Motor Function Flashcards
Which has more prominent muscle wasting, myopathies or neurogenic wasting (conditions where muscles have been denervated)
Neurogenic wasting
Where do most fibres in the pyramidal tract decussate
Medulla - most fibres decussate here to form the lateral corticospinal tracts in the spinal cord
What do fasciculations indicate
LMN lesion - generally proximal and severe, especially at anterior horn cell level
A patient has wasting of the small muscles of the hand with wasting of the thenar eminence.
Where is the lesion
Proximal lesion - anterior horn cell, root (C8/T1), or plexus
A patient has wasting of the small muscles of the hand but the thenar eminence is spared.
Where is the lesion
Peripheral nerve lesion - ulnar neuropathy
A patient has wasting of the thenar eminence only.
Where is the lesion
Peripheral nerve lesion - median neuropathy
What is the stretch reflex
Passive stretch of a muscle –> afferent impulses to spinal cord –> activates the motor neurone –> reflex contraction
This response causes normal muscle tone. Interruption of this reflex arc (eg. LMN damage) causes flaccidity
What is the characteristic quality of hypertonia caused by UMN damage
Clasp knife rigidity
What is the supinator catch
A miniature version of the clasp-knife effect - elicited by supinating and pronating the forearm. May be the only feature of a subtle UMN lesion
What is pronator drift
The affected limb will pronate and drift downwards when arms outstretched, palms facing upwards and the eyes are shut.
A sign of mild upper limb UMN damage
On a patient being told to raise their leg, no movement is made and no contraction is seen.
What is the grade of power using the Medical Research Council Scale
0 - no contraction
A patient is able to raise their leg against resistance however they are easily overpowered.
What is the grade of power using the Medical Research Council Scale
4 - active movement against gravity and resistance
A patient is able to raise their leg off the bed when asked however they cannot hold it their against resistance
What is the grade of power using the Medical Research Council Scale
3 - active movement against gravity
Where is muscle weakness in a patient with motor polyneuropathy
Distal muscles
What is meant by a “pyramidal distribution” of muscle weakness
Greater weakness of extensors than flexors in the upper limbs, and greater weakness of flexors than extensors in the lower limbs.
Caused by UMN weakness
A patient has left sided ataxia (loss of coordination).
Where is the most likely location of the lesion
Left-sided cerebellar lesion
What causes past-pointing
Dysmetria - Inability to judge distances
How do the reinforcement manoeuvres work to elicit a reflex
They increase the sensitivity of stretch receptors throughout the body
How do UMN lesions cause brisk reflexes
As a result of loss of supraspinal inhibition.
The same reason that UMN lesions cause increased tone
What causes clonus
UMN lesions causing loss of supraspinal inhibition
What is a pendular reflex associated with
Cerebellar disease - causing the reflex to swing back and forth
What is a slow relaxing reflex associated with
Hypothyroidism
In trying to elicit the Babinksi reflex, the patients big toe dorsiflexes and the other toes fan out.
What is this and what causes it
A positive Babinski reflex caused by a UMN lesion
What gait is caused by spastic paraparesis
Scissoring gait - UMN lesion affecting both legs
What condition may cause a scissoring gait
Spastic cerebral palsy
What gait is caused by spastic hemiparesis
Circumduction gait - UMN lesion affecting one side of the body
What condition may cause a circumduction gait
Stroke
What gait is caused by bilateral foot drop
Steppage gait - LMN lesion affecting both legs
What condition may cause steppage gait
Guillain-Barre syndrome
Herniated lumbar disk
MS
What gait is caused by a cerebellar lesion
Broad-based, staggering gait - unable to walk heel-toe
What are the features of Parkinsonian gait
Stooping posture
Rigid shuffling gait
No arm swing
What conditions may cause a patient to have to support their head with their hand under their chin
Due to weakness of neck extension - relatively uncommon
Myasthenia gravis
Polymyositis
Motor neurone disease
What causes truncal ataxia (if severe may mean the patient is unable to sit unsupported)
Damage to the cerebellar midline (vermis)
