Abnormal lateral geniculate nucleus and optic chiasm in human albinism

Abstract

Our objective was to measure how the misrouting of retinal ganglion cell (RGC) fibers affects the organization of the optic chiasm and lateral geniculate nuclei (LGN) in human albinism. We compared the chiasmal structures and the LGN in both pigmented controls and patients with albinism by using high-resolution structural magnetic resonance imaging (MRI). We studied 12 patients with oculocutaneous albinism and 12 age-matched pigmented controls. Using a 3T MRI scanner, we acquired a T1 -weighted three-dimensional magnetization-prepared rapid gradient-echo (MPRAGE) image of the whole brain, oriented so that the optic nerves, chiasm, and tracts were in the same plane. We acquired multiple proton density-weighted images centered on the thalamus and midbrain, and averaged them to increase the signal, enabling precise manual tracing of the anatomical boundaries of the LGN. Albinism patients exhibited significantly smaller diameters of the optic nerves, chiasm and tracts, and optic chiasm and LGN volume compared with controls (P < 0.001 for all). The reductions in chiasmal diameters in the albinism compared with the control group can be attributed to the abnormal crossing of optic fibers and the reduction of RGCs in the central retina. The volume of the LGN devoted to the center of the visual field may be reduced in albinism due to fewer RGCs representing the area where the fovea would normally lie. Our data may be clinically useful in addressing how genetic deficits compromise proper structural and functional development in the brain.

Aberrant visual pathway development in albinism: From retina to cortex

“…The post orbital visual pathway was studied using high‐resolution T1‐weighted MRI imaging to measure cisternal optic nerves, chiasm, optic tracts and V1 cortical thickness. Our aim was to confirm previous reports regarding altered morphology of these structures in PWA (Schmitz et al, ; Bridge et al, ; Mcketton et al, ).…”

“…It had been hypothesised by the authors of these earlier studies that the finding of smaller optic nerves, chiasm and tract in albinism could be due to the underdevelopment of the fovea (Von dem Hagen et al, ; Mcketton et al, ). Although we did not see any relationship between foveal development and the physical size of the chiasm, our DTI data shows significant relationship between foveal development and number of streamlines crossing the chiasm.…”

“…We have previous shown that reduced RGC numbers shown in animal studies translates to thinner peripapillary nerve fibre layer (ppRNFL) thickness (Mohammad et al, 2015). This in turn leads to smaller optic nerves and chiasm which have been demonstrated in persons with albinism (PWA) using magnetic resonance imaging (MRI) (Schmitz et al, 2003;Mcketton, Kelly, & Schneider, 2014).…”

A Japanese Family With Autosomal Dominant Oculocutaneous Albinism Type 4

“…34 These anomalies are likely to be the direct result of decreased ganglion cell numbers in the central retina in albino patients. 33,34 In the present study, the OCT findings showed a significant reduction in the GCC thickness in the temporal parafovea in patients with foveal hypoplasia. In general, the development of the foveal pit occurs from 24 weeks of gestation and reaches adult conformation by 15 months postpartum.…”

“…5,30 Many other morphologic anomalies have been reported in the visual pathway of patients with albinism, such as reduced central retinal ganglion cell (RGC) numbers, 31 optic nerves and chiasms of smaller diameter, 32 and decreased lateral geniculate nuclei numbers 33 and gray matter volume at the occipital cortex. 34 These anomalies are likely to be the direct result of decreased ganglion cell numbers in the central retina in albino patients.…”