Psychotic disorder in which symptoms occur in episodes, with intervening periods in which the mental powers are also in decline. The patient’s train of thought is difficult to follow, particularly because nonexistent words are sometimes used as if they were common currency (’neologisms’). Consciousness is undisturbed, and the mood is not strikingly impaired, but certain ideas and delusions exert excessive influence: the patient is under the influence of other human beings, ‘rays’, poisons, and so on. Behaviour can be bizarre, with loss of decorum, hallucinations, and ceaseless, pointless, pseudo-scientific rumination on large and all-embracing topics. The illness is preceded by personality disorders, and the patient has often functioned below par for years. The process usually begins between the ages of 15 and 30, sometimes gradually, sometimes abruptly. Personality declines, contact with the patient is more difficult and he or she withdraws increasingly into his own world. It is not possible to distinguish the condition from other forms of psychosis, or to indicate a cause, hence the decline in use of the term schizophrenia. Instead symptoms are named and treated using neuroleptics, often without high hopes of curing the root cause. Sciatica Severe stabbing and radiating pain in one leg caused by irritation of or pressure on the sciatic nerve, the large nerve that runs from the base of the spine and down the back of the leg. The pain radiates from the buttock to the upper rear section of the leg, the back of the knee, the outer side of the lower leg and the foot. Pain increases if the leg is bent or the hip flexed. The most usual cause is a slipped disc, in which part of the nerve is trapped. In older patients arthrosis of the vertebrae can reduce the nerve apertures in the spinal column, which also causes sciatica. Less common causes are pressure on the nerve by tumours in the spinal column or abdomen, inflammation of the nerve or damage to it from a poorly executed injection into, or a fall onto, the buttocks. Disc disorders can cause bilateral sciatica (affecting both legs). Radiating abdominal pain may not be due to a constricted nerve, but to muscular pain or pain caused by a hip disorder.