June5 M1-NMJ and Muscle Flashcards Preview

Bloc H - Movement > June5 M1-NMJ and Muscle > Flashcards

Flashcards in June5 M1-NMJ and Muscle Deck (19)
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1
Q

NMJ injury: charact of the typical things you look at for UMN vs LMN (weakness, atrophy, fasciculations, reflexes, tone + sensory involvement also)

A
  • weakness has fatigue component (get even weaker with use)
  • NO atrophy
  • NO hyporeflexia
  • NO fasciculations
  • NO sensory involvement
2
Q

muscle injury: charact of the typical things you look at for UMN vs LMN (weakness, atrophy, fasciculations, reflexes, tone + sensory involvement also)

A
  • weakness is proximal
  • ATROPHY
  • NO fasciculations
  • NO hyporeflexia
  • NO sensory involvement
3
Q

clinical case 1 of kid with proximal leg weakness (hip muscles), difficulty running, difficulty standing, falls and trips easily: what will you find on physical exam if muscle problem

A
  • proximal weakness
  • atrophy (thigh muscles). NMJ = no atrophy
  • normal muscle tone
  • normal reflexes (NO hyporeflexia)
  • negative Babinski
  • NO fasciculations
  • NO sensory involvement (normal sensation)
4
Q

clinical case 1: muscle atrophy indicates what

A

LMN involvement

+ NMJ problem less likely

5
Q

clinical case 1: normal sensation indicates what

A

injury to root and nerves less likely (AHC still possible bc gives no sensory involvement)

6
Q

clinical case 1: no fasciculations and normal reflexes indicate what

A

injury to AHC, root and nerves is less likely

7
Q

clinical case 1: proximal weakness indicates what (points to what)

A

think of myopathy

8
Q

clinical case 1 DMD (Duchenne muscular dystrophy) cause

A
  • mutation in gene for dystrophin
  • dystrophin is a protein that connects cytoskeleton (contractile) elements of the muscle cell to the cell membrane. (the cell membrane is connected to ECM via other proteins)
9
Q

ddx for myopathies like case 1

A
  • muscular dystrophies (inherited)
  • inflammatory myopathies (dermatomyositis, polymyositis, inclusion-body myositis, etc.)
  • toxic myopathies (medications like statins or steroids OR thyroid disease
  • other hereditatory myopathies (metabolic like disorders of glycogen or fatty acid metabolsim, mitochondrial myopathies)
10
Q

some common toxic myopathies

A
  • steroid myopathy (proximal weakness)
  • statin myopathy (from mild myopathy to muscle aches and pain to fulminant necrotizing inflammatory myopathy)
  • hyper CK(creatine kinase)-emia
11
Q

important questions in history and things to check when suspect a myopathy (muscle as cause of weakness and LMN problem)

A
  • ask if difficulty standing up, going up stairs, getting into car, combing hair (proximal weakness)
  • look for muscle atrophy
  • think of medication induced myopathy
12
Q

symptoms typical of an NMJ disorder

A
  • fatiguable weakness. with a repetitive movement
  • NO atrophy
  • NO fasiculation
  • NO hyporeflexia
  • NO sensory involvement
13
Q

clinical case 2: diplopia (see double) that resolves if cover one eye, symptoms worse in the evening, right eyelid droops and more at the end of the day: what makes you think of an NMJ problem?

A
  • fatiguable weakness (gets worse at the end of the day)

- repetitive movement (muscles in eye lids)

14
Q

different diseases of the NMJ

A
  • Lambert-Eaton myasthenic syndrome (disease of Ca channels)
  • botulism (Abs to proteins that dock vesicles so never released)
  • myashtenia gravis (Abs to AchR)
  • congenital (genetic) myasthenic syndromes
  • anaesthesia (succinylcholine blocked the AchR)
15
Q

myasthenia gravis (most well defined autoimmune disease) charact

A
  • Abs to nAchR
  • remove Ab = heals
  • inject Ab = disease
  • plausible mechanism = AchR-like Ags found in the thymus
  • associated with thymomas and thymic hyperplasia
  • presence of other Abs, which explains seronegative patients (without AchR Abs)
16
Q

myasthenia gravis typical presentation

A
  • starts with bulbar (head) symptoms: ptosis (drooling eyelid) and diplopia, fatigue
  • can be very focal (dysphagia, head drop)
  • no pain
  • no sensory involvement (bc NMJ)
  • possible respiratory muscle weakness
17
Q

one quick trick to dx myasthenia gravis

A

ice pack test. cold temperature improves neuromuscular transmission. wait a bit and see if improves the diplopia and ptosis

18
Q

botulism charact

A

-cause = 5 diff toxins produced by clostridium botulinum
-affect pre-synaptoc protein (whereas MG post synaptic) so muscarinic and nicotinic AchR synapses both affected so autonomic symptoms too
-

19
Q

what could this be?: clinical case 3: woke up double vision, bilateral ptosis later in the day, next day nausea and vomiting, slurred speech, difficulty swallowing. exam = see these things + severe opthalmoplegia, unreactive pupils, bilateral facial weakness, severe weakness of shoulder and hip girdle muscles. normal distal strength, diminished reflexes, normal sensation

A

botulism
(think NMJ bc weakness, no sensory involvement and many muscle groups in diff places affected) botulism bc quick onset.
-note: hyporeflexia not characteristic of NMJ problem.
-note: proximal weakness typical of muscle prob