Term
| types of peripheral nerve degeneration |
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Definition
axonal: Wallerian, dying-back
demyelinating
neuronopathy |
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Term
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Definition
response of the distal part of an axon to nerve transection
1. breakdown (cut) of axon AND myelin sheath
2. macrophages remove myelin and axonal debris
3. sprouting of axons from the proximal stump; simultaneous proliferation of Schwann cells in tube (endonerium) from by original Schwann cell basal lamina
4. axon extends by 1-3mm/day |
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Term
| Wallerian degeneration - recovery |
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Definition
after recovery, nerve may not have completely normal function
distance between Nodes of Ranvier is decreased
de/re-generation of innervated muscle occurs too |
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Term
| axonal degeneration / dying-back |
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Definition
resembles Wallerian, but cause is METABOLIC ABNORMALITY, not trauma
damage process is in the nerve, most distal areas at risk to degenerate first
degeneration starts furthest from cell body and moves proximally |
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Term
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Definition
primarily a disease of myelin, NOT the nerve cell itself
affects some Schwann cells, spare others
starts near node of Ranvier; macrophages and Schwann cells remove myelin debris
widening nodes may cause conduction block when large area gets damaged |
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Term
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Definition
primary abnormality within the cell body, not the axon
sensory involved more often than motor |
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Term
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Definition
motor unit = a single motor neuron and all the muscle fibers that it innervates
motor units intermingle |
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Term
motor units
myopathic vs. neuropathic damage |
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Definition
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Term
| neurogenic muscle atrophy and grouping |
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Definition
fiber type grouping is sign of neuropathic change
when one motor unit dies, a neighnboring one takes over some of the "orphaned" muscle fibers in the area
results in less heterogeniety; expkansion of anterior horn cells area of coverage
increased amplitude and duration in EMG testing |
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Term
| electrodiagnostic studies |
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Definition
the most consistently helpful type of test in the diagnosis of peripheral nervous system disorders
-nerve conduction studies
-tests of NMJ transmission
-needle electromyogram (ENG) |
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Term
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Definition
electric stimulus applied to peripheral nerve and the amplitude of response and conduction velocity are measured
can evaluate over sensory and motor nerves; best used for assessing large-fiber somatic nerves
can detect which nerves are most affected and if the damage reflects primarily axonal loss or demyelination |
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Term
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Definition
amplitude: reflects the NUMBER of nerve fibers present; measured by the height of the waveform
velocity: primarily assesses the myelin sheath around nerve fibers |
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Term
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Definition
integrity of NMJ assessed through repeated stimulation of the motor nerve
normal NMJ has adequeate reserve to that each stimulus will result in an AP
NMJ disorder - synaptic transmission sometimes fails with repeat stim
characteristic patterns of failure can help differentiate pre- from post-synaptic defects |
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Term
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Definition
records the electrical activity of muscle fibers preceding muscle contraction
very sensitive to denervation and can distinguish between neuropathic and myopathic changes |
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Term
EMG
neuropathic vs. myopathic change |
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Definition
Neuropathic
higher amplitude bc more muscle fiber activity per motor unit, longer duration bc longer electrical activity bc the fibers within the motor unit are more geographically widespread
Myopathic
each individual motor unit is smaller; decreased amplitude and duration |
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Term
| testing sensory vs. motor nerves |
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Definition
for sensory nerve:
conduction velocity = distance / latency
for motor nerve:
conduction velocity = distance AB / (latencyB - latencyA)
latency: time from stimulus to initial deflection |
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Term
| electrodiagnostic results for demyelinating neuropathy |
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Definition
very decreased conduction velocity
some decreased amplitude
-all axons are in tact, but move slower because of no myelin |
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Term
| electrodiagnostic results for axonal neuropathy |
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Definition
decreased conduction velocity
very decreased amplitude
-speed ok because myelin is still in tact, but axons are affected |
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Term
differential diagnoses for polyneuropathy:
DANG THeRAPIST |
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Definition
D iabetes
A lcohol
N utritional
G uillanin-Barre
T oxic
H
E riditary
R ecurrent
A myloid
P orphyria
I nfections
S ystemic
T umors |
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Term
Diabetic neuropathy
*D*ang therapist |
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Definition
| most common cause of neuropathy; also common in patients with impaired glucose tolerance |
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Term
| subtypse of diabetic neuropathy |
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Definition
*distal, symmetric, sensory>motor*
small fiber (painful)
autonomoic
proximal (looks like cancer; motor, wt loss)
compression mononeuropathy (carpal tunnel) |
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Term
diabetic neuropathy
