Lesions Of The Motor System Flashcards
What are the upper motor neurone signs?
Hyperreflexia - loss of descending inhibition of reflexes
Hypertonia - reflex circuit no longer inhibited due to loss of descending inhibition to LMNs. Agonistic and antagonistic muscles equally affected
Spastic paralysis
Babinski sign
Myoclonus - spasmodic involuntary contractions of muscles
Choreas- additional spasmodic muscle movements
Bradykinesia, pill rolling, torticollis, shuffling gait, pronator drift
What is a normal and abnormal response to the test for Babinski sign?
Normal: flexion of toes
Abnormal: abduction of toes and excessive dorsiflexion of the big toe (positive Babinski sign)
What specifically can be damaged to produce a lower motor neurone sign?
Cell bodies of α-motorneurones
Axons of α-motorneurones
The NMJ
The muscle itself
Lower motor signs?
Flaccid paralysis
Muscle atrophy
Areflexia and atonia
Fasciculations
What causes fasciculations?
Muscle is dennervated
The nAChR become hyper-receptive to any neurotransmitter substance
Therefore any molecule vaguely resembling ACh can cause excitation of the receptor at the NMJ, causing slight muscle contractions
When can a lower motor neurone lesion not be repaired?
If the cell body is damaged
Can get wallerian degeneration of the axon
What happens to the bladder of there is a lower motor neurone lesion?
Damage to above the S2-4 level
Consequent loss of parasympathetic and afferent neurones
Get overflow incontinence and no ability to micturate
What happens to the bladder if there is an upper motor neurone lesion?
Damage to T12 and above
Result in automatic reflex bladder
Loss of descending inhibitory control resulting in loss of bladder control and involuntary leakage of urine
Produces urge urinary incontinence
Where is the most common site for damage of an upper motor neurone?
Internal capsule
Cerebral cortex
