RESUMEN
17 cases reviewed prospectively over a period of 4 months highlight the varied appearance of blood-fluid levels in intracranial cystic lesions of different aetiologies; a finding which has not featured significantly in the medical literature. Four types of intracranial cysts demonstrating blood-fluid levels have been categorised according to the nature of the pathology, i.e. primary neoplasms of the brain, metastatic deposits to the brain in cases of extraneural malignancies, lesions of vascular aetiology and intraparenchymal bleeds secondary to trauma. The group of four primary intracranial neoplasms lists an oligodendroglioma, a recurrent tumour in a case of Von Hippel-Lindau syndrome, a Grade 3 astrocytoma and an acoustic schwannoma. Four cases of metastatic deposits to the brain were each secondary to primary malignant neoplasms of the breast, liver, ovary and lung. Of seven cases of a vascular aetiology, three resulted from arterial infarction, two from hypertension and one each from venous infarction and following anticoagulant therapy. Intracranial cysts within tumours have been postulated to occur secondary to a breakdown of the blood-brain barrier (BBB) rather than as a result of tumoural degeneration, as was thought probable earlier.