A case of hereditary hemorrhagic teleangiectasia (HHT) or Rendu-Osler-Weber disease with neurological involvement is reported. The patient presented a difuse cortical dysfunction with seizures after a gastric haemorrhage disturbance. The authors could not find vascular malformations of brain or pulmonary arteriovenous fistula (PAVF), so a anoxic encephalopathy followed a shock or a microangiopatic dysfunction is postulated. The main neurological manifestations of HHT are discussed, emphasizing in the first place the role of the PAVF on the genesis of cerebral hypoxemia and brain abscess and occasionally a cerebral thrombosis caused by polycytemia and in the second place the vascular malformations of brain and spinal cord. The portal-systemic encephalopathy may also occur as a neurological complication in few cases.