Localizing the lesion Flashcards

1
Q

Describe the corticospinal tracts

A

Carry motor information from the precentral gyrus of the frontal cortex up to synapse with anterior horn cells in the spinal cord

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2
Q

Describe the pattern of weakness in an UMN lesion

A

Pyramidal pattern
Arm - extensors are weaker
Leg - flexors are weaker

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3
Q

Where does spasticity develop in an UMN lesion

A

Spasticity occurs in the stronger muscle groups (arm - flexors, leg - extensors)

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4
Q

How does spasticity manifest?

A

Increased tone that is velocity dependent (The faster you move patients muscles, greater the resistance till it suddenly gives way like a clasp knife)

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5
Q

Does muscle wasting occur with an UMN lesion?

A

No - disuse atrophy however may occur

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6
Q

Describe the reflexes in an UMN lesion

A

Hyperreflexia
Positive Babinski sign - upgoing plantars
Clonus (elicited by rapidly dorsiflexing the foot, <3 rhythmic downward jerks of the foot are normal)

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7
Q

What can UMN mimic in the first few hours?

A

LMN

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8
Q

Where is the damage in an UMN lesion

A

Anywhere in the corticospinal tract

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9
Q

Where is the damage in a LMN lesion

A

Anywhere from the anterior horn cells distally, including nerve roots, plexuses and peripheral nerves

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10
Q

What does the pattern of weakness in a LMN lesion correspond with?

A

The muscles supplied by the involved neurons

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11
Q

Describe the tone in muscles when a LMN lesion is present?

A

Hypotonia/flaccidity - the limb feels soft and floppy, providing little resistance to passive stretch

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12
Q

Describe the signs present in the muscles in LMN lesions

A

Wasting and fasciculations

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13
Q

What are fasciculations

A

spontaneous involuntary twitching

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14
Q

Describe the reflexes in a LMN lesion

A

Hyporeflexia (reduced/absent)

Plantars remain flexor

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15
Q

What is the main differential of a LMN lesion

A

Primary muscle disease

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16
Q

How do you distinguish between primary muscle disease and a LMN lesion

A

In LMN lesion - symmetrical loss, reflexes reduced/absent and there is no sensory component

17
Q

List some conditions which may present with mixed UMN and LMN signs

A

MND
B12 deficiency
Taboparesis

18
Q

How do pain and temperature sensations travel?

A

Along small fibres in peripheral nerves and the anterolateral (spinothalamic) tracts in the cord and brainstem

19
Q

How does joint position and vibration sense travel?

A

In large fibres in peripheral nerves and the large dorsal columns of the cord

20
Q

Which classification chart is used to grade power?

A

MRC classificaiton

21
Q

Describe the MRC classification

A

Grade 0 - No muscle contraction
Grade 1 - Flicker of contraction
Grade 2 - Some active movement
Grade 3 - Active movement against gravity
Grade 4 - Active movement against resistance
Grade 5 - Normal power (allow for age)

22
Q

Where would the lesion be in a cranial nerve palsy contralateral to a hemiplegia?

A

Brainstem injury on the side of the cranial nerve palsy

23
Q

Describe the signs of a cord lesion

A

LMN signs at the level of the lesion
UMN signs below the level of the lesion
Sensory level is the hallmark

24
Q

What picture do hemi-cord lesions present

A

Brown sequard

25
Describe the Brown sequard picture
``` Dorsal column loss (joint position sense and vibration) on the same side as the lesion Spinothalamic loss (pain and temperature) on the opposite side of the lesion ```
26
When might a dissociated sensory loss occur?
In cervical cord lesions
27
Describe a dissociated sensory loss
Loss of joint position and vibration sense without the loss of pain and temperature
28
What do peripheral neuropathies cause?
Distal weakness
29
How does the weakness in Guillian barre present?
Distal weakness which ascends over time