Postsurgical craniospinal emergencies constitute an important aspect of neuroradiology because early, accurate diagnosis forms the basis for rapid, optimally undertaken treatment and potentially improved patient outcomes. The correct interpretation of cranial and spinal imaging studies requires an extensive knowledge of the underlying pathology as well as the specific operative techniques used, making a close cooperation between neuroradiologist and neurosurgeon imperative. The imaging findings in postsurgical emergencies depend on the site of the operation, the surgical technique and the clinical status of the patient. As a general rule, the choice of the neuroradiological modality for the study of such pathology depends primarily on specific clinical indicators. For acute phase evaluations of the skull, CT remains the diagnostic technique of choice. This is both because there are no contraindications to the use of CT in patients with metal cerebral aneurysm clips or in the presence of patient support devices (as with MRI), as well as for the very short time period required for performing the examination. This being said, MRI is the most sensitive technique for use in spinal cord evaluation, in particular for the evaluation of haemorrhage, oedema and ischaemia. Nevertheless, CT and traditional radiography still play an important role in the evaluation of the spinal column itself, such as the investigation of suspected postsurgical vertebral collapse or signs and symptoms linked to the malpositioning or movement of implanted surgical spinal appliances. It should be highlighted that the diagnostic sensitivity of both CT and MR in evaluating the skull and, especially, the spinal cord, is substantially reduced by the presence of artefacts caused by the ferromagnetic materials used or implanted during surgical procedures (e.g., clips, shunt catheters, plates, screws, rods and metal residues from drilling and bone resection). In order to minimize this phenomenon, fast spin echo sequences (44-46, 54) are used in MRI; because these acquisitions are less sensitive to magnetic susceptibility than are conventional sequences, there is a consequent reduction in the artefacts induced by the ferromagnetic material. Moreover, these sequences are particularly useful for studying the spinal subarachnoid spaces and the meningeal nerve root sheaths. In this chapter, we will outline the most common postsurgical neuroradiological emergencies, discussing both those following cranial surgery and those subsequent to spinal operative procedures; emergencies secondary to hypophyseal surgery will be dealt with separately.
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