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)
what can injure the brachial plexus (and be a cause of PNS injury causing LMN symptoms)
- clavicular fracture
- penetrating neck injuries
- stretch injuries
- neoplasm
- inflammatory
different stretch injuries that can cause brachial plexus injury
- childbirth or adult stretch causing Erb-Duchenne palsy (upper plexus) = head was stretched or Dejerine Klumpke palsy (lower plexus) = arm was stretched
- trauma
- operative
Erb-Duchenne palsy symptoms
proximal damage
- can’t move whole arm
- waiter tip position shoulders dropped, muscles in upper arm relaxed, in lower arm very contracted
Dejerine-Klumpke palsy symptoms
lower plexus damage
- claw hand
- can’t close hand
- distal muscles are weak
- loss of sensation
example of inflammatory conditions that can affect the brachial plexus
- idiopathic brachial neuritis (autoimmune post infection) or Parsonage-Tuner syndrome for the familial form
- Guillain-Barré (autoimmune)
idiopathic brachial neuritis symptoms
- acute very severe pain near clavicular region lasting a week
- as pain gets better, weakness of some muscles of arms and shoulders starts
radiculopathy is what
damage to nerve root (dorsal or ventral root)
-can be from herniating disk compressing it
how radiculopathy is differentiated from idiopathic brachial neuritis
- radiculopathy = the pain lasts for weeks (not just one week)
- radiculopathy = the weakness, the pain and the muscle atrophy are mild
why lumbo-sacral plexus called like that
bc have lumbar plexus more anterior (local nerves, femoral n, obturator n) and sacral plexus more posterior (local nerves, sciatic n.) and L4 and L5 roots axons join the sacral plexus
name of the end of the spinal cord + its level
conus medullaris. is at L1-L2 (where the spinal cord ends)
what’s the lumbo-sacral trunk
the axons from L4-L5 of lumbar plexus that go joint the sacral roots to form the sacral plexus
lumbo-sacral trunk location and how can get injured
travels across pelvic brim. moves straight down laterally
-can get injured if something pushes on it or on the bone of the pelvis
example of injuries of lumbosacral trunk
compression against posterior pelvis during childbirth (less common)
-causes L4-L5 injury, weakness of muscles below the knee, foot drop, difficulty walking
injury that is not to the lumbosacral trunk and that is not to be confused with a compression of the lumbosacral trunk against posterior pelvis during childbirth
- femoral nerve neuropathy (childbirth complication)
- happens bc compression in groin of woman during lithotomy position when someone helps delivery
- symptoms = weak quads and hyperexension (not weakness of muscles below the knee)
how can the lumbar plexus get injured
anything retroperitoneal
- hematoma** in anti-coagulated pts especially (in iliacus m. or psoas m. for example)
- cancer (direct or radiation)
- proximal diabetic neuropathy (painful, patchy, may have a vascular cause). is different from the common distal symmetrical polyneuropathy of diabetes
typical presentation for lumbar plexus injury caused by hematoma
leg weakness (+ the typical decreased bulk, fasciculation, hyporeflexia) + no clear pattern of injury (nerve or root) + know pt is anticoagulated
how can the sacral plexus get injured
nothing specific. some examples are:
- cancer (direct or radiation)
- proximal diabetic neuropathy (painful, patchy, may have a vascular cause). is different from the common distal symmetrical polyneuropathy of diabetes
* nerves outside territory of scatic n. may be injured (gluteal nerves, pudendal n.)
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)
important thing about plexus injury and distance of lesions
- can have both proximal and distal lesions
- can have distal lesions only and still be plexus
- proximal lesion (with distal or not) = think of plexus more
(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)
