Chapter 50 disorders of motor function
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Chapter 50 Disorders of Motor Function. Motor Cortex. Highest level of motor function Precise, skillful, intentional movements Speech, flexor muscles of limbs, etc. Controlled by the primary, premotor and supplementary motor cortices in the frontal lobe

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Chapter 50 Disorders of Motor Function

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Chapter 50 disorders of motor function

Chapter 50Disorders of Motor Function


Motor cortex

Motor Cortex

  • Highest level of motor function

    • Precise, skillful, intentional movements

      • Speech, flexor muscles of limbs, etc.

    • Controlled by the primary, premotor and supplementary motor cortices in the frontal lobe

      • Receives information from the Thalamus, cerebellum and basal ganglia


M otor c ortex

Motor Cortex

Primary motor cortex

Responsible for execution of a movement.

Adjacent to central sulcus

Motor Humunculus

Premotor cortex

(areas 6 and 8)

Generates intricate plan of movement.

Throwing a ball or picking up a fork


Motor cortex1

Motor Cortex

Supplementary motor cortex

  • Involved in the performance of complex, skillful movements

    • (areas 6 and 8)


Homunculus

Homunculus


Basal ganglia

Basal Ganglia

  • A group of deep, interrelated subcortical nuclei that play an essential role in control of movement

  • Receives indirect input from the cerebellum and from all sensory systems, including vision, and direct input from the motor cortex

    • Functions in the organization of inherited and highly learned and rather automatic movement programs

    • Also involved in cognitive and perception functions


Structural components of the basal ganglia

Structural Components of the Basal Ganglia

  • Caudate nucleus

  • Putamen

  • Globuspallidusin the forebrain

    • SubstantiaNigra (midbrain)

    • Subthalamic nucleus


Structural components of the basal ganglia1

Structural Components of the Basal Ganglia

  • Caudate + Putamen =Striatum

  • Putamen + GlobusPallidus = Lentiform nucleus


Motor system overview

Motor System Overview

  • Cortex sends messages to the caudate and putamen of the basal ganglia

    • Acts on the Thalamus

    • Then to the supplementary motor cortex for review and editing

    • Then to the primary motor cortex, premotor cortex and primary somatosensory cortex

    • Then to the brain stem and spinal cord

  • The cerebellum – ensures the desired movements occur smoothly


Basal ganglia1

Basal Ganglia

  • Basal Ganglia monitors sensory information coming into the brain

    • sends it to the right place to be stored as a memory


Four functional pathways involving basal ganglia

Four Functional Pathways Involving Basal Ganglia

  • A dopamine pathway from the substantianigra to the striatum

  • A γ-aminobutyric acid (GABA) pathway from the striatum to the globuspallidus and substantianigra

  • Acetylcholine-secreting neurons, which are important in networks within the neostriatum

  • Multiple general pathways from the brain stem that secrete norepinephrine, serotonin, enkephalin, and several other neurotransmitters in the basal ganglia and the cerebral cortex


Thalamus

Thalamus

  • It relays to the cerebral cortex information received from other regions of the brain and spinal cord.

  • Sends information down spinal cord to the body

    • a brain “switching station”


Thalamus1

Thalamus

  • The cerebral cortex is interconnected with the Thalamus

    • Excitatory circuit

      • If unmodulated would cause hyperactivity = stiffness and rigidity with a continuous tremor (tremor at rest)

      • Basal Ganglia modulates the Thalamic excitability by an inhibitory loop


Chapter 50 disorders of motor function

  • The cerebellum receives continuous information about the sequence of muscle contractions from the brain

  • Receives sensory information from the peripheral parts of the body

    • Proprioception

      • sequential changes in the status of each body part


Brain stem

Brain Stem

Midbrain

  • Associated with vision, hearing, motor control, sleep/wake, arousal (alertness), and temperature regulation

