Peripheral Neuropathy: Part I Flashcards
The parts of the nervous system outside of the brain and spinal cord
- cranial nerves (#12)
- spinal nerves and their roots and branches (#31) - 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal
- peripheral nerves
- neuromuscular junctions
what type of nerve carries sensory signals from the PNS toward the CNS
afferent
what nerves carry motor signals from the CNS to the target cell (PNS)
efferent
contains the nucleus of the neuron
cell body
nerve fibers that carry information away from the cell body
axon
carries information to the cell body
dendrite
a fatty layer of tissue that insulates the axon to allow for better neurotransmission
myelin sheath
a chemical synapse formed by the motor neuron and a muscle fiber
Neuromuscular junction
the arterial blood supply of the nerve fibers
Vasa Nervorum
pathophgys of PNS disorders
- Nerve cell body disorders - motor dysfunction or sensory dysfunction. Rarely both at the same time
- Axonal Disorders - metabolic in nature; distal-to-proximal sx. Small nerve fibers affected (sharp pain and burning sensations)
- Disorders of the myelin sheath = slower nerve conduction. Large nerve fibers affected (buzzing and tingling sensations)
- Vasa Nervorum - inflammation (vasculitis) or ischemic damage to arterioles that supply axon. MC affecting distal ⅔ of the limb
- Disorders of the neuromuscular junction = malfunction of chemical synapse
Only one nerve is affected
Injury or compression to specific nerve
Results in sensory/motor dysfunction distal to area of damage
Ex: Carpal Tunnel Syndrome
Mononeuropathy
- isolated damage to at least 2 separate and unrelated nerve areas
- Often seen in systemic diseases
- DM, vasculitis, rheumatoid arthritis, systemic lupus erythematosus
Multiple mononeuropathy/mononeuritis multiplex
- Multiple nerves affected
- Due to a multifocal disease process
- Results in a symmetric sensory, motor or mixed deficit
- Usually more pronounced distally
- Example: Diabetic peripheral neuropathy
Polyneuropathy
Damage or irritation to a nerve plexus
Usually due to trauma or radiotherapy
May mimic spinal cord injury or disease
Plexopathy
Plexopathy MC happens where?
brachial and lumbosacral
damage or irritation to one or more spinal nerve roots (as it exits the spine)
Will likely follow a dermatomal distribution
Example: herniated disc, VZV (shingles)
Radiculopathy
hx of peripheral neuropathy
- What systems are involved? - Motor, sensory, autonomic or combos
- What is the distribution of sx?
- Distal, proximal, ascending pattern
- Focal, multifocal
- Asymmetric vs symmetric - What is the nature of the sensory involvement?
- Temperature loss/burning/stabbing pain (small fiber)
- Vibratory or proprioceptive loss (large fiber) - What is the timeline?
- Acute (days-4 wks)
- Subacute (4-8 wks)
- Chronic (>8 wks) - Is there evidence of UMN involvement?
- Muscle weakness, spasms, spasticity
- PE: hyperreflexia, clonus, hypertonia, (+) Babinski - Is there evidence for a hereditary neuropathy?
- Are there any associated comorbidities?
- Cancer, DM, connective tissue disease, autoimmune disease, infection
- Meds that may cause toxic neuropathy
- Preceding events, drugs, toxins
PE in peripheral neuropathy
- Motor - atrophy, ROM, muscle strength, weakness proportionate to atrophy
- Sensory
- pinprick/light touch for small fibers
- vibration for large fibers
- proprioception - DTR
- Cranial nerves
what electrodiagnostic studies should be used in combination with each other in assessing a patient for peripheral nerve disease
Nerve Conduction Study and Electromyography
indications for electrodiagnostic studies
- motor deficits
- sensory deficits or changes
Measures how fast an electrical impulse moves through a nerve
- can assess both motor & sensory nerves
- determines the location and extent of neuropathy
Nerve Conduction Study (NCS)
describe procedure of Nerve Conduction Study (NCS)
- Two electrodes are placed on the skin over the nerve
- One electrode stimulates the nerve with a very mild electrical impulse
- The other electrode records the electrical impulse
- Performed on each individual nerve being tested
complications of nerve conduction study (NCS)
Complications rarely occur - electrical injury from stray leakage currents (most often seen in the ICU setting)
CI for nerve conduction study (NCS)
external pacemaker wires - risk of electrical injury to the heart
what is done if a pt with a ICD/internal pacemaker needs a nerve conduction study?
