Motor Unit Flashcards
Lower Motor Neuron (LMN) System
- Includes cell bodies in anterior horn of spinal cord and their axons, and the nuclei of cranial nerves III-X and their axons.
- Contain somatic motor components including innervation of skeletal muscles and muscle spindles.
- A lesion in these structures results in peripheral neuropathy or LMN dysfunction.
Peripheral Neuropathies
Involve lesions of the LMN system and may be located in anterior horn cells of spinal cord, spinal nerves, peripheral nerves, and cranial nerves.
• Lesions can result from nerve root compression, trauma, toxins, infections, neoplasms (ie: neuromas), vascular disorders, and congenital malformations.
• Distorts/interrupts messages betw brain and body.
OT Assessments for Motor Unit Disorders
- COPM
- Occupational profile
- Performance in ADLs/IADLs
- Performance patterns
- Client factors (MMT, ROM, pain, sensory, coping)
- Activity demands
- Contexts
Guillain-Barré Syndrome (GBS)
(ghee-YAN bah-RAY)
• Acute inflammatory disorder in which body’s immune system attacks part of peripheral nervous system.
• Myelin sheath destroyed
• No known cause or cure; often occurs after upper respiratory or gastrointestinal viral infection, usually within 1-2 weeks.
• Occasionally triggered by surgery or vaccinations
• Initial symptoms: weakness, sensory changes in legs
• Rapidly progressing ascending symmetric weakness of bilateral extremities, usually distal to proximal (Feet to trunk)
• Inability to feel textures, heat, pain, etc.
• Tingling first appears distally (hands and feet), as those nerve signals have the farthest to travel
• May affect respiration or swallowing; may result in complete paralysis
• Muscle belly pain is of concern
• Usually at weakest state in 3rd-4th week
• THREE PHASES of progression: 1) ACUTE (up to 4 weeks), 2) PLATEAU (when physical state stabilizes, but no recovery); lasts a few weeks, 3) RECOVERY (slowly begins to recover abialities/symptoms subside).
• May completely recover, but 20-30% have residual deficits.
Medical Treatments for GBS
Immunomodulatory therapy:
• Plasmapheresis: separates blood from plasma and return to body—reduces acute phase; or
• Intravenous immunoglobulin (IVIg): injection of proteins that immune system uses to fight invaders; can lessen immune attack on nervous sys and hasten recovery.
Poliomyelitis (Polio)
Virus that causes polio; passed into mouth in unsanitary conditions; peaked in US in 1952; last indigenous case reported in 1979.
3 types:
• SPINAL Polio (79% of cases 1969-79); asymmetric paralysis mainly in legs.
• BULBAR Polio (2%); cranial nerves affected; oral/facial weakness
• BULBOSPINAL Polio (19%); combo of above 2 types
• Asymmetry can cause deformities such as contractures, scoliosis, subluxation
• Sensation/cognition remain intact
Postpolio Syndrome (PPS)
Exacerbation of existing polio cases.
• 12-20 million people still alive with polio
• 25-40% of them will have new muscle pain, weakness or paralysis
• No longer infectious
• In tx, emotional aspects as disabling as physical (devastating to see it return)
• Fatigue and pain most common issues
Peripheral Nerve Injuries
3 Main Upper Extremity Injuries:
1) Axillary Nerve
2) Brachial Plexus (C5-T1)
3) Long Thoracic Nerve
- Caused by MVA, falls, sports, GSW, violence
- Crushed, severed or compressed nerve
- Results in muscle weakness or flaccid paralysis, depending on extent of nerve damage
- Deep tendon reflexes depressed or absent
- Sensation along cutaneous surface depressed/absent
- Also may have trophic changes: dry skin, hair loss, cyanosis, brittle nails, painless skin ulcers, slow wound healing in area of involvement.
