Ipsilateral hemiparesis: the forgotten history of this paradoxical neurological sign

OBJECTIVEEstablishing the neurological localization doctrine for the contralateral hemispheric control of motor functions in the second half of the 19th century, researchers faced the challenge of recognizing false localizing signs, in particular paradoxical or ipsilateral hemiparesis (IH). Despite tremendous progress in current methods of neuroradiological and electrophysiological exploration, a complete understanding of this phenomenon has yet to be attained.METHODSThe authors researched the well-described cases of hemiparesis/hemiplegia ipsilateral to an intracranial lesion published in the scientific literature in the pre-MRI era (before 1980). A comprehensive review of the physiopathological mechanisms proposed for paradoxical hemiparesis throughout this period, as well as the pathological evidence substantiating them, is provided.RESULTSA collection of 75 patients with hemiparesis/hemiplegia ipsilateral to the primary intracranial lesion reported between 1858 and 1979 were eligible for analysis. Most cases occurred in adults with supratentorial, slowly developing, extraparenchymatous mass lesions, such as neoplasms (38%) or chronic subdural hematomas (36%). Physiopathological theories proposed by the neurologists who investigated IH can be grouped into 4 major concepts: 1) lack of anatomical decussation of the corticospinal tract; 2) impaired functional activation of the contralateral hemisphere by the lesioned dominant hemisphere through the callosal connections; 3) Kernohan’s notch phenomenon, or mechanical injury of the contralateral cerebral peduncle against the free edge of the tentorium; and 4) cerebrovascular dysfunction involving the contralateral hemisphere owing to kinking and mechanical flattening of the carotid artery contralateral to the primary intracranial lesion.CONCLUSIONSIH represents a still underdiagnosed paradoxical neurological phenomenon. With the aid of modern neuroradiological and neurophysiological methods, Kernohan’s peduncle notch mechanism has been confirmed to cause IH in many of the cases reported in recent decades. Nevertheless, alternative functional and/or vascular mechanisms must be investigated further for unexplained IH cases, in particular for transitory IH without evidence of peduncle injury. The historical theories reviewed in this paper represent a conceptual framework that may be helpful for this purpose.

Does Early Bilingual Acquisition Affect Hemispheric Preferences during Simultaneous Interpretation?

Based on data from an earlier study (Lambert 1993), and on a propositional approach developed by Lemieux (1995), who refined quality of interpretation measurements sufficiently to determine a right-ear superiority at the beginning of a message and a left-ear superiority at the end of a message, the present study went one step further to examine the role played by experience, age and age of bilinguality, all possible factors influencing the hemispheric control of interpretation. Results indicated that the number of years of experience influences the quality of interpretation in that the more experienced interpreters interpreted better, regardless of ear of input. But overall results point to the possibility that hemispheric preferences for linguistic analysis might be much more under an interpreter’s voluntary control than first anticipated.