Extraocular phenotyping of mitochondrial optic neuropathy

The presence of clinical neurophtalmologic manifestations in neurodegenerative disease of early onset such as the hereditary spastic paraplegias (HSP), spino cerebellar ataxias (SCA) or hereditary sensory motor neuropathies (HSMN) has been an inconstant element often reported in case descriptions. A more widespread and subclinical involvement of the retina and the optic nerve however is suspected in most of these conditions. Mitochondrial dysfunction is frequently recognized in the pathophysiology underlining the above mentioned neurodegenerative genetically determined conditions. Retina and the optic nerve are privileged target tissues where mitochondrial pathology is expressed. We systematically explored in a cohort of patients with early onset molecularly defined HSP, SCA or HSMN the occurrence of subclinical involvement of the visual system, with the aim of establishing its real prevalence and its correlation with functional and neuroimaging data. The definition of a typical pattern of alteration may contribute to the inclusion of neuro-ophtamological measures as sensible objective biomarkers of disease and indicators for disease severity and progression.