Description

Sensorimotor impairments following stroke can lead to substantial disability involving the upper extremity. These impairments often involve complex pathological changes across multiple joints and multiple degrees of freedom of the arm and hand, thereby rendering them difficult to diagnose and treat. Many potential mechanisms, such as muscle weakness, motoneuronal hyperexcitability, and elevated passive joint impedance, can contribute to the impairments, thereby making it difficult to discern where best to focus treatment.

Objectives: The objectives of this study are to quantify the progression of neuromechanical properties throughout the upper extremity during recovery from stroke.

Specific Aim 1: The specific aim is to examine neuromechanical properties throughout the entire upper extremity and corticomotor excitability in stroke survivors over a period of 6 months and throughout the progression from the acute to the subacute to the chronic phases of recovery.

Hypothesis: Excessive local and cross-coupled stiffness, heteronymous reflexes, corticomotor excitability, and diminished individuation and proprioceptive acuity will be present among multiple degree of freedom in the upper limb. The stiffness and spasticity will increase with time post-stroke.

The aim of this study will be addressed through a longitudinal evaluation of stroke survivors over the first 6 months following the stroke. Specifically, upper extremity control and neuromechanical properties will be measured at 7 different time points over the six months.

36 stroke survivors from 18-85 years old will be recruited over the duration of the study. A group of 20 healthy subjects will be recruited to obtain the normal values of the neuromuscular and biomechanical properties.

In an initial screening session, after the subject has consented, a research personnel will check the subject's health status and conduct clinical examinations in order to determine if the subject meets the inclusion and exclusion criteria. During the screening session, the subject will participate in several clinical assessments. The screening evaluations will take about one half hour.

If the subject qualifies for the study, the subject will participate in evaluation sessions at 7 time points spaced throughout the study. For each evaluation session, participants will be asked to come to our laboratories. Evaluation of participants will have neuromechanical and clinical components. The neuromechanical components of the evaluation will take approximately 3 hours, and the clinical evaluation will need about 2.5 hours.

Neuromechanical evaluations: In diagnosing the multi-joint and multi-degree of freedom (DOF) neuromechanical changes at the upper impaired limb, the IntelliArm will operate both passive and active modes. During neuromechanical evaluations, the subject will sit upright on a barber's chair and the trunk will be strapped to the backrest of the chair. The subject's arm, forearm and hand will be strapped to the corresponding braces which are attached on the robotic arm. The relevant servomotor-axles of the IntelliArm are aligned with the subject's arm at the shoulder, elbow, wrist, and metacarpophalangeal (MCP) joints. The adjustments will be made for the robotic arm to work properly with each subject.

Electromyography (EMG) system may be employed for recording the muscle activities at the upper impaired limb. The skin over the muscle belly will be cleaned with an alcohol pad and may be shaved by disposable razors. Self-adhesive electrodes will be placed on the cleaned sites and connected to the instrument and computer. The surface electrodes may be put on several different muscle bellies, including Flexor digitorum superficialis (FDS), Extensor digitorum (ED), Flexor carpi radialis (FCR), Extensor carpi radialis longus (ECRL), Biceps Brachii (BB), Triceps Brachii long head (TBLH), Deltoid anterior (DA), and Deltoid posterior (DP).

After all preparations are made, the evaluation will begin with the passive movement first. In the passive mode, the multi-joint arm robot will move the shoulder, elbow, wrist and fingers of the impaired arm of stroke survivors throughout the ROMs both simultaneously and individually in well-controlled spatial and temporal patterns with multi-axis torques and positions measured at the shoulder, elbow, wrist and MCP joints. Those joints will be moved one at a time or all of them will be moved together randomly, and the movements will be repeated for up to 5 times in each condition. After finishing the evaluation of passive motion, the participant will randomly be asked to move each joint of the upper limb or move the whole upper limb from one place to another, and will need each participant to repeating the movement for up to 5 times in each condition. Each neuromechanical evaluation will take approximately 3 hours.

The joint torque and angular displacement of each joint will be recorded. During the evaluation sessions, participant's reflex responses and muscle activities, such as hyperexcitability of the flexors and voluntary contractions of agonist and antagonist muscles at each joint, will be recorded and monitored through the skin electrodes with wireless EMG system. The electrodes are just used for recording the signal generated by the muscles and the participant will not feel any shocks during the evaluations. Non-invasive electroencephalography (EEG) electrodes may be attached on the scalp to record brain activity signals. A video or some photos may be taken as an option to evaluate the movement patterns during the evaluations.

Measures of stiffness and of hyperexcitability of the finger/wrist flexor muscles, namely spasticity and relaxation time, will also be made using techniques investigators have implemented successfully in the past. Spasticity of wrist/hand muscles will be measured as the reflex response to imposed rotation of the wrist joint. A servomotor will create either fast wrist rotation to invoke a stretch reflex or slow constant-velocity rotation to measure nominally passive stiffness. Wrist angle, angular velocity, and torque are recorded for analysis of spasticity. EMG recordings will be obtained with surface electrodes from selected superficial muscles. Relaxation time will be quantified by examining flexor muscle activity. The subject will be instructed to grip maximally upon hearing an audible tone. The subject should then relax the grip as quickly as possible after hearing a second tone. The relaxation time is defined as elapsed time from the second tone to the point at which the flexor muscle magnitude returns to the baseline level + three standard deviations.

Clinical evaluations: During clinical evaluations subjects will undergo a battery of standardized clinical assessments. These assessments require subjects to complete functional movements and tasks using the arms and hands. The clinical assessments to be administered include those listed below.

Screening Mini Mental State Exam Chedoke McMaster Stroke Assessment: Impairment Inventory of Arm and Hand

Full Evaluation Sessions Graded Wolf Motor Function Test (WMFT) Fugl-Meyer Upper Extremity (FMUE) Chedoke McMaster Stroke Assessment: Impairment Inventory of Arm and Hand Action Research Arm Test (ARAT) Nottingham Sensory Assessment Modified Ashworth Scale (MAS) Grip Strength & Pinch Strength