RAISED INTRACRANIAL PRESSURE DEFINITION Raised intracranial pressure is defined as an intracranial pressure greater than 20 cm of cerebrospinal fluid. This may form part of the syndrome known as Benign Intracranial Hypertension or be due to cerebral oedema. TOXIC CAUSES Benign Intracranial Hypertension Ampicillin Lead (especially in children) Lithium Metronidazole Nalidixic Acid Nitrofurantoin Oral contraceptives Tetracycline. Vitamin A Cerebral oedema Most often secondary to cerebral hypoxia. Other toxic causes include: Cellular hypoxic damage (carbon monoxide, hydrogen sulfide) Ethylene glycol Insulin Glutethimide Methanol Oral hypoglycaemic agents. Valproic acid NON-TOXIC CAUSES Benign Intracranial Hypertension Hypovitaminosis A Idiopathic Dural sinus thrombosis Cerebral oedema Central nervous system infection Cerebrovascular accidents Head trauma Space-occupying lesions CLINICAL FEATURES Altered mental state, headache, nausea, vomiting, diplopia, blurred vision (papilloedema), blindness. In cerebral oedema, a progression of these features is seen, including loss of consciousness, systolic hypertension, bradycardia, convulsions and, in severe cases, cerebral herniation. RELEVANT INVESTIGATIONS Analytical toxicology, especially blood lead concentration. Acid-base status. Liver function tests, including prothrombin time. CT scan head. TREATMENT Furosemide 40 mg intravenously and/or mannitol 0.5 to 1 g/kg intravenously may be used to lower raised intracranial pressure. In those who require intubation, adequate ventilation and, in some cases, hyperventilation. CLINICAL COURSE AND MONITORING Vital signs Fluid and electrolyte balance Neurological status Intracranial pressure monitoring, where appropriate. Repeat CT scan of head, where appropriate. LONG-TERM COMPLICATIONS Benign intracranial hypertension may sometimes be accompanied by long-term visual impairment. In patients with cerebral oedema, the long-term outlook is that of the underlying condition. AUTHOR(S)/REVIEWERS Authors: Drs Sonia GonzÓlez and Luis C. Heuh, CIAT, Montevideo, Uruguay. Peer Review: Cardiff 9/96: L. Lubomirov, T. Meredith, A. Nantel, H. Persson, K. Venter.