Neurology LMN and UMN Lesions Quiz
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Questions and Answers

What is the expected reflex response in a patient with a lower motor neuron (LMN) lesion?

  • Normal reflexes
  • Clonus
  • Hyperreflexia
  • Hyporeflexia or areflexia (correct)
  • A lesion in which structure causes hyperreflexia?

  • Efferent nerve
  • Upper motor neuron (correct)
  • Cerebellum
  • Afferent nerve
  • Which statement best describes the impact of a cerebellar lesion on muscle strength?

  • Causes muscle weakness contralateral to the lesion
  • Causes spastic paralysis
  • Causes muscle weakness ipsilateral to the lesion
  • Does not cause muscle weakness (correct)
  • A patient presents with ataxia. Where is the most probable location of the lesion?

    <p>Cerebellum</p> Signup and view all the answers

    What type of paralysis results from an upper motor neuron (UMN) lesion?

    <p>Spastic paralysis</p> Signup and view all the answers

    What is a key characteristic of flaccid paralysis?

    <p>Hyporeflexia or areflexia</p> Signup and view all the answers

    Where does the corticospinal tract synapse?

    <p>Anterior horn cell</p> Signup and view all the answers

    If a patient has a cerebellar lesion on the right side of their brain, on which side will their ataxia be observed?

    <p>Ipsilateral (right) side of the body</p> Signup and view all the answers

    A lesion in the corticobulbar tract results in what type of facial palsy?

    <p>Contralateral central facial palsy</p> Signup and view all the answers

    In the case of a lower motor neuron lesion, what is the primary characteristic of the affected muscles?

    <p>Flaccidity and weakness</p> Signup and view all the answers

    If the left motor cortex is damaged, which side of the face will show symptoms in central palsy?

    <p>The right side of the face</p> Signup and view all the answers

    Damage to the lower motor neuron (LMN) results in what specific outcome?

    <p>Severe paralysis due to denervation</p> Signup and view all the answers

    What is the final common pathway as described in the text?

    <p>The lower motor neuron pathways</p> Signup and view all the answers

    An occlusion of the anterior cerebral artery (ACA) would most likely result in which of the following?

    <p>Contralateral weakness affecting the leg more than the arm.</p> Signup and view all the answers

    The upper motor neuron (UMN) is analogous to what in the context of controlling the lower motor neuron (LMN)?

    <p>A teacher</p> Signup and view all the answers

    Which neurotransmitter is primarily associated with the direct activation pathways in the motor system?

    <p>Glutamate</p> Signup and view all the answers

    How are the upper and lower face innervated by the facial nerve?

    <p>The upper face is innervated by ipsilateral fibers, and the lower face is innervated by contralateral fibers.</p> Signup and view all the answers

    What differentiates peripheral facial palsy from central facial palsy regarding the side of the lesion?

    <p>Peripheral palsy occurs ipsilaterally; central palsy occurs contralaterally</p> Signup and view all the answers

    Fibers from the primary motor cortex pass through which structure before diverging into the corticospinal and corticobulbar tracts?

    <p>Posterior limb of the internal capsule</p> Signup and view all the answers

    A lesion in the posterior limb of the internal capsule would most likely result in which of the following?

    <p>Contralateral weakness with equal severity in the arm and leg</p> Signup and view all the answers

    In the spinal cord, where are the arm fibers located in the lateral corticospinal tract relative to the leg fibers?

    <p>Medial</p> Signup and view all the answers

    Where are the corticospinal tracts located within the midbrain?

    <p>Middle 2/3 of the cerebral peduncle</p> Signup and view all the answers

    Which of the following describes the function of the direct activation pathways?

    <p>To initiate and control skilled voluntary activity</p> Signup and view all the answers

    A tumor pressing from outside the spinal cord would likely result in which of the following?

    <p>Ipsilateral leg weakness</p> Signup and view all the answers

    Which term describes severe paralysis affecting all four limbs?

    <p>Quadriplegia</p> Signup and view all the answers

    Where do lower motor neurons that control arm and leg movements originate?

    <p>Ventral horn of the spinal cord</p> Signup and view all the answers

    A patient experiences weakness on the right side of their body. Which term best describes this condition?

    <p>Hemiparesis</p> Signup and view all the answers

    A lesion to which structure would NOT result in real muscle weakness?

