Lesions of the Pontine Tegmentum and Conjugate Gaze Paralysis

Abstract

Lesions in medial portions of nucleus reticularis magnocellularis (NRM) between the trochlear and abducens nuclei produced paralysis of ipsilateral conjugate horizontal gaze in monkeys. This region has been designated as the paramedian zone of the pontine reticular formation (PPRF). Gaze palsy was not produced by pontine lesions outside this region. Anatomic changes produced by the PPRF lesions were (1) loss of crossing fibers between the lesions and the midline, (2) demyelination and gliosis rostral to the lesions in the region lateral to the median longitudinal fasciculus (MLF), and (3) a loss of giant cells in NRM lateral to the lesions. These changes were probably due to destruction of neurons in the medial pontine reticular formation. The MLFs and the oculomotor and abducens nuclei appeared normal in most of these animals.