Peripheral NS Disorders Flashcards
Wallerian degeneration
disintegration of myelin or axons distal to site of injury
neuronal/axonal degeneration
distal dying of axons and loss of myelin after damage to cell body of neurons
demyelination
loss of myelin sheath
symptoms assoc. with small nerve fibers
neuropathic pain
disturbance of temp. sensation
autonomic dysfunction
symptoms assoc with large nerve fibers
loss of vibration/joint sense
weakness
fasciculations
loss of DTRs
symmetric proximal and distal weakness with sensory loss
GBS, CIDP
symmetric distal weakness with sensory loss
drug-induced, toxic and metabolic, hereditary, amyloidosis
asymmetric distal weakness with sensory loss; multiple nerves
vasculitis, HNPP, infections (leprosy, sarcoid, Lyme, HIV)
single nerve signs
compressive mononeuropathy or radiculopathy
asymmetric distal weakness WITHOUT sensory loss
motor neuron disease
multifocal motor neuropathy
asymmetric proximal and distal weakness with sensory loss
polyradiculopathy or plexopathy meningeal carcinomatosis lymphomatosis HNPP hereditary neuropathy
symmetric sensory loss w/o weakness
cryptogenic sensory neuropathy
metabolic, drug-induced, toxic
leprosy
asymmetric proprioceptive sensory loss w/o weakness
sensory neuronopathies
consider paraneoplastic, Sjogrens, vitamin B6 tox, HIV, cisplatinum toxicity
autonomic symptoms
DM, amyloidosis, GBS, vincristine, porphyria, HIV, idiopathic pandysautonomia
first line tests for PNS disorders
CBC ESR/CRP glucose, HbA1C or 2 hr OGTT rheumatoid - ANA, anti-ENA, RF renal and LFTs vit B12 and MMA levels TFTs serum and urine protein electrophoresis
RF for peripheral neuropathy
diabetes mellitus
alcoholism
non-alcoholic liver dz
malignancy
VITAMINS mnemonic
Vitamin deficiency/vasculitis Infections - leprosy, TB Toxic - amiodarone, lead, vincristine, chemotherapy A - amyloid Metabolic - alcohol, DM, porphyria, hypothyroidism, liver/renal Idiopathic/Inherited Neoplasms Systemic - SLE, Sjogrens, RA, MM
polyneuropathy
involvement of multiple peripheral nerves, usually legs»_space; arms and distal»_space; proximal
mononeuropathy
involvement of single nerve
mononeuropathy multiplex
involvement of several individual nerves in a multifocal distribution
MC infections assoc with GBS
campylobacter jejuni
CMV
EBV
target of autoimmune response in GBS
gangliosides
- anti GM1, anti-GD1a, anti-GQ1b, anti-GD1b
typical presentation of GBS
rapidly evolving, ascending areflexic motor paralysis w/ or w/o sensory disturbances; initial symptoms consist of tingling/pins and needles sensations in feet
symptoms of GBS
neuropathic pain
areflexic paralysis
bulbar and resp. mm weakness
autonomic dysfunction
Miller-Fisher variant of GBS
gait ataxia, areflexia, external ophthalmoplegia usually w/o limb ; nerve conduction studies are normal, anti-GQ1b ab’s
electrodiagnostic findings in GBS
prolonged distal latencies
prolonged or absent F waves
conduction block
decreased motor unit recruitment
how do you measure respiratory function in GBS pt
measure FVC and negative inspiratory pressure
- if FVC < 15 ml/kg, ICU and intubate
Tx of GBS
plasmaphoresis or IVIG
CF of CIDP
slowly evolving weakness in legs with widespread areflexia and loss of vibratory sense (large fiber); weakness of neck flexors and painful paresthesias may be present
about 10% of pts with CIDP have associated illness…
HIV
monoclonal gammopathy
Hodgkins lymphoma
tx of CIDP
periodic IVIG therapy
steroids - 90% improve but 50% relapse
azathioprine
pure motor multiple mononeuropathy with predominance in males that can occur at any age
multifocal motor neuropathy
CF in multifocal motor neuropathy
slowly progressive, asymmetric, distal limb weakness that begins in the arms (in distribution of individual nerves)
dx of multifocal motor neuropathy
conduction block in motor nerves in areas not prone to compression
- high IgM anti-GM1
Tx of multifocal motor neuropathy
IVIG
rituximab
immunosuppressants - cyclophosphamide
symmetric sensorimotor neuropathy that affects legs»_space; arms, causing prominent large-fiber sensory loss and sensory ataxia as well as weakness
neuropathy due to MM or MGUS
Dx of neuropathy due to MM or MGUS
significant demyelination and axonal loss
anti-MAG neuropathy responds to
rituximab
chronic progressive distal symmetric diabetic polyneuropathy
mixed sensory-autonomic-motor polyneuropathy (can be small fiber, large fibers and autonomic)
diabetic proximal motor neuropathy (Diabetic amyotrophy)
severe thigh and back pain, followed w/in weeks by mild to severe hip/thigh mm weakness with mm atrophy
who is more susceptible to compression neuropathies?
