Synopsis Major clinical neurological features were seen in 13 of 25 consecutive patients with the haemolytic uraemic syndrome (HUS). Convulsions were present in 11 of these patients Hemiparesis, aphasia, coma, and decerebrate spasms were other manifestations and these were associated with a mortality of 90% compared with an overall mortality of 45%. Two case histories are given in which neurological involvement was the presenting and predominant clinical feature. Neuropathological examination showed hypoxic and/or ischaemic lesions and cerebral oedema as the most frequent changes, but did not reveal distinctive vascular lesions similar to those seen in the kidney. The diagnosis of HUS should be considered in severe acute and subacute encephalopathies of obscure origin in childhood.

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Dissecting aneurysm of the internal carotid artery, without preceding trauma, is a rare event. We have been unable to find a previous case report. One case of dissecting aneurysm of the internal carotid artery following head injury has been reported (Dratz and Woodhall, 1947), and two cases after carotid puncture for arteriography (Sirois, Lapointe, and Cote, 1954; de Grood, 1954) where the common carotid dissection extended into the internal carotid arteries. As an extension of a dissecting aneurysm of the aorta Shennan (1934) reported five cases. The following case, apart from its rarity, is of both radiological and pathological interest. Case Report A.R. (N.H. 75263), a man, 41 years of age, was admitted to the National Hospital, Queen Square, on October 16, 1957, under the care of Dr. John Marshall. The history obtained on admission was from an accompanying letter which stated that the patient had developed a right hemiparesis on the day before admission. The development of paresis was over a period of several hours. There was a past history of cystitis. At the time of admission he was conscious but unable to speak or comprehend spoken commands. His eyes were deviated to the left and he appeared to have a right homonymous hemianopia. There was a right hemiparesis with weakness of the right side of the face. The lower limb was weaker than the upper limb. Tone was increased in both upper limbs and in the right lower limb. The tendon reflexes were more active on the right. A grasp reflex was present on the left side and the plantar responses were bilaterally extensor. There was a response to pin prick on both sides. The blood pressure was 149/95 mm. Hg. No other abnormality was found on general examination.

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Morphological features of three models of portal-systemic encephalopathy in the rat were studied and compared with plasma ammonia levels and clinical observations. Carbon tetrachloride-induced cirrhosis with terminal coma produced a wide variety of structural changes in the brain whose severity was related to plasma ammonia levels at the time of death. These changes included diffuse gliosis, Alzheimer cells and focal neuronal necrosis but did not include spongiform changes in cerebral or cerebellar cortex. Porta-caval anastomosis (PCA) did not appear to produce any significant neurological symptoms. Rats with PCA of durations 1-30 weeks were studied and over this time the structural changes included astrocytic nuclear swelling, swelling of perivascular astrocytic foot-processes and spongiform change in the molecular layer of the cerebellum. No evidence of Alzheimer cells or gliosis was seen and plasma ammonia levels at no stage exceed twice the normal levels. Porta-caval anastomosis followed by gavage feeding with ammoniated cationic exchange resin produced severe neurological symptoms and marked hyperammonaemia. In these animals not only astrocytes but oligodendrocytes and neurons showed nuclear and cytoplasmic swelling and numerous Alzheimer type II cells were seen, together with a diffuse gliosis, but no evidence of spongiform change in the cerebral or cerebellar cortex was seen. It is concluded that ammonium ions are important in the genesis of morphological changes in the brain in rat models of portal-systemic encephalopathy, but the relevance of these changes to neurological dysfunction is uncertain.