Exam 2: PNS Pt2 Flashcards
What are the two primary muscle types skeletal muscle is composed of?
Type I (slow twitch) Type II (fast twitch)
are intermixed in “checkerboard” pattern
What is the general term for primary muscle disease? How does it manifest?
myopathy; most likely to cause segmental necrosis and regeneration of ind. muscle fibers
What is the general term for secondary muscle disease due to disrupted innervation? How does it manifest?
neuropathy; cause grouped atrophy and fiber type grouping
What does the loss of normal “checkerboard” pattern of muscle fibers and the result of larger, but fewer motor units tell us?
the case of myathenia is due to Neuropathic changes
What will both neuropathies and myopathies possibly involve?
- muscle tissue atrophy
- fibrosis
- fatty replacement (fibrofatty infiltrate)
What does the presence of fibrofatty infiltrate indicate in skeletal muscle tissue disorders?
that the causative pathology is chronic
What follows prolonged disuse of skeletal muscle tissue and primarily involves atrophy of Type II muscle fibers? What are frequent causes of this?
Disuse atrophy
casting, bed rest, pareplegia or quadraplegia
What may develop in patients with elevated glucocorticoid (corticosteroid) levels
Glucocorticoid atrophy; most likely cause atrophy of type II muscle fibers (due to hypercortisolism)
What is defined by the presence of hypercorticolism that involves “wasting” (atrophy) of musculature in extremities, due to glucocorticoid atrophy?
Cushing Syndrome (typically due to corticoidsteroid meds or tumor of pit. gland = Cushing disease, or adrenal glands)
Who does Cushing syndrome characteristically affect?
young adult females
What are features of Cushing Syndrome?
- moon face
- truncal obesity and purple striae
- insomnia
- hirsutism
- “buffalo hump”
- osteoporosis
- mood swings, depression, psychosis
- menstrual abnorms, or infertility
What represents a group of related genetic disorders that interfere with productions of proteins needed to produce and maintain healthy muscle mass?
Muscular Dystrophy
What do conditions that fall under the category of Muscular Dystrophy manifest like?
progressive weakness and muscle atrophy, primarily w/in skeletal muscle tissue, but cardiac muscle tissue may also be involved
What is a form of muscular dystrophy that results from X-linked mutations in dystrophin gene (DMD gene)?
Dystrophinopathies
codes for protein Dystrophin
What does the protein dystrophin function to do?
What occurs if it is absent?
functions to stabilize muscle fibers during contraction
muscles have reduced stiffness, and are more prone to tearing, and overall stability is reduced
T/F. Dystrophinopathies cause segmental necrosis of myocytes.
true
causing creatine kinase levels in blood to rise
What may the severe atrophy ass. with Dystrophinopathies be masked by?
due to ingrowth of fibrofatty infiltrate
What are two kinds of Dystrophinopathies?
- Duchenne Muscular Dystrophy (DMD)
2. Becker Muscular Dystrophy (BMD)
What is the most common form of muscular dystrophy? How many ppl does it affect?
Duchenne Muscular Dystophy (DMD)
~1 in 3,500 males
What is Gower sign characteristic of?
Duchenne Muscular Dystrophy (DMD)
–must use upper extremity to assist in standing from a seated or squatting position (due to lower extremity and pelvic girdle weakness)
What develops from an X-linked recessive DMD mutation that causes absence of dystrophin, and is the most severe?
Duchenne Muscular Dysrophy (DMD)
absence of dystrophin causes muscle tissues to breakdown at a faster rate than can be repaired
What develops from an X-linked recessive DMD mutation that causes absence of dystrophin, and is less severe, progressing at a slower rate?
Becker Muscular Dystrophy (BMD)
-manifests in late childhood or young adulthood
T/F. Duchenne Muscular Dystrophy is a mutation that is congenital and therefore manifests at birth.
