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Neuromuscular Disorders<br />Saad Al Juma <br />R3 <br />
In MNL :<br />Poliomyelitis is the protypicaldisease <br />In Poliomyelitis weakness can be asymmetrical or more often sym...
In MNL :<br />Amyotrophic lateral sclerosis is the prototypical disease <br />In Poliomyelitis weakness can be symmetrical...
In Amyotrophiclateralsclerosis<br />It affects the anterior horn cells and results in lower motor neuron disease without s...
In Amyotrophiclateralsclerosis<br />Poliomyelitis affects the anterior horn cells and results in lower motor neuron diseas...
In MNL all are true except:<br />lesions at the level of the brainstem or above produce bilateral weakness <br />bilateral...
In MNL :<br />lesions at the level of the brainstem or above produceunilateralweakness <br />bilateral weakness caused by ...
In Neuropathies , all are true EXCEPT :<br />a grip strength or foot-drop may be noted first<br />patients usually note a ...
In Neuropathies :<br />a grip strength or foot-drop may be noted first<br />patients usually note a slowly progressive cou...
In Myopathies , all are true EXCEPT: <br />Myopathies produce generalized, symmetrical weakness<br />muscle tone is usuall...
In Myopathies<br />Myopathies produce generalized, symmetrical weakness<br />muscle tone is usually diminished, but sensat...
In MG all the following are true except:<br />Normally, vital capacity values range from 60 to 70 mL/kg.<br />the forced v...
In MG :<br />Normally, vital capacity values range from 60 to 70 mL/kg.<br />the forced vital capacity reaches 15 mL/kg, i...
In Diseases of the Neuromuscular Junction Repeated stimulation leads to diminishing motor strength, which is caused by :<b...
In Diseases of the Neuromuscular Junction Repeated stimulation leads to diminishing motor strength, which is caused by :<b...
decrease in the release of ACh may produceexcept<br />decreased visual acuity<br />low-grade fever<br />dry, flushed skin<...
decrease in the release of ACh may produce:<br />decreased visual acuity<br />low-grade fever<br />dry, flushed skin<br />...
All are true about Myopathies , except:<br />generalized, symmetrical weakness<br />Reflexes are present<br />muscle tone ...
All are true about Myopathies :<br />generalized, symmetrical weakness<br />Reflexes are present<br />muscle tone is usual...
Lambert-Eatonmyasthenicsyndromeall are false except :<br />50% of cases are associated with non small cell carcinoma of th...
Lambert-Eatonmyasthenicsyndrome:<br />50% of cases are associated with small cell carcinoma of the lung<br />Clinically in...
Regarding MG , all are true except:<br />Age of onset is bimodal<br />MG results from autoantibodies directed against the ...
Regarding MG :<br />Age of onset is bimodal<br />MG results from autoantibodies directed against the nicotinic acetylcholi...
What is Edrophoniumtest ?<br />
What is Edrophoniumtest ?<br /><ul><li>Edrophonium (Tensilon) test:
measure distance from upper to the lower eyelid before and after IV edrophonium (AChE blocking agent)
 give test dose first 1-2mg IV , if no ADR/no improvement
 3mg, if no response
 5mg (max 10mg)
watch for bradycardia (only perform when pt on monitor with Atropine at bedside DUE TO BRADY AND SECRETIONS ISSUES.)
  contraindicated in COPD/asthma pts because of risk of secretions.</li></ul>reports of FP with botulism<br />
What is Icepacktest ?<br />
What is Icepacktest ?<br />it is applied to the affected eye for approximately 2 minutes<br />the distance between the lid...
defined as respiratory failure leading to mechanical ventilation<br />Occurs in 15 to 20% of patients with MG<br />within ...
In MyasthenicCrisis : <br />defined as respiratory failure leading to mechanical ventilation<br />Occurs in 15 to 20% of p...
BONUS QUESTION<br />
Medications precipitate MG crisis<br />
Medications precipitate MG crisis<br />
Regarding MG Management all are true EXCEPT:<br />in the setting of acute exacerbation of MG , The use of intravenous pyri...
Regarding MG Management:<br />in the setting of acute exacerbation of MG , The use of intravenous pyridostigmine is NOT re...
