Flashcards in Neuromuscular disorders Deck (10)
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1
Motor unit components
-Anterior horn cell (LMN cell body)
-Peripheral nerve axon + myelin
-Neuromuscular junction
-Muscle
-Diseases of anterior horn cell or peripheral axon/myelin are called neurogenic
-Diseases of neuromuscular junction are called junctional d/o
-Diseases of the muscle are called myopathic d/o
2
Sx localization of lesions
-Muscle weakness distribution (proximal= more LMN, distal= more UMN)
-Presence or absence of sensory functioning, reflexes, fatigability
-Mode of spread (cranial-> limbs or vice versa)
-Presence or absence of cramps or fasiculations
3
Serum CPK
-Serum creatine-phospho kinase
-Elevated in myopathic d/o (destruction of muscle tissue)
-Normal to slightly elevated in neurogenic, normal in junctional
4
Nerve conduction
-Abnormal in neurogenic d/o
-If due to axonal degeneration, will see a normal or slightly decreased conduction velocity w/ a decrease in amplitude of evoked response
-If due to segmental demyelination will see conduction velocities greatly decreased
5
Other neuromuscular tests
-Repetitive nerve stimulation studies: abnormal in NMJ d/o (tests for muscle fatigueability or facilitation)
-Electromyographic evaluation (EMG): at rest and during effort
-Muscle or nerve biopsy: histological staining
6
Amyotrophic lateral sclerosis (ALS)
-Anterior horn cell d/o (motor neuron disease)
-Etiology is unknown
-Age of onset is in mid/later years of life
-Clinical presentation: purely motor w/ asymmetric muscle weakness (can be proximal, distal or bulbar, but usually distal)
-Usually associated w/ CST degeneration, starts at feet and progresses upwards
-There is sparing of EOMs and sphincter muscles
-Cramps and fasiculations are common initial symptoms
-Muscle atrophy w/ progression, finally respiratory and swallowing impairment
7
Guillain barre syndrome (GBS)
-Demyelinating neuropathy
-Etiology: immune mediated
-Clinical presentation: starts in lower extremities then ascends to involve the upper extremities and cranial nerve muscles
-Sx: mild sensory but predominantly motor weakness
-Autonomic Sx very common, respiration involved during rapid progression
-Blood tests that may need to be done: HIV, campylobacter, lyme disease
8
Myasthenia gravis
-NMJ d/o
-Etiology: autoimmune attack against nicotinic receptor, also associated w/ thymic abnormalities
-Age of onset: various (anytime)
-Clinical features: Sx begin in EOM and other cranial nerve muscles followed by proximal muscle weakness
-Also see fatigue ability worsened by activity
-Further Sx include ptosis, double vision, dysphagia, nasal voice, weak jaw closure and neck extensors, proximal muscle weakness and then respiratory muscle involvement
-One way to Dx is abnormal thymic tissue (hyperplasia and thymomas) on radiographs
9
Lamber-eaton myasthenia syndrome (LEMS)
-Presynaptic d/o
-Etiology: autoimmune, often secondary to neoplasm (like small cell lung cancer)
-Age of onset: mid-late years
-Clinical features: fatigue, proximal muscle weakness and autonomic dysfunction (cholinergic hypofunction)
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