Exam 2: PNS Pt1 Flashcards
What are the two primary patterns of peripheral nerve injury?
- Axonal Neuropathy
2. Demyelinating Neuropathy
What describes the fragmentation of the axon and myeling that occurs distal to the area of the injured axon?
Wallerian degeneration
What does Axonal neuropathy manifest like?
direct injury to peripheral axon involving degeneration of distal portion of axon and eventually myelin
What describes the discontinuous internode demyelination caused by demyelinating neuropathies?
segmental demyelination
Is repair of axonal neuropathy or demyelinating neuropathy possible? If so, what is the result?
Yes, but…
- decrease in axonal density and nerve condution velocity test (NCV)
- thin myelin and shorted internodes and decrease in NCV
What describe damage to a individual peripheral nerve? How do they manifest?
Mononeuropathy; isolated motor or sensory defects
What are some examples of trauma that may result in mononeuropathy?
- carpal tunnel syndrome
- follow inf. disease–Lyme Disease
What describes damage to multiple peripheral nerves? How does it manifest
polyneuropathy; symmetric sensory or motor defects; longest axons–therefore begin in distal extremities (“stalking-and-glove”)
What is paraesthesia?
abnormal “pins and needles” sensation that is frequently ass. with numbness or burning
What are some conditions that may cause Polyneuropathy?
- advanced diabetes mellitus
- toxic exposures (led toxicity, binge drinking alc)
- vitamin deficiencies
- autoimmmune conditions
What syndrome is a poorly-understood immune-condition causing acute demyelination primarily of motor neurons in lower extremities?
Guillian-Barre Syndrome (GBS)
How does Gullian-Barre Syndrome manifest?
- acute onset of lower extremity weakness and lack of stability standing/walking
- *ascending paralysis–> “rubbery legs”
Can Gullain-Barre Syndrome be lethal?
yes, if ascending paralysis reaches muscles of respiration (diaphragm)
What PNS disorder has a bimodal distribution that most likely occurs in individuals b/w 15-35 or 50-60 years?
Gullian Barre Syndrome
What is the recovery rate from Gullian Barre Syndrome?
~90% self-recover, but may be weeks to years
younger–full recovery
older– may experience Chronic Inflam. Demyelinating Polyneuropathy
What inflammatory env. exposure is known to stimulate the majority of the infection related cases of GBS?
Campylobacter jejuni (~30% of all cases)
–still 60% idopathic
What is a chronic immune-mediated demyelinating disorder that causes sensory and motor neuropathies that persists for at least 2 months in duration?
Chronic Inflammatory Demyelinating Polyneuropathy (CIDP)
What age and sex does CIDP(chronic inflammatory demyelinating polyneuropathy) MC affect? How common is CIDP?
2x-males; ages 40-60
1 in 20,000
What is a characteristic feature of Schwann cells involved in chronic inflammatory demyelinating polyneuropathy?
“onion bulb” appearance due to replapsing of demyelination and remyelination that occurs
What are some risk factors for developing chronic inflammatory demyelinating polyneuropathy (CIDP)?
- various forms of “immune dyregulations” - - history of Lupus (SLE) or HIV
What are the symptoms that manifest with chronic inflammatory demyelinating polyneuropathy (CIDP)?
insidious onset of:
- limb weakness
- ataxia
- loss of balance
- paresthesia
- fatigue
- muscle pain/cramping
- radiculopathy (nerve pain)
- decrease deep tendon reflexes
What involves axonal and demyelinating nerve damage in patients with long-term diabetes mellitus?
Diabetic Neuropathy
What is the MC form of peripheral neuropathy?
Diabetic Neuropathy
Even though completely not understood, what does Diabetic neuropathy develop in part from?
oxidative injury to body’s microvasculature (vasa nervorum) following prolonged periods of hyperglycemia
What is Diabetes mellitus?
