Myoclonus and mitochondrial myopathy.

The CNS diseases that are associated with mitochondrial myopathy have been reviewed in this chapter. The disorders causing myoclonus have been compared to those in which myoclonus has been reported. Both groups have been associated with lactate and pyruvate accumulation, and both have a wide spectrum of clinical and pathologic findings. Deficiency of components of the respiratory chain has been offered as an explanation for the mitochondrial accumulation in the muscles of these patients. Skeletal muscle respiratory-chain components may be deficient, and there is experimental evidence that indicates that mitochondria will proliferate in muscle and other tissues when vital nutrients are withheld. There are two features of these patients that separate them from other patients with myoclonus. The first is the elevation of serum lactate and pyruvate due to deficient oxidative phosphorylation. The second is a pedigree that indicates maternal inheritance.