    Pons

  • Nuclei that deal primarily with sleep, respiration, swallowing, bladder control, hearing, equilibrium, taste, eye movement, facial expressions, facial sensation, and posture


Brain stem1

Brain Stem

Medulla

  • Contains the cardiac, respiratory, vomiting and vasomotor centers dealing with autonomic, involuntary functions

    • Breathing, heart rate and blood pressure


Spinal cord structure and function

Spinal Cord Structure and Function

  • White Matter Pathways

    • Myelinated axons surrounding gray matter = cell bodies and their synaptic interconnections

  • Central Butterfly of Gray Matter

    • Collections of motor neurons with related function in the anterior horns

    • Sensory relay neurons in the posterior horn


Chapter 50 disorders of motor function

Dorsal

Ventral


Ascending sensory pathways

Ascending (Sensory) Pathways

  • AnterolateralSpinothalamic Tract

    • Carries information from pain, temperature and crude touch receptors to the thalamus (relay station of the brain)

    • First neuron synapses in the dorsal horn

    • Second neuron crosses the cord to the region ventral to the central canal and travels in the spinothalamic tract to the thalamus


Chapter 50 disorders of motor function

Ascending Pathways


Ascending sensory pathways dorsal columns

Ascending (Sensory) PathwaysDorsal Columns

  • Medial Leminiscal Pathways

    • Carries information from the skin of the lower and upper limbs (light touch, vibration, ability to discriminate between adjacent stimuli, pressure)

    • Carries information from shoulder, arm and finger on position and tension in muscles and tendons, movement, etc.

    • Dorsal root ganglion to the cord, to the dorsal column of white matter, to a nucleus in the medulla to the thalamus to the cortex for conscious perception


Chapter 50 disorders of motor function

Descending Pathway


Descending motor pathways

Descending (Motor) Pathways

  • Lateral Corticospinal Tract (Pyramidal Tract)

    • Carries movement signals from the cerebral cortex to the motor neurons in the spinal cord

      • Crosses over in the medulla

      • Travels down the cord in a lateral position

    • Passes into the gray matter in the cord to synapse with the motor neuron


Descending motor pathway

Descending (Motor) Pathway

  • Extrapyramidal Pathways (Multineuronal Pathways)

    • Provides for the support of movements of the lateral corticospinal tract

      • Movements of the trunk, proximal limb muscles, balance, posture, orienting to sight or sound and more.


Chapter 50 disorders of motor function

Pyramidal motor system

  • Originates in the motor cortex

  • Controls all of our voluntary movements

  • Consists of upper motor neurons in the Primary Motor Cortex and lower motor neurons in the anterior horn of the spinal cord

Extrapyramidal motor system

  • Originates in the basal ganglia

    • Includes the substantianigra, caudate, putamen, globuspallidus, thalamus, and subthalamic nucleus.

  • Provides background for the more crude, supportive movement patterns


Amyotrophic lateral sclerosis als

Amyotrophic Lateral Sclerosis (ALS)

  • Rapidly progressive weakness, muscle atrophy, spasticity, dysphagia

  • Early symptoms: muscle weakness in an arm or leg, twitching, slurred speech

  • Death within 2-3 years due to respiratory compromise

  • Sensory and cognitive function are unaffected


Locations of motorneurons affected by als

Locations of MotorneuronsAffected by ALS

  • The anterior horn cells of the spinal cord are affected

  • Death of LMNs leads to denervation, with subsequent shrinkage of musculature and muscle fiber atrophy.