Regarding P.E in M.G :<br />The fall in AChR levels is not associated with improvement in symptoms of MG. <br />complicati...
Regarding P.E in M.G :<br />The fall in AChR levels is associated with improvement in symptoms of MG. <br />There is a ris...
Regarding Botulism , all are true except: <br />Most common type is infant Botulism <br />Clostridium botulinum is an anae...
Regarding Botulism :<br />Most common type is infant Botulism <br />Clostridium botulinum is an anaerobic, spore-forming b...
In Botulism , all are true except :<br />There is no pain <br />The onset of symptoms is 6 to 48 hours after the ingestion...
In Botulism :<br />There is no pain <br />The onset of symptoms is 6 to 48 hours after the ingestion of tainted food<br />...
Regarding Botulisim antitoxin<br />there is a risk of anaphylaxis and serum sickness<br />It is known to decrease ventilat...
Regarding Botulisim antitoxin<br />there is a risk of anaphylaxis and serum sickness<br />although it is not clear that th...
In TickParalysis, all are true except<br />an acute, ascending, flaccid motor paralysis<br />Usually starts after 6-12 day...
In TickParalysis<br />an acute, ascending, flaccid motor paralysis<br />Usually starts after 1-2 days from female tick has...
In ThyrotoxicPeriodicParalysis , all are true EXCEPT: <br />It is due to decreased sodium-potassium adenosine triphosphata...
In Thyrotoxic Periodic Paralysis<br />It is due to increased sodium-potassium adenosine triphosphatase activity<br />Treat...
In Familial Periodic Paralysis all are true EXCEPT: <br />autosomal-dominant disorders of ion channels<br />intermittent a...
In Familial Periodic Paralysis: <br />autosomal-dominant disorders of ion channels<br />intermittent attacks of flaccid ex...
Which of the following statements is true?<br />a. Herpes zoster is often associated with motor dysfunction with or withou...
The answer is c. <br />Ramsay-Hunt syndrome refers to herpes zoster involving the tympanic membrane, ear canal, and other ...
2. A 34-year-old woman with known myasthenia gravis presents in respiratory distress. She is unable to move without assist...
The answer is b<br />You should be able to differentiate a myasthenic crisis from a cholinergic crisis.<br />Both can pres...
A 13-year-old girl presents with a 3-day history of malaise, low-grade fever, and double vision with unilateral ptosis. Th...
The answer is d<br />Both botulism and diphtheria may present with acute bulbar nerve palsies, weakness of any or all extr...
A 34-year-old woman with myasthenia gravis presents with flank pain and fever of 103.4◦F. She is allergic to penicillin, a...
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Nm disorder

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  1. 1. Neuromuscular Disorders<br />Saad Al Juma <br />R3 <br />
  2. 2. In MNL :<br />Poliomyelitis is the protypicaldisease <br />In Poliomyelitis weakness can be asymmetrical or more often symmetrical<br />The cerebrospinal fluid analysis resembles that of aseptic meningitis.<br />Patients initially have a clinical picture similar to that of viral meningitis <br />
  3. 3. In MNL :<br />Amyotrophic lateral sclerosis is the prototypical disease <br />In Poliomyelitis weakness can be symmetrical or more often asymmetrical <br />The cerebrospinal fluid analysis resembles that of viral meningitis.<br />Patients initially have a clinical picture similar to that of viral meningitis…..<br />
  4. 4. In Amyotrophiclateralsclerosis<br />It affects the anterior horn cells and results in lower motor neuron disease without sensory involvement<br />Results from a degeneration of the motor neuron with sensory involvement. <br />complain of dysarthria or ptosis<br />findings include hyporreflexia, muscle wasting, and fasciculation<br />Pain is not a component of the clinical picture….<br />
  5. 5. In Amyotrophiclateralsclerosis<br />Poliomyelitis affects the anterior horn cells and results in lower motor neuron disease without sensory involvement<br />Results from a degeneration of the motor neuron without sensory involvement. <br />complain of dysarthria or dysphagia<br />findings include hyperreflexia, muscle wasting, and fasciculation<br />Pain is not a component of the clinical picture….<br />
