Abnormal head oscillations in neuro-ophthalmology and neuro-otology

The study describes the clinical phenomenology and contemporary pathophysiology of concurrent oscillations of the eyes and the head that are present in neurological conditions with diverse causes.

One classic example is spasmus nutans in which the eye oscillations are the primary cause, whereas head nodding is thought to be an operant conditional response that suppresses the eye oscillations to facilitate clear vision. The second example is a combination of head tremor and inadequate compensatory eye movements because of vestibular hypofunction leading to the illusion of pendular nystagmus - hence, the condition is called pseudonystagmus. Cerebellar degeneration in ataxia-telangiectasia or synchronized spontaneous discharge from the inferior olive and cerebellum in the syndrome of ocular palatal tremor with dystonia are examples of eye and head oscillations because of the impairment in cerebellar outflow. Infantile nystagmus syndrome also presents with eye and head oscillations, but here the relationship between the two types of oscillations differs among patients and is still unclear.

The clinical features and putative pathophysiology of diverse disorders of the eyes and head that produce unwanted oscillations are reviewed. Key clinical pearls that are essential to separate these disorders at the bedside are also emphasized.