  • The UMNsof the cerebral cortex are affected later

  • Lastly the motor nuclei of the brain stem, particularly the hypoglossal nuclei are affected

Lou Gehrig


Chapter 50 disorders of motor function

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Steven Hawking


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http://vimeo.com/27944955

http://www.youtube.com/watch?v=-qFSMXEYC3c


Spinal cord trauma

Spinal Cord Trauma

  • Often leads to paraplegia or quadriplegia depending on the location and extent of the injury

  • Hyperextension Injury

    • When the forehead is struck and driven posteriorly

      • Diving impact in shallow water

      • May tear the anterior spinal ligament and spinal cord may contact the vertebral body


Trauma to the spinal cord

Trauma to the Spinal Cord

  • Hyperflexion Injury

    • When the head of shoulders are struck from behind by an object of

      considerable weight or from a fall


Spinal cord trauma1

Spinal Cord Trauma

  • Concussion

    • Mild injury, transient and reversible

    • Contusion

      • Severe trauma with hemorrhagic necrosis, edema and softening of the cord – Myelomalacia,

      • or

        blood in the cord – Hematomyelia

    • Laceration or Tansection


Chapter 50 disorders of motor function

Cervical Contusion


Disorders arising in the basal ganglia

Disorders Arising in the Basal Ganglia

  • Characteristics of Disorders of the Basal Ganglia

    • Involuntary movements

    • Alterations in muscle tone

    • Disturbances in body posture


Characteristics of disorders of the basal ganglia

Characteristics of Disorders of the Basal Ganglia

  • Involuntary movements

  • Alterations in muscle tone

  • Disturbances in body posture


Types of involuntary movement disorders

Types of Involuntary Movement Disorders

  • Tremor = Trembling or vibrating

  • Tics = A habitual spasmodic contraction of the muscles, most often in the face

  • Chorea = Irregular writhing movements

  • Athetosis = Wormlike twisting of limb

  • Ballismus = Violent flinging motion of limbs

  • Dystonia = Abnormal posture

  • Dyskinesias = Bizarre wriggling movements

    • TardiveDyskinesia

      • Develops due to use of antipsychotic medications


Parkinson disease

Parkinson Disease

  • Characteristics

    • 0.3% of the general population has Parkinson Disease = 80,000 people

    • Usually begins after 50 years of age

    • Affects men twice as often as women

    • Course of the disease is 10-20 years

  • Clinical syndrome

    • Parkinsonism

  • James Parkinson, 1817 = ‘shaky palsy’


Parkinson disease1

Parkinson Disease

  • Degeneration of pigmented neurons (containing dopamine) in the substantianigra

  • Cause unknown: May be environmental/genetic

  • Early symptoms: tremor, rigidity, slow movement

  • Later: cognitive problems, dementia, dyskinesia

  • Gross: atrophy of substantianigra

  • Microscopic: Lewy bodies (inclusions in neurons)


Parkinson disease2

Parkinson Disease

  • Cogwheel-type motion

    • Ratchet-like movements

  • Bradykinesia

    • Slowness initiating and performing movements

  • Difficulty walking

  • Neuropsychiatric disorders


Chapter 50 disorders of motor function

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Parkinson disease (R) : atrophy of substantianigra


Chapter 50 disorders of motor function

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Parkinson disease: Lewy body


Chapter 50 disorders of motor function

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Michael J. Fox and Muhammad Ali


Chapter 50 disorders of motor function

  • http://www.youtube.com/watch?v=xuVY7wS25rc&feature=related


Huntington disease

Huntington Disease

  • Degeneration of basal ganglia and cerebral cortex

  • Early symptoms: lack of coordination, unsteady gait

  • Later: chorea (involuntary writhing), psychiatric symptoms, dementia

  • Autosomal dominant mutation on chromosome 4

  • Begins in 30s-40s; slow progression over 10-20 years


Chapter 50 disorders of motor function

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Read this story about Katharine and her family:

http://www.nytimes.com/2007/03/18/health/18huntington.html


Multiple sclerosis ms

Multiple Sclerosis (MS)

  • ADemyelinatingDisease of the CNS

    • Most common non-traumatic cause of neurologic disability among young and middle-aged adults

    • Characterized by exacerbations and remissions over many years in several different sites in the CNS

      • Initially, there is normal or near-normal neurologic function between exacerbations.

