June4 M2-Brachial and LS Plexus Flashcards
(EXAM) most common causes of peripheral (upper limb, lower limb) neuromucscular problems
-damage to nerve roots (radiculopathy)
-damage to peripheral nerves (carpal tunnel syndrome, etc.)
(plexus lesions are much less common)
brachial plexus and lumbosacral plexus are in CNS or PNS
PNS
3 common problems from PNS damage
- weakness
- numbness
- pain
typical signs of lower motor neuron damage
- weakness
- decreased reflexes
- atrophy
- fasciculation
upper motor neuron def
- cell body in cerebral cortex.
- starting point for decision to move muscle
- long axon, synapses with LMN whose cell body is in the spinal cord
lower motor neuron (anterior horn cell) def
- cell body in spinal cord
- long axon, travels out of spinal cord in nerve root, plexus and peripheral nerve and eventually synapses on target muscle
weakness is in which of LMN vs UMN problem
in both** you’re gonna use other signs to distinguish if the weakness is from UMN vs LMN injury
UMN injury signs
- weakness
- normal muscle bulk
- increased reflexes
- increased muscle tone
- positive Babinski
- fasciculation absent (abnormal spontaneous contraction)
LMN injury signs
- weakness
- decreased muscle bulk
- decreased reflexes
- normal muscle tone
- negative Babinski
- fasciculation present
what does LMN injury indicate
a PNS injury, problem
(imp) how information travels to muscle and gets through spine (descending info)
- UMN descending axons
- synapse with anterior horn cell (LMN, called like that too bc cell body in anterior horn of spinal cord)
- ventral root
- plexus
- nerve
- NMJ
- muscle
(imp) how information (sensory) travels from muscle back to the brain
- peripheral nerves
- dorsal root including DRG (dorsal root ganglion)
- ascending axons
how information is transmitted during reflex arcs
- peripheral nerves (sensory neuron)
- dorsal root including DRG
- ventral root
- plexus
- nerve
- NMJ
- muscle
how to go about a LNM injury
- know that PNS problem and consider that problem can be anywhere in the pathway the LMN takes (anterior horn cell (LMN), ventral root, plexus, nerve, NMJ, muscle)
- which muscles have symptoms (weak, hyporeflexion, fasciculation, decreased bulk) and do they have a common level, what nerve would that be
signs that the PNS injury for LMN symptoms is in the plexus
- BOTH motor and sensory symptoms
- unilateral (doesn’t mean it can’t be bilateral)
- proximal involvement (can have distal too)
- complexity (can’t localize one nerve or one root)
- clinical context (hx, mechanism, right after birth)