The somatotopic organization of the facial nucleus and the distribution of the corticofacial projection in the monkey were studied by the use of retrograde and anterograde transport of horseradish peroxidase. Facial motor neurons innervating lower facial muscles were primarily found in the lateral part of the nucleus, those supplying upper facial muscles in the dorsal part of the nucleus, and those innervating the platysma and posterior auricular muscles in the medial part of the nucleus. Descending corticofacial fibers innervated the lower facial motor nuclear region bilaterally, although with contralateral predominance. The upper facial motor nuclear regions received scant direct cortical innervation on either side of the brain. Our results indicate that upper facial movement, like that at the shoulder, is relatively preserved in upper motor neuron palsy because these motor neurons receive little direct cortical input. By contrast, the lower facial muscles, like those of the hand, are more severely affected because their motor neurons normally depend upon significant cortical innervation.
The topographical organization of the contralateral cortical projections of the motor hand area was studied with autoradiographic methods in 11 macaque monkeys. Two general observations were noted in the material studied. (1) The commissural cortico-cortical connections of the motor hand area were directed to the contralateral precentral gyrus. The projections were preferentially directed to both homotopic and non-homotopic areas. (2) Focally labeled areas of motor cortex (diameter 900 micrometers) gave rise to individual terminal columns of label (diameter 600-900 micrometers). Larger areas of labeled motor cortex, (3,000 micrometers in diameter) gave rise to contralateral terminal bands of label. These bands (600-1,000 micrometers in width) were oriented in an antero-posterior direction and appeared to be formed by a sequence of adjacent labeled columns.
Radiotherapy for gliomatosis appears to stabilize or improve neurologic function in some patients. Its impact on survival will await additional reports and longer follow-up.
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