NEUROMUSCULAR DISEASES Flashcards
The multiple nuclei of each fiber, which are
oriented parallel to its longitudinal axis and may number in the thousands, lie beneath the plasma membrane (sarcolemma); hence they are termed _____
subsarcolemmal, or
sarcolemmal n u clei.
Extensions of the plasma membrane into the
fiber form the ________
which are extracellular channels of communication with
the intracellular sarcoplasmic reticulum.
transverse tubular system (T tubules),
The junctional gap between
the T tubules and SR is occupied by protein formations
that are attached to the SR and are referred to as_________ the latter have been identified as ________
and are responsible for the release of calcium from
the SR,
junctional
feet;
ryanodine receptors
The individual muscle fibers are surrounded by
delicate strands of connective tissue ___________
which provide their support and permit unity of action.
(endomysium),
In addition to motor nerve endings, muscle contains several types of sensory endings, all of them mechanoreceptors:
______ subserve the
sensation of deep pressure-pain;
_________are pressure sensors;
and the _________ are tension receptors and
participate in the maintenance of muscle tone and
reflex activity.
Free nerve endings
Ruffini and pacinian
corpuscles
Golgi tendon organs and muscle spindles
Histochemical studies of skeletal muscles have disclosed
that within any 1 muscle, there are subtle metabolic differences
between fibers, certain ones (type 1 fibers) being
_______ and
others (type 2 fibers) having the opposite distribution
richer in oxidative and poorer in glycolytic enzymes
Normal muscle is endowed with a population ofembryonic muscle precursor cells, known as ______ and, as a result, it possesses a remarkable capacity
to regenerate, a point often forgotten
satellite
cells,
After fusion of the myoblasts, a series
of cellular events including the sequential activation of myogenic transcription factors leads to ______
myofibril
formation.
At all ages, disuse of muscle decreases
fiber size by as much as _______
30 percent
_____ in which clusters of 20 to 30 fibers are all reduced in diameter to about the same extent, and random
________
group atrophy
single-fiber atrophy.
An elusive syndrome of lifelong
exercise intolerance, often accompanied by muscle cramps during exercise, has been traced in a limited number of cases to mutations in the ______
cytochrome b gene of
the mitochondrial DNA
In the ________ there is a rapid failure of contraction in the affected muscles during sustained or repetitive
activity.
myasthenic states
The opposite of the myasthenic phenomenon, an increment in power with a series of several voluntary
contractions is a feature of the ___
Lambert-Eaton myasthenic
S1Jndrome,
In both these instances there is an increase in the amplitude of compound
muscle action potentials on the nerve conduction studies obtained following brief exercise (10 to 15 sec), or at
high rates of repetitive nerve stimulation (20 to 50 Hz),
LEMS and Botolinum
In myxedema, for example, stiffness and slowness of contraction in a muscle such as the quadriceps
may be seen on change in posture _________
and by direct percussion of a muscle, and there is an
associated prolonged duration of the tendon reflexes.
(contraction myoedema)
A prolonged failure of relaxation following contraction of a muscle is characteristic of
_______
myotonia
a phenomenon easily distinguished
from the electrically silent local bulge _________ induced by tapping the muscle of a myxedematous or cachetic
patient and from the brief fascicular contraction that is induced by tapping a normal or partially denervated
muscle called _________
myoedema
idiomuscular contraction.
In _________ one observes paradoxical myotonia, which refers to an increase in the degree of myotonia during a series of contractions
paramyotonia congenita
In practice, the term _______is applied (somewhatindiscriminately as discussed previously) to all states of
fixed muscle shortening
contracture
Flexor fibrous contracture of the
arms is a prominent feature of the _____
Emery-Dreifuss form
of muscular dystrophy.
springy nature of the
resistance, coincident with increased tautness of muscle
and tendon during passive motion,
ankylosis
________is another form of fibrous contracture
that is found in newborns, involving multiple muscle
groups; it occurs in association with several diseases that
have two features in common: an onset during intrauterine
life and an alteration of the neural or muscular apparatus
that results in muscular weakness
Arthrogryposis
The_________) in children is yet
another form of fibrous contracture, presumably the
result of an unusual axial muscular dystrophy
rigid spine syndrome (RSS
_______ a common finding in otherwise
normal individuals, can be identified by the lack of muscular
weakness and atrophy and by the small-size muscle
fascicles involved and repetitive appearance in only or
regions
Benign fasciculations,
________is a less common
condition, in which there are repeated twitchings and
rippling of a muscle at rest.
Myokymia
familial (X-linked recessive) type of myalgia and cramps
associated with a deletion of the first third of the ________ which is the one implicated in Duchenne
dystrophy
dystrophin
gene,
_______ is characterized by continuous,
painful leg cramps, alopecia universalis, and diarrhea
Satoyoshi syndrome
When weakness
of the orbicularis oculi (muscles of eye closure) is
added to weakness of eye opening (levator palpebrae;
ptosis),
MG and (progressive external ophthalmoplegia [PEO]) .
