Localizing the lesion

Question 1

Describe the corticospinal tracts

Answer 1

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

Question 2

Describe the pattern of weakness in an UMN lesion

Answer 2

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

Question 3

Where does spasticity develop in an UMN lesion

Answer 3

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

Question 4

How does spasticity manifest?

Answer 4

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

Question 5

Does muscle wasting occur with an UMN lesion?

Answer 5

No - disuse atrophy however may occur

Question 6

Describe the reflexes in an UMN lesion

Answer 6

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

Question 7

What can UMN mimic in the first few hours?

Answer 7

LMN

Question 8

Where is the damage in an UMN lesion

Answer 8

Anywhere in the corticospinal tract

Question 9

Where is the damage in a LMN lesion

Answer 9

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

Question 10

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

Answer 10

The muscles supplied by the involved neurons

Question 11

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

Answer 11

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

Question 12

Describe the signs present in the muscles in LMN lesions

Answer 12

Wasting and fasciculations

Question 13

What are fasciculations

Answer 13

spontaneous involuntary twitching

Question 14

Describe the reflexes in a LMN lesion

Answer 14

Hyporeflexia (reduced/absent)

Plantars remain flexor

Question 15

What is the main differential of a LMN lesion

Answer 15

Primary muscle disease

Question 16

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

Answer 16

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

Question 17

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

Answer 17

MND
B12 deficiency
Taboparesis

Question 18

How do pain and temperature sensations travel?

Answer 18

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

Question 19

How does joint position and vibration sense travel?

Answer 19

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

Question 20

Which classification chart is used to grade power?

Answer 20

MRC classificaiton

Question 21

Describe the MRC classification

Answer 21

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)

Question 22

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

Answer 22

Brainstem injury on the side of the cranial nerve palsy

Question 23

Describe the signs of a cord lesion

Answer 23

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

Question 24

What picture do hemi-cord lesions present

Answer 24

Brown sequard

Question 25

Describe the Brown sequard picture

Answer 25

``` 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 ```

Question 26

When might a dissociated sensory loss occur?

Answer 26

In cervical cord lesions

Question 27

Describe a dissociated sensory loss

Answer 27

Loss of joint position and vibration sense without the loss of pain and temperature

Question 28

What do peripheral neuropathies cause?

Answer 28

Distal weakness

Question 29

How does the weakness in Guillian barre present?

Answer 29

Distal weakness which ascends over time