  6. 6. In MNL all are true except:<br />lesions at the level of the brainstem or above produce bilateral weakness <br />bilateral weakness caused by lesions above the spinal cord is associated with a change in mental status or cranial nerve involvement<br />Lesions of the central nervous system result in spasticity, hyperreflexia, and extensor plantar reflexes<br />bilateral upper motor neuron signs with normal mental status, neuroimagingshould focus on looking for a lesion in the spinal cord<br />
  7. 7. In MNL :<br />lesions at the level of the brainstem or above produceunilateralweakness <br />bilateral weakness caused by lesions above the spinal cord is generally associated with a change in mental status or cranial nerve involvement<br />Lesions of the central nervous system result in spasticity, hyperreflexia, and extensor plantar reflexes<br />when bilateral upper motor neuron signs are found in conjunction with normal mental status, diagnostic testing including neuroimaging should focus on looking for a lesion in the spinal cord<br />
  8. 8. In Neuropathies , all are true EXCEPT :<br />a grip strength or foot-drop may be noted first<br />patients usually note a slowly progressive course of symptoms.<br />A disorder of transmission often leads to increased production of AChreceptors.<br />Patients usually have intact sensation sensation.<br />
  9. 9. In Neuropathies :<br />a grip strength or foot-drop may be noted first<br />patients usually note a slowly progressive course of symptoms.<br />A disorder of transmission often leads to increased production of AChreceptors.<br />Patients exhibit varying degrees of altered sensation<br />
  10. 10. In Myopathies , all are true EXCEPT: <br />Myopathies produce generalized, symmetrical weakness<br />muscle tone is usually diminished, but sensation is preserved.<br />Generally cause muscle pain and tenderness<br />Reflexes are present but diminished<br />
  11. 11. In Myopathies<br />Myopathies produce generalized, symmetrical weakness<br />muscle tone is usually diminished, but sensation is preserved.<br />Metabolic disorders affecting muscle strength are painless in nature<br />Reflexes are present but diminished<br />
  12. 12.
  13. 13. In MG all the following are true except:<br />Normally, vital capacity values range from 60 to 70 mL/kg.<br />the forced vital capacity reaches 15 mL/kg, intubation is necessary<br />Arterial blood gas is helpful as most of the patients have sufficient protective reserve and hypercapniadevelps early<br />presence of swallowing and a strong cough suggests that the patient has sufficient protective and ventilatory reserve<br />
  14. 14. In MG :<br />Normally, vital capacity values range from 60 to 70 mL/kg.<br />the forced vital capacity reaches 15 mL/kg, intubation is necessary<br />Arterial blood gas is not necessarily helpful because functional reserve can be severely diminished by the time a patient develops either hypercarbia or hypoxia<br /> presence of swallowing and a strong cough suggests that the patient has sufficient protective and ventilatory reserve<br />
  15. 15. In Diseases of the Neuromuscular Junction Repeated stimulation leads to diminishing motor strength, which is caused by :<br />the blockage of the receptors as in organophosphate poisoning<br />a decrease in the amount of ACh released as in botulism<br />inactivating Ach by irreversibly binding with it as in MG<br />Down regulation of the Ach receptors as in Atropinized patients <br />
  16. 16. In Diseases of the Neuromuscular Junction Repeated stimulation leads to diminishing motor strength, which is caused by :<br />the blockage of the receptors as in MG<br />a decrease in the amount of ACh released as in botulism<br />inactivating Ach by irreversibly binding with it as in organophosphate poisoning<br />Down regulation of the Ach receptors as in Atropinized patients <br />
  17. 17. decrease in the release of ACh may produceexcept<br />decreased visual acuity<br />low-grade fever<br />dry, flushed skin<br />Bradycardia<br />urinary retention<br />
  18. 18. decrease in the release of ACh may produce:<br />decreased visual acuity<br />low-grade fever<br />dry, flushed skin<br />Tachycardia<br />urinary retention<br />
  19. 19. All are true about Myopathies , except:<br />generalized, symmetrical weakness<br />Reflexes are present<br />muscle tone is usually diminished<br />sensation is lost <br />Are always painful<br />
  20. 20. All are true about Myopathies :<br />generalized, symmetrical weakness<br />Reflexes are present<br />muscle tone is usually diminished<br />sensation is preserved<br />Are always painful<br />
