Visual, ocular motor, and cochleo-vestibular loss in patients with heteroplasmic, mater nally-inherited diabetes mellitus and deafness (MIDD), 3243 transfer RNA mutation

Background: Mitochondrial encephalopathy, lactic acidosis, and stroke-like symptoms (MELAS) and MIDD (maternallyinherited diabetes mellitus and deafness) are caused by A3243G transfer RNA mutations that affect mitochondrial function. Hearing loss and early onset diabetes mellitus constitute the main MIDD phenotype. Regarding the ophthalmologic manifestations of MIDD, we hypothesized that decreased vestibulo-ocular reflex (VOR) gain in patients with MIDD may contribute to impaired dynamic visual acuity. Methods: Neuro-ophthalmologic, neuroimaging, and neurootologic evaluations were performed in 2 nonrelated patients with MIDD who complained of oscillopsia with head movement. We obtained quantitative recording of the horizontal and the vertical VOR, using the video head impulse test device. Results: In the 2 patients, we detected visual, ocular motor, and vestibular abnormalities. Decreased VOR gain in the planes of all 3 semicircular canals and impaired dynamic visual acuity was demonstrated in both cases. Conclusions: MIDD patients are primarily recognized by their advanced hearing loss or deafness, early onset diabetes mellitus, and lactic acidosis. Decreased vision in these patients relates primarily to peri-macular retinal atrophy. In addition, loss of vestibular function causes poor dynamic visual acuity. Both patients, in their late fifties, had evidence of progressive central and peripheral nervous system dysfunction.