    <p>Lack of Motivation</p> Signup and view all the answers

    What is 'paresis' defined as in the text?

    <p>A lesser degree of paralysis</p> Signup and view all the answers

    Where do the upper motor neurons originate?

    <p>Cerebral cortex</p> Signup and view all the answers

    Which of the following is a common symptom associated with weakness?

    <p>Incoordination of movement</p> Signup and view all the answers

    Which of the following best describes 'plegia'?

    <p>Complete loss of movement</p> Signup and view all the answers

    What is the correct term for severe paralysis of the legs?

    <p>Paraplegia</p> Signup and view all the answers

    Which of the following is NOT a location where motor fibers can be injured resulting in weakness?

    <p>Lack Of Rigidity</p> Signup and view all the answers

    What type of muscle weakness is associated with neuromuscular junction disorders?

    <p>Fluctuating weakness</p> Signup and view all the answers

    A lesion in the motor cortex will cause paralysis on which side of the body?

    <p>Contralateral</p> Signup and view all the answers

    According to Table 4, what is the consequence of a small lacunar infarct on the face?

    <p>Unaffected</p> Signup and view all the answers

    Based on Table 4, what effects does a Middle Cerebral Artery (MCA) infarct have on the arm?

    <p>Spastic Paralysis</p> Signup and view all the answers

    According to Table 4, what is the impact of a small lacunar infarct on the leg?

    <p>Unaffected</p> Signup and view all the answers

    According to Table 4, what is the impact of a Middle Cerebral Artery (MCA) infarct on the face?

    <p>Central Weakness</p> Signup and view all the answers

    What type of paralysis is typically associated with a corticospinal tract lesion?

    <p>Spastic paralysis</p> Signup and view all the answers

    According to Table 4, what is the severity of leg paralysis caused by a Middle Cerebral Artery (MCA) infarct?

    <p>Mild</p> Signup and view all the answers

    How many decussations are present in the dentato-thalamo-cortical and dentato-rubro-thalamo-cortical tracts?

    <p>Two, one in the dentato-thalamic fibers and one in the corticospinal tract</p> Signup and view all the answers

    Which side of the body does the cerebellum control, given the two decussations in the dentato-thalamo-cortical and dentato-rubro-thalamo-cortical tracts?

    <p>Ipsilateral side</p> Signup and view all the answers

    An infarct in the anterior cerebral artery (ACA) typically presents with which of the following clinical signs with respect to weakness?

    <p>Differential weakness in the arm and leg.</p> Signup and view all the answers

    A lesion in the internal capsule typically results in which of the following clinical signs?

    <p>Dense hemiplegia of both the arm and the leg with the same degree of weakness.</p> Signup and view all the answers

    In a brainstem lesion resulting in crossed signs, which of the following combination of findings would be most likely?

    <p>Ipsilateral peripheral facial weakness and contralateral UMN weakness.</p> Signup and view all the answers

    What type of facial weakness accompanies a lesion in the facial nerve?

    <p>Ipsilateral peripheral weakness.</p> Signup and view all the answers

    A patient presents with right arm spastic paralysis and right leg spastic paralysis. Where is the most likely location of the lesion, given these findings?

    <p>Right Upper Cervical Spinal Cord.</p> Signup and view all the answers

    What are the expected motor findings in both arms and legs in a transverse myelopathy of the entire upper cervical cord?

    <p>Bilateral spastic paralysis of both arms and legs.</p> Signup and view all the answers

    A patient presents with right arm flaccid paralysis and right leg spastic paralysis. Where is the likely location of the lesion?

    <p>Right Cervical Spinal Cord (C5-C8).</p> Signup and view all the answers

    A patient exhibits right arm flaccid paralysis and no leg weakness. Where is the most likely site of injury?

    <p>Right Cervical Roots or Brachial Plexus.</p> Signup and view all the answers

    A patient has right leg spastic paralysis, but no arm weakness. Where is the most likely location of the lesion?

    <p>Right Thoracic Spinal Cord.</p> Signup and view all the answers

    What are the expected lower extremity findings in a transverse myelopathy of the entire thoracic spinal cord?

    <p>Bilateral spastic paralysis.</p> Signup and view all the answers

    Which type of paralysis will be observed with a lesion of the lumbar spinal cord on one side?

    <p>Ipsilateral flaccid paralysis.</p> Signup and view all the answers

    What is characteristic about lumbar root or plexus lesions?