      • As the disease progresses, there is less improvement between exacerbations and increasing neurologic dysfunction.


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Multiple sclerosis

Multiple Sclerosis

  • Most common demyelinating disorder

  • Etiology unknown; related to autoimmunity

  • Variety of motor and sensory symptoms

  • Relapsing-remitting course

  • Plaques (areas of demyelination) in brain, cord


Chapter 50 disorders of motor function

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Multiple sclerosis


Chapter 50 disorders of motor function

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Multiple sclerosis plaques around ventricles


Guillain barre syndrome

Guillain-Barre Syndrome

  • Acute peripheral neuropathy

  • Progressive, ascending weakness

  • Usually self-limited (but may involve respiratory muscles, requiring respiratory intensive care)

  • Autoimmune attack on peripheral nerve resulting in demyelination and conduction block


Segmental demyelination

Segmental Demyelination

  • Disorder of the Schwann cells

    • Guillain-Barré Syndrome

      • Autoimmune disorder

        • Linked to CMV, Campylobacter jejuni, and Epstein-Barr Virus

      • Common in people of both sexes between ages 30 and 50

      • Can replace the Schwann cells

      • New myelin sheath is thin and subject to injury

  • A serious disorder that occurs when the body's defense (immune) system mistakenly attacks part of the nervous system. This leads to nerve inflammation that causes muscle weakness.


Guillain barr syndrome

Guillain-Barré Syndrome

  • Symptoms

    • Rapidly progressing limb weakness and loss of tendon reflexes

    • Flaccid paralysis

    • Pain

    • May lead to death due to ventilatory failure and autonomic disturbances

  • Treatment

    • Plasmapheresis

    • Intravenous Immunoglobulin therapy

    • 80-90% achieve a gull and spontaneous recover in 6 to 12 months


Alzheimer disease

Alzheimer Disease

  • Most common cause of dementia in the elderly

  • Symptoms:

    • Early on: forgetfulness, memory disturbances

    • Language deficits, loss of learned motor skills, alterations in mood/behavior, disorientation

    • Finally: patient becomes profoundly disabled, mute, immobile

  • Gross: Cortical atrophy, neuronal loss

  • Microscopic: neurofibrillary tangles, neuritic plaques


Alzheimer disease1

Alzheimer Disease

  • Neurofibrillary tangles

    • Cytoplasmic bundles of filaments encircling the nucleus of pyramidal calls

    • Tau protein

  • Amyloid beta protein

    • Produced instead of an integral protein

    • Triggers an inflammatory response


Chapter 50 disorders of motor function

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Alzheimer disease: brain atrophy


Chapter 50 disorders of motor function

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Alzheimer disease: brain atrophy


Chapter 50 disorders of motor function

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Alzheimer disease: brain atrophy


Chapter 50 disorders of motor function

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Alzheimer disease: progression


Chapter 50 disorders of motor function

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Alzheimer disease: plaques and tangles


Chapter 50 disorders of motor function

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Alzheimer disease: plaques (L) and tangles (R)


Components of the peripheral nervous system

Components of the Peripheral Nervous System

  • Motor and sensory branches of the cranial and spinal nerves

  • The peripheral parts of the autonomic nervous system

  • Peripheral ganglia

    • Neuron cell bodies grouped together in the PNS


Disorders of skeletal muscle groups

Disorders of Skeletal Muscle Groups

  • Muscular atrophy

    • If a normally innervated muscle is not used for long periods, the muscle cells shrink in diameter, lose much of their contractile protein, and weaken.

