Alterations in Motor Function PDF

Alterations in Motor Function NURS 245 Akshay Sharma, MBBS, MPH, PhD  Outline Organization & control of motor function Upper motor neuron disorders Multiple sclerosis, amyotrophic lateral sclerosis, spinal cord injuries Disorders of the...

Alterations in Motor Function NURS 245 Akshay Sharma, MBBS, MPH, PhD  Outline Organization & control of motor function Upper motor neuron disorders Multiple sclerosis, amyotrophic lateral sclerosis, spinal cord injuries Disorders of the cerebellum & basal ganglia Cerebellar ataxia, cerebellar tremor, Parkinson’s disease Lower motor neuron disorders Muscle atrophy, muscular dystrophy, myasthenia gravis, carpal tunnel syndrome, Guillain-Barré syndrome, spinal muscular atrophy  Learning Objectives Discuss the organization and control of motor function (including motor neurons, descending pathways, and neuromuscular junctions) Discuss the pathophysiology and clinical manifestations of multiple sclerosis Discuss the pathophysiology and clinical manifestations of amyotrophic lateral sclerosis Distinguish between different spinal cord injuries (including tetraplegia/quadriplegia, paraplegia, and spinal shock) Describe the characteristic features of cerebellar disorders (including cerebellar ataxia and cerebellar tremor) Discuss the pathophysiology and clinical manifestations of basal ganglia disorders (including dystonia, chorea, and hemiballismus)  Learning Objectives Discuss the pathophysiology and clinical manifestations of Parkinson’s disease Distinguish between disuse muscle atrophy and denervation muscle atrophy Discuss the pathophysiology and clinical manifestations of muscular dystrophy (including Duchenne muscular dystrophy and Becker muscular dystrophy) Discuss the pathophysiology, clinical manifestations, and clinical diagnosis of myasthenia gravis Discuss the pathophysiology and clinical manifestations of carpal tunnel syndrome and Guillain-Barré syndrome Describe the pathophysiology and clinical manifestations of spinal muscular atrophy Organization & Control of Motor Function  Motor System Key functions Plan and execute smooth, purposeful, and coordinated body movements Maintain posture (i.e. the relative position of various body parts with respect to one another and the external environment) Motor system is organized as a functional hierarchy Motor cortex (highest level of function) Cerebellum and basal ganglia Brainstem – connect parts + relay information Spinal cord (lowest level of function)  Motor System (1) Motor Cortex Comprised of three areas located in the frontal lobe – Primary motor cortex, premotor cortex, and supplementary motor cortex &Controls precise, skillful, and intentional movements ↓ movements we want to make  Motor System (2) Cerebellum + basal ganglia Assist in planning and executing motor movements Cerebellum – timing coordination accuracy , , Basal ganglia – gracefullness (3) brainstem Connects the cerebrum and cerebellum to the spinal cord – relays motor information in a caudal direction (4) Spinal cord Has motor neurons that contain efferent nerve fibers - (axons) that relay motor information to the body going to muscles Motor System  Motor System cell bodies of motor neurons are located within thecNs/spinal cord) Cross-section of the spinal cord depicting dorsal (sensory) roots and ventral (motor) roots of a pair of spinal nerves Back of the body Cell bodies of sensory neurons are located Cell bodies of outside the motor CNS in clusters neurons are called ganglia located in the CNS ↓ Front of the body relay into from the front  Motor System I. Motor neurons II. Descending pathways -Sending into to the muscles III. Neuromuscular junctions  I. Motor Neurons luppers (lower Motor neurons – Categorized into UMNs and LMNs (1) upper motor neurons (UMNs) Extend from the motor cortex to the brainstem or the & - ventral horns of the spinal cord I front Cell bodies and axons are located entirely in the CNS (2) lower motor neurons Extend from the brainstem or the ventral horns of the spinal cord to the skeletal muscle fibers & Cell bodies are located in the CNS - Axons are located in the PNS eventually lead to the > - Skeletal muscle