Progressive cortical visual failure associated with occipital calcification and coeliac disease with relative preservation of the dorsal ‘action’ pathway

Abstract

We describe the first reported case of a patient with coeliac disease and cerebral occipital calcification who shows a progressive and seemingly selective failure to recognise visual stimuli. This decline was tracked over a study period of 22 years and occurred in the absence of primary sensory or widespread intellectual impairment. Subsequent tests revealed that although the patient was unable to use shape and contour information to visually identify objects, she was nevertheless able to use this information to reach, grasp and manipulate objects under central, immediate vision. This preservation of visuo-motor control was echoed in her day-to-day ability to navigate and live at home independently. We conclude that occipital calcification following coeliac disease can lead to prominent higher visual failure that, under prescribed viewing conditions, is consistent with separable mechanisms for visual perception and action control.

Introduction

Some cases of coeliac disease are associated with bilateral occipital calcification (BOC). All such cases reported have manifested as occipital epilepsy (Gobbi, 2005, Gobbi et al., 1992). We describe below a case of coeliac disease who shows occipital calcification that is indistinguishable from that found for cases of epilepsy, but who developed a gradually progressive cortical visual disorder. We are unaware of any reports of cortical visual failure in such patients. A prominent feature of the visual loss was the preservation of visual processing for ‘action’, as originally defined by Goodale and Milner (1992).

Paroxysmal visual disturbances have been reported in some patients with BOC, but the symptoms are short-term, non-progressive in severity or type and usually involve low-level sensory disturbances such as flashing lights, spots, blurriness or brief stereotyped complex visual hallucinations due to occipital epilepsy (Pfaender et al., 2004). No reports of progressive and selective loss of higher visual function have been identified, indeed there have been no reports of visual impairment of any kind in this group of patients until very recently when a patient who presented with epilepsy but who was left with a static defect following treatment of the coeliac disease was highlighted (Millington, James-Galton, Barbur, Plant, & Bridge, in press). By contrast, patients with structural lesions to the occipital lobe usually present with a homonymous visual field defect; a complete or partial visual field loss in the contralateral half of the visual field of each eye. The visual field loss may be clinically total but there may be residual vision such as blindsight or the Riddoch phenomenon (see Weiskrantz, 1997). Less commonly after an occipital lesion, positive symptoms arise which may be epileptic but also include the filling-in of scotomas, palinopsia, cerebral polyopia and release hallucinations (see Fraser, Newman, & Biousse, 2011). Although often present in cases of visual agnosia and optic ataxia, occipital lesions by themselves have yet to be shown to be sufficient for either condition to occur (see Barton, 2011).

The present case of BOC is especially intriguing because the visual failure is most prominent for processes involving perception, while those involving action are relatively preserved. Numerous lines of evidence suggest that visual perceptual and action processes dissociate, at least to some extent, in the human brain (see Goodale, 2014). That is to say, the mechanisms underlying object identification are partly distinct from those underlying object reaching, grasping and manipulation. Some of the most compelling evidence has come from patients who, following brain injury, show evidence under particular viewing conditions of disordered object recognition in the absence of optic ataxia. Perhaps the most well-known case is that of DF (Milner et al., 1991) who, following carbon monoxide poisoning, could not recognise objects but nevertheless was able to reach out, grab and manipulate them in a manner indicative of spared shape and size processing. Only two other patients have been sufficiently characterised as to show a similar dissociation (patient SB – Dijkerman, Lê, Démont, & Milner, 2004; patient JS – Karnath, Rüter, Mandler, & Himmelbach, 2009). However, a handful of other patients have presented with a clearly documented visual form agnosia that, although not formally assessed, seemed to be unaccompanied by visuo-motor disorder (Adler, 1944, Barton et al., 2004, Benson and Greenberg, 1968, Campion and Latto, 1985, Landis et al., 1982). In all these patients, the dissociation emerged suddenly from an acquired brain injury and, in all but one case, involved lesions that extended beyond occipital-temporal cortex. In the current case, it emerged very gradually in the absence of insult and was accompanied by a circumscribed pattern of cortical calcification in lateral-occipital cortex. Below we report the changing profile of the patient's visual function over a period of 22 years. The studies conducted have been clinical in nature so focused on what she cannot do rather than what she can, so tend to involve recognition and matching tasks.