Abnormal visual pathways in human albinos studied with visually evoked potentials

doi:10.1016/0014-4886(79)90052-9

Experimental Neurology

Volume 65, Issue 3, September 1979, Pages 667-679

https://doi.org/10.1016/0014-4886(79)90052-9 Get rights and content

Abstract

Numerous investigations in albino mammals using neurophysiological and neuroanatomical techniques report an abnormal crossing projection from the temporal retina. Recent studies in human albinos suggest a similar defect. Averaged visually evoked potentials to flashed checkerboard patterns were recorded bilaterally from the scalp overlying the occipital regions in normal and albino human subjects. Square stimulus patterns (10°) were presented to the nasal-temporal retina and hemipatterns to the nasal or temporal retina of each eye. Observations of visual fields, monocular acuities, and stereopsis were recorded. Normal left and right hemispheric responses were symmetrical to monocular nasal-temporal stimulation; in albinos the contralateral early latency responses were larger than the ipsilateral. In monocular nasal stimulation in albinos and in normals, the amplitude of contralateral evoked responses was larger than the ipsilateral; in normals the largest responses to temporal stimulation were ipsilateral. By contrast, temporal retina stimulation of albinos usually produced larger early latency components contralaterally. Temporal stimulation at 5° from the vertical meridian in albinos produced larger contralateral responses. Stimulation beyond 15° gave smaller components contralaterally; new larger amplitude components appeared ipsilaterally. At 30 and 45° eccentricity, ipsilateral responses were reduced. Albino subjects had normal monocular visual fields but failed to fuse stimuli from random dot stereograms. Results of this study provide further evidence for abnormal visual pathways and functional anomalies in human albinos.

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Cited by (38)