(DM or diabetes) = metabolic disorder characterized by prolonged levels of hyperglycemia
involves type I DM, type 2 DM, and gestational diabetes
What are the small arteries that supply blood and nutrients to peripheral neurons called?
vasa nervorum
injuried in Diabetic neuropathy
What is the most common way that Diabetic neuropathy manifests?
effects longest neurons
- MC way = distal symmetric sensorimotor polyneuropathy
- beings as paresthesia and follows “stalking-and-glove” pattern
T/F. When it comes to paresthesia of different pathologies, motor dysfunction comes before sensory dysfunction.
False– sensory before motor
What do the sensory abnormalities associated with Diabetic neuropathy put the individual at risk for?
undetected wounds that become infected and cause gangrenous necrosis (typically toes or feet)
What individuals are prone to ulcerations on the skin (feet) due to poor wound healing from microvascular injury?
inds with Diabetic Neuropathy
What is the term for when the ANS is injured due to long-term diabetes? What may this cause?
Autonomic Neuropathy
- bowel, bladder, cardiac, or sexual dysfunction
What are four pathologies that Diabetic Neuropathy may cause?
- Autonomic Neuropathy
- Lumbosacral Radiculopathy
- Diabetic Retinopathy
- Diabetic Nephropathy
What will lumbosacral radiculopathy (a potential result from diabetic neuropathy) manifest as?
asymmetric pain, weakness, or atrophy in lower extremities
What pathology may result in blindness that could be caused by Diabetic neuropathy?
Diabetic Retinopathy
Diabetic Neuropathy may cause Diabetic Nephropathy. What does that put the individual at risk for?
(glomerulonephritis)–> kidney failure
What is characterized by progressive joint destruction, dislocations, and pathologic fxs following a neuropathy that reduced lower extremity joint sensation?
Neuropathic arthropathy (Charcot joint or neuropathic joint)
Where is neuropathic arthropathy lost likely to occur?
in weight-bearing joints; like foot, ankle, or hip following unperceived trauma
What is the most common cause of someone developing a Neuropathic joint (neuropathic arthropathy)?
What could be other causes?
Diabetic Neuropathy
spinal cord injury, syphilis, leprosy
How does Neuropathic arthropathy manifest/ what are the symptoms?
- severe swelling
- permanent joint destruction
- severe disability
What are additional causes of Peripheral Nerve Injury?
- drugs/ toxic env. exposures (lead)–> may interfere with cytoskeleton of peripheral neurons (affect longest axons to distal extremities)
- Systemic Vasculitis
How would Systemic Vasculitis cause peripheral nerve injury?
inflam. may extend to peripheral nerves and cause injury or induce ischemia
How many people with Systemic Vasculitis have peripheral nerve injuries at time of their Dx?
~1/3
What conditions characteristically cause systemic vasculitis?
- systemic lupus erythematosus
- polyarteritis nodosa
- rheumatoid arthritis
What represents a related group of inherited neuropathies that collectively affect about 1 in 2,500 individuals?
Charcot-Marie-Tooth Disease (CMT)
When does Charcot-Marie-Tooth Disease (CMT) most likely onset? What does it commonly present with?
first two decades of life
progressively worsening lower extremity weakness and difficulty walking (ataxia)
What inherited disease as it gets more severe has a noticeable foot drop and a “steppage gait” that develops, and may involve pes cavus development?
Charcot-Marie-Tooth Disease (CMT)
What is pes cavus?
a high arched foot that does not flatten wen weight-bearing
What form of CMT disease develops following an inherited PMP22 gene mutation?
(CMT 1); mutation results in formation of abnormal myelin and causes demyelination atrophy
Disorders of the neuromuscular junction produce a wide variety of what kind of defects?
motor defects
What are the three characteristic examples that we are focusing on that cause neuromuscular disorders?
autoimmune, paraneoplastic, or infectious origin
What are the four neuromuscular junction disorders we are discussing?
- Myasthenia gravis
- Lambert-Eaton syndrome
- Tetanus
- Botulism
What autoimmune condition involving antibodies against an inds own postsynaptic ACh receptors? What does this cause?