  • Muscular dystrophy

    • Genetic disorders that produce progressive deterioration of skeletal muscles because of mixed muscle cell hypertrophy, atrophy, and necrosis


Muscular dystrophy

Muscular Dystrophy

  • Involves the motor neuron

    • Probably do not involve the nervous system

  • Slow progressive onset of muscle weakness


Duchenne muscular dystrophy

Duchenne Muscular Dystrophy

  • 1:3500 male births

    • Inherited recessive single-gene defect

      • On short arm of X chromosome

    • Gene codes for dystrophin

      • Connects Z-lines to connective tissue surrounding muscle

    • Break down of sarcolemma = necrosis of muscle fibers


Duchenne muscular dystrophy1

Duchenne Muscular Dystrophy

Symptoms usually appear before age 6 and may appear as early as infancy. They may include:

Fatigue, mental retardation, muscle weakness (begins in legs and pelvis), difficulty with motor skills (running, jumping hopping), frequent falls

May be confined to wheelchair by age of 12


Signs and tests

Signs and Tests

  • A complete nervous system (neurological), heart, lung, and muscle exam may show:

  • Abnormal heart muscle

  • Congestive heart failure

  • Arrhythmia

  • Scoliosis

  • Respiratory disorders

  • Muscle wasting


Tests

Tests

  • Electromyography (EMG)

  • Genetic tests

  • Muscle biopsy

  • Serum CPK


Treatments

Treatments

  • There is no known cure for Duchenne muscular dystrophy.

  • Treatment aims to control symptoms to maximize quality of life.

    • Gene therapy may become available in the future.


Becker muscular dystrophy

Becker Muscular Dystrophy

  • Very similar to Duchenne muscular dystrophy

    • Becker muscular dystrophy gets worse much more slowly

  • 3 - 6 out of every 100,000 males

  • X-linked

    • Manifests later in childhood of adolescence


Question

Question

  • Which motor system is responsible for crude muscle movements?

  • Pyramidal motor system

  • Extrapyramidal motor system


Answer

Answer

b. Extrapyramidalmotor system: This system originates in the basal ganglia and provides background for the more crude, supportive movement patterns.


Neuromuscular junction

Neuromuscular Junction

  • Serves as a synapse between a motor neuron and a skeletal muscle fiber

  • Consists of the axon terminals of a motor neuron and a specialized region of the muscle membrane called the endplate

  • The transmission of impulses is mediated by the release of the neurotransmitter acetylcholine from the axon terminals.

  • Acetylcholine binds to receptors in the endplate region of the muscle fiber surface to cause muscle contraction.


Alterations of neuromuscular function

Alterations of Neuromuscular Function

  • Drugs and Toxins can alter neuromuscular function by changing the release, inactivation, or receptor binding of acetylcholine.

    • Curare acts on the post-junctionalmembrane of the motor endplate to prevent the depolarizing effect of the neurotransmitter.

      • Used during many types of surgical procedures

    • Clostridium botulinumblocks acetylcholine release and results in paralysis

      • Botox

    • Organophosphatesblock acetylcholinesterase

      • Nerve gases and pesticides


Myasthenia gravis

Myasthenia Gravis

  • Definition

    • Disorder of transmission at the neuromuscular junction that affects communication between the motoneuron and the innervated muscle cell

  • Cause

    • Autoimmune disease caused by antibody-mediated loss of acetylcholine receptors in the neuromuscular junction

      • Sensitized Helper T Cells

        • Antibody directed attack on receptors


Myasthenia gravis1

Myasthenia Gravis

  • Muscle weakness and fatigability with sustained effort

    • Ptosis due to eyelid weakness

    • Diplopia

    • Progresses to generalized weakness

  • Myasthenic crisis

    • Compromised ventilation

    • Usually during a period of stress


Diagnosis

Diagnosis

  • Tensilon or Edrophonium test

    • Acetylcholinesterase inhibitor

      • Patient feels little to no weakness for a short period of time

  • MUSK antibodies

  • http://www.youtube.com/watch?v=k7YX9kuWrxA


Treatment

Treatment

  • Pyridostigmine and neostigmineare the drugs of choice

    • Drug used to inhibit acetylcholinesterase

  • Plasmapheresis

    • Removes antibodies from circulation

    • http://www.youtube.com/watch?v=AwAs7uUZJVE

  • Intravenous immunoglobulin

    • Unknown how it works


Causes of polyneuropathies

Causes of Polyneuropathies

  • Immune mechanisms (Guillain-Barrésyndrome, rheumatoid arthitis, lupus, hypothyroid)

