The pathology is damage to the core of the brain including the thalamus and mamillary bodies. Its most striking clinical feature is loss of memory, which can be permanent. It is usually found in severe alcoholics, but can also result from pernicious vomiting of pregnancy (hyperemesis gravidarum), because the requirement for thiamine is much increased in pregnancy; nearly 200 cases have been reported. The cause is vitamin B1 (thiamine) deficiency. This has been available for treatment and prevention since 1936, so the occurrence of this syndrome in pregnancy should be extinct. But these cases continue to be reported – more than 50 in this century – from all over the world, including some from countries with advanced medical services; most are due to rehydration without vitamin supplements. A pregnant woman who presents in a dehydrated state due to pernicious vomiting urgently needs thiamine, as well as intravenous fluids. Vascular disorders Various vascular disorders occasionally cause psychosis, especially cerebral venous thrombosis. Puerperal women are liable to thrombosis, especially thrombophlebitis of the leg and pelvic veins; aseptic thrombi can also form in the dural venous sinuses and the cerebral veins draining into them. Most patients present with headache, vomiting, seizures and focal signs such as hemiplegia or dysphasia, but a minority of cases have a psychiatric presentation. The incidence is about 1 in 1,000 births in Europe and North America, but much higher in India, where large series have been collected. Psychosis is occasionally associated with other arterial or venous lesions: epidural anaesthesia can, if the dura is punctured, lead to leakage of cerebrospinal fluid and subdural haematoma. Arterial occlusion may be due to thrombi, amniotic fragments or air embolism. Postpartum cerebral angiopathy is a transitory arterial spasm of medium caliber cerebral arteries; it was first described in cocaine and amphetamine addicts, but can also complicate ergot and bromocriptine prescribed to inhibit lactation. Subarachnoid haemorrhage can occur after miscarriage or childbirth. All these usually present with neurological symptoms, and occasionally with delirium. Epilepsy Women with a lifelong epileptic history are liable to psychoses during pregnancy, labour and the puerperium. Women occasionally develop epilepsy for the first time in relation to their first pregnancy, and psychotic episodes have been described. There are over 30 cases in the literature. Hypopituitarism Pituitary necrosis following postpartum haemorrhage (Sheehan's syndrome) leads to failure and atrophy of the gonads, adrenal and thyroid. Chronic psychoses can supervene many years