Frequency

No routinely-collected statistics provide data about patients in PVS because this syndrome is not recognized by the International Classification of Diseases. Information comes either from clinical series of patients in acute care facilities with traumatic or nontraumatic coma, some of whom become vegetative, and of patients with an established vegetative state in long-term care, or from planned surveys of vegetative patients in various institutions in a defined community. Estimates of the frequency of vegetative cases and of the distribution of causes vary widely according to the source of the data, and not all distinguish clearly between incidence (new cases per year) and prevalence (cases extant at any one time). A major problem is that vegetative patients are distributed in many different types of institution including acute hospitals, geriatric or young chronic sick units, mental hospitals, rehabilitation units, nursing homes and charitable care facilities. A significant number of vegetative patients are cared for at home. Of 847 vegetative children in a Californian study (1), 25% were being cared for at home, as were about half of 458 cases identified in the UK by responses to a telephone helpline following a television programme on the vegetative state in 1994. Patients at home will not be discovered by surveys of institutions.

Differences of definition are another source of variation in estimates of frequency (Tables 2.1–2.6). How long patients had to have been vegetative for inclusion in a survey has varied from 2 weeks (2) to 6 months (3).