  21. 21. Lambert-Eatonmyasthenicsyndromeall are false except :<br />50% of cases are associated with non small cell carcinoma of the lung<br />Clinically includes weakness that improves with use of muscles…..<br />autonomic dysfunction, most commonly seen as flushed skin.<br />Management with IVIG has been reported to be sufficient.<br />
  22. 22. Lambert-Eatonmyasthenicsyndrome:<br />50% of cases are associated with small cell carcinoma of the lung<br />Clinically includes weakness that improves with use of muscles<br />autonomic dysfunction, most commonly seen asdry mouth.<br />Management primarily focuses on treating the underlying neoplastic disorder<br />
  23. 23. Regarding MG , all are true except:<br />Age of onset is bimodal<br />MG results from autoantibodies directed against the nicotinic acetylcholine receptor (AChR) at the neuromuscular junction<br />Ocular symptoms are often the first manifestation of MG<br />Bulbar muscles are spared<br />
  24. 24. Regarding MG :<br />Age of onset is bimodal<br />MG results from autoantibodies directed against the nicotinic acetylcholine receptor (AChR) at the neuromuscular junction<br />Ocular symptoms are often the first manifestation of MG<br />Bulbar muscles may be involved<br />
  25. 25.
  26. 26. What is Edrophoniumtest ?<br />
  27. 27. What is Edrophoniumtest ?<br /><ul><li>Edrophonium (Tensilon) test:
  28. 28. measure distance from upper to the lower eyelid before and after IV edrophonium (AChE blocking agent)
  29. 29.  give test dose first 1-2mg IV , if no ADR/no improvement
  30. 30.  3mg, if no response
  31. 31.  5mg (max 10mg)
  32. 32. watch for bradycardia (only perform when pt on monitor with Atropine at bedside DUE TO BRADY AND SECRETIONS ISSUES.)
  33. 33. contraindicated in COPD/asthma pts because of risk of secretions.</li></ul>reports of FP with botulism<br />
  34. 34. What is Icepacktest ?<br />
  35. 35. What is Icepacktest ?<br />it is applied to the affected eye for approximately 2 minutes<br />the distance between the lids is measured again<br />prospective evaluation of the ice bag approach found the test result to be positive (an improvement in distance of at least 2 mm) in 80% of patients with MG and in no patients without MG.[7]<br />
  36. 36. defined as respiratory failure leading to mechanical ventilation<br />Occurs in 15 to 20% of patients with MG<br />within the first 2 years of disease onset<br />precipitant may not be found in 3 % of cases<br />In MyasthenicCrisis all are true Except: <br />
  37. 37. In MyasthenicCrisis : <br />defined as respiratory failure leading to mechanical ventilation<br />Occurs in 15 to 20% of patients with MG<br />within the first 2 years of disease onset<br />precipitant may not be found in 30% of cases<br />
  38. 38. BONUS QUESTION<br />
  39. 39. Medications precipitate MG crisis<br />
  40. 40. Medications precipitate MG crisis<br />
  41. 41. Regarding MG Management all are true EXCEPT:<br />in the setting of acute exacerbation of MG , The use of intravenous pyridostigmine is recommended<br />the initiation of corticosteroids in patients with moderate to severe weakness may improve the outcome<br />Thymectomy is recommended for patients younger than 60 <br />IVIG is preferred over PE due to the side effects of the later.<br />
  42. 42. Regarding MG Management:<br />in the setting of acute exacerbation of MG , The use of intravenous pyridostigmine is NOT recommended<br />the initiation of corticosteroids in patients with moderate to severe weakness may improve the outcome<br />Thymectomy is recommended for patients younger than 60 <br />IVIG is preferred over PE due to the side effects of the later.<br />
  43. 43. Regarding P.E in M.G :<br />The fall in AChR levels is not associated with improvement in symptoms of MG. <br />complications include hypotension or anticoagulation. <br />It is safe in children.<br />many case series showed long-term benefit in myasthenic crisis.<br />
  44. 44. Regarding P.E in M.G :<br />The fall in AChR levels is associated with improvement in symptoms of MG. <br />There is a risk of complications from hypotension or anticoagulation. <br />Because of safety concerns, clinical trials have not been done in children.<br /> Although there are no randomized controlled studies, a review yielded many case series with short-term benefit, especially in myasthenic crisis.<br />
