Electrophysiolocal findings in Mohr-Tranebjærg syndrome / Alterações eletrofisiológicas na síndrome de Mohr-Tranebjærg

Mohr-Tranebjærg syndrome (MTS) is an X-liked recessive rare syndrome also known as deafness-dystonia syndrome. The severity of the symptoms may vary, but they progress usually to severe deafness and dystonia and sometimes they are accompanied by cortical deterioration of vision and mental deterioration. The purpose of this paper is to illustrate a very interesting case of Mohr-Tranebjærg syndrome. A 24-year-old italian man with Mohr-Tranebjærg syndrome underwent full field electroretinography (ERG) and visual evoked potentials (VEPs). Fundus examination showed apparently normal retina with pallor of the optic disc. Pattern reversal VEP and flash VEP responses were non-recordable. ERG showed amplitude reduction of the fotopic, scotopic and 30 Hz flicker responses revealing generalized retinal dysfunction with reduction of cone and rod responses. The progressive neurodegeneration in Mohr-Tranebjærg syndrome can be also associated with a retinal degeneration.

A síndrome de Mohr-Tranebjærg é rara, com herança recessiva ligada ao X, conhecida também como síndrome da surdez-distonia. A intensidade dos sintomas pode variar e normalmente, evoluem para uma surdez profunda e a distonia, algumas vezes, vem acompanhados por deterioração visual e mental. O objetivo deste trabalho é ilustrar um caso muito interessante dessa doença. Um homem, italiano, de 24 anos, com a síndrome de Mohr-Tranebjærg, foi submetido ao exame de eletrorretinografia de campo total (ERG) e ao exame de potencial evocado visual (PEV) (padrão e flash). No exame do fundo do olho era presente uma palidez do nervo óptico com retina, aparentemente, sem alterações. No exame do eletrorretinografia de campo total ERG detectou-se redução das amplitudes das respostas fotópicas, escotópicas e ao flicker de 30 Hz, demonstrando uma disfunção generalizada da retina, com redução da função dos cones e bastonetes. A progressiva neurodegeneração da síndrome de Mohr-Tranebjærg pode ser também associada à degeneração da retina.

Alterações eletrofisiológicas na doença de Oguchi / Electrophysiological findings in Oguchi disease

Descrever as alterações eletrofuncionais em um caso raríssimo da Doença de Oguchi. Paciente do sexo feminino, italiana de 17 anos de idade se queixava de cegueira noturna. A resposta escotópica de bastonetes, do ERG era não registrável. A resposta escotópica ao estímulo branco forte demonstrava uma diminuição de amplitude da onda B. As respostas ao flicker de 30Hz e ao EOG eram dentro dos limites da normalidade. Era presente o fenômeno de Mizuo-Nakamura. Os exames eletrofuncionais são muito importantes no diagnóstico de certeza da doença de Oguchi. É nítida, no presente caso, a discordância entre EOG e ERG. Considerando a função dos bastonetes, as respostas normais do EOG contrastam com a ausência de respostas dos bastonetes em condições escotópicas no ERG. Mais estudos são necessários para entender o complexo mecanismo eletrofuncional dessa doença e melhor definir a origem dos componentes sensíveis à luz do EOG...

To describe the electrophysiological alterations in a very rare case of Oguchi's disease. A 17-year-old italian girl complaining of night blindness underwent complete ophthalmological exams, including electrophysiological tests. Rod responses were nondetectable in full-field electroretinogram (ERG). The photopic ERG funtions, including the 30 Hz flicker ERG response was normal, while the scotopic b-wave was diminished in amplitude. The electrooculography (EOG) ratios within the normal range were 208% in the right eye and 222% in the left eye. The Mizuo-Nakamura phenomenon was present. The electrophysiological tests are important tools in Oguchi's disease diagnosis. In the present case, it's clear the non correspondance between EOG and ERG. Considering the rod function, the normal EOG ratio contrast with non-detectable rod ERG responses. More studies are necessary to understand the compless electrofuntional mecanism of the disease helping to understand the origin of the light-sensitive component of the EOG...

Visual evoked potential importance in the complex mechanism of amblyopia.

To compare the visual evoked potential (VEP) responses of amblyopic eyes with VEP responses of sound eyes in amblyopic children. A study of 65 amblyopic children with pattern-reversal VEPs elicited by checkerboard stimuli with large, medium and small checks. The children were classified into three groups: Group A, 22 children with anisometropic amblyopia; Group B, 16 children with exotropic strabismic amblyopia; and Group C, 27 children with esotropic strabismic amblyopia. Visual acuity (VA) was significantly worse in the amblyopic eye as compared to the sound eye. However, no statistically significant difference was found between the amblyopic and sound eye of amblyopic children in the three groups for VEP P1 amplitude and latencies for any check sizes. VEP is a very important tool in understanding the complex amblyopic mechanism. Although the sound eye has superior VA, the absence of differences in VEP P1 amplitudes and latencies demonstrate the functional abnormality of the eye considered 'good'. More studies are necessary to explain why the sound eye in amblyopic children cannot be considered completely normal. Special attention should therefore be paid to amblyopic treatment, as patching can have a negative effect on the sound eye.