Neuromuscular disorders 1: Myopathies and Dystrophies

Last updated on Sunday, January 11 2009 by jdmiles

There is a wide array of pathology associated with nerve and muscle diseases. This section will go into categories of muscle and nerve disorders, and certain specific disorders in depth.

Try the most recent additions to this section - an overview by jdmiles of the congenital myopathies (see the text link at the bottom of this page) and a video presentation on "Denervation, Dystrophy, and Disorders of Energy Metabolism" by gliageek (see the video link, just below this description).

As always, your comments are welcome. To leave feedback, please use the comment box at the bottom of the page you're commenting on.

Enjoy.

Related videos:

Denervation, Dystrophy, and Disorders of Energy Metabolism
A video presentation on Denervation, Dystrophy, and Disorders of Energy Metabolism

Related images:

Example of trichrome stain
This is an example of a muscle specimen stained with Gomori trichrome. On trichrome, muscle typically shows up as a greenish blue (or in this case, just green). This particular muscle biopsy is an example of nemaline rod myopathy. The nemaline rods are...

Core myopathy: ATPase stain
In patients with structured cores, ATPase staining is preserved

Central core disease: Cytochrome oxidase staining
In Central Core Disease, areas devoid of oxidative enzyme staining involve most or all of the legnth of the muscle fibers

Central Core Disease: NADH
Although any of the oxidative enzyme stains will demonstrate cores, NADH staining often shows the best contrast

Centronuclear myopathy, Paraffin x200
Predominance of atrophic fibers with central nuclei (type 1 by ATPase staining)

Gomori trichrome stain: hyaline inclusions x200
Blue-green cytoplasmic inclusions typically seen in myofibrillary (Z-line related) myopathies

Gomori trichrome: Nemaline myopathy x400
Cytoplasmic aggegates of thread-like purplish inclusions composed of alpha-actinin and other proteins

NADH stain: Tubular aggregates x400
Subsarcolemmal proliferations of sarcoplasmic reticulum are best stained with NADH and may be seen in several myopathies, although classical associated with the periodic paralyses

Gomori trichrome: Tubular aggregates x400
Remniscient of mitochondrial proliferations, but don't react with SDH or COX

Tubular Aggregates H&E stain
Tubular aggregates may appear as basophilic aggregates within the cytoplasm of muscle fibers. Concentration within one region of the sarcoplasm distinguishes these aggregates from mitochondrial proliferation.

Diabetic thigh infarct x200
focal geographic necrosis of skeletal muscle, similar to, but much larger then had seen in dermatomyositis. Abundant mesenchyma proliferation gives rise to a mass lesion which may be mistaken for sarcoma.

Congenital muscular dystrophy x200
This section came from the thigh of a 6-year-old boy with a family history of muscle weakness. Although routine neuro- imaging was normal, autopsy demonstrated subtle neuronal migration defects with focal cobblestone lissencephaly, consistent with Fukayama muscular dystrophy.

Dysferlinopathy x100
This biopsy was obtained from a 45-year-old male with a 20 year history of progressive muscle weakness and a family history of similar illnesses.

Myofibrillary myopathy, H&E stained slide x 100
The myofibrillary myopathies are a somewhat confusing conglomeration of muscle diseases characterized by dissolution and aggregation predominately affecting Z-band proteins. On H&E stains focal cytoplasmic accentuations represent accumulations of these abnormally processed proteins

Necrotizing myopathy in a patient with rhabdomyolysis, H&E stained section x 400
Many patients with rhabdomyolysis demonstrate corresponding necrosis of muscle fibers on biopsy.

Ring fibers, H&E stain section
Ring fibers (also sometimes referred to as ringbinden) consist of muscle fibers where a zone of myofibrils at the periphery of the muscle fiber becomes oriented at right angles to the central axis of the muscle fiber. Although a mechanistic explanation of...

Ring fibers, NADH-TR histochemical staining
NADH-TR staining highlights cross striations within the peripheral myofibrils oriented at right angles to the long axis of the muscle fiber.

Ring fibers, trichrome staining of muscle
Ring fibers are also well visualized on trichrome staining, and manifest the same staining characteristics as the remainder of the muscle fiber.

Titinopathy, paraffin-embedded H&E stained section of muscle x 200
Titinopathy is one of the group of myofibrillary myopathies which clinically may present as isolated tibial myopathy in adults.

Mitochondrial Inclusions
Paracrystalline (parking lot) inclusions are classically seen with electron transport chain defects, though it does not distinguish among them.

Unstructured mini-core, electron micrograph
Unstructured mini-cores consist of focal areas within the muscle fiber devoid of mitochondria and normal sarcomere structure. Glycogen may be increased in these regions, as is seen in this electron micrographs

Review of the relevant anatomy

Inclusion Body Myositis

Inflammatory Myopathy

Storage diseases

Congenital Myopathies