Mitochondrial dysfunction due to Leber's hereditary optic neuropathy as a cause of visual loss during assessment for epilepsy surgery.

Assessment for epilepsy surgery may require invasive measures such as implantation of intracranial electrodes or the Wada test. These investigations are commonly well tolerated. However, complications, including visual disturbances of various etiologies, have been reported. Here we describe two patients with pharmacoresistant temporal lobe epilepsy (TLE) who displayed loss of vision in the context of presurgical assessment and in whom mutations associated with Leber's hereditary optic neuropathy (LHON) were detected. Genetic analysis revealed in one patient the frequent mitochondrial G11778A LHON mutation in ND4. In the second patient, the mitochondrial C4640A mutation in ND2 was detected. This rare LHON mutation enhanced the sensitivity of the patient's muscle and brain tissue to amobarbital, a known blocker of the mitochondrial respiratory chain. Mitochondrial dysfunction has been reported in epilepsy. Thus, the presence of LHON mutations can be a rare cause of visual disturbances in patients with epilepsy and may have predisposed to development of epilepsy.

Electroretinographic assessment and diagnostic reappraisal of children with visual dysfunction: a prospective study.

PURPOSE: To assess the presence or absence of a retinal cause of visual impairment using electroretinography (ERG) in children with no obvious discernable cause on ocular examination. DESIGN: Prospective observational case series. MATERIALS AND METHODS: A prospective study was carried out involving 120 children with the mean age 4.4+/-3.2 years with visual dysfunction. All children underwent ERG under general anesthesia using a special handheld mini-Ganzfeld (Kurbisfeld) dome. RESULTS: Fifty-two (43.3%) children were male and 68 (56.7%) were female. The clinical diagnosis was as follows: Leber's congenital amaurosis (LCA) (n=47), achromatopsia (n=25), congenital stationary night blindness (CSNB) (n=9) and others (unclassifiable, n=39). The visual acuity ranged from perception of light (PL) to PL with projection in children with LCA. In the rest (n=73), some sort of visually guided behavior was discernable. Following ERG, a diagnostic reappraisal resulted as follows: LCA (n=49), achromatopsia (n=28), CSNB (n=4), cone-rod dystrophy (n=22), rod-cone degeneration (n=7), normal (n=8) and others (unclassifiable, n=2). Except for the two unclassifiable cases, ERG was successful in the diagnosis or exclusion of retinal dysfunction in the rest. By Pearson Chi-square test, there was a statistically significant association between the clinical and ERG diagnosis (P < 0.001). CONCLUSION: LCA was the commonest cause of visual dysfunction in our series. A statistically significant correlation between clinical and electrophysiological diagnosis was seen. ERG helped in firmly establishing the presence or absence of global retinal dysfunction in the majority (118/120) of pediatric patients with visual dysfunction.