The clinical features of albinism and their correlation with visual evoked potentials

Abstract

Aim: To investigate the relation between the clinical and electrophysiological abnormalities of patients undergoing visual evoked potential investigation for albinism. Methods: 40 subjects with a probable or possible clinical diagnosis of albinism underwent pattern appearance and/or flash visual evoked potential (VEP) examination. The VEP findings are correlated with the clinical features of albinism determined by clinical examination and orthoptic assessment. Results: The majority of patients with clinical evidence of albinism showed a contralateral predominance in the VEPs. There was close correlation between the clinical signs of albinism and the degree of contralateral VEP predominance. This manifested as an interhemispheric latency asymmetry to monocular pattern appearance stimulation but amplitude asymmetry to flash stimulation. The strongest correlation for pattern appearance interhemispheric latency difference was with foveal hypoplasia (rho = 0.58; p = 0.0003) followed by nystagmus (rho = 0.48; p = 0.0027) and iris transillumination (rho = 0.33; p = 0.039). The VEP abnormalities were of greater magnitude in those patients with most features of albinism. Several patients with apparently mild disorders of ocular pigmentation had small but significantly abnormal VEP latency asymmetries. Conclusion: There is a strong association between the magnitude of the interhemispheric latency asymmetry of the pattern appearance VEP, and of amplitude asymmetry of the flash VEP, with the clinical signs of albinism. The data are consistent with a spectrum of abnormalities in albinism involving both clinical expression and electrophysiological misrouting, which is wider than previously recognised.

Detection of Visual Activation in the Rat Brain Using 2-deoxy-2-[18F]fluoro-d-glucose and Statistical Parametric Mapping (SPM)

“…Moreover, albino specimens show a larger crossed pathway than uncrossed pathway, thus favoring a better visualization of the visual pathway by FDG-PET imaging [23][24][25].…”

Electrophysiological assessment of optic nerve disease

“…Not all patients display all signs, and recent work points to albinism being a spectrum of disease rather than an 'all or nothing' phenomenon. 67 Although the diagnosis is not usually difficult in oculocutaneous albinism, the absence of cutaneous signs in ocular albinism does not facilitate diagnosis. However, the albinoid misrouting present in both forms may readily be demonstrated by VEP recording using multiple channel VEP recording from multiple posteriorly situated electrodes.…”

“…However, the albinoid misrouting present in both forms may readily be demonstrated by VEP recording using multiple channel VEP recording from multiple posteriorly situated electrodes. 67,68 (see Figure 4). In adults, the abnormality is best demonstrated using a pattern appearance stimulus; in younger patients a diffuse flash stimulus is effective.…”

“…In adults, the abnormality is best demonstrated using a pattern appearance stimulus; in younger patients a diffuse flash stimulus is effective. 67,69 Indeed, it has recently been reported that there are dynamic changes occurring in the intracranial visual pathways of albinos such that flash VEPs normalise with age, but the pattern appearance VEPs become more abnormal with advancing years. 70 Other optic nerve disorders Toxic or nutritional optic nerve dysfunction manifests the expected electrophysiological abnormalities.…”

Light response differences in the superior colliculus of albino and pigmented rats

“…Albinos show a reduced number of rod photoreceptors and chiasmal misrouting (uncrossed pathway is reduced relative to the crossed pathway) [5,11,17]. These abnormalities may be explained in terms of disturbed neurogenesis consequent to the melanin deficiency.…”