fibers  I. Motor Neurons ends in - -- & ends in the spinal cord the brainstem Note – LMNs are under the control of the UMNs  II. Descending Pathways UMNs descend through the CNS in many pathways (or tracts), which are broadly categorized into – Pyramidal tracts and Extrapyramidal tracts (1) Pyramidal tracts Originate in the motor cortex and traverse the medullary pyramids: Paired white matter bundles in the brainstem Voluntary control of the head, face, and body muscles Corticobulbar tracts – Carry motor fibers from the cortex to the#brainstem: head / face movements Corticospinal tracts – Carry motor fibers from the cortex to the spinal cord: limp and trunk movement :  -- II. Descending Pathways - Note on corticospinal tracts: & 80-90% of fibers in the corticospinal tracts cross over to the other side of the brainstem at the level of the medullary pyramids and descend in the opposite side of the spinal cord – Lateral corticospinal tract: travels down control limb movements e staysint the spinal cord - 10-20% of the fibers in the corticospinal tracts do not cross over and descend in the same side of the spinal cord – Anterior corticospinal tract: control trunk movements Porth, Essentials of Pathophysiology: Concepts of Altered Health States, Fourth Edition  II. Descending Pathways (2) extrapyramidal tracks Originate in the brainstem in regions that are not part of - the medullary pyramids Unconscious and automatic control of body muscles (regulate balance and posture) Carry motor fibers from different parts of the brainstem to the spinal cord Note on synapses: single axon No synapses exist within the descending pathways UMNs synapse with the LMNs at the termination of the pyramidal and extrapyramidal tracts  III. Neuromuscular Junctions LMNs emerging from the ventral horns of spinal cord segments innervate skeletal muscle fibers Motor unit = single LMN skeletal muscle fibers + innervated by the axon terminals Region on each muscle fiber where the axon terminal of a LMN ends – endplate region endplate # region S ↑ ventral spinal cord segments  Spinal Reflexes Simple, involuntary responses initiated by stimuli at the sensory receptors that “buy time” to plan and execute more complex, voluntary responses Sensory receptors in skin – + actile mechanoreceptors Sensory receptors in muscles and tendons – proprioceptors (i) Muscle spindles – detect stretch (ii) Golgi tendon organs – detect tension Spinal reflexes initiate movements to avoid hazards and are mediated by the spinal cord without requiring input from the brain ↳ avoid hazards that could harm us  Spinal Reflexes * Dull hand away if not Sequence of events in a spinal reflex: Afferent neurons relay somatosensory information (e.g. muscle length and tone) from the sensory receptors to the dorsal horns of the spinal cord (back) Somatosensory information is relayed from the dorsal & horns to the ventral horns -front) LMNs (efferent neurons extending from the ventral horns of the spinal cord to the skeletal muscle fibers) initiate reflex contraction or relaxation Note – Higher brain centersD can regulate spinal reflexes (as the UMNs synapse with the LMNs) = sensory-back motor-front  Spinal Reflexes -add additional communication fast ! Almost instant ! j "middle men" LMN Interneuron LMN Excessive stretching Excessive stretching of of the muscle the GTO (when the spindle causes muscle contracts) causes reflex contraction reflex relaxation Muscle spindle reflex is Golgi tendon organ reflex is monosynaptic: polysynaptic: exists only one synapse Multiple synapses exist between sensory and between the sensory and motor neuron absence : of motor neurons /because of interneurons the presence of interneurons Upper Motor Neuron Disorders  Upper Motor Neuron Disorders UMN damage can result in: Spasticity – stiffness of affected muscles contractions of affected muscles Clonus – involuntary Hypertonia – ↑ muscle tone than normal spinal reflexes Hyperreflexia – quicker UMNs descending in the pyramidal tracts are more commonly affected Corticobulbar tracts – Control head and face movements * Corticospinal tracts – Control limb (lateral tract) and - trunk (anterior tract) movements -  Upper Motor Neuron