Diagnosing LMN disorders Flashcards
How will damage to LMN present?
- wasting
- decreased tone
- decreased reflexes
- extensor plantar response
How will damage to UMN present?
- no wasting
- increased tone
- increased reflexes (lose inhibition of reflexes)
- increased plantar response
(brisk reflexes and spasticity)
What are radiculopathies?
damage to nerve root
What are neuropathies?
damage to peripheral nerve
What are myopathies?
damage to muscle fibres
How do myopathies present?
- proximal weakness
- symmetrical weakness
- Can be painful
- reflexes spared until late
- limited muscle wasting until late in disease
How do NMJ disorders present?
- fatiguable muscle weakness (gets worse on repetition)
- involves extra ocular muscles (ophthalmoplegia, ptosis and diplopia)
- involves bulbar muscles (chewing and swallowing)
What are polyneuropathies?
diffuse damage of peripheral nerves (mononeuropathy is one nerve)
How do polyneuropathies present?
- length dependent (distal nerves affected first)
- symmetrical
- weakness (can also have sensory loss)
- reflexes absent
- distal wasting
How do MNDs present?
- Painless progressive weakness and wasting - Eye movements normal - Sensation normal - UMN and LMN signs - present with respiratory muscle weakness
What are the important questions to ask in LMN lesion?
1) pattern of weakness (proximal v distal)
2) speed of onset
3) pain?
4) sensory loss?
5) symptoms of respiratory
6) muscle weakness
What LMN disorders present with pain?
radiculopathy
some peripheral neuropathies
some muscle diseases
(no pain in MND or NMJ)
What disorders will present with sensory loss?
peripheral neuropathies
radiculopathies
not in muscle, NMJ or MND
What should examination include for LMN lesion?
- wasting (MND or peripheral nerve)
- fasiculations (possible MND or proximal nerve)
- look at trunk and back
- check feet (hammer toes or pes cavus possibly peripheral neuropathy)
proximal symmetrical weakness?
myopathy
Distal symmetrical?
polyneuropathy
affecting one nerves muscles?
mononeuropathy
affecting one spinal root muscles?
radiculopathy
absent/ reduced reflexes?
peripheral neuropathy
normal/reduced reflexes?
myopathy
increased reflexes with other LMN symptoms?
MND
distal symmetrical sensory loss?
peripheral neuropathy
sensory loss of one nerve area?
mononeuropathy
What are the possible investigations for LMN lesions?
CK blood test neurophysiology muscle biopsy MRI spine Muscle MRI (reveal pattern of muscle wasting) Genetic testing
What are the pathological causes of increased Creatine Kinase?
+ 10,000 = rhabdomyolysis, muscular dystrophy
+ 1000 = many myopathies cause
How can muscle biopsy help diagnose LMN lesions?
- myopathy vs neuropathy
- inflammation
- metabolic myopathies
- mitochondrial myopathies
- specific features of genetic myopathies
What is a common hereditary peripheral neuropathy?
Charcot Marie Tooth
