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Neurology > Upper motor lesion > Flashcards

Upper motor lesion Flashcards

1
Q

What is an upper motor neuron lesion (UMNL)?

A

A lesion that occurs in the central nervous system (brain or spinal cord) affecting neurons that carry motor signals from the brain to the lower motor neurons.

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2
Q

What are common causes of upper motor neuron lesions?

A

Stroke, multiple sclerosis, traumatic brain injury, cerebral palsy, and spinal cord injury

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3
Q

What is the difference between upper motor neurons (UMNs) and lower motor neurons (LMNs)?

A

UMNs originate in the brain and spinal cord and regulate LMNs, which directly innervate muscles.

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4
Q

What is “hyperreflexia”?

A

Exaggerated reflex responses, a common feature of UMNL due to the loss of inhibitory signals from the brain.

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4
Q

What is “spasticity” in the context of UMNL?

A

Increased muscle tone with resistance to passive movement, typically more pronounced in flexor muscles of the arms and extensor muscles of the legs.

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4
Q

What are the classic signs of upper motor neuron lesions?

A

Muscle weakness, spasticity, hyperreflexia, and the presence of pathological reflexes like the Babinski sign.

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5
Q

How does muscle weakness present in UMNL?

A

Weakness in UMNL typically affects groups of muscles rather than individual muscles, and it’s more pronounced in specific muscle groups depending on the location of the lesion.

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5
Q

What is “clonus”?

A

Repetitive, rhythmic muscle contractions typically seen in UMNL when a muscle is stretched.

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6
Q

What is the Babinski sign, and how does it relate to UMNL?

A

The Babinski sign is the upward movement of the big toe upon stimulation of the sole, which indicates an upper motor neuron lesion.

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7
Q

What is “disuse atrophy” in UMNL?

A

Muscle wasting due to reduced movement or use, seen over time in UMNL but less severe compared to LMNL.

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8
Q

What is the difference in atrophy between upper motor neuron lesions and lower motor neuron lesions?

A

Atrophy is mild in UMNL due to disuse, whereas it is more severe in LMNL because of direct denervation.

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9
Q

What is “decerebrate posturing”?

A

An abnormal body posture that involves extension of the arms and legs, seen in severe UMNL affecting the brainstem.

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9
Q

What is the “pyramidal weakness” pattern seen in UMNL?

A

A characteristic pattern where flexor muscles of the arms and extensor muscles of the legs are predominantly affected, leading to difficulty with specific movements.

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10
Q

What is “spinal shock”?

A

A temporary loss of motor, sensory, and reflex functions below the level of spinal cord injury, with gradual return of some reflexes, often associated with UMNL.

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11
Q

What is “decorticate posturing”?

A

An abnormal posture where the arms are flexed and legs extended, indicative of a lesion above the red nucleus in the brainstem, typically involving UMNs.

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12
Q

What happens to deep tendon reflexes in UMNL?

A

Deep tendon reflexes become hyperactive due to the loss of inhibitory control from the brain.

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13
Q

How is muscle tone affected in UMNL?

A

Muscle tone is increased, leading to spasticity and resistance to passive movement.

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14
Q

What is the significance of a positive Hoffman sign in UMNL?

A

A positive Hoffman sign (flicking the nail of the middle finger causing thumb flexion) is a sign of UMN damage in the cervical spinal cord.

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15
Q

What is “pronator drift”?

A

A sign of UMNL where a patient’s arm drifts downward and pronates when held outstretched, indicating weakness.

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15
Q

What are “pathological reflexes”?

A

Reflexes like the Babinski sign and Hoffman’s sign that appear in the presence of UMNL and indicate damage to the corticospinal tract.

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16
Q

How does the “pattern of weakness” differ between UMNL and LMNL?

A

UMNL weakness typically follows a pyramidal distribution, affecting extensors of the upper limbs and flexors of the lower limbs, while LMNL weakness is more localized.

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17
Q

How does voluntary movement change in UMNL?

A

Voluntary movements become slow, weak, and less coordinated, especially in fine motor tasks.

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18
Q

What is the typical effect of UMNL on gait?

A

Patients with UMNL often develop a spastic gait, where one leg may drag or appear stiff.

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19
Q

How does UMNL affect fine motor control?

A

Fine motor control is impaired due to weakness and spasticity, making tasks like writing or buttoning difficult.

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20
Q

What are the common sites of upper motor neuron lesions?

A

The motor cortex, corticospinal tracts, internal capsule, brainstem, and spinal cord.

20
Q

What is the role of the corticospinal tract in UMNL?

A

The corticospinal tract transmits motor commands from the brain to the spinal cord, and lesions here lead to typical UMN signs such as spasticity and hyperreflexia.

21
Q

What is the prognosis for recovery in UMNL?

A

Recovery varies depending on the cause and extent of damage, but UMNLs often lead to chronic spasticity and weakness despite rehabilitation.

22
Q

What are common treatment strategies for spasticity in UMNL?

A

Physical therapy, muscle relaxants like baclofen, and sometimes botulinum toxin injections are used to manage spasticity.

23
Q

Why does spasticity occur in UMNL?

A

Spasticity occurs due to a loss of inhibitory signals from the brain to the muscles, resulting in excessive contraction in response to stretch.

24
Q

What is “motor neuron disease” in the context of UMNL?

A

A neurodegenerative disorder, like amyotrophic lateral sclerosis (ALS), that affects both upper and lower motor neurons.

24
Q

How do UMNLs affect reflex arcs?

