Gerstmanns syndrome: Where does it come from and what does that tell us?

Josef Gerstmann was first to describe patients with a selective association of finger agnosia, left-right confusion, acalculia and agraphia. Traditionally, the syndrome he introduced has been taken to indicate left parietal lobe damage, but intraoperative electrostimulation studies have failed to generate all four symptoms from a single site in the parietal cortex. On the basis of recent functional and structural neuroimaging results in healthy adults, we propose that the selective association of symptoms in pure Gerstmanns syndrome could instead be explained by a white matter lesion at a very specific location that results in intraparietal disconnection. This result has implications for our understanding of lesion-induced cognitive dysfunction. It suggests expanding the classical concept of disconnection from disruption along a single long-distance fiber tract to situations where a conjoint disruption of separate fiber tracts determines the clinical syndrome. Such situations will arise only if a lesion affects the specific location where these separate fiber tracts happen to touch or cross each other. Given the complexity of fiber pathways in the brain, it is obvious that this mechanism can account for the huge variability in how different symptoms group together in individual patients. © 2011 Future Medicine Ltd.