Eye movement disorders and neurological symptoms in late‐onset inborn errors of metabolism

Abstract

Inborn errors of metabolism in adults are still largely unexplored. Despite the fact that adult‐onset phenotypes have been known for many years, little attention is given to these disorders in neurological practice. The adult‐onset presentation differs from childhood‐onset phenotypes, often leading to considerable diagnostic delay. The identification of these patients at the earliest stage of disease is important, given that early treatment may prevent or lessen further brain damage. Neurological and psychiatric symptoms occur more frequently in adult forms. Abnormalities of eye movements are also common and can be the presenting sign. Eye movement disorders can be classified as central or peripheral. Central forms are frequently observed in lysosomal storage disorders, whereas peripheral forms are a key feature of mitochondrial disease. Furthermore, oculogyric crisis is an important feature in disorders affecting dopamine syntheses or transport. Ocular motor disorders are often not reported by the patient, and abnormalities can be easily overlooked in a general examination. In adults with unexplained psychiatric and neurological symptoms, a special focus on examination of eye movements can serve as a relatively simple clinical tool to detect a metabolic disorder. Eye movements can be easily quantified and analyzed with video‐oculography, making them a valuable biomarker for following the natural course of disease or the response to therapies. Here, we review, for the first time, eye movement disorders that can occur in inborn errors of metabolism, with a focus on late‐onset forms. We provide a step‐by‐step overview that will help clinicians to examine and interpret eye movement disorders. © 2018 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

Eye movement disorders in inborn errors of metabolism: A quantitative analysis of 37 patients

“…Clinical examination of eye movements is not difficult, and can be performed quickly. 8,11,12 Our results showed that the type of eye movement disorder, with a few exceptions, is often not related to a specific type of IEM. Only in NP-C and Kearns-Sayre syndrome, the observed eye movement disorders are a known characteristic of the IEM.…”

“…[4][5][6] Interestingly, abnormal eye movements appear to be a frequent symptom as well, but are frequently missed as physicians do not always look for them, and patients may only complain about nonspecific symptoms, such as vertigo, imbalance, and frequent falling. 7,8 Recognition of eye movement disorders in patients is important because they may serve as an additional clue in the diagnosis of an IEM. In the literature, specific patterns of ocular motor disorders are described and linked to specific types of IEMs.…”

How to detect late-onset inborn errors of metabolism in patients with movement disorders – A modern diagnostic approach

“…Eye movement disorders are frequent in IEMs [8], but regain little attention as patients themselves do not always complain about visual disturbances. Recognition of an eye movement disorder can help to diagnose an IEM.…”

Measuring saccades in patients with Niemann-Pick type C: A comparison between video-oculography and a novel eye tracking test based on continuous psychophysics

“…Furthermore, vertical supranuclear gaze palsy (VSGP) is a key feature. It is detected in 66 % of the patients with NP-C [4] , although this might be an underestimation as it is frequently overlooked [5] .…”