Acute direct and indirect lesions of the brain stem--CT findings and their clinical evaluation.

Abstract

Since the introduction of computer tomography (CT) (Ambrose 1973, Hounsfield 1973) it has become an essential instrument in the diagnosis of acute intracranial lesions. The precise analysis of the CT and in particular the evaluation of the basal cisterns, yields results which are already wellknown, basically, from post-mortem investigations and clinical findings. However, while these were retrospective analyses and results, serial CT examinations which are free of risk for the patient and can be used in correlation with the clinical neurological findings, allow important assertions intra vitam, as well as a definitely better assessment of the prognosis. In addition to acute supratentorial lesions, acute and subacute infratentorial lesions are analysed and their clinical significance described. In this way, for the first time, the dynamics of the mechanical factors in raised intracranial pressure can be analysed. Important conclusions are drawn for the clinical management of the patients, and even some new indications for operation. Analysis of the acute hyperdense brain stem lesions--pathognomonic for haemorrhages--allows for the first time the diagnosis and continuous observation of traumatic and secondary haemorrhages caused by raised pressure, as well as spontaneous ones. As regards the mortality and morbidity, the results in this large series of traumatic and secondary haemorrhages are in striking contrast to previous analyses based on post mortem findings. Acute hypodense brain stem lesions are not amenable to any definite pathogenetic classification--softening, inflammatory lesions, tumours and oedema must all be considered. With acute lesions we are only dealing with infarcts, which are only incompletely assessable in the computer tomogram, and their diagnosis must still depend on the clinical findings. Secondary ischaemic lesions in acute raised intracranial pressure are identifiable in over 18% as infarcts which involve the entire territory of an artery. These additional space-occupying lesions are only survived by 11% of the patients. Hence the correlation which has been established between the basal cisterns and intracranial pressure is of great clinical significance. From our own research group several reports on different aspects of raised intracranial pressure and lesions of the brain stem have appeared since 1979. Similar analyses of partial aspects of the basal cisterns, have been published only recently, and came essentially to the same conclusions.