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
tingling or shock-like pain on volar wrist percussion over the carpal tunnel
Tinel sign
pain or paresthesia in the distribution of the median nerve when the patient flexes/extends (respectively) both wrists to 90° for 30-60 seconds
Phalen/“Prayer” sign
induced numbness/tingling by direct pressure over the carpal tunnel for 30 sec
Carpal compression test
raising the hands above head for 1-2 minutes - if positive will reproduce the symptoms of CTS
The hand elevation test
highest sensitivity and specificity of all CTS PE testing
The hand elevation test
MC DDX of CTS
Cervical radiculopathy
work-up for CTS
-
NCS/EMG - 1st-line- confirms & assesses severity
- Mild: sensory conduction delay only
- Moderate: sensory and motor delays
- Severe: evidence of axon loss (low amplitude of AP) -
Imaging - US/MRI
- Indicated if suspected structural abnml of wrist: atypical electrodiagnostic testing, tumor or cyst, deformity, other bone/joint disease
tx options for CTS
-
nonsurgical options
- Modify activities and avoidance of precipitating activities
- Neutral position (cock-up) wrist splints, esp at PM, x 3 mo
- Glucocorticoid/anesthetic injection into carpal tunnel
- Carpal bone mobilization - OT/PT
- “natural” therapies - yoga, Vit B, US therapy - Surgical decompression by dividing the transverse carpal ligament
Plan of care for CTS will be case based. General recommendations are….
- Mild-moderate / pregnant
- conservative therapy (splint, steroid injection) for 4-12 wks
- consider surgery for non-pregnant patients who fail conservative therapy - Severe - conservative tx while awaiting surgical consultation
complications of CTS
if left untreated - loss of nerve function (sensory and/or motor), muscle wasting
what is tarsal tunnel syndome
A compression of the tibial nerve as it passes through tarsal tunnel underneath the flexor retinaculum at the level of the medial ankle and supplies plantar flexors, the sole of the foot and toes.
cause of tarsal tunnel syndrome and which is MC
- MC - fracture or dislocation
- Scar tissue, tumor, ganglion cyst
tarsal tunnel syndrome is MC in who?
uncommon
May be MC in athletes
presentation of tarsal tunnel syndrome
-
Paresthesias and diffusely localized pain involving sole of the foot, the distal foot, the toes, and occasionally the heel
- Worse at PM, walking, prolonged standing, dorsiflexion, eversion
- Tenderness and/or swelling over the tarsal tunnel
- Decreased sensation over the plantar surface
- +/- Tinel’s sign - tap over nerve, posterior to the medial malleolus
- (+/-) weakness
- Atrophy of intrinsic foot musculature (severe)
work-up for tarsal tunnel syndrome
- X-ray and/or MRI of foot will be normal
- Xray - if suspected bony fracture, deformity or misalignment
- MRI - if suspected soft tissue mass or tumor - NCS - may be helpful in confirming diagnosis¹
- often requires comparison with unaffected foot
- (+) will show prolonged tibial motor latencies and slowing of conduction velocities
tx for tarsal tunnel syndrome
- Trial of conservative therapy if no hx of trauma
- Conservative - NSAIDs, shoe modification, orthotics - Steroid injection if failure of conservative therapy
- Surgical decompression of the tibial nerve if severe or refractory to treatment
- Less effective than in CTS
complications of tarsal tunnel syndrome
permanent loss of nerve function, muscle wasting
when to refer for tarsal tunnel syndrome
no response to conservative tx; significant discomfort or impairment in ADLs; noted muscle weakness or atrophy
cause of ulnar nerve palsy
- Compression of the ulnar nerve at one of 2 locations
- Cubital Tunnel or Guyons’ Canal -
Cubital Tunnel
- trauma (distal humeral fracture, nerve lacerations, perioperative injury)
- blunt trauma “funny bone”
- compression/friction (osteophytes, arthritis, synovitis) -
Guyons’ Canal
- trauma (laceration, carpal fracture, repetitive blunt trauma/pressure)
- space occupying lesions (ganglion cysts, tumors)
2nd MC focal neuropathy
Ulnar Nerve Palsy
RF for Ulnar Nerve Palsy
occupation (leaning on elbows/prolonged elbow flexion), baseball, cycling, karate
symptoms of ulnary nerve palsy
- Sensory: paresthesias in 4th & 5th digits, aching elbow/wrist pain, worse at PM
- Triggers - sustained elbow flexion, sustained or repetitive grip, leaning on elbow/wrist, repeated pronation/supination - Motor: overall less common
- Mild weakness to severe wasting
- Loss of dexterity - Guyon’s canal - sx will vary based upon which branch of the ulnar nerve is affected
symptoms of ulnary nerve palsy
- Tenderness over Cubital/Guyons’ tunnel
-
Decreased sensation over ulnar distribution
- assess all 3 major ulnar sensory territories - Tinel’s sign at elbow or wrist
- Reproducible sx w/ extreme flexion of elbow and/or compression of Cubital/Guyons’ canal
- Weakness/atrophy of hypothenar eminence and interossei (see next slide)
