Nuclear medicine in neurological emergencies

Abstract

The observation, clinical evaluation and prognosis of coma patients is always a demanding matter and one that requires reliable diagnostic instruments capable of providing answers in real time. This evaluation is further complicated by the varying aetiology of comas of acute onset. Some of the most frequent causes of coma include: head injuries, brain tumours, cerebrovascular lesions, meningitis, encephalitis and cerebral abscesses, epilepsy (postcritical coma), exogenous intoxication, endogenous intoxication (metabolic coma, severe hydroelectrolytic imbalances), respiratory insufficiency, and cardiocirculatory insufficiency. However, irrespective of the cause of the coma, the pathophysiology of functional brain damage rests on dynamic factors whose evolution must be recognized and monitored with care. We believe that in neuroresuscitation, alongside the essential, accurate objective neurological examination and monitoring of cardiorespiratory and metabolic functions, diagnostic examinations with medical instruments are finding an increasingly important place. It is now possible to study the many aspects of cerebral pathophysiology using neurophysiological (e.g.: EEG, evoked potentials), morphological (e.g.: CT, MRI) and functional (e.g.: PET, SPECT) methods aimed at swiftly understanding events that alter the balance between the various components of the cranioencephalic system and cerebral perfusion. Alterations in cerebral perfusion can be studied using two possible categories of analysis: invasive (e.g.: measuring ICP; measuring the jugular venous saturation of oxygen, SvjO2; conventional selective angiography) and noninvasive (transcranial Doppler [TCD] and radionuclide scintigraphy of brain perfusion [SPECT]). The introduction of SPECT into clinical neuroresuscitation practice has made it possible to obtain more rapid and accurate diagnoses and make more certain prognostic judgements. The most satisfactory results have been obtained in the examination of postanoxic coma, where perfusion parameters have proved reliable for guiding therapy, and in cases of suspected brain death, where SPECT is useful in dispelling doubts in either direction. In cases of posttraumatic coma or coma caused by stroke, brain perfusion as determined by SPECT has enabled a more certain prognostic prediction. © 2006 Springer Berlin Heidelberg.