Objective: To describe mirrored-self misidentification (MSM) occurring in corticobasal syndrome (CBS) without early dementia

Background: CBS is a neurodegenerative syndrome characterized by asymmetric parkinsonism and cortical dysfunction including apraxia, alien limb phenomenon, and cortical sensory deficits. Neuropsychiatric manifestations are increasingly recognized in atypical parkinsonism, but delusional misidentification syndromes remain rarely reported in CBS. MSM is characterized by failure to recognize one’s own reflection despite preserved understanding of mirror function and has been mainly described in Alzheimer disease and dementia with Lewy Bodies.

Method: Clinical and neuroimaging data were retrospectively reviewed from a patient followed in a referral center for movement disorders in Brazil.

Results: A 60-year-old woman developed progressive asymmetric motor impairment affecting the left upper limb. Over the following years she evolved with rigid-akinetic parkinsonism, myoclonus, ideomotor and ideational apraxia, cortical sensory deficits, hemispatial neglect, and alien limb phenomenon. Seven years after disease onset, she developed failure to recognize her own reflection, reporting that the person in the mirror was someone else, although she retained intellectual awareness of mirror function. The symptom produced significant emotional distress and required environmental adaptation. Serial cognitive assessments demonstrated predominant executive, visuospatial, and language impairment with relatively preserved episodic memory in early stages. Brain magnetic resonance imaging revealed progressive asymmetric frontoparietal cortical atrophy, more pronounced in the right hemisphere. Parkinsonian symptoms showed partial response to levodopa.

Conclusion: This case highlights MSM as a rare neuropsychiatric manifestation of CBS occurring even without early dementia. Right parietal dysfunction may disrupt neural networks involved in visuospatial processing, body representation, and self-recognition, leading to dissociation between perceptual processing and personal identity attribution. Recognition of such phenomena may broaden the clinical spectrum of CBS and provide insight into the neural basis of self-recognition.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/mirrored-self-misidentification-expands-the-neuropsychiatric-spectrum-of-corticobasal-syndrome/