Mitochondrial encephalomyopathies (MEMP) are
rare diseases caused by a disturbance of the mitochondrial chain of respiration. This prevents
pyruvate from being completely integrated into the
tricarboxylic acid (Krebs') cycle, and hence there is an accumulation of
lactate. Histologically this is marked by the appearance of "ragged red fibres" in the light microscope which, in the electron microscope, are eventually recognised as typical accumulations of pathological mitochondria. The clinical pattern can vary greatly and ranges from
ophthalmoplegia via mainly myopathic to encephalopathic forms. The pattern of signs and symptoms enables subclassification into three main syndromes (10): The
Kearns-Sayre syndrome (KSS), "
myoclonus epilepsy with ragged red fibres
syndrome" (MERRF) and "
mitochondrial myopathy,
encephalopathy,
lactic acidosis and strokelike episodes
syndrome" (MELAS). Intermediate types, however, are frequent. Furthermore, quite a large number of other syndromes such as the "Toni-Fanconi-Debré syndrome" can be classified among the group of
mitochondrial encephalomyopathies.--The patient must be classified as a risk patient. Disturbances of cardiac conduction may require a transient or permanent pacemaker. Increase in
oxygen requirement must be avoided to prevent increase in
lactate levels and development of
lactate acidosis. The severity of the
myopathy makes it necessary to exercise caution in the use of
benzodiazepines and long-term relaxants. When using local anaesthetics one should consider both their negative dromotropism and the resulting reduction of the epileptic threshold. There is a relative
contraindication for spinal and epidural anaesthesia.(ABSTRACT TRUNCATED AT 250 WORDS)