L26 - muscle weakness Flashcards
UMN origin
primary motor cortex
LMN origin
ventral horn of spinal cord
how to examine weakness
look for positive signs such as muscle volume, strength, tone, reflexes and involuntary movements
(observation, sensory, tone, power, reflexes)
muscle tone of UMN causes of muscle weakness
increased
reflexes in UMN causes of muscle weakness
increased
plantars in UMN muscle weakness
increased
muscle tone of LMN causes of muscle weakness
decreased
reflexes in LMN causes of muscle weakness
decreased
plantars in LMN muscle weakness
decreased
causes of UMN muscle weakness
stroke
infection
tumour
degeneration
clinical findings in UMN muscle weakness
weakness
mild atrophy
brisk reflexes
upping plantars
clinical findings in LMN muscle weakness
weakness
mild atrophy
depressed or absent reflexes
down going plantars
common LMN pathologies in muscle weakness
muscle neuromuscular junction nerve root pathology anterior horn
natures of LMN muscle weakness
- axonal loss pathology
- demyelination pathology
myopathy clinical features
- Progressive weakness (rapid or slow), usually proximal
- Normal reflexes
- Normal tone
- Moderate wasting
causative agent of myopathy
genetic
inflammatory
metabolic
clinical features of myasthenia gravis
weakness fatigability worse as the day goes by normal sensation normal reflexes repetitive nerve stimulation
muscle disease
myopathy
example of neuromuscular junction disorder
myasthenia gravis
causative agent of myasthenia gravis
any problem affecting receptors on muscles
example of focal nerve pathology causing muscle weakness
carpal tunnel syndrome
features of carpal tunnel syndrome
Pins and needles
Numbness
Pain in sensory distribution of median nerve (digit 1,2,3)
Worse at night
Weakness in motor part of median nerve
Reduced pin prick sensation
Very severe weakness of muscles in median nerve region
polyneuropathy
multiple peripheral nerves become damaged
clinical features of polyneuropathy
Symptoms are more diffused like in upper and lower limb Pins and needles Numbness Burning sensation Tingling Weakness if motor nerves involved
causes of polyneuropathy
diabetes
example of root pathology causing muscle weakness
radiculopathy
radiculopathy
pinching of nerve at spinal level
clinical features of radiculopathy
Sensory and motor symptoms in distribution of specific nerve root
Back pain if lower spinal problem
Neck pain if upper spinal problem
why is dorsal root ganglion spared in most spine pathologies
it lies outside the spinal cord
how to differentiate between spinal nerve pathologies or root pathologies
normal sensory and electrodiagnostic tests for spine pathologies as dorsal root ganglion lies outside of the spinal cord
motor neuron disease
disease of motor neurones (upper or lower or both)
clinical features of motor neurone disease
Painless
Progressive Bulbar palsy –> weakness in the tongue and the face and the palate
Dysphasia, dysarthria, nasal regurgitation and aspiration
Progressive muscle weakness
causes of motor neuron disease
sporadic
5-15% genetic
two main electrodiagnostic tests
nerve conduction studies (NCS) needle electromyography (EMG)
nerve conduction study - 2 types
median nerve sensory study
median nerve motor study
median nerve sensory study
Electrodes on hand and arm - along median nerve
At wrist = recording electrodes
On thumb = stimulatory electrodes
Stimulate median nerve at thumb and response will be recorded at the median nerve at the wrist
median nerve motor study
Electrodes on small muscle in hand supplied by median nerve = abductor pollicis brevis
Stimulatory electrodes on median nerve
Electric stimulus to median nerve and response is recorded from abductor pollicis brevis on the screen
= compound muscle action potential seen on the screen
Electromyography (EMG)
A fine needle is inserted in a muscle
We record from motor units in the muscle
Activate the muscle (in this case to flex the bicep, bend the elbow)
Motor unit action potentials
By looking and listening to this activity, we can differentiate between different pathologies
EMG findings: Spontaneous activity
When we insert the needle – any activity which is recorded when muscle is relaxed and not stimulated
E.g., fibrillation potentials and positive sharp waves
Motor unit
number of muscle fibres supplied by a single motor neuron
EMG findings: recruitment / interference patterns - NORMAL
In a normal person, there should be a screen full of motor action potential when muscle is contraction - there should be no gaps
EMG findings: recruitment / interference patterns - nerve problems / denervation
if there are gaps / reduced interference pattern
EMG findings: recruitment / interference patterns - muscle problems
with less effort, the screen can be seen to be pull but MUAP is smaller
