Vertigo is an unpleasant distortion of static gravitational orientation, or an erroneous perception of motion of either the sufferer or the environment. It is not a disease entity, but rather the outcome of many pathological or physiological processes. Vertigo is best described as a multisensory and sensorimotor syndrome with perceptual, postural, ocular motor and autonomic manifestations induced by either

– unusual and therefore unadapted (motion) stimulation of the intact sensory systems, or

– pathological (lesional) dysfunction.

Vertigo, dizziness, and disequilibrium are common complaints of patients of all ages, particularly the elderly. As presenting symptoms, they occur in 5–10% of all patients seen by general practitioners and 10–20% of all patients seen by neurologists and otolaryngologists. The clinical spectrum of vertigo is broad, extending from vestibular rotatory vertigo with nausea and vomiting to presyncope light-headedness, from drug intoxication to hypoglycemic dizziness, from visual vertigo to phobias and panic attacks, and from motion sickness to height vertigo. Appropriate preventions and treatments differ for different types of dizziness and vertigo; they include drug therapy, physical therapy, psychotherapy and surgery.

The ‘vestibular’ vertigo syndromes

Vertigo usually implies a mismatch between the vestibular, visual, and somatosensory systems. These three sensory systems subserve both static and dynamic spatial orientation, locomotion, and control of posture by constantly providing reafferent cues. The sensory information is partially redundant in that two or three senses may simultaneously provide similar information about the same action. Thanks to this overlapping of their functional ranges, it is possible for one sense to substitute, at least in part, for deficiencies in the others. When information from two sensory sources conflicts, the intensity of the vertigo is a function of the degree of mismatch; it is increased if information from an intact sensory system is lost, as for example in a patient with pathological vestibular vertigo who closes his eyes. The distressing sensorimotor consequences of the mismatch are frequently based on our earlier experiences with orientation, balance, and locomotion, i.e. there is a mismatch between the expected and the actually perceived pattern of multisensory input.

Vertigo may thus be induced by physiological stimulation of the intact sensorimotor systems (height vertigo; motion sickness) or by pathological dysfunction of any of the stabilizing sensory systems, especially the vestibular system (Table 46.1). The symptoms of vertigo include sensory qualities identified as arising from vestibular, visual, and somatosensory sources.