- “Claw hand” deformity in digits 4-5 - worse in Guyons’ canal
-
Froment sign - thumb adductor weakness
- Flexion of thumb at interphalangeal joint when attempting to oppose the thumb against resistance
DDX of ulnar nerve palsy
- Proximal lesions - C8 or T1 roots, brachial plexus lesion, upper ulnar nerve lesions
- Other neuropathy - median or radial neuropathy, DM, vitamin deficiency
- MSK - epicondylitis, OA of wrist/hand, tenosynovitis
work-up for ulnar nerve palsy
- NCS - can help localize compression to elbow or wrist
- EMG for muscle weakness
-
MRI/US utilized if electrodiagnostics are non-confirming
- will show enlargement or thickening of the nerve
complications of ulnar nerve palsy
loss of nerve function with permanent altered or absent sensation, decreased or absent motor function, muscle wasting
management of ulnar nerve palsy
-
Conservative - mild-moderate sensory loss, weakness without wasting
- Elbow: avoid prolonged flexion (brace/wrap elbow at night to keep extended), avoid leaning on the elbows
- Wrist: padded gloves for protection with occupational or recreational activities, padded bike handles -
Surgical Intervention
- Elbow: decompression or transposition
- Wrist: decompression
surgical indications for ulnar nerve palsy
- compression due to trauma or structural abnormality
- moderate or severe sx >6 mo
- refractory to conservative tx
- progressive s/s
- muscle wasting
- impairment of ADLs
cause of radial nerve palsy
compression of the nerve at various sites
- Axilla - crutch use
-
Humerus (spiral groove) - MC
- fractures of the humerus, blunt injuries, compression by prolonged tourniquet use or sleep “Saturday night palsy”, misplaced injections - Proximal Forearm (radial tunnel) - radial fractures/dislocations
- Wrist - fracture/dislocations, blunt trauma
T/F: Radial Nerve Palsy is MC than median and ulnar nerve palsies
F - less common
RF of radial nerve palsy
- crutch use
- inebriation
- improper positioning (limited mobility pts)
- frequent tight-fitting straps or gloves on wrists
- trauma
presentation of radial nerve palsy
- Motor: weakness of wrist extensors (“wrist drop”), finger extensors, thumb abduction
- Sensory - decreased sensation along the radial distribution
work-up for radial nerve palsy
often clincial
- Confirm with NCS or EMG if atypical presentation
- Imaging if hx of trauma
management for radial nerve palsy
- Acute - conservative - improves in 6-8 wks
- cock-up wrist and finger splints, avoiding further compression, f/u with serial exams
- physical therapy to avoid flexion contracture
- pain management - Severe injury secondary to trauma - f/u exams and EMG
- Persistent sx: Surgical decompression, exploration or repair of nerve
complications of radial nerve palsy
loss of nerve function (sensory/motor), muscle wasting
refer radial nerve palsy when?
No improvement in 2–3 wks - NCS/EMG to confirm and determine severity
Lack of improvement warrants further imaging and/or surgery
Previously known as tic douloureux
A neuropathic condition resulting in unilateral pain of one or more branches of CN V
Trigeminal Neuralgia (TN)
Trigeminal Neuralgia (TN) is MC in who
- Affects W>M (slight predominance)
- Onset after 40 y/o in appx 90% of pts
- typical onset of 60-70 y/o
suspected RF of TN
HTN
Migraine disorders
classifications of TN and which is MC
-
Classic (MC): compression of TN root = circumscribed area of demyelination of the nerve
- Cause: abnormally positioned artery or vein
- unclear as to how demyelination leads to the sx of TN -
Secondary TN (less common)
- MS, tumor, cyst, aneurysm or AV malformation - Idiopathic TN
symptoms of TN
-
paroxysmal episodes (“attacks”) of intense, superficial, unilateral pain in the distribution of one or more branches of the CN V
- MC V2 and/or V3
- most intense at the onset of the “attack”
- electric, shock-like, or stabbing
- lasts seconds but is repetitive - facial muscle spasms - often w/ severe pain (hint the name tic douloureux)
- if V1 - increased lacrimation, conjunctival injection, and rhinorrhea of affected side
- chronic - dull aching pain, constant in between the paroxysmal episodes
- occasionally pain will occur bilaterally but rarely at the same time
-
Reproducible “triggers” via Hx and/or PE
- Light touch of “trigger zones” can reproduce symptoms
- chewing, talking, brushing teeth, smiling, grimacing , exposure to cold air
signs of TN
- Assessment (motor and sensory) of CN V - normal
- Masseter bulk and strength - normal
- Corneal reflexes - intact
Diagnostic criteria for classic TN
- 3 attacks of unilateral facial pain fulfilling criteria B & C
- Occurring in +1 divisions of trigeminal nerve, with no radiation beyond the trigeminal distribution
- Pain has at 3 out of 4 of the following characteristics:
- Recurring in paroxysmal attacks lasting from a fraction of a second to two minutes
- Severe intensity
