Aggressive haemangiomas are rare, but knowledge of their imaging features and treatment strategies enhances the radiologist's role in their management.

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ABSTRACT. Extracranial epidural emphysema is an uncommon phenomenon that refers to the presence of gas within the epidural space. As an isolated finding, it is typically benign, but it can be a secondary sign of more ominous disease processes, such as pneumothorax, pneumoperitoneum and epidural abscess. Although the phenomenon has been cited in case reports, a comprehensive review of this topic is lacking in the radiology literature. The authors' aim is to report our experience with extracranial epidural emphysema, illustrating the spectrum of its clinical presentation. We also review the aetiology, pathophysiology, diagnosis and management of extracranial epidural emphysema. Pneumorrhachis (also known as aerorachia) is a term that has been used to describe air within the spinal canal. It can be separated into two distinct entities, epidural and intradural. In general, the presence of intradural intraspinal air has been associated with significant morbidity, while the presence of epidural air is typically more benign [1]. Epidural air within the spinal canal is best descriptively termed extracranial epidural emphysema and has been described sporadically in case reports. The purpose of this pictorial review is to present a diversity of clinical scenarios that can give rise to extracranial epidural emphysema and to discuss its pathophysiology, diagnosis and management. Methods and materialsA comprehensive literature search was conducted on the MEDLINE database using PubMed. Keywords including pneumorrhachis, pneumosaccus, aerorachia, intraspinal pneumocele, pneumomyelogram, epidural emphysema and epidural pneumatosis were used in the literature search. In addition to a review of the literature, four cases of extracranial epidural emphysema collected at our institution are also reported. They illustrate the common pathways of extracranial epidural emphysema.All the clinical records were reviewed for demographic data, symptoms and duration of symptoms. The study did not require approval from the institution's Investigation Review Board. However, the Brooke Army Medical Center Department of Clinical Investigation reviewed and approved the manuscript for publication. Results Case 1A 59-year-old male complained of left flank pain. He had a non-contrast CT of the abdomen and pelvis that showed a left ureterovesical junction stone. The examination also revealed severe degenerative disc disease at L4-5 and L5-S1 disc spaces with vacuum disc phenomenon and extracranial epidural emphysema behind the L5 vertebral body (Figure 1a,b). Case 2A 20-year-old male presented with diabetic ketoacidosis and crepitus in the neck and upper chest. He had palpable crepitus over his jaw and a friction rub on cardiac examination. A CT scan of the chest showed severe pneumomediastinum tracking from the mediastinum into the soft tissues of the neck, anterior and posterior chest wall with pneumopericardium and extracranial epidural emphysema (Figure 2a,b). Case 3A 49-year-old male with Crohn's disease presented with abdominal pain and distensi...