Disorders Characteristic feature of UMN disorders – babinski sign , fan sign Stimulation of the lateral plantar aspect of the foot leads to an extension of the big toe and fanning of other toes Examples of UMN disorders: Multiple sclerosis, amyotrophic lateral sclerosis, spinal cord injuries  Multiple Sclerosis (MS) Myelin destruction Disorder of adult onset characterized by the (Upper) destruction of myelin in the UMNs of the brain and spinal cord by autoantibodies Etiology is still not well-understood Low Vitamin D levels have been associated with increased risk in people who are genetically susceptible Physiological stress and trauma can precipitate onset Women affected more frequently than men Average survival – 25 to 35 years from appearance of signs and symptoms (cure is not ⑳available)  Multiple Sclerosis (MS) Pathophysiology – destruction of myelin results in the slowing or blocking of nerve impulses Clinical manifestations I General – Fatigue, weakness, dizziness Motor deficits – Stiffness of affected muscles, upper involuntary contractions, abnormal gait, coordination -motor problems, and slurred speech neuron Brief, intense, shock-like tingling sensation radiating down the back and legs on flexing the neck: Lhermitte's sign or barber chair sign  Multiple Sclerosis (MS) Characteristic feature – Patches of demyelination in the brain that appear as well-demarcated gray regions: plaques myelin is S white , but becomes gray http://multiple-sclerosis-research.blogspot.com/2015/01/education-whats-mri.html Amyotrophic Lateral Sclerosis (ALS) Most common neurodegenerative disease of adult onset involving the motor neurons Etiology is still not well-understood 90-95% of cases are sporadic and 5-10% of cases are inherited Multiple genetic mutations have been identified, and - the impact of environmental factors is being studied - Men affected more frequently than women Average survival – 2 to 5 years from appearance of signs and symptoms (cure is not available) Amyotrophic Lateral Sclerosis (ALS) Pathophysiology “Amyotrophy” – Atrophy muscle fibers due of to the degeneration of the LMN cell bodies inthe ventral horns of the spinal cord “Lateral sclerosis” – degeneration of axonsin the lateral cortispinal tract we fibrous tissue replacement Clinical manifestations Progressive stiffness of the affected limb muscles, involuntary contractions, dysphagia, weakness, and slurred speech Death may occur due to respiratory muscle involvement Amyotrophic Lateral Sclerosis (ALS) Lou Gehrig – Renowned New York Yankees baseball player diagnosed with ALS in 1939 (at the age of 36) and died in 1941 died within : two years Amyotrophic Lateral Sclerosis (ALS) Ice Bucket Challenge to raise awareness and funds for ALS research (July-August 2014)  Spinal Cord Injuries Damage to the UMNs in the spinal cord can result in motor deficits Etiology Fracture or dislocation of the vertebrae (e.g. car - accidents, gunshot wounds) Excessive flexion, i.e. forward bending of the head (e.g. - strike from behind) -Excessive extension, i.e. backward bending of the head (e.g. fall in which the chin is the point of impact) Compression of the vertebrae (e.g. high velocity blow to the top of the head)  Spinal Cord Injuries http://goodcarwrecklawyer.com/dallas-injury-lawyers-common-injuries | https://www.depuysynthes.com/patients/aabp/resources/articles_learn/id_59  Spinal Cord Injuries (1) tetraplegia/auadriplegia “-plegia” = paralysis in Greek Impairment or loss of motor function after damage to the UMNs in the cervical segments of the spinal cord ↳ higher segments Affects functioning in the arms (bilateral), trunk, pelvic organs, and legs (bilateral) Increases vulnerability to pressure sores, osteoporosis, respiratory infections, deep vein thrombosis, and cardiovascular disease  Spinal Cord Injuries (2) Paraplegia “-plegia” = paralysis in Greek Impairment or loss of motor function after damage to the UMNs in the - thoracic, lumbar, or sacral segments of the spinal cord Affects functioning in the trunk, pelvic organs, or legs (bilateral) Degree of loss of function that a person experiences (complete or partial) depends upon the level and extent of the injury  Spinal Cord