To the Editor:

I read the above captioned paper in the April issue of Neurosurgery1 and have the following comments. It appears that the respected authors have ignored recent understandings concerning the laterality of motor control as it relates to ipsilateral innervation of the nondominant side of the body.2-5 They seem to have remained captive to a sense of history writing regarding the paradox of ipsilateral paralysis. I hope, however, that the following paper and pencil exercise will help acquaint the authors with the modern physiological understanding of the phenomenon they sought to explain. Thus, holding a pencil in each hand, they will draw two lines by moving the hands apart, while staying on the page at all times. The test is best done with the eyes closed. Invariably, they will draw a longer and straighter line with their neurally dominant hand. The line drawn by the nondominant hand will be a shorter and wavier one. As documented elsewhere,2-5 the above described asymmetry of performance reflects direct connectivity of the dominant hand with the command center located in the major hemisphere (left, in vast majority of right handers) whereas as the nondominant hand's performance is marred by its further distance from the command structure by a callosal length as well as the distortion imposed by the additional synaptic transmissions, prior to activation of the minor hemisphere for implementing the command issued by the major.1-3 As a clinical neurologist, it is unclear to me why neuroscientists familiar with the classical paper of Kernohan and Woltman7 have always ignored the fact that only 17 of their 35 patients with supratentorial lesions had ipsilateral pyramidal signs, whereas all 35 had peduncular notching contralateral to their space-occupying lesions (ie, exactly 50% of them displayed pyramidal signs in the limbs situated directly beneath the major hemisphere).5 The finding of bimanual simultaneous drawing tests described above provides a verifiable answer to that question based on presence of directionality in callosal traffic2-5 (underpinning the lateralities of motor and sensory control).

One important corollary of the above circuitry is that the minor hemisphere, as a slave microprocessor of the major hemisphere, is incapable of initiating epilepsy.6

Disclosure

The author has no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.

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