  45. 45. Regarding Botulism , all are true except: <br />Most common type is infant Botulism <br />Clostridium botulinum is an anaerobic, spore-forming bacterium<br />types A, B, and C toxins cause human disease….<br />botulinum toxin works by binding irreversibly to the presynaptic membrane of peripheral and cranial nerves, inhibiting the release of ACh at the peripheral nerve synapse<br />
  46. 46. Regarding Botulism :<br />Most common type is infant Botulism <br />Clostridium botulinum is an anaerobic, spore-forming bacterium<br />types A, B, and E toxins cause human disease….<br />botulinum toxin works by binding irreversibly to the presynaptic membrane of peripheral and cranial nerves, inhibiting the release of ACh at the peripheral nerve synapse<br />
  47. 47. In Botulism , all are true except :<br />There is no pain <br />The onset of symptoms is 6 to 48 hours after the ingestion of tainted food<br />descending, symmetrical, flaccid paralysis<br />diplopia, dysarthria, and dysphagia are the first signs<br />Pupils are often fixed and reactive to light…<br />
  48. 48. In Botulism :<br />There is no pain <br />The onset of symptoms is 6 to 48 hours after the ingestion of tainted food<br />descending, symmetrical, flaccid paralysis<br />diplopia, dysarthria, and dysphagia are the first signs<br />Pupils are often dilated and not reactive to light…<br />
  49. 49. Regarding Botulisim antitoxin<br />there is a risk of anaphylaxis and serum sickness<br />It is known to decrease ventilator dependence <br />the antitoxin should be administered once the toxin can be identified in serum and stool<br />the antitoxin should be administered as soon as possible<br />An intravenous human botulism immune globulin (BIG-IV) has been developed for treatment of wound related botulism<br />
  50. 50. Regarding Botulisim antitoxin<br />there is a risk of anaphylaxis and serum sickness<br />although it is not clear that the antitoxin decreases ventilator dependence <br />the antitoxin should be administered as soon as possible (clinical findings and exclusion of other processes)<br />An intravenous human botulism immune globulin (BIG-IV) has been developed for treatment of infantile botulism<br />
  51. 51. In TickParalysis, all are true except<br />an acute, ascending, flaccid motor paralysis<br />Usually starts after 6-12 days from female tick has attached and begun to feed<br />fixed and dilated pupils associated with the disease.<br />Intubation may be necessary after tick removal<br />
  52. 52. In TickParalysis<br />an acute, ascending, flaccid motor paralysis<br />Usually starts after 1-2 days from female tick has attached and begun to feed<br />fixed and dilated pupils associated with the disease.<br />Intubation may be necessary after tick removal<br />
  53. 53. In ThyrotoxicPeriodicParalysis , all are true EXCEPT: <br />It is due to decreased sodium-potassium adenosine triphosphatase activity<br />Treatment of the hyperthyroid symptoms helps the treatment of the paralysis <br />There is probably a genetic feature underlying this disorder<br />all patients have thyroid function testing done after a first episode of hypokalemic paralysis<br />
  54. 54. In Thyrotoxic Periodic Paralysis<br />It is due to increased sodium-potassium adenosine triphosphatase activity<br />Treatment of the hyperthyroid symptoms helps the treatment of the paralysis <br />There is probably a genetic feature underlying this disorder<br />all patients have thyroid function testing done after a first episode of hypokalemic paralysis<br />
  55. 55. In Familial Periodic Paralysis all are true EXCEPT: <br />autosomal-dominant disorders of ion channels<br />intermittent attacks of flaccid extremity weakness associated with either hyperkalemia or hypokalemia<br />bulbar and respiratory muscles may be affected.<br />The onset of symptoms often follows a high carbohydrate intake and a period of rest.<br />An electrocardiogram, which should be done immediately<br />
  56. 56. In Familial Periodic Paralysis: <br />autosomal-dominant disorders of ion channels<br />intermittent attacks of flaccid extremity weakness associated with either hyperkalemia or hypokalemia<br />bulbar and respiratory muscles not affected.<br />The onset of symptoms often follows a high carbohydrate intake and a period of rest.<br />An electrocardiogram, which should be done immediately<br />
  57. 57.
