Localization skills: focal weakness or numbness

Question 1

For a patient with limb weakness, recognize any s/s of LMN versus UMN lesions

Answer 1

UMN lesion: severe weakness, increased tone/reflexes, may see clonus; (milder atrophy)

LMN lesion: severe atrophy, decreased tone/reflexes, may see fasciculations; (milder weakness)

Question 2

How would you recognize the difference b/w an LMN vs UMN lesion to the facial n.? What does it mean if you see loss of ant 2/3 tongue?

Answer 2

LMN: causes total ipsilateral facial paralysis. If taste of ant 2/3 tongue lost, corda tympani branch involved.

UMN lesion: causes milder contralateral lower face paralysis (can see stronger jaw-jerk reflex)

Question 3

What is bulbar palsy?

Answer 3

Weakness in chewing, speaking, or swallowing (AKA bulbar functions)

Question 4

What brain regions are involved in a bulbar lesion vs. a pseudobulbar lesion?

Explain what is meant by a pseudobulbar lesion. (would it be an UMN or LMN lesion?)

Answer 4

Bulbar: localized to lower brainstem nuclei (V, VII, IX, X, XII)

Pseudobulbar: more rostral level. Pseudobulbar lesions have same functional weakness, but causative lesions are in UMN (corticobulbar tract) which control the respective CN nuclei in the brainstem.

Question 5

What are some UMN signs in a pseudobulbar lesion?

Would you see atrophy, fasciculations, both, or neither?

Answer 5

Hyperactive jaw jerk (masseter) reflex w/o atrophy or fasciculations

Question 6

If there are no LMN or UMN signs in a patient with weakness, recognize any s/s suggesting that myopathy or a NMJ d/o is the cause.

Answer 6

a. In d/o of muscles or NMJ, sensation is preserved always, reflexes preserved initially. Weakness typically affects the proximal limbs
c. In NMJ d/o’s like myasthenia gravis, see variable weakness and fatigue of the limbs, often accompanied by ptosis, diplopia, dysarthria, dysphagia, or dyspnea.

Question 7

Are longer or shorter nerves affected first in polyneuropathy?

Answer 7

Longer

- Usually first reflex lost is Achilles

Question 8

What pattern of numbness would you see if a nerve root was damanged?

Answer 8

Dermatomal

Question 9

An intramedullary (w/in sc) lesion would cause what pattern of numbness?

What was extramedullary lesions? (eg compression)

Answer 9

Intramedullary lesion: vested loss w/sacral sparing (syrinx)

Extramedullary lesion: initial sacral sensory loss up to a level

Question 10

How would sensation be altered in a lesion to the thalamus or sensory pw to parietal lobe?

Answer 10

Contralateral hemi-sensory body + face loss