source: Ronald G. Haller, MD

Muscle histochemistry is performed on skeletal muscle biopsies and is a primary method used to help diagnose neuromuscular disorders. The muscle specimen is rapidly frozen as soon as possible after the biopsy in isopentane or Freon-22, which has been precooled in liquid nitrogen to prevent enzyme loss and structural artifacts.

A large number of histological, histochemical (enzymatic), and immunocytochemical stains can be performed on a muscle specimen which has been kept frozen and cut in a cryostat transversely into very thin, consecutive slices or sections (6-10 um) onto a glass slide. Each stain has its own staining characteristics for normal and abnormal skeletal muscle. Different histochemical stains can identify structural and enzymatic changes or abnormalities within individual muscle fibers. When these variously stained sections of a muscle biopsy are viewed in a microscope, they reveal a wide variety of colors, structures, and organelles in the muscle tissue and cells (muscle fibers). These results demonstrate either normal or abnormal structures and staining results, whose characteristics help diagnose specific neuromuscular disorders.

Specific enzyme deficiencies in skeletal muscle can be demonstrated by the absence of color in stained muscle cells. Histochemical stains for cytochrome c oxidase, myophosphorylase, phophofructokinase, myoadenylate deaminase, and succinate dehydrogenase are some of the stains used to reveal enzyme deficiencies in muscle from people with glycolytic or oxidative metabolic disorders.