Neuroradiological emergencies: diagnosis and interventions

Neuroimaging and neuro-interventional techniques play an increasingly central role in the diagnosis management and follow-up of patients with acute neurological deficits be they due to trauma or to an underlying disease of the brain or its vessels. Clinical neuroradiology relies on the application of sometimes advances imaging techniques to explore the brain and the spine. Radiology has known a series of breakthroughs since its inception more than one hundred years ago, but the progress has been especially evident over the last two decades with the development of fast Computed Tomography (CT ) scanners, fast Magnetic Resonance Imaging (MRI) techniques capable of functional imaging and of angiography-basded neuro-interventional techniques to treat cerebrovascular diseases. This has led to continuous improvements in diagnosis, clinical work-up and in patient outcomes. These advances in imaging have been in parallel with advances in treatment and thus these two sides of radiology had fed off each other and have led to clear improvements in patient outcomes. This was most spectacular with the developments of echo-planar MR imaging and diffusion imaging which both have led to almost complete changes in imaging paradigms, since it allows both faster imaging as well as imaging of tissular microstructure. However the complexity of the techniques has also increased dramatically. This is where adapting the correct technique to the correct indication is necessary. Not only must the neuroradiologist be able to follow clinical symptoms in order to assess the technique needed but he must also be able to redirect if necessary the patient to another imaging modality that may be more adequate, faster or efficient for the diagnosis. In general CT scanning is preferred for acute situations (trauma, stroke) but MRI can be more precise in order to prepare a patient for treatment. Indeed, CT is more sensitive for blood detection and to show bone trauma and can provide perfusion imaging. However MR can provide direct multiplanar imaging with many sequences that provide different information on tissular characterization. Indeed "advanced" techniques such as diffusion weighted imaging, diffusion tensor imaging, perfusion technqies and susceptibility imaging and even spectroscopy will help in identifying and characterizing sometimes small tissular changes. Depending on the presence or absence of disease activity, contrast material can be given if needed and possible. The correct indication will help the neuroradiologist to optimize imaging modalities in order to provide the best possible diagnosis and treatment in the emergency situation. Additionally, interventional neuroradiology, relying on endovascular approaches have gained in importance due to the improved treatment modalities for both embolic stroke and intracranial aneurysms.