- May produce deformities if contractures or poor joint positioning allowed to occur; particularly in hands
- Can lead to osteoporosis of bone, epidermal fibrosis of joints
Axillary Nerve Injury
C5-C6, from upper trunk of brachial plexus. Innervate deltoid and teres minor. Most commonly injured at shoulder due to dislocation or fracture of neck of humerus. Can also be compressed (crutches) or trauma (laceration).
• Weakness of deltoid limits shoulder flexion, abduction, extension, and weakness in lateral rotation of arm
• Produces asymmetry of shoulders
• ROM/MMT assessments critical
• Avoid sublux in tx by using sling or doing exercises supine or lying on noninjured side.
Brachial Plexus Injuries
C5, C6, C7, C7, T1; just posterior to sternocleidomastoid
• Typically unilateral injury occurring during birth
• In adults, traumatic injuries occur from MVA, sports, falls, blows.
2 Types of Lesions:
1) Erb-Duchenne Syndrome/Palsy
2) Klumpke’s Syndrome/Palsy
- OT involves partial immobilization and positioning
- Passive ROM to maintain joint flexibility
- Tactile/proprio sensory input exercises to incr sensory awareness
- Prevention of contractures
- Sling to support arm with Erb’s Palsy
- Short opponens hand splint for Klumpke’s Palsy
Erb-Duchenne Syndrome (Erb’s Palsy)
Lesions to upper trunk of brachial plexus, C5-C6.
• 80-90% of newborns recover within 3-24 mo.
• Muscles of shoulder/elbow affected, while hand movement is retained
• Paralysis/atrophy in deltoid, brachialis, biceps, and brachioradialis
• Arm hangs limp in internal rotation/adduction at shoulder; elbow extended; forearm pronated; wrist flexed (“waiter’s tip” position)
• Hand muscles unaffected, but functional movement of UE is extremely limited
• Custom sling to fit around humerus to support arm
Klumpke’s Syndrome/Palsy
Compression or traction to lower trunk of brachial plexus (C8 and T1); less often than Erb’s Palsy.
• Traction during birth or later in life by strong upward pull on UE when abducted
• Nerves innervate muscles for wrist and finger flexion and abduction/adduction of fingers.
• Results in claw-hand deformity (intrinsic minus hand)
• Short opponens hand splint that supports thumb in opposition often used.
Long Thoracic Nerve Injury
C5-C7; innervates serratus anterior muscle, which anchors the apex of the scapula to posterior rib cage, and scapular abduction and upward rotation.
• Not a common injury, but can occur from carrying heavy weights on shoulder (backpacks); blows to neck; compression caused by prolonged lying on lateral trunk, and wounds.
• Results in “winging” of scapula
• Difficulty flexing GH joint above shoulder level, and protracting the shoulder or scapula ab/adduction
• Wall pushup is a good screening assessment (if injured, scapula will elevate and move medially into winging).
Myasthenia Gravis (MG)
Most common chronic disease involving disorder of chemical transmission of nerve-muscle synapse (neuromuscular junction).
• Caused by autoimmune response in which antibodies block/alter/destroy receptors at nerve-muscle junction.
• Skeletal muscles, typically cranial, become weak and easily fatigued
• Symptoms usually begin around age 50, more often with men
• Initially experience oculomotor muscle drooping (ptosis), and diplopia.
• Oropharyngeal muscle weakness (difficulty chewing/swallowing/speaking)
• Weakness in limbs not typical initially, but can occur later or as muscles fatigue
• Strength decreases as day goes on
• Most have abnormalities of thymus function, or tumors (most have the gland removed)
• Most have good prognosis, live relatively normal life; might have exacerbations based on experiences
OT for Myasthenia Gravis (MG)
- Assess eating/swallowing for aspiration risk
- May have difficulty coughing/clearing due to diaphragmatic and intercostal muscle weakness
- Avoid causing fatigue (watch time of day, meds)
- Keep running record of muscle strength
- Energy conservation/work simplification
- Home safety for visual issues
