Neuro 28: UMN & LMN

brain to spinal cord

UMNs transmit info from where to where?

spinal cord to skeletal muscle

LMNs transmit info from where to where?

ventral horn

where are LMNs located

skeletal muscle

what will UMN or LMN lesions generally affect?

corticobulbar tract

volitional movement of the skeletal muscles in oral cavity, larynx, and face; terminate in motor nuclei of cranial nerves

V, VII, XI, XII

what cranial nerves does the corticobulbar tract go to?

medullary pyramids

where does the lateral corticospinal tract cross over?

corticospinal

which tract?

corticobulbar

which tract?

spinal cord level

where does the anterior corticospinal tract cross over?

sign

objective evidence of disease

symptom

patient reporting subjective evidence of disease

1. facial (lower muscles of facial expression)

2. hypoglossal (genioglossus muscle)

LMNs of the brainstem receive bilateral innervation except?

left (towards the lesion)

lesion in right motor cortex or internal capsule affecting the hypoglossal nerve will cause the tongue to deviate ?

UMN

UMN or LMN lesion?

weakness (partial paralysis)

-presia

no movement

-plegia

no movement

paralysis

weakness/no movement (imprecise term)

palsy

both LEs

para-

paraparesis

weakness of both LEs

monoparesis

weakness of one limb

facial diplegia

symmetrical facial weakness

quadriplegia

paralysis of all 4 limbs

UMN

UMN vs. LMN lesion: increased reflexes

LMN

UMN vs. LMN lesion: atrophy

both

UMN vs. LMN lesion: muscle weakness

LMN

UMN vs. LMN lesion: fasciculations/fibrillation

UMN

UMN vs. LMN lesion: increased tone

both

UMN vs. LMN lesion: sensation intact

UMN

UMN vs. LMN lesion: + Babinski sign

loss of sensation in peripheral neuropathy but not LMN lesion

how to distinguish between peripheral neuropathy and LMN lesion?

1. stroke

2. infection

3. tumor

4. TBI

5. multiple sclerosis

6. cerebral palsy

7. huntington’s disease

causes of UMN lesion (7)

MCA

arterial supply to the internal capsule

cortex or internal capsule

location of UMN lesion: results in weakness in the contralateral LE, UE, face, or combination

below pons

location of UMN lesion: face spared of weakness

below C5

location of UMN lesion: UE spared of weakness

above pyramidal decussation (90%)

location of UMN lesion: contralateral weakness

below pyramidal decussation (90%)

location of UMN lesion: ipsilateral weakness

UMN

UMN vs. LMN lesion to VII: forehead spared

LMN

UMN vs. LMN lesion to VII: whole side of face involved

~posterior limb to genu of internal capsule

location of UMN lesion: right face and UE weakness/paralysis

below pons

location of UMN lesion: right UE and LE weakness/paralysis

• C - internal capsule

• no aphasia or speech dysfunction = not cortex (D)

• face involvement = above pons (A/B)

where is the lesion most likely?

note: patient has no aphasia or speech dysfunction

LMN

UMN vs. LMN lesion: hyporeflexia or areflexia

poliomyelitis

infection of anterior horn cells with variable anatomic pattern depending on how many spinal nerve root levels are affect and where

LMN

UMN vs. LMN lesion: flaccid paralysis

1. injury to ventral horn cells or axons leaving spinal cord

2. trauma to peripheral nerve

3. infections

4. botulism (botox)

5. poliomyelitis

6. cauda equina syndrome

causes of LMN lesion (6)

myelin in the CNS

what does multiple sclerosis affect?

amyotrophic lateral sclerosis (ALS)

“no muscle nourishment”

ALS

• progressive neurodegenerative disease that affects UMNs and LMNs

• onset 50-60 years

• men > women

• military veterans

• initially: painful muscle cramping and fasciculations, dysarthria, dysphagia, and respiratory difficulties

• exam: weakness, hypertonia, hyperreflexia, atrophy, fasciculations, head droop

none

what are the effects of ALS on mental status?

respiratory failure

most common COD for ALS

1. imaging (CT, MRI, dopplers, MRA)

2. blood work (enzymes)

3. muscle biopsy

4. EMG (insertional activity)

5. MNCV

methods of dx for UMN or LMN lesions

motor nerve conduction velocity (MNCV)

nerve stimulation with electrodes and action potentials measured to determine nerve function; helps diagnose LMN lesion or peripheral neuropathy