pathoshysiology |
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Definition
*INCREASED OXIDATIVE STRESS**
increase polyol pathway activity
non-enzymatic glycation of proteins
activated protein kinase C
increase hexosamine pathway flux |
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Term
Alchololic neuropathy
d*A*ng therapist |
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Definition
neuropathy is common in alcoholics, but doesn't cause it in animals
alcohol has a direct toxic affect, but is likely also involved in malnutrition/thiamine deficiency that helps to exacerbated the effects |
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Term
Nutritional neuropath
da*N*g therapist |
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Definition
many nutritional deficiencies (and some excesses!) can cause neuropathy
B1 (thiamine)
B6 (pyridoxine) - both if too high or too low
B12 (cyanocobalamin)
Vit E |
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Term
Guillain-Barre syndrome
dan*G* therapist |
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Definition
acute inflammatory polyneuropathy
several forms
*AIDP is most common
-acute motor sensory axonal neuropathy
-acute motor axonal neuropathy
-Miller Fisher variant |
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Term
acute inflammatory demyelinating polyrdiculoneuropazthy
(AIDP) |
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Definition
most common form of Guillian-Barre syndrome
segmental demyelination, most often following stressful event to the immune system causing the immune response to launch attack on myelin
weakness peaks in ~4 weeks |
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Term
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Definition
main symptom is weakness, usually starting in LEs (danger is when/if it spreads diffusely and affects muscles of respiration)
*biggest clue is areflexia or decreased reflexes
sensory loss, facial weakness, autonomic involvement, pain/aches |
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Term
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Definition
CSF: increased protein, few/no WBCs
EMG/nerve conduction studies: *slow conduction velocities, prolonged distal latencies |
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Term
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Definition
self-limited, spontaneous recovery, but might take months
need to support patient in the acute phase to prevent complications of respiratory weakness any dysautonomia (don't hesitate to intubate - these patients can go downhill quickly!)
plasma exchange, IVIg can shorten course
PT |
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Term
Toxic neuropathy
dang *T*herapist |
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Definition
heavy metals
medications (amiodaron, cisplatin, vincristine, others)
gases
hexacarbons (glue sniffers)
organophosphates |
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Term
HEreditary neuropathy
dang t*HE*rapist |
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Definition
many types
motor-sensory: Charcot-Maire-Tooth
motor
sensory
autonomic
combos |
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Term
| Charcot-Marie-Tooth disease |
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Definition
slowly progressive weakness and sensory loss
high arches, hammer toes (common sign of long-standing neuropathy, esp hereditary)
mostly axonal/dying-back damage )get atrophy of distal leg, with more normal promimally) |
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Term
Recurrent neuropathy
dang the*R*apist |
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Definition
CIPD: chronic inflammatory demyelinating polyradiculoneuropathy
continuing to progress for more than 4 weeks |
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Term
| CIDP clinical presentation |
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Definition
segmental demyelination gradual onset (>4 weeks)
motor and sensory (large fiber)
decreased or no reflexes
(comes on more gradually than AIDP) |
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Term
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Definition
CSF: increased protein, few/no WBCs
EMG/nerve conudction: slow conduction velocity, prolonges distal latenices |
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Term
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Definition
steroids (do NOT get used in AIDP)
immunosuppressive agents
plasma exchange, IVIg for acute deterioration
PT, other supportive care |
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Term
Amyloid neuropathy
dang ther*A*pist |
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Definition
in 15-35% of patients with primary amyloidosis
may be the presenting feature
predominantly sensory, may be small fibers
(vs. AD --> amyloid in CNS)
diagnose only with muscle bx, no tx |
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Term
Porphyric neuropathy
dang thera*P*ist |
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Definition
(very rare)
neuropathy occurs with ~50% of neurovisceral attacks of acute intermittent porphyria (abnormal degredation of heme)
may mimic AIDP |
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Term
Infectious neuropathy
dang therap*I*st |
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Definition
LEPROSY (2nd most common cause of neuropathy world-wide)
diptheria (mimic AIDP)
Lyme disease
viruses (HIV, hepatitis, CMV, EBV) |
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Term
Systemic causes of neuropathy
dang therapi*S*t |
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Definition
inflammatory (sarcoidosis, lupus, polyarteritis nodosa)
uremia
hypothyroidism |
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Term
Tumors and neuropathy
dang therapis*T* |
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Definition
paraproteinemias associated with delyelinating polyradiculoneuropathy
paraneoplastic syndromes
-some tumors affect the immune system and make antibodies that go on to attack nerves |
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Term
| treatment of peripheral neuropathy |
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Definition
treat underlying cause (if you can find it!)
various meds for neuropathic pain (TCAs, AEDs, SNRI, NSAIDs)
no specific treatment for numbness and weakness |
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Term
| things to consider when narrowing the differential of polyneuropathy |
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Definition
acute vs subacute vs chronic
senosry vs motor
small vs large fiber
axonal vs demyelinating
demographic factors (known cancer, DB, family hx, ...) |
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