Unilateral alpha reactivity: an electroencephalographic finding in albinism.
Persons with various forms of albinism frequently have misrouting of their optic nerve fibers. Visual evoked potential (VEP) studies can confirm this because monocular stimulation tends to result in asymmetrical rather than symmetrical occipital response. This type of decussation abnormality is associated only with albinism. In the electroencephalogram (EEG) of normal subjects, unilateral eye opening or closing does not affect the frequency, reactivity, regulation, and symmetry of alpha rhythm. In contrast, in our study, 6 of 19 persons with oculocutaneous and ocular albinism responded to unilateral eye opening with contralateral disappearance or significant attenuation of their alpha rhythm. The most likely explanation of this phenomenon is that the visual pathway misrouting is complete or nearly complete in some children with albinism so that one rather than both occipital lobes receive visual information from each eye. This type of alpha behavior, like VEP studies, supports the diagnosis of albinism, and such testing can be easily performed during a routine EEG recording.
Smith
S A
SA
Diagnostic Neurophysiology, British Columbia's Children's Hospital, Vancouver, Canada.
Wong
P K
PK
Jan
J E
JE
D000293:Adolescent; D016117:Albinism, Ocular / Q000503:physiopathology*; D016115:Albinism, Oculocutaneous / Q000503:physiopathology*; D000513:Alpha Rhythm; D002648:Child; D002675:Child, Preschool; D005074:Evoked Potentials, Visual / Q000502:physiology; D005143:Eyelids / Q000502:physiology; D006801:Humans; D007223:Infant; D014785:Vision, Ocular / Q000502:physiology