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
For mild-mod CTS or pregnant, what is the treatment recommendation? Sev?
- Mild-Mod: Conservative therapy or surgery for non-pregnant once conservative failed.
- Sev: Conservative while awaiting surgery
What is tarsal tunnel syndrome?
Compression of tibial nerve through the tarsal tunnel underneath the flexor retinaculum at the level of the medial ankle, affecting the plantar flexors
What is the MCC of tarsal tunnel syndrome?
Fx or dislocation
MC in athletes
How does tarsal tunnel syndrome present?
- Paresthesias + diffuse localized pain of the sole, distal foot, toes, and heel
- Tenderness over the tunnel
- Decreased sensation over the plantar surface
- Possible Tinel’s sign
- Weakness
- Severe: Atrophy of the abductor hallucis
What worsens tarsal tunnel syndrome?
- Nighttime
- Walking
- Prolonged standing
- Dorsiflexion
- Eversion
If NCS is positive for tarsal tunnel syndrome, what woudl be seen?
Prolonged tibial motor latencies and slowing of conduction velocity
When are XRAY and MRI used for tarsal tunnel syndrome?
- XRAY only if fx suspected
- MRI only if soft tissue mass or tumor suspected
How do we treat tarsal tunnel syndrome?
- Conservative with NSAIDs, shoe mods, and orthotics
- Steroid injection after failure of conservative
- Surgical decomp not as effective as with CTS
When is referral indicated for tarsal tunnel syndrome?
- No response to conservative tx
- Significant discomfort/impairment in ADLs
- Noted muscle weakness or atrophy
What are the two possible locations for ulnar nerve palsy?
- Cubital Tunnel (Elbow)
- Guyons’ canal (Wrist)
What can damage the cubital tunnel?
- Trauma
- Funny bone trauma
- Compression/fricture
What two bones surround Guyons’ canal?
- Hamate
- Pisiform
What can cause ulnar nerve palsy via Guyons’ canal?
- Trauma
- Spacy occupying lesions
Wat is the 2nd MC focal neuropathy?
Ulnar nerve palsy
What are the RFs for ulnar nerve palsy?
- Occupations where you lean on your elbows
- Baseball
- Cycling
- Karate
How does ulnar nerve palsy present?
- Paresthesias in the 4th and 5th digit
- Less commonly motor changes
What triggers ulnar nerve palsy?
- Sustained elbow flexion
- Sustained/repetitive grip
- Leaning on elbow/wrist
- Repeated pronation/supination
What are the 3 possible branches of Guyons’ canal that can produce symptoms in ulnar nerve palsy?
- Superficial terminal branch
- Palmar cutaneous branch
- Dorsal cutaneous branch
How does a PE present for Ulnar nerve palsy?
- Tenderness over Cubital/Guyons’
- Decreased ulnar sensations everywhere
- Tinel’s at elbow or wrist
- Reproducible symptoms by extreme flexion
- Weakness/atrophy of the hypothenar eminence
- Claw hand, worse in Guyons’
- Froment sign: Thumb adduction weakness against resistance
When are MRI and US used for ulnar nerve palsy evaluation?
Only if electrodiagnostics are non-confirming
What is the conservative management for Ulnar nerve palsy without wasting?
- Avoid prolonged flexion of elbow
- Padding wrists
What are the surgical interventions for ulnar nerve palsies?
- Elbow: Decomp or transposition
- Wrist: Decomp
When is surgery indicated for ulnar nerve palsy?
- Compression due to trauma or structural abnormality
- Mod-Sev symptoms > 6 mo
- Refractory
- Progression
- Muscle wasting
- ADL impairment
What phenomenon is characteristic of radial nerve palsy?
Wrist drop
Inability to extend the wrist, so it drops down.
What are the possible locations that can compress the radial nerve?
- Axilla: Crutches
- Humerus spiral groove: fx, injury, compression due to tourniquets or sleep
- Proximal forearm (radial tunnel): radial fx
- Wrist: fx
What are the RFs for radial nerve palsy?
- Crutch use
- Inebriation
- Improper positioning
- Frequently tight fitting straps or gloves
- Trauma
Where is sensation decreased with radial nerve palsy?
How is radial nerve palsy typically diagnosed?
Clinically with just H&P.