Injuries (3) Spinal shock Temporary loss of spinal cord function that occurs - - immediately after a spinal cord injury (hours or days) Characterized by motor dysfunction (typically below the level of injury), sensory dysfunction, and loss of bowel and bladder control Spinal reflexes eventually recover (hours, days, weeks) Management Immobilization, e.g. cervical collars, back braces Surgery Drugs, e.g. steroids Disorders of the Cerebellum & Basal Ganglia  Cerebellar Disorders smaller brain Porth, Essentials of Pathophysiology: Concepts of Altered Health States, Fourth Edition  Cerebellar Disorders Cerebellum is vital during rapid muscular activities, such as running and typing Helps regulate the timing, coordination, and accuracy of body movements Receives afferent input from various sources Cerebral cortex, eyes, inner ears (semicircular canals and vestibules), tactile mechanoreceptors in the skin, and proprioceptors in the muscles and tendons Cerebellar disorders can occur due to an alcohol overdose, a head injury, or an infection  Cerebellar Disorders mostly too much all (1) cerebellar ataxia Lack of coordination of body movements - People walk with a wide-based, unsteady gait Excess alcohol can affect cerebellar function – inebriated persons fail the "walk-and-turn" test (2) cerebellar tremor Slow, visible tremor when performing an intended movement (e.g. trying to press an elevator button) – intention tremor Tremor becomes worse as the target is approached and a rhythmic, purposeless shaking of the limb occurs  Cerebellar Disorders Characteristic feature of cerebellar damage – dysmetria Impaired ability to judge distance or scale and control the range of motion, resulting in an overshooting or undershooting of the target & miss nose/finger  Basal Ganglia Disorders Basal ganglia are vital during slow and sustained - - body movements Help in starting, gracefully performing, and stopping skilled movements initiated by the cerebral cortex Porth, Essentials of Pathophysiology: Concepts of Altered Health States, Fourth Edition  Basal Ganglia Disorders mostly drug overdose Basal ganglia disorders can occur due to a drug - - overdose, a head injury, or an infection Clinical manifestations – Tremors and other types of involuntary movements: Repetitive muscle contractions leading to abnormal movements (anywhere in the body) – dystomia Jerky, unpredictable movements usually affecting the shoulders and hips – chored Rapid, flinging movements of the limbs on one side of the body – nemiballismus (half) Ballismus affects both sides of the body and is rare -  Parkinson’s Disease substantia nigra Progressive disorder of basal ganglia function that usually affects people >50 years Pathophysiology – degeneration of dopamine nthesizing neurons in the substantia 3 nigra Dopamine is a neurotransmitter that helps regulate movement, memory, and emotional responses Etiology is still not well-understood Characteristic feature – Lewy bodies D Abnormal aggregates of protein in the cytoplasm of the affected neurons of the basal ganglia  Parkinson’s Disease Lewy bodies appear as eosinophilic cores surrounded by pale halos ↓ https://pubmed.ncbi.nlm.nih.gov/22622968/ Tabnormal protein  Parkinson’s Disease Clinical manifestations Involuntary shaking in the distal parts of limbs (mainly the hands and feet) – tremors Stiffness of the muscles in the neck, arms, and legs – muscle ridigity Slowness in initiating and performing voluntary movements – bradykinesin Leaning forward to avoid falls – postural instability Management Regular exercise, Levodopa (increases dopamine levels) + Carbidopa (reduces dopamine breakdown) Parkinson’s Disease Lower Motor Neuron Disorders  Lower Motor Neuron Disorders LMN damage can result in: muscles Paresis – weakness of affected muscles of affected Paralysis – loss of movement muscle tone Hypotonia/Atonia – reduced/absent spinal reflexes Hyporeflexia/Areflexia – reduced/absent Broad classification of LMN disorders: I Myopathies – Affect muscle fibers Endplate disorders – Affect neuromuscular junctions types Of - Peripheral neuropathies – Affect axons of LMNs disorders leaving the spinal cord Ventral horn cell disorders – Affect cell