False. Yes, it is congenital mutation, but it manifests until childhood
What disorder appears in childhood and the child has an “inability to keep up with peers”, pelvic girdle weakness, and lower extremity weakness, and has calf muscle pseudohypertrophy?
Duchenne Muscular Dystrophy (DMD)
What disorder in advanced stages has shoulder girdle weakness and cardiorespiratory failure and is wheelchair-bound by adolescence?
Duchenne Muscular Dystrophy (DMD)
Is Duchenne Muscular Dystrophy (DMD) fatal? If so how?
yes, uniformily fatal by young adulthood
due to complications from cardiorespiratory failure
What are reasons for cardiorespiratory failure?
- lethal cardiomyopathy
- cardiac decompensation (mimic CHF)
- prolonged arrhymia
- pneumonia
T/F. Becker Muscular Dystrphy (BMD) is more common than Duchenne Muscular Dystrophy (DMD).
False. BMD is less common at 1 in 30,000 males
DMD is 1 in 3,500 males
Describe Toxic Myopathies.
- cause weakness, cramping, and pain
- occurs in older adults
- acute onset
- originate from intrinsic or extrinsic exposures
What is a common first manifestation of thyrotoxicosis and commonly manifest with muscle weakness?
Thyroxic myopathy
What causes most cases of thyrotoxicosis?
Graves Disease – an autoimmune reaction directed against TSH receptors
Who will most likely get Grave’s Disease?
adult females 40-60 years
What disease are these characteristics representing: goiter, fatigue, exopthalmosis, tachycardia, insomnia, unintended weight loss, pretibial myxedma, and is a Type II hypersensitivity?
Graves Disease
What type of necrosis of myocytes does Graves Disease typically produce?
segmental
What may develop following episodes of binge drinking resulting is a range of variability of mild muscle swelling to acute pain?
Ethanol myopathy (alcohol myopathy)
What is Ethanol myopathy likely to be described as a cause of, rather than its own disease?
rhabdomyolysis
What is the most severe consequence of Ethanol myopathy?
acute renal failure
What is Drug-induced Myopathy?
may develop following exposure to a variety of meds
poorly understood)–> describe as Adverse Drug Reaction (ADR
What type of features are caused by Drug-Induced myopathy?
- mild-to-severe myalgia
- mild-to-severe weakness
- maybe even rhabdomyolysis
What is a very common Drug-induced myopathy that involves:
- muscle pain, fatigue
- nocturnal cramping
- flu-like symptomes
- elevated creatine kinase levels ???
Statin myopathy
How many people in US use statin meds to reduce blood cholesterol levels? How those, how many experience ADR?
25%; ~2-5% ADR
T/F. Peripheral Nerve sheath tumors can be benign or malignant and manifest with Schwann cell differentiation, MC in adulthood.
Trrruuueee
What occurs when a growing neoplasm causes secondary injury by taking up space and displacing or impinging the surrounding tissues?
Mass effect
What are Schwannomas?
benign peripheral nerve sheath tumors, develop from transformed Schwann cells
Do Schwannomas have a familia ass?
90% are sporadic
but some occur in families with history of Neurofibromatosis Type 2
What is the most common type of Schwannoma?
vestibular schwannoma (AKA “acoustic neuroma”)
What tumor develops w/in cranium and commonly develops off vestibular portion of CN VIII?
Vestibular schwannoma (aka “acoustic neuroma)
still a PNS tumor
What will a vestibular schwannoma (acoustic neuroma) cause?
compression of CN VIII:
- hearing loss or tinnitius
- vertigo
- headache
- facial numbness or paralysis if compress CN VII
What is characterized by multiple schwannomas throughout the body and presents with numerous subcutaneous masses and multiple tumor w/in CNS?
Schwannomatosis
Schwannomatosis may cause multiple intracranial schwannomas, so what makes them different than a Schwannoma?
the lesions DO NOT develop in area of CN VIII (no vestibular involvement!!)
What is the primary symptom of Schwannomatosis?
