Lecture 10: Peripheral Neuropathy Part 1 Flashcards
What are the 3 general types of PNS disorders and their characteristics?
- Nerve cell body: motor or sensory. rarely both at the same time
- Axonal: metabolic, distal to proximal symptoms, small fibers usually, causing burning or sharp pain
- Myelin sheath: Large fibers, causing slowed conduction, buzzing, and tingling
If vasa nervorum is present, what part of the limb is affected?
Distal 2/3
What is the MC mononeuropathy?
Carpal Tunnel Syndrome (CTS)
What is multiple mononeuropathy/mononeuritis multiplex and common diseases for it?
- Damage to 2 separate and unrelated nerve areas
- Seen in systemic diseases like DM, vasculitis, RA, SLE
How does polyneuropathy present?
- Multiple nerves affected
- Multifocal disease process
- Symmetric deficits
- Seen more distally
Example: Diabetic peripheral neuropathy
What is a plexopathy and the 2 MC types?
- Damage or irritation to a nerve plexus
- Brachial and lumbosacral
What is a radiculopathy and common types?
- Damage or irritation to spinal nerve roots exiting the spine
- Dermatomal distribution
- Ex: herniated discs, VZV
What qualifies as acute, subacute, and chronic peripheral neuropathy?
- Acute: days to 4 weeks
- Subacute: 4-8 weeks
- Chronic: > 8 weeks
What S/S might suggest upper motor neuron involvement in peripheral neuropathy?
- Muscle weakness, spasms, spasticity
- Hyperreflexia, clonus, hypertonia, Babinski
What electrodiagnostic studies should be performed in initial evaluation of a peripheral neuropathy?
- Nerve conduction study
- Electromyography
Perform both
What exactly is a nerve conduction study? (NCS)
- Speed at which an electrical impulse moves through a nerve
- Determines both location and extent of neuropathy
What is the primary contraindication to NCS?
External pacemaker wires
For ICDs or internal pacemakers, consult cardio!
What slows nerve conduction speeds?
- Slower in infants and children
- Slower in men
- Slower in cold temperatures
In a nerve conduction study, what does decreased amplitude suggest? Decreased conduction velocity?
- Decreased amplitude = axonal degeneration
- Demyelination = slow internodal conduction and reduced conduction velocity
A for A
What does electromyography (EMG) measure?
- Electrical activity in the skeletal muscle fibers
- Insertion of needles into muscles
What is an interfering factor with EMG?
Deep brain stimulators will cause electrical artifacts
What nerve is compressed in CTS?
Median nerve
What are the components of the carpal tunnel?
- Transverse carpal ligament (Ventral)
- Carpal bones (Dorsal)
- Median nerves + 9 flexor forearm tendons pass through
Who is CTS MC in?
Women
What is the pathophysiology of CTS?
Increased pressure in the intracarpal canal
What are the RFs for CTS?
- Obesity
- Pregnancy
- DM
- RA
- OA of the hand
- Hypothyroidism
- CT Diseases
- Workplace factors
- Aromatase inhibitors
- Female
How does CTS typically present?
- Median nerve distribution
- Dull, aching
- Paresthesias
- Weakness/clumsiness of the hand
What aggravates CTS?
- Sleep
- Sustained hand or arm positions
- Repetitive movements
What are alleviating factors for CTS?
- Changing hand posture (only works early on)
- Shaking/ringing of hands
When is atrophy of the thenar eminence seen in CTS?
Late
What are the late neurovascular findings seen in CTS?
- Sensory changes only along median nerve
- Weak thumb abduction and opposition
What is the median nerve distribution?
What is SEADS?
- Swelling
- Erythema
- Atrophy
- Deformity
- Scars (surgical)
Inspection of the hand/wrist
What are the signs/tests associated with CTS?
- Tinel: (the tapping one)
- Phalen/Prayer: pain when prayer sign made
- Carpal compression: numbness/tingling when direct pressure applied
- Hand elevation test: Raising hands above head reproduces symptoms MOST SENSITIVE/SPECIFIC TEST
What is the most sensitive and specific CTS PE test?
Hand Elevation Test
What is the MC DDx for CTS?
Cervical radiculopathy
What are the first-line diagnostics for CTS?
NCS/EMG to confirm Dx and assess severity
What is considered mild CTS based on NCS/EMG? Mod/Sev?
- Mild: sensory conduction delay only
- Mod: sensory and motor
- Sev: Axon loss = amplitude decrease
When is US or MRI indicated for CTS?
Only if we suspect structural abnormalities
What are the nonsurgical options for helping CTS?
- Modifying activities
- Cock-up wrist splints
- Glucocorticoid/anesthetic injections
- OT/PT
What is the surgery for CTS?
Surgical decompression