bodies of LMNs ↳Where the cell bodies are located  Lower Motor Neuron Disorders muscle fibers Examples of myopathies: affecting actual Muscle atrophy Muscular dystrophy Example of an endplate disorder: neuromuscular Myasthenia gravis Examples of peripheral neuropathies: axons Carpal tunnel syndrome Guillain-Barré syndrome Example of a ventral horn cell disorder: cell bodies Spinal muscular atrophy  Muscle Atrophy Reduction in the diameter of muscle fibers because of a loss of actin and myosin filaments (1) disuse a trophy Muscle wasting in people experiencing temporary disabling circumstances e.g. Prolonged bed rest during hospitalization (2) denervation atrophy Muscle wasting in people experiencing disorders that deprive muscles of their normal innervation e.g. Poliomyelitis (polio): Poliovirus damages the LMNs · deprive muscles of what they would normally do  Muscular Dystrophy Group of genetic disorders, all of which lead to the progressive degeneration and necrosis of skeletal muscle fibers Pathophysiology – Affected muscle fibers are eventually replaced with fat and connective tissue, resulting in an abnormal increase in the size of the corresponding muscles: Pseudo hypertrophy Muscle weakness is gradual in onset and has a progressive course, resulting in decreased mobility, making everyday tasks difficult  Muscular Dystrophy Two most common types of muscular dystrophy: (1) duchenne muscular dystrophy (DMD) (2) becker muscular dystrophy (BMD) Both are inherited as X-linked recessive disorders Etiology Both occur due to mutations in the dystrophin gene, located on the short arm of the X chromosome Dystrophin gene codes for the dystrophin protein, a rod- shaped cytoskeletal protein that maintains the structural integrity of skeletal and cardiac muscle cells  Muscular Dystrophy Clinical manifestations of DMD Asymptomatic at birth and during infancy Signs of hip and thigh muscle weakness start appearing by 2 to 3 years – frequent falls and trouble , getting up from the floor Pseudohypertrophy of the calf muscles and behavioral disorders develop by 4 to 6 years Most patients need a wheelchair by 7 to 12 years Scoliosis develops in early adolescence - Death may occur due to the involvement of respiratory and cardiac muscles in early adulthood  Muscular Dystrophy More common in DND Gower’s maneuver – I ackof hip and thigh muscle strength causes down on the floor the child to push and climb up their legs to stand https://www.dovepress.com/current-and-emerging-treatment-strategies-for-duchenne-muscular-dystro-peer-reviewed-fulltext-article-NDT  Muscular Dystrophy Pseudohypertrophy – abnormal enlargement of affected muscles Icalf) due to infiltration of fat tissue https://www.mda.org/disease/duchenne-muscular-dystrophy/signs-and-symptoms Muscular Dystrophy Scoliosis – abnormal currenture of the Spine https://scoliosishealth.wordpress.com/  Muscular Dystrophy Clinical diagnosis Observation of voluntary movements Demonstration of a defective dystrophin gene using a blood sample Quantification of the dystrophin protein using a muscle biopsy specimen – complete lack of dystrophin noted in patients with DMB and reduced , amount of dystrophin in patients of BMD Management Splints to provide support and prevent deformities - Steroids to improve muscle regeneration -  Myasthenia Gravis Disorder of the neuromuscular junctions that affects the transmission of impulses between the LMNs and the skeletal muscle fibers Pathophysiology Autoimmune disorder – occurs due to destruction of functional acetylcholine (ACH) receptors in the endilate regions of muscle fibers by autoantibodies ACh is a neurotransmitter released from the synaptic end bulbs into the synaptic clefts when stimulated by an action potential – Binds to ACh receptors in the endplate regions of muscle fibers to initiate muscle contraction ) ↳ there is receptors being destroyed  Myasthenia Gravis Decrease in the number of functional ACh receptors in the endplate regions of muscle fibers results in a diminished motor response many many receptors ↓ getting &released NOT during action potential I ENOUGH receptors so it just & wont bind & a all enzyme !! ↓ endplate breaks down Porth, Essentials