A piece of muscle, about 2cm x 1cm x 0.5cm is usually taken from the thigh, or from the shoulder, under either general or local anaesthetic. The tissue sample is divided up into smaller pieces and each is treated differently depending on the type of investigation it is to be used for.
Muscle biopsies are performed as part of the investigation of a clinically suspected neuromuscular disorder when other less invasive tests have not provided a firm diagnosis. This is the most useful and reliable way of diagnosing a number of neuromuscular conditions.
Skeletal muscle can undergo a variety of structural changes in the diseased state. Some of these alterations are clearly visible by the light microscope, but others are more subtle, involving subcellular structures (organelles), and examination at much higher magnification is required to determine their nature and extent.
The electron microscopist must be aware of the normal structure of the tissue under examination, and also, more importantly, must be aware of the range in normal appearance.
Skeletal muscle is made up of bundles of fibres (called fascicles) which are bound together by connective tissue. Under the electron microscope individual fibres can be closely examined. In turn, fibres consist of fibrils which are regularly aligned along the length of each muscle fibre. Fibrils are made up of fine filaments which have a maximum diameter of 20nm. (100,000 nm in 1mm)