• Illustration by Rob Flewell, CMI.
    File Size: 688 KB
    Neuro-Ophthalmology/Orbit

    Anatomical scheme for the synthesis of signals for horizontal eye movements. From the horizontal semicircular canal, primary afferents of the vestibular nerve (CN VIII) project mainly to neurons of the vestibular nerve nucleus (CN VIII nucleus), which then send an excitatory connection to the contralateral abducens nucleus (CN VI nucleus). CN VI innervates the ipsilateral lateral rectus muscle and the contralateral oculomotor nerve nucleus (CN III nucleus) via the medial longitudinal fasciculus (MLF). Horizontal saccades are generated in the frontal eye field, which activates the contralateral PPRF. Burst neurons in the PPRF stimulate the ipsilateral abducens nucleus, with the subsequent pathway identical to that subserving horizontal vestibular-generated eye movements. Some neurons in the PPRF project to the nucleus prepositus hypoglossi (NPH) (the neural integrator) and then to the abducens nucleus.