    <p>No loss of bladder or bowel control.</p> Signup and view all the answers

    In the provided context, what is the primary difference in the presentation of an upper cervical spinal cord lesion compared to a lumbar spinal cord lesion?

    <p>Upper cervical lesions cause both arm and leg weakness while lumbar lesions primarily cause leg weakness.</p> Signup and view all the answers

    Study Notes

    Motor System Overview

    • The motor system coordinates movement, planning, and execution.
    • Ataxia describes uncoordinated movements.
    • Muscle paralysis or weakness results from damage to the upper or lower motor systems.

    Motor Neuron System

    • Movement requires two interacting neuronal systems:
      • Upper Motor Neuron (UMN): Originates in the cerebral cortex. Synapses with the lower motor neuron.
      • Lower Motor Neuron (LMN): Originates in the brainstem (facial muscles) or ventral/anterior horn of the spinal cord (arms/legs).
    • Damage to either system affects movement.

    Paralysis and Weakness

    • Paralysis is the loss of voluntary movement.
      • Plegia: Severe paralysis (muscle strength 0-1/5).
        • Hemiplegia: One side of the body.
        • Quadriplegia: All four extremities.
        • Paraplegia: Legs.
      • Paresis: Lesser degree of paralysis (muscle strength 2-4/5).
        • Hemiparesis: One side of the body.
    • Weakness: A variety of causes including body malaise, lack of motivation, depression, incoordination, rigidity, and true muscle weakness (motor fibers damaged).

    Motor Pathways

    • Direct activation pathways:
      • Corticospinal tract: Initiates and controls voluntary, skilled activity.
        • 90% decussate (cross over) at the medulla → lateral corticospinal tracts.
        • 10% do not decussate → anterior corticospinal tracts.
      • Corticobulbar tract: Controls cranial nerves (e.g., III, IV, VI, V, VII, IX, X, XI, XII) for facial and other movements.
    • Indirect activation pathways: Includes reticulospinal, vestibulospinal, rubrospinal, and tectospinal tracts.
      • These pathways are involved in postural control, reflexive reactions and coordination.

    Neurotransmitters

    • Glutamate: Neurotransmitter at UMN-LMN synapse, within the brainstem (corticobulbar) and spinal cord (corticospinal)
    • Acetylcholine: Neurotransmitter at neuromuscular junction.

    Vascular Supply of the Motor System

    • Middle Cerebral Artery (MCA): Supplies areas for face, arm, and hand control; occlusion leads to contralateral weakness affecting face and arm more than leg.
    • Anterior Cerebral Artery (ACA): Supplies areas for leg control; occlusion leads to contralateral weakness affecting leg more than arm.

    Primary Motor Cortex

    • Located in the precentral gyrus (frontal lobe, Brodmann area 4).
    • Dedicated areas for face, tongue, and hand movements due to their complex functions.
    • Major source of upper motor neurons.

    Corticospinal and Corticobulbar Tracts

    • Corticospinal tract ends in the spinal cord.
    • Corticobulbar tract ends in the brainstem (cranial nerves).

    Upper vs. Lower Motor Neuron Paralysis

    • Upper Motor Neuron (UMN) lesions: Spasticity, hyperreflexia, Babinski sign (extensor plantar response), atrophy.
    • Lower Motor Neuron (LMN) lesions: Flaccidity, hypotonia, loss of reflexes, fasciculations, fibrillations, atrophy.

    Reflexes

    • Reflexes are the simplest motor coordination, using afferent and efferent arcs.
    • Stretch reflex (e.g., knee-jerk reflex) is a monosynaptic reflex that occurs at the spinal cord level.
      • Affected by damage to upper motor neurons or lower motor neurons.

    Cerebellar System

    • The cerebellum coordinates movement.
    • Cerebellar damage causes ataxia (incoordination) ipsilateral to the lesion.
      • Does not cause muscle weakness.

    Localization of Lesions

    • Lesion location in the brain, brainstem, or spinal cord determines the specific muscle group weakness, affecting either upper limbs or lower limbs first.

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    Description

    Test your knowledge on the reflex responses associated with lower and upper motor neuron lesions. This quiz covers key concepts related to muscle strength, paralysis types, and cerebellar lesions. Assess your understanding of the nervous system and its implications on reflexes and motor control.

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