  • Toxic agents (arsenic polyneuropathy, lead polyneuropathy, alcoholic polyneuropathy)

  • Metabolic diseases (diabetes mellitus, uremia, chronic kidney disease)

  • Low levels of vitamin B12 or other problems with your diet

  • Poor blood flow to the area


The end

THE END


Nerve root injuries

Nerve Root Injuries

  • Herniated or Ruptured intervertebral disk

    • Sensory deficits

      • Spinal nerve root compression

      • Paresthesias and numbness

        • Particularly of the leg and foot

        • Knee and ankle reflexes also may be diminished or absent

    • Motor weakness and Pain


Question1

Question

  • Lead toxicity would result in which of the following conditions?

  • Mononeuropathies

  • Polyneuropathies

  • Upper motor lesion

  • Myasthenia gravis


Answer1

Answer

  • Mononeuropathies

  • Polyneuropathies: Polyneuropathies would result from systemic exposure to lead.

  • Upper motor lesion

  • Myasthenia gravis


Spinal cord injury sci

Spinal Cord Injury (SCI)

  • Definition

    • Damage to the neural elements of the spinal cord

  • Causes

    • Motor vehicle crashes, falls, violence, and sporting activities

  • Involvement

    • Most SCIs involve damage to the vertebral column and/or supporting ligaments as well as the spinal cord.

    • Commonly involve both sensory and motor function


Types of injuries to the vertebral column

Types of Injuries to the Vertebral Column

  • Fractures

  • Dislocations

  • Subluxations


Types of incomplete spinal cord injuries

Types of Incomplete Spinal Cord Injuries

  • Central cord syndrome

  • Anterior cord syndrome

  • Brown-Séquard syndrome

  • Conusmedullaris syndrome


Areas affected by sci

Areas Affected by SCI

  • Spinal reflexes

  • Ventilation and communication

  • Autonomic nervous system

  • Temperature regulation

  • Edema and deep vein thrombosis

  • Sensorimotor function


Areas affected by sci cont

Areas Affected by SCI (cont.)

  • Skin integrity

  • Pain reception

  • Bladder and bowel function

  • Sexual function


Question2

Question

Demyelination is the causative factor in which disease?

  • Parkinson disease

  • ALS

  • Multiple sclerosis


Answer2

Answer

  • Parkinson’s disease

  • ALS

  • Multiple sclerosis: MS is caused by an autoimmune attack on the oligodendrocytes (and Schwann cells in the peripheral nervous system) of the CNS.


Classifications of muscles

Classifications of Muscles

  • Extensors

    • Muscles that increase the angle of a joint

  • Flexors

    • Muscles that decrease the angle of a joint


Components of the neuromuscular system

Components of the Neuromuscular System

  • Neuromuscular unit containing motor neurons

  • Myoneural junction

  • Muscle fibers

    • Actin and Myosin

  • Spinal cord

  • Efferent pathways from the brain stem circuits


Requirements of motor systems

Requirements of Motor Systems

  • Upper motoneurons project from the motor cortex to the brain stem or spinal cord.

