ALl-Adawi, Samir, College of Medicine, Sultan Qaboos University, P.O.Box 35, Al-Khod 123, Muscat, Sultanate of Oman. Institute of Psychiatry, Kings College, De Crespigny Park, Denmark Hill, London, UK. Regional Neurological Rehabilitation Unit, Homerton Hospital, Homerton Row, London, E9 6SR, U.K.