Syndrome of the third frontal convolution: Léon Ectors´ legacy on paradoxical ipsilateral hemiparesis

Since the crossed control of sensitive-motor body functions by the contralateral cerebral hemispheres was recognized in the early 18th century, clinicians have been baffled by patients developing a motor deficit involving the extremities on the same side as an intracranial lesion. In the first third of the 20th century, three main hypotheses were proposed to explain this so-called ipsilateral or paradoxical hemiparesis: (1) the absence of decussation of the corticospinal tracts; (2) diaschisis, or blocking of the normal input to a brain region anatomically distant from the injured site; and (3) compression of the contralateral cerebral peduncle against the tentorial border, also known as the Kernohan-Woltman notch phenomenon. Here, we deal with the less widely known contributions of the Belgian neurosurgeon Léon Ectors, who included this paradoxical deficit within a neurological syndrome he considered highly specific for an early diagnosis of those meningiomas growing over the third frontal convolution. The present manuscript includes a systematic review of the cases of ipsilateral hemiparesis secondary to intracranial masses reported in ancient and modern scientific medical literature. We also address in-depth the physiopathological theories accounting for this syndrome and contrast them with Léon Ectors' observations.