consult cardiology
NCS are generally safe to use within 6 inches of pacemakers or ICD’s
what factors affect NCS?
- age - nerve conduction velocities (NCV’s) are slower in infants and children
- sex - NCV slower in men than women
-
temperature - decreased NCV’s in colder temperatures
- arms and legs must be kept at specific temperatures to allow for more precise testing
NCS shows a reduced amplitude
what does this mean?
Axonal degeneration
NCS shows a slow internodal conduction and reduced conduction velocity
what does this mean
Demyelination
assess electrical activity in the skeletal muscle fibers which is then transmitted onto a graph
Electromyography (EMG)
describe procedure of Electromyography (EMG)
- one or more small needle electrodes are inserted into muscle
- measurements are taken of electrical activity of muscle during rest, slight contraction and forceful contraction
- stronger contraction of muscle produces larger AP
complications of Electromyography (EMG)
Significant complications are rare
- bleeding, bruising, infection, nerve injury, pneumothorax, other local traumas
- electrical injury due to stray leakage currents (ICU setting)
interefering factors of EMG
electrical artifacts are seen in pts w/ deep brain stimulators used for the tx of movement disorders
A set of neurologic symptoms resulting from compression of the median nerve
Carpal Tunnel Syndrome (CTS)
anatomy of carpal tunnel
- transverse carpal ligament (flexor retinaculum) ventral border
- carpal bones dorsal border
- median nerve and 9 flexor forearm tendons pass through
CTS is MC in who?
2-4x MC in women
pathophys of CTS
Increased pressure in the intracarpal canal
- direct compression damages nerve fiber
- impaired axonal transport
- compression of vessels leading to ischemia
causes of CTS
- synovitis of flexor tendons
- anatomically small canal
- mass lesion
- edema or inflammation resulting from systemic condition
RF for CTS
- Systemic conditions
- Obesity
- Pregnancy
- DM
- Rheumatoid Arthritis (RA)
- Osteoarthritis (OA) of the hand
- Hypothyroidism
- CTD - Other factors
- Genetic predisposition
- Aromatase inhibitors (anastrozole)
- Workplace
- Female gender
symptoms of CTS
- Standard sx - Occurring in median nerve distribution
- Dull, aching discomfort in the hand, forearm, or upper arm
- Paresthesia (tingling, burning, numbness) median nerve root distribution
- Weakness/clumsiness of hand - Aggravating factors
- Sleep
- Sustained hand or arm positions (driving)
- Repetitive movements of hand/wrist
3.Alleviating factors
- Changing hand posture (not as effective in late dz)
- Shaking/ringing of the hands
signs of CTS
-
Inspection
- SEADS: swelling, erythema, atrophy, deformity, and (surgical) scars.
- Atrophy of thenar eminence -late finding - Palpation: carpals including “snuff box,” distal radius/ulna, distal radioulnar joint
- ROM: flexion, extension, radial/ulnar deviation
-
Neurovascular: strength, dermatomal sensation in all regions, capillary refill/pulses
- (+) sensory changes along median nerve but not thenar eminence - late finding
- (+) weak thumb abduction and opposition - late finding - Tinel sign, Phalen/“Prayer” sign, Carpal compression test, The hand elevation test
Inspection, palpation, ROM, vascular assessment will likely be UNREMARKABLE