- Electric shock-like, shooting, stabbing, or sharp in quality
- At least 3 attacks precipitated by innocuous stimuli to the affected side of the face (some attacks may be, or appear to be, spontaneous) - No neurologic deficit
- Not better accounted for by another ICHD-3 diagnosis
Features indicative of secondary causes of TN instead of classical TN
- shingles lesions or hx of shingles affecting the trigeminal nerve
- trauma near or to the trigeminal nerve in the preceding 3-6 months
- age < 40 y/o
- bilateral sx
- hx of multiple sclerosis
- sensation loss in one or more of the trigeminal nerve branches
work-up for TN
MRI with/without contrast (alt: CT)
- Used to differentiate classic vs secondary
- Indication recommendations vary
- Some say all TN d/t unknown etiology should have MRI
- Some say only if r/o secondary causes
possible DDX of TN and their signs
- Herpes zoster - PE - rash
- Postherpetic neuralgia - Hx of HZ rash
- Trauma to TN - Hx of trauma
- Demyelination from MS - Hx of MS or demyelination seen on MRI
- Non-vascular space-occupying lesion compressing trigeminal nerve - MRI
- Dental pathology/disease - Hx - pain is dull and constant
- Cluster HA/migraine - V1 distribution hx - pain sx last longer > TN
management for TN
-
carbamazepine - anticonvulsant
- Start 100 mg BID, titrate gradually by 200 mg daily to effective dose (max 1200 mg daily)
- Tapering the dose is recommended once pain control is achieved - Alt: oxcarbazepine - also 1st line agent (HLA-B 15:02 allele)
- Additional “add-ons” for breakthrough sx
- lamotrigine (Lamictal)
- gabapentin (Neurontin)
- topiramate (Topamax)
- tizanidine (Zanaflex)
- baclofen
Who to assess the HLA-B 15:02 allele for carbamazepine when managing TN? why?
Pts of Asian ancestry
avoid carbamazepine - at risk for Steven-Johnsons Syndrome or Toxic Epidermal Necrolysis
course of classic TN
- Episodes last weeks-months, followed by pain-free intervals
- Remission often occurs within first 12 months with future recurrence likely
management for refractory TN
refer to neurology for consideration of botox (weak data to support effectiveness) or refer for surgical evaluation
A lower-motor-neuron facial nerve (CN VII) paralysis
Bell’s Palsy
causes of Bell’s Palsy
unknown
possible viral (HSV, VZV), inflammatory, autoimmune, and ischemic etiologies
pathophys of bell’s palsy
unknown
theory - edema and ischemia results in compression of the facial nerve within this bony canal
bell’s palsy is MC in who/when?
- occurs mostly in colder months
- peak occurrence between 20-40 y/o
- increased risk in pregnancy and DM
presentation of bell’s palsy
- Acute onset facial weakness → paralysis over a 48-hr period
- poor eyelid closure - Associated with:
- post auricular pain, otalgia
- hyperacusis
- decreased tearing
- reduced sense of taste on affected side
- tingling, numbness of the cheek/mouth
- facial spasm (rare)
DDX of bell’s palsy and how to tell the difference
- CVA, GBS, basilar meningitis, tumor - more than CN VII involvement, other motor or sensory sx are present
- CN VII neoplasm - slowly progressive paralysis, facial spasm, severe pain, recurrent palsy, and other CN involvement
- Lyme Disease - NE US or travel during warm seasons
- Ramsay Hunt syndrome (HZ oticus) - paralysis associated w/ severe pain and hearing loss, w/wo vesicular rash
- CNS lesion proximal to facial nerve (supranuclear lesion) - weakness of lower face only
work-up for bell’s palsy
- Dx: clinical, acute work up not indicated
- Labs/imaging may be needed to rule out Ddx
- Electrodiagnostic testing only if complete facial paralysis
- NCS - comparison of both sides - a difference >90% = poorer prognosis
- Electroneurography - uses EMG to measure degeneration of nerve - Degeneration > 90% occuring within first 3 wks = more guarded prognosis - only 50% will recover full facial movement
management for bell’s palsy
- Pharm - if sx onset within < 5 d
- Prednisone (60 to 80 mg/day) x 5 days followed by a 5 day taper
- +/- valacyclovir 1000 mg TID x 1 wk - Eye care
- Risk of corneal drying, abrasion and visual loss
- Indicated for inadequate eye closure
- Lubrication drops/ointment - “artificial tears”
- Eye patch at PM
indications to add valacyclovir for bell’s palsy
- vesicular lesions are observed in the palate or external auditory canal
- no movement of the forehead
- incomplete eye closure
monitoring for bell’s palsy
- Follow until complete resolution
-
Imaging if sx > 8 wks or progression after 3 wks
- Image: brain, temporal bone, and parotid gland - should cover full course of facial nerve
- MRI w/ gadolinium - better for soft tissue structures
- CT w/ contrast - better for bony detail
consult/referral when for bell’s palsy?
- Neurology/ENT
- if initial presentation isn’t classic Bell’s Palsy
- if sx last > 8 wks or progress as previously noted - Ophthalmology
- persistent dry eye or painful eye
