A disconnection account of Gerstmann syndrome: functional neuroanatomy evidence.
OBJECTIVE
To examine the functional neuroanatomy that could account for pure Gerstmann syndrome, which is the selective association of acalculia, finger agnosia, left-right disorientation, and agraphia.


METHODS
We used structural and functional neuroimaging at high spatial resolution in healthy subjects to seek a shared cortical substrate of the Grundstörung posited by Gerstmann, ie, a common functional denominator accounting for this clinical tetrad. We construed a functional activation paradigm that mirrors each of the four clinical deficits in Gerstmann syndrome and determined cortical activation patterns. We then applied fiber tracking to diffusion tensor images and used cortical activation foci in the four functional domains as seed regions.


RESULTS
None of the subjects showed parietal overlap of cortical activation patterns from the four cognitive domains. In every subject, however, the parietal activation patterns across all four domains consistently connected to a small region of subcortical parietal white matter at a location that is congruent with the lesion in a well-documented case of pure Gerstmann syndrome.


CONCLUSIONS
Our functional neuroimaging findings are not in agreement with Gerstmann's postulate of damage to a common cognitive function underpinning clinical semiology. Our evidence from intact functional neuroanatomy suggests that pure forms of Gerstmann's tetrad do not arise from lesion to a shared cortical substrate but from intraparietal disconnection after damage to a focal region of subcortical white matter.
Rusconi
Elena
E
Institut Nationale de la Santé et de la Recherche Médicale (INSERM), Unité 562, Gif-sur-Yvette, France.
Pinel
Philippe
P
Eger
Evelyn
E
LeBihan
Denis
D
Thirion
Bertrand
B
Dehaene
Stanislas
S
Kleinschmidt
Andreas
A
D001931:Brain Mapping / Q000379:methods; D002540:Cerebral Cortex / Q000033:anatomy & histology* / Q000502:physiology* / Q000503:physiopathology; D007839:Functional Laterality / Q000502:physiology*; D005862:Gerstmann Syndrome / Q000473:pathology* / Q000503:physiopathology; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D011597:Psychomotor Performance / Q000502:physiology; D055815:Young Adult