Objective: We present a patient with a neurodegenerative disease where visuoperceptual testing led to a new working diagnosis of corticobasal degeneration (CBD)

Background: CBD is a relatively rare neurodegenerative disease associated with diverse clinical phenotypes. In 2003, the notion emerged that CBD might present as a visuoperceptual disorder, based on 2 cases confirmed on postmortem examination [1]. The 2013 criteria [2] state that visuospatial deficits, as part of a frontospatial syndrome, represent a phenotype associated with CBD pathology. In contrast to the 2008 criteria, symmetric onset of motor symptoms is allowed in the 2013 criteria. We reported previously that visual agnosia represents a clinical feature which may facilitate the in vivo discrimination between CBD and progressive supranuclear palsy [3]. Here, we present a case in which the detection of a frontospatial syndrome lead to rejection of the working hypothesis of Primary Lateral Sclerosis (PLS) in favor of CBD.

Method: An elderly man was examined because of progressive imbalance over the last 5 years. He had increased muscle tone in the lower limbs with upgoing plantar reflexes and a pathological masseter reflex. MRI of the brain did not show abnormalities. FDG-PET demonstrated moderately reduced tracer uptake in the posterofrontal and anteroparietal cortices and subcortical asymmetry with reduced uptake thalamic and high striatal on the right. The initial working hypothesis was PLS, but phosphorylated neurofilament (heavy subunit) levels were normal. Two years later, cognitive complaints arose and neuropsychological testing was planned.

Results: Using the visual object and space perception battery (VOSP), impaired object decision was detected (13/20, Z = -1.78). He was unable to copy drawings of a cube or overlapping rectangles. CIT-Spect confirmed a symmetrical dopaminergic deficit. The working diagnosis was changed to possible CBD. During follow-up, he developed left-sided dystonia and non-fluent aphasia, also suggestive of underlying CBD.

Conclusion: We hypothesize that visuoperceptual testing represents an opportunity for early diagnosis of CBD. We have so far reported 2 cases in which the detection of visuoperceptual impairment led to a new working diagnosis of CBD. Future work should include neuropathologically validated cohort studies to document the prevalence and specificity of visuoperceptual impairment in CBD.

References: [1] Tang-Wai DF, Josephs KA, Boeve BF, Dickson DW, Parisi JE, Petersen RC. Pathologically confirmed corticobasal degeneration presenting with visuospatial dysfunction. Neurology. 2003;61(8):1134-1135. [2] Armstrong MJ, Litvan I, Lang AE, et al. Criteria for the diagnosis of corticobasal degeneration. Neurology. 2013;80(5):496-503. [3] Bergmans B, Deryck O, Bruffaerts R. Pearls & Oy-sters: Visual agnosia: An overlooked cortical sign. Neurology. 2016;87(19):e237-e238.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/visuoperceptual-impairment-a-key-feature-in-the-diagnosis-of-corticobasal-degeneration/