Skeletal Muscle / PNS Pathology Flashcards
What do degenerating vs regenerating neurons in the periphery look like?
Degeneration – Macrophages invading numerous nuclei surrouding the axons
Regeneration – Enlarged Nuclei and blue cytoplasm
What is a unique chracteristic of re-innervation of muscle fibers?
–Grouping of similar type of fibers, contrary to mixed types throughout
How can you tell neurogenic or myopathic muscle reactions?
Neurogenic – angulated fibers, nuclear clumps, NO Necrosis or inflammation
Myopathic – round fibers - central nuclei - NECROSIS
EMG can be used for testing
What syndrome causes degradation of upper and lower motor neurons that progresses over time with emotion lability?
Amyotrophic Lateral Sclerosis
What are the most common neurons affects in ALS?
- -Motor Neurons
- - Anterior Horn – atrophy of nerve roots
What is the most likely diagnosis of a 7 year old with trunkal/proximal muscle weakness, progressive dysphasia, and needing help to breath on respiratory due to the proximal weakness?
Spinal Muscular Atrophy
- -Deletion of SMN1 (Survival Motor Neuron)
- -Autosomal Recessive – two deletions required
What is the protein that maintains integrity of muscle cells from physical stress and torsion?
– Dystrophin
if missing, then any action of the muscle can induce damage
If a 9 year old male experiences progressive proximal muscle weakness, wide gait, difficulty with Gower’s maneuver, winged scapula, and elevated CK levels in serum?
Duchenne Muscular Dystrophy
- Very minimal amount of Dystrophin present
- Upregulated Utropin in muscles (to compensate)
If a 64 year old male presents with years of progressive proximal weakness, what might be a likely diagnosis?
Becker Muscular Dystrophy
–Abnormal Dystropin and reduced quantity
How are Duchenne and Becker muscular dystrophies similar?
Both are X-linked Recessive
If there is a finding of expanded CTG repeats of the DMPK gene, what might be the disorder?
Myotonic Dystrophy
–Dysfunction of the
What is the most common muscular dystrophy in adults?
Myotonic Dystrophy
- -Autodominant
- -Genetic Anticipation, more repeats pass on
What are unique exam findings with Myotonic Dystropy?
- Difficulty Releasing Grip – impaired Cl- conduction
- Distal hands and feet weakness
- Elongated face - temporal wasting
- cardiac arrthymias
How is Myotonic Dystrophy different from other dystrophies?
Myotonic – there is nothing wrong with Dystrophin
- no destruction of muscle fibers
- internal nucleation
How do mitocondrial myopathies lead to disease?
- -Due to inefficient production of ATP and then the cell is unable to function normally and oxidative damage also builds up, b/c no energy to combat them.
- -Causes degradation of the cells
What condition is associated with mitochondrial myopathy?
MELAS
Mito Myopathy, Encephalopathy, Lactic acidosis, stroke-like episodes
Why? – Not enough ATP being produced and cells become ischemic intermittently, thus reason for lactic acidosis
What are the main clinical criteria for MELAS?
Stroke-like episodes, non-vascular in origin
Encephalopathy – neurodegenerative
Lactic Acidosis, ragged red fibers
What are the most common types of glycogen storage diseases?
Myopathic Form – problem in muscles and exercise intolerance with cramps and myoglobinuria
Generalized Forms – Pompe’s Disease
–effects many organs, mostly heart - early death
What would a main histologic finding be of various tissues with Pompe’s Disease?
Vacuoles filled with glycogen-products
- pools of glycogen
Which inflammatory myopathy is associated with females, erythematous lesions over the knuckles and rash on the eyes?
Dermatomyositis
What kind of immune response is responsible for Polymyositis?
CD8+ T cells – attacking muscle fibers
- -Symmetric proximal muscle weakness
- -associated with other auto immune diseases
What is the underlying pathology for Dermatomyositis?
Microvascular being attacked by complement and antibodies
Muscle Biopsy: Perifascicular Atrophy in the muscle
(Since that part of the muscle fibers only have single blood supply, so they die, deeper have dual)
If a 56 year old male is evaluated by muscle biopsy and found to have rimmed vacuoles and tubulofilamentous inclusions, what might be a clinical symptom?
Dysphasia
–Deep finger flexor atrophy and quad atrophy
Which of the inflammatory myopathies can be found in children?
Dermatomyositis
What might happen if a patient has prolonged use of high dose steroids?
- -Proximal Muscle Weakness
- -Atrophy of Type 2B Fibers
What are the two types of peripheral nerve pathologies?
Neuronopathy – Axon degenerating back proximally
Wallerian – focal lesion degenerates distally
Where does Mononeuritis Multiplex usually affect?
Vasculitis
–Ulnar nerve – hand weakness
–Distal sciatic – foot drop
Dx – via nerve biopsy with inflammation
What are the common manifestations of Leprosy?
- Exposure to Mycobacterium leprae
- Usually coming from another country previously in their life and get it years later (incubation)
- Hypopigmented Lesions
- Neuromas
What pathology common has an “onion bulb” formation on histology?
Charcot Marie Tooth Type 1A
- -gradual myelin loss
- -autodominant PMP22 mutation/duplication
- -usually affects the LONGEST nerves
What kind of distribution is Diabetic Neuropathy?
–Sock and Glove numbness/tingling
