Cortical sensory loss (also called tactile agnosia) is a core feature of corticobasal syndrome (CBS) that results from dysfunction in the somatosensory [cortex](/brain-regions/cortex) and associated cortical networks. This sensory deficit is a hallmark of cortical involvement and helps differentiate CBS from other movement disorders.
Clinical Presentation
Core Features
Tactile Agnosia
Inability to recognize objects by touch despite intact primary sensation
Patient can detect touch, pressure, temperature, but not identify objects
Tested by asking patient to identify common objects with eyes closed
Astereognosis
Inability to recognize object shape/form by touch
Cannot identify letters drawn on palm
Common in CBS due to parietal cortex involvement
Graphesthesia
Inability to recognize symbols drawn on skin
Deficit in spatial and tactile integration
Two-Point Discrimination Impairment
Requires larger distances to distinguish two points
Reflects cortical rather than peripheral dysfunction
Pattern and Distribution
Asymmetric: Strongly correlates with the affected hemisphere
Contralateral: Affects side opposite to cortical pathology
Upper limb predominance: Hands most commonly affected
Progressive: Typically worsens over time
Prevalence
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Cortical Sensory Loss in Corticobasal Syndrome
Overview
Cortical sensory loss (also called tactile agnosia) is a core feature of corticobasal syndrome (CBS) that results from dysfunction in the somatosensory [cortex](/brain-regions/cortex) and associated cortical networks. This sensory deficit is a hallmark of cortical involvement and helps differentiate CBS from other movement disorders.
Clinical Presentation
Core Features
Tactile Agnosia
Inability to recognize objects by touch despite intact primary sensation
Patient can detect touch, pressure, temperature, but not identify objects
Tested by asking patient to identify common objects with eyes closed
Astereognosis
Inability to recognize object shape/form by touch
Cannot identify letters drawn on palm
Common in CBS due to parietal cortex involvement
Graphesthesia
Inability to recognize symbols drawn on skin
Deficit in spatial and tactile integration
Two-Point Discrimination Impairment
Requires larger distances to distinguish two points
Reflects cortical rather than peripheral dysfunction
Pattern and Distribution
Asymmetric: Strongly correlates with the affected hemisphere
Contralateral: Affects side opposite to cortical pathology
Upper limb predominance: Hands most commonly affected
Progressive: Typically worsens over time
Prevalence
50-70% of CBS patients develop cortical sensory loss
30-40% present with sensory complaints as early feature
Strong predictor of CBS vs PSP (rare in PSP)
More common than in other atypical parkinsonian disorders