We have presented a patient with a relatively rare syndrome of alexia without agraphia, which occurs as a consequence of vascular lesion in the left medial occipitotemporal gyrus and splenium of corpus callosum (Figures 1, 2 and 3) with abnormalities in the visual field (right sided homonymous hemianopsia),
visual agnosia and anomia for colors, objects and numbers [2, 7], with all modalities of writing preserved.
KBS should be kept in mind in the differential diagnosis of patients who present with
visual agnosia, hypersexuality, emotional behavioral changes, hyperorality or hypermetamorphosis.
Whereas
visual agnosia causes patients to be unable to recognise stimuli, visual anomia (also referred to as optic aphasia), (17) is a condition in which patients are incapable of naming objects due to damaged connections between the visual and language centres of the brain.
In the neuropsychological evaluation, severe cognitive deficits were found: apperceptive
visual agnosia, spatial agnosia, constructional apraxia, ideomotor apraxia and a significant alteration in coding and recovery of verbal episodic memory.
In order to compare the specificity of the effect of degraded visual perception on visual memory, we included a second group of four control subjects (mean age = 12.25, SD = 1.26) with unilateral early-onset brain lesions, normal general cognitive abilities, and no evidence of
visual agnosia (neurological controls).
Patient assessments: Patients' cognitive function was assessed using the MMSE [11], the Abbreviated Mental Test Score (AMTS) [13] and by a selection of tests from the CAMCOG component of the CAMDEX [8], including those examining praxis and
visual agnosia. From these data it was possible to generate objectively measured sub-scores for variables that paralleled the above five domains of cognitive function (see Appendix).
has it two/four/six legs?) by patients with
visual agnosia (Riddoch & Humphreys, 1987; Warrington, 1975).
When asked what they see, one answers, "Image on a computer, horizontal lines." The other ventures, "Spot of color." When the doctor adds the sound of waves to the film, however, they both exclaim, "It's the sea." These men suffer from profound
visual agnosia - a glove, a rose, a loved one are no longer recognizable to them.
Table 1 General symptoms resulting from stroke * Headaches * Mental confusion, disorientation and memory deficits * Aphasia * Agnosia * Apraxia * Seizures * Vertigo * Dysarthria * Incontinence * Hemiplegia or hemiparesis * Perceptual defects Table 2 Common vision impairments resulting from stroke * Strabismus * Gaze palsy * Nystagmus * Diplopia * Lagophthalmos * Dry eye * Visual acuity reduction * Visual field defects * Unilateral neglect * Visual midline shift *
Visual agnosia * Cortical blindness * Photophobia * Contrast sensitivity impairment * Visual hallucinations * Light and dark adaptation impairment
Farah,
Visual Agnosia, MIT Press, Cambridge, UK, 1990.
They cover vascular cognitive development; cognitive and behavioral disorders according to stroke site and side; motor and gestural disorders; aphasic, arthric, calculation, and auditory disorders; hemineglect, Anton-Babinski, and right hemisphere syndromes;
visual agnosia and Balint syndrome; executive and memory disorders; behavioral and mood disorders; and dementia and the management of vascular cognitive impairment.
All this suggests that Dennis'
visual agnosia results from damage to his stored perceptual knowledge of what objects look like and what colour they should normally be.
