MR demonstration of leukoencephalopathy associated with mitochondrial encephalomyopathy: case report.

The mitochondrial encephalomyopathies are a heteroge­ neous group of disorders characterized by mitochondrial dys­ function that produce multisystem symptoms. This disorder affects both the central and peripheral nervous systems, skeletal muscles, heart, endocrine glands, gastrointestinal tract, hematopoietic system, and kidneys (Table 1) (1). Pa­ tients with mitochondrial encephalomyopathy can be divided into two large groups (1). In the first group, severe mitochon­ drial dysfunction results in patients who are usually quite ill at birth, who deteriorate rapidly, and who die soon thereafter. Included in this group of mitochondrial disorders are Alper, Canavan, Leigh, Menke, and Zellweger syndromes. In the second group of patients the individual appears normal at birth, with progressive neurologic deficits developing later. Included in this group are Kearns-Sayre syndrome (KSS); mitochondrial encephalomyopathy, lactic acidosis, and strokelike episodes (the MELAS syndrome); and myoclonic epilepsy with ragged red fibers (MERRF). Clinically, patients in this latter group commonly present with progressive exter­ nal ophthalmoplegia plus abnormalities in one or more of the other systems. The diagnosis can be established by muscle biopsy, which characteristically shows ragged red fibers with the Gomori trichrome stain, reflecting abnormal accumulation of mitochondria in the muscle fibers (2). Most of the literature on mitochondrial encephalomyopathy discusses the clinical, pathologic, genetic, and biochemical abnormalities associated with this disorder. A limited number of articles describe the neuroradiologic manifestations of mi­ tochondrial encephalomyopathy (3-13). We report a patient with mitochondrial encephalomyopathy in whom the CNS abnormalities are characterized by increased signal in the white matter on T2-weighted MR images. Because of the rarity, complexity, and varied clinical manifestations of mito­ chondrial encephalomyopathy, this article will not only discuss the radiologic features of this disorder but also will review the clinical features and provide pertinent background information on the biochemical and genetic aspects.