of Pathophysiology: Concepts of Altered Health States, Fourth Edition excess ACH reducing in size  Myasthenia Gravis Clinical manifestations Initial signs are due to extraocular muscle weakness: - (1) Ptosis – drooping of the upper eyelids (2) Diplopia – double vision Difficulty in swallowing – Due to pharyngeal muscle dysphagia weakness Speech impairment – Due to laryngeal muscle weakness - Difficulty in lifting objects or walking – Due to arm or leg & muscle weakness Signs and symptoms tend to progress over time, usually reaching their worst within a few years  Myasthenia Gravis Complication – med emergency & asthenic crisis : Sudden worsening of signs and symptoms during a - period of stress (infection, pregnancy, surgery) Breathing may be compromised to the extent that respiratory support is needed ACH StOPS from *D ↓ enzyme * Clinical diagnosis working Tensilon test – injection of tensilon + lanticholinesterase drug) temporarily muscle strength Management Anticholinesterase drugs, immunosuppressive therapy  Peripheral Neuropathies Diverse group of conditions, all of which affect one - - or more peripheral nerves, typically causing numbness or weakness - Neuropathies are classified into: - Mononeuropathies – e.g. Carpal tunnel syndrome Iones Polyneuropathies – e.g. Guillain-Barré syndrome (many) -  Mononeuropathies Usually caused by local disorders that affect only a single peripheral nerve Compression – e.g. Tumor Trauma – e.g. Invasive surgical procedure Infection – e.g. Varicella-zoster virus Schicken pox) Characterized by sensory or motor deficits Pure sensory neuropathy – Sensory disturbances (e.g. - cant pain) but no muscle weakness feel/ tingling Pure motor neuropathy – Muscle weakness but no & sensory disturbances (e.g. pain)  Carpal Tunnel Syndrome Pathophysiology – Compression of the median nerve as it travels with the flexor tendons through a canal made by the carpal bones and the transverse carpal ligament: entrapment motor neuropathy trapped I and mushed & http://www.patienteducationcenter.org/articles/carpal-tunnel-syndrome/  Carpal Tunnel Syndrome Risk factors Repetitive hand movements especially when the wrist is - flexed, e.g. typing Inflammation of the flexor tendons on the palm, e.g. - rheumatoid arthritis Clinical manifestations very specific * Pain, tingling, and numbness of the thumb, index finger, middle finger, and half of the ring finger Management ↳ NSAIDs, steroids, splints to immobilize the wrist at night · avoid excessive wrist flexion  Polyneuropathies Usually caused by systemic disorders that result in the demyelination or axonal degeneration of multiple peripheral nerves Fres Immune system disturbances – e.g. HIV/AIDS Exposure to toxins – e.g. Lead Metabolic disturbances – e.g. Diabetes Characterized by sensory or motor deficits that are bilaterally symmetrical =Longest axons are involved first, with the signs and symptoms usually beginning in the extremities -why feet happens first for diabetics  Guillain-Barré Syndrome autoimmune disorder Pathophysiology – Destruction of the myelin sheath of peripheral nerves by autoantibodies: demyelinating Polyneuropathy http://jamanetwork.com/journals/jama/fullarticle/645193  Guillain-Barré Syndrome Clinical manifestations Starts as an acute, flu-like illness, followed by pain, tingling, and numbness on slight movements in thighs, back, and shoulders *Ascending muscle weakness of the limbs can result in symmetrical paralysis ↑ V Involvement of the respiratory muscles in severe cases can result in&death Management IV immunoglobulins (from donated blood that contains healthy antibodies), physical therapy =>  Spinal Muscular Atrophy Genetic disorder characterized by the progressive - degeneration of LMN cell bodies in the ventral horns of the spinal cord Pathophysiology – LMNs die due to low levels of the survival motor neuron Clinical manifestations ↑ Severe hypotonia – floppy infant/baby syndrome" Atrophy of muscles used for activities such as controlling head movement, sitting up, and walking  Spinal Muscular Atrophy 6 week and 1 year old infants with hypotonia - muscle wasting Volpe J: Neurology of the Newborn, 4th ed., Philadelphia, 2001, WB Saunders