    • Directly or indirectly innervate the lower motoneurons or contracting muscles

    • Motor unit is a motor neuron and all the muscle fibers it innervates

  • Sensory feedback from the involved muscles

    • Continuously relayed to the cerebellum basal ganglia and sensory cortex

  • Functioning neuromuscular junction that links nervous system activity with muscle contraction


Mechanisms controlling coordinated movement

Mechanisms Controlling Coordinated Movement

  • Agonists

    • Promote movement

  • Antagonists

    • Oppose movement

  • Synergists

    • Assist the agonist muscles by stabilizing a joint or contributing additional force to the movement


Motor unit

Motor Unit

  • The motor neuron and the muscle fibers it innervates

    • A single motor neuron may innervate a few thousand muscle fibers

  • Upper motor neurons

  • Lower motor neurons


Disorders of motor function

Disorders of Motor Function

Upper motoneuron (UMN’s)

  • Originate in the motor region of the cerebral cortex or brain stem

    • Carries motor information down spinal cord to stimulate target muscle

  • Lesions can involve the motor cortex, the internal capsule, or other brain structures through which the corticospinal or corticobulbar tracts descend, or the spinal cord


Chapter 50 disorders of motor function

1. Paralysis or weakness of movements of the affected side but gross movements may be produced.

  • No muscle atrophy is seen initially

    2. Babinski sign is present:

    3. Loss of performance of fine-skilled voluntary movements especially at the distal end of the limbs

    4. Superficial abdominal reflexes and cremasteric reflex are absent.

    5. Spasticity or hypertonicity of the muscles.

    6. Clasp-knife reaction: initial higher resistance to movement is followed by a lesser resistance

    7. Exaggerated deep tendon reflexes and clonus may be


Disorders of motor function1

Disorders of Motor Function

Lower motoneurons (LMN’s)

  • Connects the brainstem and spinal cord to muscle cells

    • Brings nerve impulses from upper motor neuron to the muscles

  • Lesions disrupt communication between the muscle and all neural input from spinal cord reflexes, including the stretch reflex, which maintains muscle tone


Signs of lower motor neuron lesions lmnl

Signs of Lower Motor Neuron Lesions (LMNL)

1. Flaccid paralysis of muscles supplied.

2. Atrophy of muscles supplied.

3. Loss of reflexes of muscles supplied.

4. Muscles fasciculation (contraction of a group of fibers) due to irritation of the motor neurons – seen with naked eye


Cerebellum associated movement disorders

Cerebellum-associated movement disorders

  • Causes

    • Congenital defect, vascular accident, or growing tumor

  • Types

    • Vestibulocerebellarataxia

      • Not smooth movement

    • Decomposition of movement

    • Cerebellartremor

      • Rhythmic back-and-forth movement of a finger or toe

      • Cannot maintain a fix on the body part


Spinal cord

Spinal Cord


Spinal cord1

Spinal Cord


Peripheral nerve regeneration

Peripheral Nerve Regeneration

  • Damage to a peripheral nerve axon due to injury or neuropathy

    • Results in degenerative changes, followed by breakdown of the myelin sheath and Schwann cells

  • Regeneration factors

    • Proximity to soma

    • Crushing vs. cutting


Peripheral neuropathy

Peripheral Neuropathy

  • Definition

    • Any primary disorder of the peripheral nerves

  • Results

    • Muscle weakness, with or without atrophy and sensory changes

  • Involvement

    • Can involve a single nerve (mononeuropathy) or multiple nerves (polyneuropathy)


Mononeuropathies

Mononeuropathies

  • Caused by localized conditions such as trauma, compression, or infections that affect a single spinal nerve, plexus, or peripheral nerve trunk

    • Fractured bones may lacerate or compress nerves.

    • Excessively tight tourniquets may injure nerves directly or produce ischemic injury.

    • Infections such as herpes zoster may affect a single segmental afferent nerve distribution.


Mononeuropathies1

Mononeuropathies

  • Carpal Tunnel Syndrome

    • Compression-type mononeuropathy

      • Median nerve compression

    • Tinsel Sign

      • Development of a tingling sensation in palm by light percussion on median nerve at the wrist


Polyneuropathy

Polyneuropathy

  • Involves demyelination or axonal degeneration of multiple peripheral nerves that leads to symmetric sensory, motor, or mixed sensorimotor deficits

    • Typically, the longest axons are involved first, with symptoms beginning in the distal part of the extremities.


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