  58. 58.
  59. 59.
  60. 60.
  61. 61.
  62. 62.
  63. 63. Which of the following statements is true?<br />a. Herpes zoster is often associated with motor dysfunction with or without a rash.<br />b. Acute rabies infection typically begins as a Ramsay-Hunt syndrome before progressing to severe throat spasm and to cardiac and renal failure.<br />c. Weakness or diplopia when fatigued may be the only complaint with multiple sclerosis.<br />d. Treatment for polymyositis is early administration of systemic steroids.<br />e. Serum calcium should be measured in patients with recurrent generalized weakness that follows periods of heavy exertion or that is present upon awakening.<br />
  64. 64. The answer is c. <br />Ramsay-Hunt syndrome refers to herpes zoster involving the tympanic membrane, ear canal, and other areas in the distribution of the sensory branches of the facial nerve. <br />Herpetic zoster may result in motor abnormalities in up to 25% of cases.<br />Weakness or diplopia only on exertion is a common complaint in early cases of multiple sclerosis. Another early presenting sign is retrobulbar neuritis; in fact, 50–75% of cases occur in patients who develop multiple sclerosis.<br />Steroids may transiently exacerbate weakness in patients with polymyositis and should not be started on patients who will be discharged from the ED.<br />Acute periodic paralysis appears to involve abnormalities in cellular function, possibly related to potassium transport. The disease is most common in young men. No specific physical findings may be found and it is often misdiagnosed as hysterical in origin<br />
  65. 65. 2. A 34-year-old woman with known myasthenia gravis presents in respiratory distress. She is unable to move without assistance. Her vital signs are: temperature 36◦C (96.8◦F), heart rate 50/min, blood pressure 100/60 mm Hg, respiratory rate 35/min and shallow. She is drooling and has upper airway rhonchi and bilateral wheezing. Her respiratory rate appears to be decreasing. You immediately:<br />a. Administer 2–4 mg of intravenous edrophonium.<br />b. Perform endotracheal intubation.<br />c. Administer 1 mg of atropine; if there is an improvement in her wheezing, administer pralidoxime.<br />d. Start an intravenous atropine drip.<br />e. Arrange emergent hyperbaric therapy.<br />
  66. 66. The answer is b<br />You should be able to differentiate a myasthenic crisis from a cholinergic crisis.<br />Both can present with progressive muscle weakness and respiratory depression, dysphagia, and other physical signs. Bradycardia, wheezing, and salivation suggest cholinergic crisis. <br />A common error is to mistake a cholinergic as a myasthenic crisis and administer additional acetylcholinesterase inhibitor. <br />The immediate treatment for either type is ABCs and intubation at the first clinical signs of respiratory failure. <br />In a cholinergic crisis, atropine can be used for the muscarinic symptoms, but it is not a substitute for airway management and ventilatory assistance.<br />
  67. 67. A 13-year-old girl presents with a 3-day history of malaise, low-grade fever, and double vision with unilateral ptosis. The potential diagnosis of botulism is best supported by finding:<br />a. Acute renal failure.<br />b. Cardiac failure.<br />c. Bilateral numbness of hands and feet.<br />d. Acute urinary retention.<br />e. Pseudomembranouspharyngitis.<br />
  68. 68. The answer is d<br />Both botulism and diphtheria may present with acute bulbar nerve palsies, weakness of any or all extremities, and cholinergic manifestations, such as urinary retention and colicky pain.<br />In both diseases, the most common early neurologic findings are ptosis, double vision, and difficulty in accommodation. <br />Diphtheria is an acute febrile illness. A primary symptom is a severe pseudomembranouspharyngitis presenting with severe throat pain and excessive saliva production.<br />In diphtheria, cardiotoxic and renal abnormalities are direct results of the elaborated bacterial toxin.<br />
  69. 69. A 34-year-old woman with myasthenia gravis presents with flank pain and fever of 103.4◦F. She is allergic to penicillin, and despite boluses of intravenous fluid and antibiotic therapy, she becomes hypotensive. A medicine that you can safely use in her management is:<br />a. Gentamicin.<br />b. Vecuronium.<br />c. Lidocaine.<br />d. Procainamide.<br />e. Succinylcholine.<br />
  70. 70. The answer is c<br />Aminoglycoside antibiotics have some curare-type effects on the motor endplate; if they are used in the myasthenic patient, the physician should be prepared to treat paralysis and respiratory arrest. Obviously, these patients are more susceptible to muscle-paralyzing agents as well. Phenytoin, quinidine, procainamide, and lithium can also adversely affect patients with myasthenia gravis.<br />
  71. 71. Curare (Chondodendrontomentosum), <br /><ul><li>a South American vine native to the Amazon Basin.
