Upper Extremity Motor Control Pathology

- Spatiotemporal organization (timing & coordination)

- Force control

- Response time

what are the motor components needed for UE motor function/control

- Internal representation

- Change of strategy - adaptation

- Anticipation - learning

what are the cognitive components needed for UE motor function/control

- Range of motion

- Biomechanical relations between body segments

- Stiffness and flexibility properties

what are the musculoskeletal components needed for UE motor function/control

1. Locate Target "Visual Regard"

2. Reach

3. Grasp

4. Manipulate

5. Release

Phases of Reach and Grasp Tasks

- Problems with timing and inter-joint coordination

- Rubrospinal takes on greater role if CST is damaged (flexor excitation, extensor inhibition)

what are Reaching and Grasping Deficits seen when Both systems (CST, Rubrospinal tract, Reticulospinal tract) commonly affected with lesions

Subjects flexed shoulder, flexed elbow, and extended wrist

what is a common UE flexor synergy pathology

- Smooth trajectory.

- Precise & accurate endpoint placement near target.

what does normal movement inter joint coordination control entail

how would a cerebellar lesion affect normal movement of inter joint coordination and control

- Movement decomposition into UE reach components (i.e. shoulder flex, elbow ext).

- Dysmetria-over/under shooting the target

Spasticity

exaggerated stretch reflex activity and muscle hypertonia with velocity-dependent resistance to passive stretch.

key points about spasticity examination

- Normally assessed at a single joint.

- Traditional clinical measure: (Modified) Ashworth Scale7

- May coincide with adaptive soft tissue shortening (contracture).

- Fast reaching can trigger spasticity making reaching more difficult

how does somatosensory deficits affect reach and grasp

- Deafferentation impairs reach and grasp.

- Success with single joint movements due to pre-programmed muscle activation, so feedback not necessary.

- Success with visual feedback.

- Difficulty with complex functional movement

what does Normal anticipatory control in grip force entail

- Scaling forces prior to grip-and-lift.

- Internal representation together with sensory feedback used to preprogram forces.

- Adult skill level by 6-8 years old (some evidence says later).

Impaired Precision Grip due to PD

- Intact internal representation of object.

- Manipulation deficits (over-gripping) may be compensatory due to tremor or impaired sensorimotor integration

how does PD affect grip and lift tasks

- Increased time to develop grip force (bradykinesia)

- PD slower adaptation of grip force (loading phase).

- High grip force may be compensatory - higher safety margin to avoid dropping object.

- Difficulty unloading

cerebellum

what brain area is important for adapting to changes in task demands for grip and lift.

what are Musculoskeletal problems that can affect reach and grasp

- Pain and/or stiffness - lead to disuse, atrophy

- Constraint-induced movement therapy (CIMT)

- ROM - restrictions may change inter-joint coordination.

what are cognitive problems that can affect reach and grasp

- Processing time, object recognition, prediction, adaptation

- Internal representation

what does internal representation as a cognitive component of reach and grasp entail

- General neural process which resolves sensory ambiguities.

- Synthesize information from different sensory modalities.

- Combine efferent and afferent information.

how does apraxia affect reach and grasp

- Ideational (Frontal) apraxia: loss of connection between intention and execution.

- Errors of performance ... not hand movement

- Difficulty with overall action planning/processing

Left

The ____ hemisphere controls high level motor processing.

Visual Regard → Reach → Grasp → Manipulation → Release

what is a process of reach and grasp

key points about reach and grasp pathologies

- Problems with each phase of UE control are common in neurologic pathology.

- Causes are complex because of interacting neural pathways needed for UE control.

- Phases can be affected separately or with overlapping impairments.

- Visual, vestibular, and somatosensory (sensory elements) deficits all can affect UE control.

- Deficits are typically contralesional, but subtle deficits may be ipsilateral to lesion.

- Apraxia is neither sensory nor motor in origin, but rather a problem with the motor planning and intent.

neurologic pathology

Problems with each phase of UE control are common in what type of pathologies

motor planning

Apraxia is neither sensory nor motor in origin, but rather a problem with the _____ and intent.