A

Reflex arcs remain intact but become hyperactive due to the loss of inhibitory signals from the brain.

24
Q

What happens to sensation in UMNL?

A

Sensory loss is variable and depends on the location of the lesion, but UMNLs primarily affect motor function.

25
Q

What is the typical pattern of recovery in UMNL?

A

Recovery often begins with the return of reflexes and can include partial return of motor function, though spasticity and weakness may persist.

25
Q

What differentiates a “complete” from an “incomplete” UMNL?

A

A complete UMNL results in total loss of voluntary movement below the lesion, while incomplete UMNL causes partial weakness with some preserved function.

26
Q

What role do rehabilitation therapies play in managing UMNL?

A

Physical and occupational therapies focus on improving strength, flexibility, and coordination to maximize function.

27
Q

How does the size of the lesion affect UMNL symptoms?

A

Larger lesions generally cause more severe symptoms, including greater weakness and more pronounced spasticity.

28
Q

What is the role of the internal capsule in UMNL?

A

The internal capsule carries motor signals between the brain and spinal cord, and lesions here cause significant UMNL symptoms like weakness and spasticity.

28
Q

Why is muscle fasciculation absent in UMNL?

A

Fasciculations are a sign of lower motor neuron damage, not typically seen in UMNL where the upper motor neurons are affected.

29
Q

How does an upper motor neuron lesion affect muscle stretch reflexes?

A

Muscle stretch reflexes become exaggerated due to the loss of descending inhibitory control.

30
Q

What is the first step in localizing an upper motor neuron lesion?

A

Begin with a detailed motor examination, assessing muscle strength, tone, and reflexes in different regions of the body.

31
Q

What is the effect of UMNL on muscle bulk?

A

Muscle bulk is preserved initially, but disuse atrophy can occur over time if the affected muscles are not used

32
Q

What type of weakness pattern is typically associated with upper motor neuron lesions?

A

UMN lesions often cause a pyramidal pattern of weakness, affecting the extensors of the arms and the flexors of the legs more than other muscle groups.

33
Q

How does bilateral limb weakness help localize a UMN lesion?

A

Bilateral weakness suggests a lesion in the spinal cord or brainstem, especially if both legs or all four limbs are involved.

33
Q

What can unilateral weakness of the face, arm, and leg suggest about the location of a UMN lesion?

A

Unilateral weakness of these areas indicates a contralateral lesion in the cerebral cortex or the internal capsule.

34
Q

What is the significance of spasticity in a UMN lesion localization?

A

Spasticity indicates chronic UMN lesions and can help localize the lesion to descending motor tracts in the brain or spinal cord.

35
Q

How does a positive Babinski sign help localize a UMN lesion?

A

A positive Babinski sign indicates a lesion in the corticospinal tract on the contralateral side to the abnormal toe response.

35
Q

How do reflex changes help localize a UMN lesion?

A

Hyperreflexia suggests a UMN lesion, with reflex changes typically occurring below the level of the lesion.

36
Q

What does pronator drift indicate in localizing UMN lesions?

A

Pronator drift suggests weakness due to an upper motor neuron lesion, often indicating a lesion in the contralateral motor cortex.

37
Q

How does clonus assist in localizing an upper motor neuron lesion?

A

Clonus (especially at the ankle or wrist) indicates hyperreflexia, which points to a UMN lesion above the level of the reflex arc.

38
Q

What does spastic gait suggest about the location of a UMN lesion?

A

A spastic gait suggests a lesion in the corticospinal tracts, typically involving the spinal cord or brainstem.

39
Q

How can upper limb spasticity localize a UMN lesion?

A

Spasticity in the upper limbs suggests a lesion in the cervical spinal cord or brain on the contralateral side.

40
Q

What does quadriplegia (weakness in all four limbs) suggest about the location of a UMN lesion?

A

Quadriplegia points to a lesion at or above the cervical spinal cord level.

41
Q

How does hemiplegia (one-sided weakness) localize a UMN lesion?

A

Hemiplegia suggests a lesion in the contralateral cerebral hemisphere or internal capsule.

42
Q

How can reflex asymmetry help localize a UMN lesion?

A

Reflex asymmetry, with hyperreflexia on one side, suggests a lesion on the opposite side of the brain or spinal cord.

43
Q

How does a lesion in the brainstem typically present in terms of UMN signs?

A

A brainstem lesion can cause crossed motor deficits, with cranial nerve deficits on one side and hemiplegia on the opposite side.

44
Q

What does pure lower limb spasticity suggest about the UMN lesion location?

A

Spasticity confined to the lower limbs suggests a lesion in the thoracic or lumbar spinal cord.

45
Q

How does the presence of cranial nerve involvement help localize a UMN lesion?

A

Involvement of cranial nerves with UMN signs in the limbs suggests a brainstem lesion, where the cranial nerve nuclei are located.

46
Q

How does facial weakness help localize a UMN lesion?

A

Central facial weakness (involving only the lower face) indicates a lesion in the contralateral motor cortex or internal capsule.

47
Q

What does bilateral spasticity in the lower limbs suggest?

A

Bilateral spasticity of the lower limbs suggests a lesion in the spinal cord (such as in thoracic regions) or bilateral lesions in the brain.

48
Q

How does sensory loss associated with UMN signs help in localization?

A

Sensory loss combined with UMN signs can help pinpoint the lesion to a specific area of the spinal cord or brain, such as in a stroke involving both motor and sensory pathways.

Neurology (7 decks)

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