  72. 72. The undersides of the leaves are white-tomentose.
  73. 73. An extract from the bark and stems is the source of a potent isoquinoline alkaloid used in the deadly poison curare. Amazonian Indians use the gummy extract to coat the poison darts of their blowguns. The alkaloid D-tubocurarine blocks acetylcholine receptor sites at neuromuscular junctions, causing relaxation and paralysis of muscles, including respiratory organs and the heart.
  74. 74. In fact, D-tubocurarine has been used to relax the heart muscle during open heart surgery.
  75. 75. It has also been used to treat the spastic paralysis of tetanus toxin from the bacterium Clostridium botulinum. Tetanus toxin causes uncontrollable muscle contraction throughout the body.</li></li></ul><li>Neuropathy is differentiated from myopathy in that:<br />a. Neuropathies progress proximally.<br />b. Myopathies affect distal and proximal muscle groups equally.<br />c. Myopathies and neuropathies both have prominent sensory findings.<br />d. Myopathies often have striking weakness of the small muscles of the hands.<br />e. Myopathies have relatively preserved deep tendon reflexes. <br />
  76. 76. The answer is a<br />Neuropathies tend to have the following characteristics: <br />proximal progression of symptoms<br />sensory deficits often in a stocking glove distribution<br />early loss of DTRs. <br />Myopathiescharacteristically present with<br />proximal motor weakness<br />myalgias<br />delayed loss of DTRs<br />CPK enzymes may be elevated. <br />There are exceptions to these generalizations.<br />
  77. 77. Lambert-Eaton MyasthenicSyndrome<br />results from an autoimmune attack directed against the voltage-gated calcium channels (VGCCs) on the presynaptic motor nerve terminal. <br />This results in a loss of functional VGCCs at the motor nerve terminals. The number of quanta released by a nerve impulse is diminished. <br />However, because presynaptic stores of ACh and the postsynaptic response to ACh remain intact, rapid repetitive stimulation or voluntary activation that aids in the release of quanta will raise the endplate potential above threshold and permit generation of muscle action potential. <br />As neuromuscular transmission is completed at additional neuromuscular junctions, a transient increase will occur in the strength of the muscle. <br />Parasympathetic, sympathetic, and enteric neurons are all affected.<br />Clinically, this phenomenon is noted by the appearance of previously absent tendon reflexes following a short period of strong muscle contraction by the patient.<br />
  78. 78. Myasthenia Gravis<br />Autoantibodies (immunoglobulin G [IgG]) develop against ACh nicotinic postsynaptic receptors for unknown reasons, although certain genotypes are more susceptible.2 Cholinergic nerve conduction to striated muscle is impaired by a mechanical blockage of the binding site by antibodies and, ultimately, by destruction of the postsynaptic receptor.Patients become symptomatic once the number of ACh receptors is reduced to approximately 30% of normal. The cholinergic receptors of smooth and cardiac muscle have a different antigenicity than skeletal muscle and are not affected by the disease.The role of the thymus in the pathogenesis of myasthenia gravis is not entirely clear, but 75% of patients with myasthenia gravis have some degree of thymus abnormality (eg, hyperplasia in 85% of cases, thymoma in 15% of cases). Given the immunologic function of the thymus and the improvement in the clinical condition of patients following thymectomy, the thymus is suspected to be the site of autoantibody formation. However, the stimulus that initiates the autoimmune process has not been identified<br />
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