Myasthenia Gravis
inhibits myocyte depolarization and causes painless muscle weakness (myasthenia)
What is Myasthenia Gravis a classic example of?
a Type II Hypersensitivity Reaction
What makes the muscle weakness ass. with Myasthenia Gravis worse? Better?
Worse– muscle activation, physical activity, and electrical simtulation
Better–rest
What is the most characteristic feature of Myasthenia Gravis? What are some other features?
unilateral or bilateral ptosis (eyelid drooping)
also axial and limb girdle weakness
In Myasthenia Gravis, weakness of extraocular eye muscles may cause what? What if face or throat muscles are effected?
diplopia
dysphagia, dysarthria, difficulty chewing, or inhibited facial expressions
What is considered a “myasthenic crisis”?
when muscle of respiration become affected in Myasthenia Gravis, and cause dyspnea
this is a medical emergency requiring mechanical ventilation for survival
Most patients with Myasthenia Gravis experience enlargement of what gland?
thymus gland, due to:
- thymic hyperplasia (60% cases)
- thymoma (20% cases)
(B cells play a role)
What individuals are most likely to get Myasthenia Gravis?
reproductive age females OR older adult males
~2 in every 100,000
What procedure may reduce the severity of Myasthenia Gravis or even cure it?
thymectomy
What autoimmune condition involves formation of anitbodies against one’s own presynaptic calcium ion channels? What does this cause?
Lambert-Eaton Syndrome (LES)
inhibits release of ACh in neuromuscular junction–> preventing myocyte depolarization –> causing myasthenia
What characteristic of Lambert-Eaton syndrome (LES) mimics Myasthenia Gravis? What makes these disease different?
limb girdle muscle weakness
LES improves with repetitive electronic stimulation
What does Lambert-Eaton Syndrome improve with repetitive electronic stimulation?
intracellular calcium ions build up to cause ACh release
T/F. Lambert-Eaton Syndrome is fairly common.
False– it is rare, ~5 per 1,000,000
40% of people with Lambert-Eaton Syndrome also have what?
Small Cell Lung Cancer
this 40% also represent the 3% of all patients with small celll lung cancer
What is it considered when LES (Lambert-Eaton Syndrome) develops in patients with small cell lung cancer?
paraneoplastic syndrome
What age is LES (Lambert-Eaton Syndrome) most likely to affect?
older adults; average age of Dx is ~ 60
What are two infectious neuromuscular disorders we are focusing on?
- Tetanus
2. Botulism
What is Tetanus characterized by?
muscle spasms following an infection with Clostridium tetani found in soil, dust, and manure as an endospore and thrives in anaerobic env.
How does an inf. with Clostridium tetani create these muscle spasms ass. with tenanus?
it produces naturally-occuring neurotoxin that binds to peripheral nerve terminals and blocks release of inhibitory NTs (glycine and GABA)–> therefore increase in ACh activity
Where are the MC places for muscle spasms ass. with tetanus?
- jaw –> “lockjaw”
- neck, back, abdomen muscles
What percentage of cases is tetanus lethal? why?
10% all cases; if affects muscles of respiration or cardiac musculature
When tetanic spasms involve the spinal muscles, a state of severe hyperextension may occur, what is that called?
opisthotonus
What is Botulism?
a condition characterized by muscle flaccidity following an infection with Clostridium botulism, present in bee honey or improperly canned foods
Why is it recommended to not give babies/infants honey?
could cause botulism–> “infant botulism” or “floppy baby syndrome”
90% of all cases in US are in infants
How does Clostrium botulism actually cause muscle flaccid paralysis?
- survives in intestines and produces natural-occuring neurotoxin
- inhibits release of ACh into neuromuscular jxn —> therefore causing muscle weakness/flaccidity
What are other symptoms/manifestations of botulism besides muscle flaccidity?
- blurred vision
- bilateral ptosis
- difficultiy speaking, chewing
- dysphagia
What peripheral neuropathy tends to develop superior-to-inferior, aka “descending paralysis”?
Botulism
What percentage of cases of Botulism are lethal?
5% due to muscles of respiration becoming involved and causing dyspnea or lethal respiratory paralysis
