Poor Neck Proprioception May Cause Balance Deficits in Myotonic Dystrophy 1

Study Overview
=================
Brief Summary
-----------------
Impairment of balance and gait are frequent complaints in patients with myotonic dystrophy type 1 (DM1). In these persons, there is an increased risk for stumbles and falls when compared to normal subjects. An underestimated cause of falls might be the weakness of neck flexor muscles (due to cervical ataxia). It is well known that fibres of muscle spindles are receptors combining a specialized sub-set of muscle fibers with a specialized array of both sensory and motor nerve fibers. Spindles transduce into neural afferent discharges the muscle length and length changes. They are very dense in deep neck muscles, are crucial to body balance and gage orientation, and are severely affected in DM1. Preliminary results suggest that falls could reflect imbalance. These indicate that cervical ataxia may come into play because of muscle spindle fibre disruption. In light of the current knowledge on the physiology of balance and on the association between balance deficits and cervical dystonia in other clinical conditions (e.g., whiplash injury), a rationale is therefore offered to a confirmation of the hypothesis that DM1 patients may suffer from cervical ataxia. The primary endpoint is the demonstration of an association between balance deficits in standing and cervical proprioception deficit in adults affected by Myotonic dystrophy 1. Secondary endpoints are: the investigation of the correlation among the two deficits and the clinical conditions of patients, the definition of normative data in the measure of cervical proprioception in a sample of healthy participants. It is expected that high scores in postural balance, obtained on the posturographic Equitest™-Sensory Organization Test-SOT, correspond to high levels of repositioning accuracy in tests of cervical repositioning and low SOT scores correspond to low accuracy. Moreover, it is expected that an association exists among the two deficits and the clinical situation of the patients. Results from the present pilot study will allow an estimate of the sample size for future experimental protocols. The evidence for an association between balance deficits and cervical ataxia would be of obvious relevance to the patients. This would also support the hypothesis that neck muscle spindles may be especially affected in DM1. This would highlight that muscles are also crucial sensory organs, involved in the perception of joint position, muscle strength, and fatigue. Results from the present study might allow the definition of new rehabilitative programs, such as treatments through a neck strengthening (and thus stiffening) exercise program. This study, therefore, might stimulate new research hypothesis at the neurophysiologic level and possibly lead to findings generalizable from DM1 to other forms of myopathy.

Official Title
-----------------
Poor Neck Proprioception May Cause Balance Deficits in Myotonic Dystrophy 1

Conditions
-----------------
Myotonic Dystrophy 1

Intervention / Treatment
-----------------
* Other: Healthy subjects
* Other: Pathologic group


Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion Criteria: Diagnosis of DM1 since at least 5 years; Ability to stand erect with open eyes for at least 20 s; Rivermead Mobility Index (RMI) score ≥ 10/15; Visual acuity > 10/20, also with corrective lenses; Mini Mental State Examination (MMSE) score ≥ 26/30; ability to wittingly sign the informed consent form. Exclusion Criteria: neurological or orthopedic pathologies with impact on balance; pregnancy; previous orthopedic surgical intervention; head or neck trauma in the 6 months preceding the study; other pathological conditions which could alter balance; drug therapy, underway for less than one month before the study, with impact on balance.

Ages Eligible for Study
-----------------
Minimum Age: 18 Years
Maximum Age: 50 Years

Sexes Eligible for Study
-----------------
All

Accepts Healthy Volunteers
-----------------
No

Study Plan
=================
How is the study designed?
-----------------

Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Healthy participants<br>At least 25 healthy participants aged from 18 to 50 years old. Participants will be excluded if pregnant. | Other: Healthy subjects<br>* Participants will be tested for their foot dominance by means of the Waterloo footedness questionnaire-revised, their hand dominance by means of the Edinburgh inventory, and their eyedness Coren's Lateral Preference Inventory. Participants will perform a cervical repositioning test. They will seat in a chair in front of a Plexiglas screen with the eye closed. The operator will guide the participant in four positions: at 30° right/left rotation and at 25° extension/flexion. The participant will be then asked to reproduce the angle. Each movement will be repeated four times in a random order. The whole sequence will be repeated by another second operator. Both the tests will be repeated after two weeks. Head movements will be detected using an optoelectronic system using passive markers positioned on the head of the participant.<br>|
| Pathologic group<br>At least 22 participants with diagnosis of Myotonic Dystrophy 1. | Other: Pathologic group<br>* Clinical evaluation of the participants will be performed by means of the Myotonic Dystrophy Health Index (MDHI), the Rivermead Mobility Index (RMI), the Fall Events Questionnaire, and the Dizziness Handicap Inventory- short form (DHIsf). Participants will perform a cervical repositioning test. Participants will seat in a chair in front of a Plexiglas screen with the eye closed. The operator will guide the participant in four positions: at 30° right/left rotation and at 25° extension/flexion. The participant will be then asked to reproduce the angle. Each movement will be repeated four times in a random order. Head movements will be detected using an optoelectronic system using passive markers positioned on the head of the participant. Participants will then perform test of balance in standing, using the EquiTest platform. Individuals will be requested to perform three different tasks: sensory organization test, adaptation test-upward tilt, and adaptation test-downward tilt.<br>|

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| SOT score | The patient's task is to maintain an upright stance during 3 20 s trials under six different conditions, including platform and visual surround 'tuned' with individual's sagittal oscillation. The SOT score will be calculated by comparing the sagittal oscillation of the body's centre of mass (COM) to the maximal sagittal oscillation. Score is averaged across the six conditions (range 0 - 100 the higher the score, the lower the oscillation). | Day 1 | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Head Repositioning Accuracy, HRA | The head repositioning accuracy in percentage will be computed as the joint position error (JPE) divided by the target position. The JPE will be computed as the absolute difference between the target position and the measured position. | Day 1 | 

 Terms related to the study
=================
Keywords Provided by Centre Hospitalier Valida
-----------------
Myotonic Dystrophy 1, Accidental falls, Ataxia, Postural balance, Rehabilitation