We investigated the correlations of deletions of mitochondrial DNA in skeletal muscle with clinical manifestations of mitochondrial myopathies, a group of disorders defined either by biochemical abnormalities of mitochondria or by morphologic changes causing a ragged red appearance of the muscle fibers histochemically. We performed genomic Southern blot analysis of muscle mitochondrial DNA from 123 patients with different mitochondrial myopathies or encephalomyopathies. Deletions were found in the mitochondrial DNA of 32 patients, all of whom had progressive external ophthalmoplegia. Some patients had only ocular myopathy, whereas others had Kearns-Sayre syndrome, a multisystem disorder characterized by ophthalmoplegia, pigmentary retinopathy, heart block, and cerebellar ataxia. The deletions ranged in size from 1.3 to 7.6 kilobases and were mapped to different sites in the mitochondrial DNA, but an identical 4.9-kilobase deletion was found in the same location in 11 patients. Biochemical analysis showed decreased activities of NADH dehydrogenase, rotenone-sensitive NADH-cytochrome c reductase, succinate-cytochrome c reductase, and cytochrome c oxidase, four enzymes of the mitochondrial respiratory chain containing subunits encoded by mitochondrial DNA. We conclude that deletions of muscle mitochondrial DNA are associated with ophthalmoplegia and may result in impaired mitochondrial function. However, the precise relation between clinical and biochemical phenotypes and deletions remains to be defined.

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Results of this study modified our approach in patients with TLE. Interictal epileptiform discharges localized to one temporal lobe on serial routine EEGs or during LTM may be adequate to identify the epileptogenic zone in patients with MRI-identified unilateral medial temporal lobe atrophy.

Summary:Purpose: To determine if using more stringent criteria for cryptogenic Lennox-Gastaut syndrome (LGS) would result in an improved prognosis for that group. Cryptogenic, symptomatic, and non-cryptogenic LGS patients without etiology (indeterminate) were compared with respect to seizure and cognitive outcome.Methods: Retrospective chart review was performed on 245 patients seen at the Mayo Clinic Rochester from 1976 to 1997, with a diagnosis of either LGS or slow spike wave on EEG.LGS was confirmed in 107 (64 male, 43 female) patients. This group was divided into cryptogenic, symptomatic, and indeterminate groups containing 23,47, and 37 patients, respectively. In this study, cryptogenic patients all had normal development before onset of LGS, absence of dysmorphic features, normal neurologic examination, and normal magnetic resonance (MRI) brain imaging. Of the 107 patients, 74 had 2 3 years of follow-up. Results:LGS onset in the 107 patients occurred at a median age of 4.0 years (range, 0.6-28.9 years). When last seen, 63% of those with symptomatic LGS had more than three seizures a day compared with 50% of cryptogenic and 34% of indeterminate patients. The most common seizure types were tonic (77%), atypical absence (61 %), and generalized tonic-clonic (56%). Only three patients, all part of the indeterminate group, were seizure free at last follow-up.Conclusions: Using stringent criteria in defining the cryptogenic subgroup resulted in no significant difference in seizure outcome. Individuals with a normal cognitive outcome did not segregate into one etiologic subgroup, but did have LGS onset at an older age.