Charcot's erroneous double-semidecussation scheme for the retinocortical visual pathways.

Jean-Martin Charcot, often lauded for his seminal contributions, is seldom critiqued for his blunders. One such blunder was his double-semidecussation scheme for the retinocortical visual pathways, proposed in 1875 to explain, on neuroanatomic grounds, cases of hysteria that manifest hysterical amblyopia accompanied with ipsilateral hemianaesthesia. Charcot's scheme was inconsistent with the older, broadly correct scheme of Prussian ophthalmologist Albrecht von Gräfe. Charcot failed to perform clinicopathologic correlation studies. His analysis relied on a series of mistaken conclusions he made in conjunction with Swiss-French ophthalmologist Edmund Landolt: (1) only an optic tract lesion could produce a homonymous hemianopsia; (2) cerebral lesions, if they ever produced homonymous hemianopsia, did so by secondary effects (e.g. pressure) on the optic tracts; and (3) damage to the cortical projections from the lateral geniculate produces a crossed amblyopia. Challenges to Charcot's theory came from within France by 1880. By 1882, Charcot recognized that his scheme was erroneous, and he approved a thesis by his pupil Charles Féré that reverted to Gräfe's scheme with an ill-conceived modification to accommodate Charcot's concept of hysterical cerebral amblyopia. A critique by American neurologist Moses Starr in 1884 argued for Gräfe's scheme and refuted Charcot's erroneous scheme and its subsequent derivatives.