Flashcards in Muscle & Nerve Path Deck (33):
Peripheral causes of numbness
2. peripheral entrapment neuropathy
4. Brachial plexus lesions
Can nerves store energy?
Not very much - so much has good circulation to meet the high metabolic demand
spontaneous contraction of de-innervated muscle fibers
spontaneous discharge of a motor unit due to irritation or damage
Amyotrophic lateral sclerosis (ALS)
degeneration of anterior horn cells and upper motor neurons - many genetic factors (SOD is most common mutation)
lower motor neuron symptoms
atrophy, fasciculations, decr. reflexes
upper motor neuron symptoms
spasticity, incr. reflexes, upgoing toes
Primary lateral sclerosis
like ALS but only affects lower motor neurons and has better prognosis (10+ yrs)
ALS disease progression
starts unilaterally and spreads to both sides in months, survival is 3-5 yrs, death due to respiratory weakness and infection
Tx for ALS
nothing good. Riluzole can delay progression slightly
3 patterns of peripheral neuropathy
Characteristics of mononeuropathy
often due to trauma causing nerve entrapment, presents with paresthesias when the region is tapped (Tinel sign)
Causes of radiculopathy
1. intervertebral disc herniation (young)
2. degenerative changes (older)
Characteristics of radiculopathy
symptoms follow a well defined pathway, symptoms often caused by stretching or pinching when coughing, sneezing..etc. Usually not a lot of sensory loss bc of degree of overlap with other nerves.
diffuse peripheral nerve damage
What is the most common cause of polyneuropathy?
Diabetes (after that many things can cause it - nutritional deficiencies (B12), infections, toxins, metabolic issues, inflammation...etc).
What is Guillain-Barre?
autoimmune syndrome following infectious disease that presents with acute, rapid severe weakeness (polyneuropathy)
condition caused by decr. blood flow to nerves or an autoimmune destruction of axon or myelin that can happen most commonly with diabetes in the lumbar plexus. causes decr. patellar reflex
autoimmune disease against nicotinic receptors at the NMJ. leads to ptosis, diplopia, weakness with sustained or repetitive use of the muscle
myasthenic syndrome that may be associated with carcinoma - defective Ca channel leads to hip girdle weakness that progresses. weakness improves with exercise (facilitation)
What virus can produce impairment of the NMJ?
C. Botulinum with Botulinum toxin (binds synaptobrevin and blocks Ach release)
Classic presentation of myopathies
symmetrical, proximal muscle weakness and incr. muscle enzymes (CK levels). must biopsy to be sure.
What are 3 categories of myopathies that cause muscle cell destruction?
1. Muscular dystrophies
2. Metabolic Myopathies
3. Inflammatory Myopathy
What are muscular dystrophies?
noninflammatory degenerative conditions of muscle (ex. Duchenne, Becker, facioscapulohumoral, limb-girdle, oculopharyngeal, & myotonic dystrophies)
Duchenne and Becker Dystrophies
X-linked recessive disorder due to mutated dystrophin
Duchenne - presents in boys in childhood (kids never run) - death in 20's due to cardiomyopathy
Becker's - milder version of Duchenne
What are metabolic myopathies?
Myopathies due to thyroid disease, meds, toxins, mitochondrial myopathies - present with exercise intolerance or cramping
What is polymyositis?
inflammatory myopathy characterized by insidious, symmetrical onset of proximal weakness in 30-60 yr olds
What is dermatomyositis?
polymyositis presentation + red/purple rash (esp over eyelids and joints) - high association with lymphoma and other cancers
What is inclusion body myositis?
It is a slowly progressing inflammatory myopathy that often present distally in hands.
What are two categories of diseases that cause functional deficits in muscles (channelopathies)?
1. myotonic disorders (2 types - distal and proximal)
2. periodic paralysis
What is the difference between congenital myotonia and paramyotonia congenita?
congenital myotonia - sx improve with exercise
paramyotonia congenital - sx worsen with exercise
Limb Girdle Dystrophy
Muscual dystrophy that can be caused by many different mutations that progresses slowly and can stop altogether - present in adolescence or early adulthood