Visually evoked potentials
2019, Handbook of Clinical Neurology
Citation Excerpt :
In 1974, using scalp-recorded flash VEPs, four genetic forms of human oculocutaneous albinism exhibited electrophysiologic evidence of reduced uncrossed optic fibers (Creel et al., 1974). Similar results were published for human ocular albinos (Creel et al., 1978) and replicated in early studies by Taylor (1978) and Coleman et al. (1979). Reviews of research in this area include: Guillery (1974, 1996), Hoffmann et al. (2006), Neveu and Jeffery (2007), Bridge et al. (2014).
The term visually evoked potential (VEP) refers to electrical potentials recorded from scalp overlying visual cortex that have been extracted from the electroencephalogram by signal averaging. Usually the recording electrode is placed on the midline of the occipital scalp at the back of the head. VEPs are used to quantify the functional integrity of the optic nerves, pathways to the visual cortex of the brain, and occipital cortex. Any abnormality that affects the visual pathways or visual cortex in the brain can affect the VEP. Examples include slowing neuronal transmission, such as produced by myelin plaques common in multiple sclerosis, or gliomas on optic nerves in neurofibromatosis slowing the speed of the VEP wave peaks. Compression of the optic pathways, such as from hydrocephalus or from a pituitary tumor, affects the VEP. There are several methods of recording VEPs. In patients over about 3 years of age VEPs are usually recorded using a video monitor presenting patterned stimuli. In sedated patients and infants, flashes of light from a strobe flash or an array of LEDs are used to stimulate the eye. Multifocal VEPs expand the visual field topographic mapping to beyond 40 degrees of the central visual field.
Evoked Potential Analysis of Visual Pathways in Human Albinism
1994, Ophthalmology
Purpose: To explore the abnormal crossing of the retinogeniculate pathways in human albinos with visual-evoked potentials (VEPs).
Methods: The authors studied the symmetry of the topographic distribution of pattern onset/offset VEPs over the posterior part of the scalp elicited by monocular stimulation of each eye in 31 consecutive patients with different types of albinism.
Results: Twenty-one patients had asymmetric responses, with the major amplitude recorded over the lateral part of the scalp contralaterally to the stimulated eye in 14 patients and ipsilaterally in 7 patients. In two patients, the responses had a symmetric topographic distribution. In eight patients, the amplitude was so low that studying the symmetry was not possible.
Conclusions: These findings demonstrate a non-uniform pattern of asymmetry as a result of the miswiring of the visual pathways in human albinism. Moreover, the low amplitude of the VEP recorded in a consecutive series of patients shows the difficulty of the study of this phenomenon in a clinical setting.
Detection and maturation of VEP albino asymmetry: an overview and a longitudinal study from birth to 54 weeks
1992, Behavioural Brain Research
The genetic anomaly in albinism prevents adequate melanin metabolism within the fetal eye cup and stalk. This results in severe disruption of pre- and postnatal retinal development and the condition of abnormal temporal retinal projections. The obligate misrouting of retinalgeniculate-cor projections in albinism can be detected in the topographical representation across the occiput of the visual evoked potential (VEP). Age-dependent misrouting detection methods are described which yield 100% detection rates with zero false positives across the life span. By combining appropriate state-defined neonatal recording procedures with the albino infant VEP test paradigm, the presence of aberrant optic pathway projections was observed in a 5-day-old full-term infant. Maximum asymmetry was observed within a long-latency window of the response which shifted during the postpartum period to shorter latencies. Longitudinal studies show two specific latency regions of significant VEP asymmetry. The first occurs within 40–70 ms after stimulus onset and remains constant across the age range. The second, more robust, cluster of asymmetry occurs within a longer latency window and shows an age-related shift towards shorter latencies. The decreasing latency of this asymmetry is concomitant with normal maturational changes of the evoked response. These results show that VEP misrouting can be extended to reliable albino diagnosis within the neonatal period and to the assessment of visual maturation.
Albinism
1985, Survey of Ophthalmology
Albinism is the term applied to a heterogeneous group of genetically determined disorders characterized by hypopigmentation and affecting the eyes. After describing the clinical features of albinism in general, the authors discuss the various forms of oculocutaneous albinism, ocular albinism, and albinoidism that are of interest to the ophthalmologist. Emphasis is placed on the ocular features of each form. The visual pathway abnormalities and the clinical management of albinism are discussed.
Visual and auditory anomalies in Chediak-Higashi syndrome
1983, Electroencephalography and Clinical Neurophysiology
Albinism is correlated with misrouting of decussating retinal fibers in the brain. There is also evidence of anomalies of decussating auditory pathways in albinos. The Chediak-Higashi syndrome (CHS) is a rare form of partial albinism which includes increased susceptibility to infections, a hemorrhagic tendency and peripheral polyneuropathies. Binocular and monocular pattern-onset visually evoked potentials (VEPs) and monaural auditory brain stem responses (ABRs) were recorded from 4 subjects with CHS. Three of the CHS demonstrated asymmetric monocular VEPs and failed the Titmus stereovision test. All 4 CHS produced asymmetric ABRs similar to those reported for albinos. Although the hair, skin and irises are relatively well pigmented in CHS, these individuals apparently have anomalies of their central visual and auditory pathways.
L'albinisme s'accompagne d'une perturbation de la décussation des fibres rétiniennes dans le cerveau. Il existe également des données concernant des anomalies de décussation des voies auditives chez l'albinos. Le syndrome de Chediak-Higashi (SCH) est une forme rare d'albinisme partiel qui s'accompagne d'une augmentation de la sensibilité aux infections, d'une tendance aux hémorragies et de polyneuropathies périphériques. Les potentiels évoqués visuels à l'apparition d'un pattern présenté soit en monoculaire, soit en binoculaire, ainsi que les réponses auditives monaurales du tronc cérébral ont été enregistrés chez 4 sujets SCH. Trois des 4 patients ont présenté des PEV monoculaires asymétriques et n'ont pas réussi le test Titmus de Stéréovision. Les 4 sujets SCH ont développé des réponses auditives du tronc cérébral asymétriques identiques à celles déjà rapportées pour les albinos. Bien que les cheveux, la peau et l'iris soit relativement bien pigmentés chez les SCH, ces sujets présentent apparemment des anomalies dans les trajets suivis par les voies centrales visuelles et auditives.
Auditory brainstem anomalies in albino cats. I. Evoked potential studies
1983, Brain Research
The amount of melanin pigmentation in the inner ear is positively correlated with the general pigmentation of the body and specifically with the amount of pigment in the eye. The misrouting of retinofugal projections which accompanies ocular and oculocutaneous albinism has been thought to be a defect in decussation unique to the visual system. Evidence suggests that functional abnormalities may also exist in the auditory systems of albino humans and animals. To evaluate this possibility, evoked potential techniques were used to examine the functional anatomy of decussating brainstem auditory pathways in albino and pigmented cats.
Auditory brainstem responses (ABRs) were recorded from albino, pigmented, and Siamese cats using monaural stimulation. ABRs were recorded ipsilateral and contralateral to the stimulated ear. The albinos were complete tyrosinase-negative (cc), not the dominant white (W) variety associated with deafness. In pigmented cats, the amplitudes of ABRs recorded with the reference electrode ipsilateral to the stimulated ear and the ABRs recorded using the reference contralateral to the stimulated ear did not differ by more than 40% for individual components appearing between 2 and 4 ms after stimulus onset. In albino cats the components at these latencies were obliterated or greatly attenuated in the ABR recorded using the reference contralateral to the stimulated ear. These data indicate that anomalies may exist in the brainstem at the level of the acoustic striae, superior olivary nuclei and/or trapezoid body in tyrosinase-negative albino cats.

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¹: Preliminary results of this study were presented at the 60th Annual Meeting of the Federation of American Societies for Experimental Biology, Anaheim, CA, 1976.

View full text

Abnormal visual pathways in human albinos studied with visually evoked potentials

Abstract

Physiol. Behav.

Exp. Neurol.

Brain Res.

Brain Res.

Electroenceph. Clin. Neurophysiol.

Electroenceph. Clin. Neurophysiol.

Electroenceph. Clin. Neurophysiol.

A paradox in the lateralisation of the visual evoked response

Nature (London)

Visual electroencephalographic computer analysis (VECA): A new electrophysiological test for the diagnosis of optic nerve lesions

Neurology

Evoked potentials from the human scalp to visual half-field stimulation

J. Physiol. (London)

Visual system anomaly associated with albinism in the cat

Nature (London)

Retinogeniculate projections in albino and ocularly hypopigmented rats

J. Comp. Neurol.

Visual system anomalies in human ocular albinos

Science

Asymmetric visually evoked potentials in human albinos: Evidence for visual system anomalies

Invest. Opthalmol.

Visually evoked response: Use in neurologic evaluation of posttraumatic subjective visual complaints

Arch. Ophthalmol.

Human albinism: Light and electron microscopy study

Arch. Ophthalmol.

The primary optic projections in the rabbit. An experimental degeneration study

J. Comp. Neurol.