#78 - Path of Nerve and muscular disorders. Flashcards
In which type of neuropathy can a biopsy be helpful?
Mononeuropathy multiplex.
NOT distal, symmetrical polyneuropathy.
Best place to biopsy a nerve
Sural nerve -
sensory only
small patch on foot
nerve never functions again
How to diagnose hereditary peripheral neuropathies (Charcot-Maria-Tooth disease)
physical exam + nerve conduction studies
- Then, genetic testing
- no biopsy.
When looking at a muscle biopsy, what are the primary differences between neurogenic and myopathic disorders?
Neurogenic -
- atrophy only
- fiber type regrouping
Myopathic -atrophy AND hypertrophy. -necrosis -regeneration -inflamation -internally placed nuclei -fibrosis etc.
Pneumonic for remembering the characteristics of Type 1 muscle
One mighty slow fat red ox
1 = type 1, m= lots of mitochondria, slow twitch, lipid in them (fat), red meat, ox=oxidative.
Differentiate acute denervation vs. chronic denervation on a mm biopsy.
Acute denervation - angulated atrophic fibers in SMALL groups.
Chronic denervation - angulated atrophic fibers in LARGE groups.
as time goes on, motor units get bigger (more cells/neuron), then, with each neuron that dies, bigger groups of cells become atrophic.
What are the histologic characteristics of muscular dystrophy?
- myonecrosis
- regeneration
- atrophy/hypertrophy.
- endomysial fibrosis (scarring in the muscle)
- END STAGE: fatty replacement and lots of scarring.
No inflammation - differentiates from myositis.
What are the histologic characteristics of myositis? (early and late stage)
- inflammation and necrosis at the early stage
- LATE STAGE
- fibrosis
- regeneration of myocytes.
Characteristic pattern of atrophy in dermatomyositis
perifascicular necrosis, inflammation, and MHC class 1 expression..
differentiate between dermatomyositis and inclusion body myositis
inclusion body myositis has the same characteristics as dermatomyositis PLUS rimmed vacuoles (collections of lysosomes)
Spaces in between muscle cells on a cross section - diagnosis?
Glycogen storage disease - McArdle.
You stain for LAMP2 protein (lysosomal protein) in a mm biopsy and it lights up like a christmas tree. Diagnosis?
Pompe disease. (lysosomal abnormality)
What do mitochondrial myopathies look like on H&E
Ragged red fibers (proliferation of mitochondria).
What do mitochondrial myopathies look like on electron microscopy
Clumps of mitochondria outside cells
-“blocks” of crystallized protein inside mitochondria
3 categories of congenital myopathies
1-Thin filament affected - nemaline myopathy
2-Core myopathy - affects Calcium channels
3 - Centronuclear myopathy - endosomal processing affected.
nemaline myopathy
histology
blue dots in mm cells (on trichrome and H&E)
Centronuclear myopathy histology
nuclei in the middle of the mm cell
Core myopathy histology
white space in middle of muscle cells - extruded mitochondria
Becker Muscle Dystrophy immunofluorescence
Need to stain against the epitope that is
part of the deleted part of the gene. if you
stain to other parts it will look normal
major categories of peripheral nerve vs. skeletal mm pathology
Peripheral Nerve
- demyelination/remyelination
- axonal degeneration
Skeletal mm
- inflammatory myopathy
- muscular dystrophy
- congenital myopathy
- toxic/metabolic myopathy