What other symptoms can occur?
widespread and intense pain due to compression of sensory nerves
- weakness, paresthesia, and bowel or bladder problems
What are Neurofibromas?
benign nerve sheath tumors of PNS
90% are isolated tumors; but if genetic condition (Neurofibromatosis Type I) will have mult.
What type of tumor develops from a transformed nonmyelinating Schwann cell and may develop w/in dermis or in a “plexiform” location?
Neurofibromas
Where do dermal neurofibromas develop? Where do plexiform neurofibromas develop?
Dermal–> w/in an subcutaneous area and are small and round or large and disfiguring
Plexiform–> in body’s plexuses; brachial or lumbosacral plexus (more likely to cause permanent neurological damage)
Do Neurofibromas have a risk of malignant transformation?
Yes, small risk; and resulting tumor = malignant peripheral nerve sheath tumor
What is an autosomal dominant genetic disorder that develops from a mutation in NF1 gene and results in multiple cutaneous and plexiform neurofibromas?
Neurofibromatosis Type 1
NF1 = TSG
Besides the cutaneous and plexiform neurofibromas ass. with NF1, what other characteristics manifest?
- cafe-au-lait-spots
- freckles in axilla and groin
- Lisch nodules on iris of eye
When do most growths of Neurofibromatosis Type 1 appear?
childhood or adolescence and may enlarge into adulthood
T/F. Neurofibromatosis Type 1 increase risk of learning disabilities, attention deficit disordors, and seizures.
True (even though have normal intelligence)
How common is Neurofibromatosis Type 1? How does it arise?
~1 in 3,000
from inherited or sporadic NF1 mutation
About __ percent of all Neurofibromatosis Type 1 patients have a neurofibroma that transitions into cancerous mass, known as ______________
10%; malignant peripheral nerve sheath tumor
What is defined by the presence of a “bilateral vestibular schwannomas”?
Neurofibromatosis Type 2 (NF2)
T/F. Neurofibromatosis Type 2 obviously have neurofibromas due to its name.
FALSE!!!!
What develops from an autosomal dominant mutation in the Merlin gene?
Neurofibromatosis Type 2
Merlin gene = TSG
Individuals with Neurofibromatosis Type 2 have an increased risk of developing what three things?
- mulitple schwannomas
- meningiomas (CNS)
- ependymomas (CNS)
About how many people get Neurofibromatosis Type 2? How does it arise?
~1 in 50,000
1/2 inherited and 1/2 sporadic mutations to Merlin gene
What develop from transformed neurofibromas and about 1/2 of all cases occur in patients with Neurofibromatosis Type 1 (NF1)?
Malignant peripheral nerve sheath tumors
What are cancerous tumors that manifest with some degree of Schwann cell differentiation?
Malignant peripheral nerve sheath tumors
When do Malignant peripheral nerve sheath tumors develop?
adulthood
How do Malignant peripheral nerve sheath tumors manifest?
- highly anaplastic cellular appearance
- high rate of growth and infiltrate quickly
- common on extremities
- painless or painful surrounded by edema
What is a non-neoplastic reactive lesion following transsection of a peripheral nerve?
Traumatic Neuromas (aka amputation neuromas)
How do Traumatic Neuromas (aka amputation neuromas) manifest?
- peripheral neuron will try to produce axonal sprout after injuried
- sprouts “miss there target” at distal transected nerve and develop a haphazard mixture of axons, Schwann cells, and CT
After injury to a peripheral nerve, what develops following an axonal sprout “missing its target” and developing haphazard mixture of axons, Schwann cells, and CT?
Traumatic Neuromas (aka amputation neuromas)
T/F. Traumatic Neuromas are painful, but are non-invasive and have NO malignant potential
True
What is the name given to traumatic neuroma that develops b/w the 3rd and 4th metatarsal heads (of the foot)?
Morton’s Neuroma
Describe how Morton’s Neuromas manifest?
Who are they MC in?
due to location, are painful when weight-bearing– “standing on pebble, rock, or marble”
10x MC in women
