The Kernohan-Woltman phenomenon and laterality of motor control: fresh analysis of data in the article "Incisura of the crus due to contralateral brain tumor".

In as much as Hussain et al. in their article, Brainstem ischemia in acute herniation syndrome [1], like Ritter et al. [2] in Brain stem blood flow, pupillary response and outcome in patients with severe head injuries have argued in favor of an alternative explanation (vascular, as opposed to mechanical) for the clinical findings in those with expanding hemispheric lesions, i.e. the presence of ipsilateral pyramidal signs, the following analysis of data in the Kernohan and Woltman article [3] provides fresh insight as to the physiological nature of the problem (hitherto ignored). As seen in the Fig. 7 of Kernohan andWoltman (reproduced below), whereas all of the 35 cases with supratentorial tumors had notching in the contralateral cerebral peduncle, only half of those (17 cases) where “symptomatic” (showed ipsilateral pyramidal signs). The remainder (18 cases) was “asymptomatic.” Clearly, notching of peduncles in the series by Kernohan and Woltman had nothing to do with presence of signs ipsilateral to the expanding lesion. The only alternative explanation under these circumstances would be the emergence of ipsilateral signs as a result ofwithdrawal of normal excitatory influences arising from the command center (major hemisphere) in the 17 symptomatic cases; causing physiological paralysis of the minor hemisphere and the emergence of pyramidal signs ipsilateral to the lesion (i.e. deafferentation, diaschisis, of the nondominant hemisphere). On the other hand, expanding lesions of the minor hemisphere in the asymptomatic camp did not cause ipsilateral signs (notwithstanding the presence of notching), because there are no motor communications from theminor to major hemisphere (hemisphere of action) [4–6]. This newanalysis of the unique series of Kernohan andWoltman provides for an alternative physiological explanation for variations of symptoms in similar cases mentioned by the authors [3]; without