Clinical and Diffusion Tensor MRI Findings in Congenital Homonymous Hemianopia

Mapping degeneration of the visual system in long-term follow-up after childhood hemispherectomy - A series of four cases

OBJECTIVE

Although hemidisconnection surgery may eliminate or reduce seizure activity in patients with epilepsy, there are visual, cognitive and motor deficits which affect patients' function post-operatively, with varying severity and according to pathology. Consequently, there is a need to map microstructural changes over long time periods and develop/apply methods that work with legacy data.

METHODS

In this study, we applied the novel single shell 3-Tissue method to data from a cohort of 4 patients who were scanned 20-years following childhood hemidisconnection surgery and presented with variable clinical outcomes. We have successfully reconstructed tractography of the whole visual pathway from single shell diffusion data with reduced number of gradient directions.

RESULTS

All patients presented with degeneration of the visual system characterised by low fractional anisotropy and high mean diffusivity. There were no apparent microstructural differences between both optic nerves that could explain the different level of visual function across patients. However, we provide evidence suggesting an association between the level of visual function and DTI metrics within the remaining components of the visual system, particularly the optic tract, of the contralateral hemisphere post-surgery.

SIGNIFICANCE

We believe this study suggests that diffusion MRI can be used to monitor the integrity of the visual system following hemispherectomy and if extended to larger cohorts and a greater number of time-points, including pre-surgically, can provide a clearer picture of the natural history of visual system degeneration. This knowledge may in turn help to identify patients at greatest risk of poor visual outcomes that might benefit from rehabilitation therapies.

Congenital geniculate quadruple sectoranopia with occipital heterotopia

Purpose

To report a case of congenital geniculate quadruple sectoranopia associated with occipital heterotopia.

Observations

A 51-year-old healthy woman was incidentally found to have a left incongruous quadruple sectoranopia. Analysis of the macular ganglion cell complex (GCC) revealed homonymous hemianopic thinning of the inner layer of the retina. Brain magnetic resonance imaging (MRI) showed congenital occipital heterotopia, characterized by hypertrophy of the right parahippocampal gyrus, lingual gyrus, and isthmus of the cingulate gyrus, with shrinkage of the white matter. In addition, serial coronal images on a short tau inversion recovery (STIR) sequence demonstrated an atrophic right optic tract.

Conclusion and importance

Congenital geniculate quadruple sectoranopia is extremely rare and may be caused by congenital occipital heterotopia.