diabetics
CF in diabetic polyneuropathy
neuropathic pain/dysesthesias
distal, symmetric, slowly progressive sensory loss in legs before arms
autonomic insufficiency
weakness
symptomatic tx of neuropathic pain
TCAs
duloxetine
anticonvulsants - gabapentin, pregabalin, lamotrigine
uremic neuropathy
symmetric, distally predominant sensorimotor axonal polyneuropathy; foot drop and leg weakness are major manifestations
what other neuropathy can mimic GBS with rapidly evolving weakness or paralysis, and areflexia and abdominal pain
porphyric neuropathy
critical illness neuropathy
in 50% of pts with severe medical illness in ICU > 2 weeks; first manifestation could be difficulty weaning from ventilator
CF in Charcot-Marie tooth disease
presents in adolescence with symmetric, slowly progressive, distal muscular atrophy of legs and feet; pts also have hammer toes and pes cavus
CMT-2
axonal motor neuropathy
MC infectious cause of neuropathy world-wide
leprosy
CF of leprosy neuropathy
mononeuropathy multiplex with predilection for cooler areas (nose, ears, distal limbs); DTRs are usually preserved with nerve hypertrophy which is palpable
pandysautonomia
acquired disorder, usually immune in nature that follows a viral infection, in which both PNS and SNS are affected
CF of charcot-marie tooth disease
- AD
- atrophy of calves (champagne bottle)
- peripheral nerves palpably enlarged
- large fiber sensory loss
- absent ankle jerk reflexes
Dejerine-Sottas disease (HSMN III)
rare, pediatric dz with AR inheritance
- severe weakness/numbness
- markedly enlarged peripheral nerve with onion bulb formation
- slowed conduction velocities
triad of peripheral neuropathy, retinitis pigmentosa and dry/scaly skin
Refsum’s dz - HSNM IV
- AR disorder with accumulation of phytanic acid
Tx of Refsum’s dz
dietary restriction of phytanic acid and plasmaphoresis
what cancer causes purely sensory neuropathy
small cell ca of lung
four systemic infections w/ high incidence of neuropathy
leprosy
syphillis
HIV
diphtheria
diabetic amyotrophy
ischemic infarction of lumbosacral plexus
cause of mononeuropathy mutliplex
ischemic infarction of vasa nervorum due to vasculitis (ie. SLE, RA, PAN, DM)
patho of distal axonopathy
metabolic abnormality causes failure of protein synthesis and axonal transport, resulting in degeneration of distal regions of axons
what axons are most susceptible to metabolic injury?
small diameter axons - initial sx. incl autonomic dysfunction and small fiber sensory modalities (pain/temp)
2 MC forms of demyelinating neuropathy
GBS
CIDP
general characteristics of demyelinating neuropathy
affect large diameter myelinated axons
- significant motor weakness
- large fiber sensory loss (incl loss of vibration and proprioception)
diphtheric neuropathy
toxin inhibits Schwann cell production of myelin, prod. severe weakness and large fiber sensory loss
somatic motor neuronopathies
isolated involvement of ant. horn cells
- ALS and spinal muscular atrophy
somatic sensory neuronopathies
disruption of metabolism of sensory nerve cell bodies, followed by degeneration of their processes
- ex. paraneoplastic, Sjogren’s
autonomic neuronopathy
post-ganglionic autonomic neurons –> causes idiopathic orthostatic hypotension
NCS results for demyelinating neuropathies
- slowed conduction velocity
- prolonged distal latency
- dispersion of evoked compound APs
- conduction block
NCS findings in axonal neuropathies
reduced amplitude of compound motor or sensory APs
EMG findings in acute denervation
fibrillations
positive waves
EMG findings in chronic denervation
large amplitude, long duration and polyphasic voluntary motor unit potentials
- decreased recruitment of motor units
EMG findings in demyelination
decreased recruitment pattern
- voluntary motor unit potentials are normal
general indication for nerve biopsy
asymmetric, multi-focal neuropathies
- can dx. vasculitis, amyloidosis, leprosy and sarcoidosis
what nerves are taken for nerve biopsy
sural nerve
superficial radial N (UE)
what neuropathies are steroids recommended?
vasculitic neuropathies
CIDP
role of azathioprine in neuropathies
used in combo with steroids to tx. autoimmune neuropathies; allows steroids to be tapered more quickly
3 MOA of IVIG
- anti-idiotypic abs may neutralize auto-abs
- reduced complement med. damage
- down regulate immune production
in which neuropathies is IVIG beneficial
Guillan Barre
CIDP
polyneuropathy due to paraproteins
s/e of IVIG
fever, myalgia, headache, rash, aseptic meningitis and renal failure
what neuropathies are TCAs useful for
peripheral neuropathies with burning dysesthetic pains; these drugs are sedating, therefore, if taken at bedtime promote sleep
what anticonvulsants are commonly used for neuropathic pain?
carbamazepine, phenytoin, gabapentin and lamotrigine
- stabilize neuronal membranes
what type of neuropathic pain benefits from anti-convulsants
lancinating pain i.e. trigeminal neuralgia
