Neurological Protocol

The role of the neuroradiologist in stroke cases is to provide the clinician with the maximum morphological and functional information concerning the condition of the cerebral parenchyma as is possible, as well as the condition of the intra- and extracranial brachiocephalic blood vessels. One should particularly assess whether or not there is a direct causal relationship between the craniocervical vascular pattern and the stroke, whether the lesion is ischaemic or haemorrhagic, if there are signs of other vasculopathic changes, and if the aetiologic factors responsible for the stroke are intra or extracranial.

The recent development of specific fibrinolytic treatments that can potentially reverse ischaemic injury in the early stages has changed the role of imaging in this area. It is no longer sufficient to simply distinguish is chaemic alteration from primary haemorrhage.

It is now necessary to identify cerebral ischaemia within the first few hours when treatment can be most effective. It is also important to quickly distinguish normal cerebral tissue from that which is â€œat riskâ€, and that parenchyma which is irreversibly damaged. Thus, the medical imaging investigation is now a fundamental part of planning effective emergency treatment potentially capable of preventing irreversible cerebral damage and long-term patient disability. The neuroradiologist must therefore find the optimal means of supplying the required information through both invasive and non-invasive investigative methods.
Angiography has to date been the most commonly used of the available tools to analyse the brachiocephalic vascular system directly. Less invasive methods include computed tomography (CT), ultrasound and magnetic resonance imaging (MRI), both conventional (basic morphological imaging and angiography) and functional (spectroscopy, diffusion and perfusion).

Single photon emission computed tomography (SPECT) and positron emission tomography (PET) are able to show local changes in blood flow and metabolism, respectively, both markers for cerebral damage. However, these latter methods are not commonly available, and require the injection of radioactive tracers.

In emergency situations, the cerebral investigation of choice is CT due to its non-invasiveness, the fact that it is widely available, its ease and speed of use and its relatively low cost (7). CT distinguishes between haemorrhagic and ischaemic stroke at an early stage, a factor that may be of vital importance in prognosis and treatment. If the CT is negative or incongruous in some way with the clinical picture, MRI makes possible a more detailed brain investigation to be carried out non-invasively.