_______the muscles, including the levators of
the eyelids, become paralyzed almost symmetrically over
a period of years. In most cases, this disorder is a form of
mitochondrial myopathy
In PEO,
Ptosis is variable in all of these conditions. When
present in infantile myopathic disease, it is frequently
a marker of the ______
congenital myasthenic syndromes
More severe or complete facial palsy occurs
in __________ sometimes presenting
several years before weakness of the shoulder girdle
muscles.
facioscapulohumeral dystrophy,
This is
caused by weakness of the posterior neck muscles and
of the stemocleidomastoids and other anterior neck
muscles.
Camptocormia
Several recent series have suggested that
mutations in _______ that encodes for ryanodine receptor
may be a common cause of late onset axial myopathy and
neck extensor weakness-bent spine syndrome
RYRl
Asking the patient to count
aloud on 1 maximal breath can help detect __________ (counting to 20 equates with a vital capacity of
approximately________ L)
diaphragmatic
weakness
2
ocular muscle weakness, which results in strabismus
and diplopia; with weakness of the tongue, resulting
in dysarthria; and with weakness of the masseter and
pharyngeal muscles, which interferes with chewing
and swallowin
Tri c h i n o s i s
______ is practically always present in
the peripheral blood (>700 cells /mm3), although the
sedimentation rate is often normal in trichinosis
Eosinophilia
Pathology of Trichinosis
Muscle fibers undergo segmental
necrosis, and the interstitial inflammatory infiltrates
The capsules of the larvae gradually thicken
in the ______ of the infection and then calcify
first month
Treatment of Trichinosis
In patients with severe weakness and pain, a combination
of thiabendazole, 25 to 50 mg/ kg daily in divided
doses for 5 to 10 days, and prednisone, 40 to 60 mg/d,
is recommended
Most Toxoplasma
infections in immunocompetent patients, which occur
in up to ________ percent of the population
10 to 30
Tx of Toxoplasma myopathy
Sulfadiazine in combination with
pyrimethamine or trisulfapyrimidine, which act synergistically
against the toxoplasmic trophozoites, improves
the muscle symptoms and reduces serum CK
________ may first claim the
attention of the clinical myologist because of a dramatic
pseudohypertrophy of thigh and calf muscles
cysticercosis
__________
infest the paravertebral and lumbar girdle muscles in
5 percent of cases and may lead to their enlargement
Hydatids
________ are increasingly common causes of viral myositis
HIV and human T-lymphotropic (or leukemia) virus type
I (HTLV-I)
________, a drug included in many
regimens to treat HIV infections, may itself induce a
myopathy with myalgia and weakness that is, at times,
indistinguishable from HIV myopathy
(ZVD)
________virus has been isolated
from striated muscle of a few patients with viral myopathies
group B Coxsackie
A necrotizing myositis has been suspected in a
number of patients with ______
influenza
This is an idiopathic subacute or chronic and symmetrical
weakness of proximal limb and trunk muscles without dermatitis.
Polymyositis
In Polymyositis
the majority of patients are _________years of age, and a smaller group shows a peak incidence at ___________;
women predominate in all age groups
30 to 60
15 years of age
The usual mode of onset is with mainly painless weakness of the proximal limb muscles, especially of the hips and thighs and to a lesser extent the shoulder
girdle and neck muscles
Polymyositis
The presentation of muscle weakness is similar to that of
polymyositis, but the denominative feature is a rash
DM
skin rash of DM
localized or diffuse erythema,
maculopapular eruption, scaling eczematoid dermatitis, or exfoliative dermatitis.
Red, raised papules may be present
over exposed surfaces such as the elbows, knuckles, and distal and proximal interphalangeal joints
these are particularly prominent in DM of childhood.
Gottron papules
A predominance of rash over the neck and upper shoulders has been termed the V sign,
while rash over the shoulders and upper arms, _________
This distribution suggests that the skin changes reflect heightened ______
the shawl
sign.
photosensitivity
In contrast to PM, DM affects ________ about equally
children and adults
In DM
________ has been reported in nearly onethird
of the patients and a similar number have dilated
or thrombosed nail fold capillaries.
Raynaud phenomenon
The neoplastic processes linked most often with
myositis are_______ cancer in men and ____________ cancer in women
lung and colon
breast and ovarian
A true necrotizing-
inflammatory myopathy has been reported in up
to ________of lupus erythematosus
8 percent of cases
The treatment of rheumatoid arthritis
with _______increases the incidence of, or perhaps
independently precipitates, a myositis
d-penicillamine
In the majority of patients, serum levels o f C K and other
muscle enzymes, such as _______ are elevated
aldolase,
