral imagery post operation made

 -  Stimulation parameter stable since 3 months at least.

 -  Usual stop of the stimulation during the night

 Exclusion criteria:

 -  Uncontrollable medical problems not related to M-D

 -  Current active psychiatric disorder

 -  Intake during the last 3 days of drugs potentially able to modify and to influence the
 data: anti-depressants, neuroleptics, anti-emetics, amphetamines, anti
 myoclonic/dystonic drugs, alcohol, dopaminergic drug

 -  Subjects legally protected.

 -  Subjects who are not enrolled at social security.