Structural and functional neuroimaging was used to examine a common denominator for the clinical triad of Gerstmann syndrome (a selective association of acalculia, finger agnosia, left-right disorientation, and agraphia) in a study at centers in Gif-sur-Yvette and Orsay, France; and University College, London, UK. None of the five neurologically healthy right-handed volunteers (1 female, 4 male, mean age 21 years) showed parietal overlap of cortical activation patterns from the 4 cognitive domains. Instead, these specific parietal activation patterns consistently connected to a small region of subcortical parietal white matter at a location congruent with the lesion in a documented case of Gerstmann's syndrome. Gerstmann's tetrad does not arise from damage to a shared cortical substrate in the left parietal lobe but from intraparietal disconnection after damage to a focal region of subcortical white matter. 
COMMENT. In children with learning disabilities, Gerstmann syndrome is found “forme fruste” more often than a complete Grundstorung tetrad, as proposed by Gerstmann (1940). The above disconnection account of Gerstmann syndrome with subcortical white matter pathology might explain the developmental form of the syndrome sometimes encountered in children with learning and attention disorders. A familial form of the syndrome is reported in an 11-year-old boy of normal intelligence who had a profound dyscalculia with lack of cardinal/ordinal skills acquisition, dysgraphia, right-left disorientation, and finger agnosia. Several male family members also had the complete syndrome complicated by dyslexia. At birth, the boy was hypotonic, his motor development was delayed, walking independently at 2 and ½ years. Examination revealed gross and fine motor incoordination and inattention. Ordinal number use was compensated for by visual and verbal memory cues but cardinal number skills did not improve.