UMN Lesions Signs

Question 1

UMN syndrome: structures involved

Answer 1

• UMN’ s in cerebral cortex
• descending brainstem tracts
• CST of spinal cord

CST= corticospinal tract

Question 2

UMN syndrome: distribution of abnormalities

how are structures typically affected

Answer 2

• Muscles that are supplied by motor nuclei below the level of the lesion are affected in groups
• Contralateral limb muscles are affected when lesions are above decussation
• ispilateral muscles are affected when the lesion is below the decussation

Question 3

LMN syndrome: Structures involved

Answer 3

• Spinal cord or brainstem alpha motor neurons (LMN)
• PNS: motor neurons in all spinal nerves and cranial nerves (axons of LMNs)

Question 4

LMN syndrome: distribution of abnormalities

Answer 4

• effects are always segmental and limited to muscles innervated by damaged Alpha motor neurons or their axons
• individual muscles or groups of muscles are affected

Question 5

UMN

Location of lesions

Answer 5

• brain
• brainstem
• corticospinal tracts
• spinal cord

Question 6

UMN: diagnosis/pathogies

Answer 6

• CVA
• TBI
• SCI
• MS
• CP

Question 7

UMN lesions: tone and reflexes

Answer 7

• hypertonia/velocity dependent
• hyperreflexia,
• clonus,
• exaggerated cutaneous reflexes
• (+) babinski

Question 8

UMN syndrome

Involuntary movements

Answer 8

Muscle spasms
flexor or extensor

Question 9

UMN lesions

Strength/muscle bulk

Answer 9

Strength:

• weakness or paralysis
• unilateral or bilateral distribution; never focal

Muscle bulk:

• disuse atrophy
• variable
• widespread distribution

Question 10

UMN syndrome

Voluntary movements

Answer 10

• impaired or absent
• obligatory mass synergies

Question 11

LMN Lesion

Location of lesion

Answer 11

• CN nuclei/nerves
• Ventral horn cells
• spinal roots
• peripheral nerves

Question 12

LMN Lesion

Diagnosis/pathologies

Answer 12

• polio
• Guillian barre
• peripheral nerve injury
• peripheral neuropathy
• radiculopathy

Question 13

LMN Lesion

Tone&reflexes

Answer 13

• hypotonia, flaccidity
• not velocity dependent
• hyporeflexia or absent

Question 14

Paresis vs paralysis

Answer 14

• Paresis: Occurs in UMN tract lesions as consequence of inadequate facilitation of LMNs
• Paralysis: Occurs in muscles innervated by LMNs below the level of a complete spinal cord lesion

Question 15

What is an abnormal synergy

Answer 15

• abnormal coupling of movements at adjacent joints due to stereotyped coactivation of muscles
• ex; shoulder abduction and ER combined with elbow flexion when patient is attempting to reach forward
• Mechanism: loss of cortical inhibition of reticulospinal tracts
• Loss of cortical inhibition of reticulospinal tracts (disruption of selective movements)

Question 16

abnormal synergies example

Answer 16

• UE flexion synergy: shoulder ABD + ER, elbow flexion, forearm supination, wrist and finger flexion.
• LE flexion synergy: hip ER + ABD + flexion, knee flexion, ankle DF and INV, DF of toes.
• LE extension synergy: hip IR + ADD + extension, knee extension, ankle PF and INV, PF of toes

Question 17

Normal phasic stretch reflex

Answer 17

• quick stretch of a muscle, elicited by striking the muscle’s tendon, stimulates type 1a affernets from the muscle spindle
• activity of type 1a afferents causes monsynaptic excitation of alpha motor neurons to the stretched muscle resulting in an abrupt contraction of the muscle fibers
• UMN influence spinal reflexes by adjusting background level of neural activity in SC

Question 18

Normal babinski’s sign

Answer 18

• stroking from heel to ball of foot along lateral sole
• then across the ball of the foot normally causes the toes to flex
• seeing nothing is okay

Question 19

Developmental or pathological babinski

Answer 19

• in people with CST lesions or in children <2 the great toe extends
• although the other toes may fan out their movement is not required for babinski

Question 20

Abnormal Clonus

Answer 20

• Involuntary repeating rhythmic contractions of a single muscle group
• can be elicited by muscle stretch, cutaneous and noxious stimuli
• most common at the ankle
• sustained clonus repeating more than 5 times is always pathological

*tremor is not the same = alternaing agonist/anatgonist contractions

Question 21

muscle tone

Answer 21

• Resistance to stretch in resting muscle
• muscle tone is categorized on a continuum

Question 22

Muscle Tone

Resistance ranges from

Answer 22

flaccid: lack of resistance
hypotonia: abnormally low
normal:
spasticity: velocity-dependent hypertonia; abnormally high resistance that increases with faster movements
rigidiy: velocity-independent hypertonia

some basal ganglion disorders cause rigidity typically in more severe cases

Question 24

Spasticity

Answer 24

• velocity dependent hypertonia
• in spasticity the amount of resistance to passive movement depends on the velocity of movement
• both cahnges in muscle tissue and neuromuscular overactivity contribute to velocity-dependent hypertonia
• two mechanisms produce neural overactivity: hyperreflexia, reticulospinal tract overactivity