Eye-Head Movements

This chapter reviews the relationship between ocular motor and cephalomotor systems, summarizing mechanical properties of head and neck tissues, head stability, and the roles of the cervico-ocular reflex (COR), vestibulo-collic reflex (VCR), and cervico-collic reflex. Visual consequences of head translation, and motion parallax, are discussed. Behavioral properties of eye-head saccades and smooth eye-head tracking are summarized along with their interactions with the vestibulo-ocular reflex (VOR). The neural substrate for rapid and smooth eye-head movements is discussed including the nucleus reticularis gigantocellularis, superior colliculus, cerebellar vermis and fastigial nucleus. Mathematical models for eye-head behavior are presented. Clinical and laboratory evaluation of eye-head movements are outlined, with geometric corrections required during measurement of eye and head movements. Discussion of the pathophysiology of abnormal eye-head movements includes vestibular hypofunction, progressive supranuclear palsy, spasmodic torticollis (cervical dystonia), spasmus nutans, epilepsy, ocular motor apraxia, and abnormal smooth eye-head tracking in parkinsonian syndromes and cerebellar disorders.