Only need electrodiagnostics if atypical.
What is the conservative tx for radial nerve palsy?
- Wrist splint
- PT
- Pain management
What would prompt us to do surgery or follow-up EMG for radial nerve palsy?
- Surgery: If symptoms persist more than 6-8 weeks
- Trauma: follow up with EMG
When is referral warranted in radial nerve palsy?
- No improvement after 2-3 weeks
- Need for EMG/NCS to confirm and determine severity.
Normally, radial nerve palsy improves in 6-8 weeks.
What are the 3 branches of the trigeminal nerve? (CN V)
- Ophthalmic
- Maxillary
- Mandibular
What is the typical demographic/Hx of trigeminal neuralgia (TN)?
- Women
- 40+ years with typical onset of 60-70
- HTN
- Migraines
What is the underlying physiology behind classic TN?
- Compression of nerve root, causing demyelination around the area.
- MCC: Abnormally positioned artery/vein
What typically precipitates secondary TN?
- MS
- Tumors
- Cysts
- Aneurysms
- AV malformations
How does TN present?
- Paroxysms of intense, superificial UNIlateral pain along a branch.
- electric, shock-like, stabbing
- pain lasting seconds
- Facial spasms used to be called tic doloureux
How does V1 TN specifically present?
- Increased lacrimation
- Conjunctival injection
- Rhinorrhea
What are the typical branches affected in TN?
V2 and V3
How does chronic TN present?
- Dull aching pain between episodes
- Reproducible by light touch of trigger zones
How does PE typically present for TN?
Normal
What is the diagnostic criteria for classic TN?
- 3+ attacks of unilateral facial pain fulfilling criteria 2 and 3
- Occurs in 1+ divisions of trigeminal nerve without radiating beyond
- 3 out of 4 of: Recurring in paroxysms, severe intensity, electric shock-like/stabbing, or 3+ attacks precipitated by innocuous stimuli
- No neurologic deficit
- Not better accounted for by another ICHD-3 diagnosis.
What are the 4 possible characteristics for TN pain?
- Recurring in paroxysms for seconds to 2 mins
- Severe intesnity
- Electric, shock-like, stabbing
- 3+ attacks precipitated by innocuous stimuli
3 must be met to qualify.
What features would suggest secondary TN over classic?
- Shingles or hx of shingles
- Trauma near nerve in the past 3-6mo
- Younger than 40
- Bilateral
- Hx of MS
- Sensation loss in a branch
What imaging is used to differentiate between secondary and classical TN?
MRI brain w/ and w/o con
What is the primary drug to treat TN?
Carbamazepine
What is the MOA and risk of carbamazepine?
- MOA: Reducing neuron excitability
- Risk: Assess for HLA-B*15:02 allele in asians. Predisposes to SJS or TEN.
When do you taper carbamazepine dosing?
Once pain control is achieved.
What two drug classes can be added on for breakthrough symptoms in TN?
- Neuroleptics: lamotrigine, gabapentin, topiramate
- Muscle relaxants: Tizanidine, baclofen
How do you treat refractory TN?
- Botox
- Surgery
What is Bell’s palsy also known as?
CN VII palsy/Facial nerve palsy
Who is Bell’s Palsy MC in?
- Colder months
- 20-40y/o who are pregnant or diabetic
How does Bell’s palsy present?
- Acute onset facial weakness in 48hrs.
- Poor eyelid closure
- Hyperacusis
- Decreased tearing
- Tingling of cheek/mouth
- Reduced sense of taste
How do you workup Bell’s Palsy?
- Clinical Dx
- Labs/imaging only for r/o of DDx
- NCS difference of 90% or more = poor prognosis
- EMG degen of 90% within 3 weeks = poor prognosis
How do you manage Bell’s Palsy?
- Prednisone for 10 days (5 days + 5 day taper)
- Add-on valacyclovir for: lesions, no forehead mvmt, or incomplete eye closure.
- Lubrication drops and eye patch at night if eye can’t close
Only indicated if within 5 days of symptom onset
When is imaging warranted in Bell’s Palsy?
- Symptoms > 8 weeks
- Progression of symptoms after 3 weeks
You should monitor until it fully resolves
MRI of brain and face
CT w/ con or MRI w/ gadolinium
