25 Infection and Inflammatory Conditions


25 Infection and Inflammatory Conditions

25.1 Spinal Infections and Inflammatory Conditions

The spinal cord is a part of the central nervous system (CNS), and as such is surrounded by cerebrospinal fluid (CSF), has a dural covering, and is myelinated by oligodendrocytes. Accordingly, many of the inflammatory conditions that influence the brain, of both infectious and noninfectious origin, can affect the spinal cord. The appearance of these entities on imaging overlaps that of neoplastic entities.

The spinal cord is supported and protected by a dural layer within the scaffolding of the vertebral column. Nerves of the peripheral nervous system leave this protective dural covering to provide motor, sensory, and autonomic innervation to the body. This creates several compartments within which infectious and inflammatory conditions can occur. Appropriate recognition and characterization of these conditions, as well as the differentiation of infectious and inflammatory processes from one another and from potentially neoplastic conditions, can help in the planning of treatment for all of these disease entities.

The involvement by an inflammatory process of the spinal cord (a myelitis) can result in neurologic deficits that can be localized to a specific sensory level, to the point at which a horizontally oriented (transverse) line can be drawn that demarcates symptomatic from asymptomatic levels. Clinically, the inflammatory process in which this can be done is known as a transverse myelitis, and can result from infection, acute disseminated encephalomyelitis (ADEM), neuromyelitis optica (NMO), multiple sclerosis (MS), lupus, vasculitis, trauma, spinal cord infarctions, tumors, and other conditions. Accordingly, transverse myelitis is a clinical finding and not a specific disease process, for which reason transverse myelitis cannot and should not be diagnosed based upon imaging. However, transverse myelitis is often an indication for magnetic resonance imaging (MRI) of the spine, in order to identify which of the entities named above may be present. Because a clinical instance of transverse myelitis can sometimes be idiopathic, there is a clinical entity known as idiopathic transverse myelitis, which in many cases is likely to be related to an immune-mediated process, such as ADEM.

25.2 Spinal Infections

25.2.1 Extradural Infections

Extradural infections are those that involve the epidural space, the paraspinal space, and the intervertebral disk space, as well as the bone of the spine itself. Osteomyelitis of the spine often originates as diskitis. The intervertebral disk space is highly vascular in young children and may be susceptible to the hematogenous spread of infection. It is important to keep in mind that in young children a spinal infection such as diskitis/osteomyelitis may present as limping, hip pain, or a refusal to bear weight. The first signs of diskitis may be narrowing of the joint space on radiographs (Fig. 25.1). On MRI, there will be fluid within the disk space and heterogeneous enhancement in the disk and adjacent soft tissues. Diskitis may result in osteomyelitis of the adjacent vertebra, or the infection causing it may extend into the paraspinous soft tissues with the development of an abscess, such as in the psoas muscles (Fig. 25.2). This may be amenable to computed tomography (CT)–guided drain placement, particularly if the infection does not respond to intravenous (IV) antibiotics. An extradural infection that extends into the epidural space can result in an epidural abscess that may narrow the thecal sac and is typically a neurosurgical emergency (Fig. 25.3).

Fig. 25.1 Diskitis. (a) Sagittal T2W image of the spine of a 6-year-old girl with back pain shows nonvisualization of the L3–L4 disk space (red arrow) and a heterogeneous marrow signal in the adjacent vertebra (red arrowhead). (b) Axial T2W image shows edema in the right (red arrow) and to a lesser extent the left (red arrowhead) psoas muscles. This represents L3–L4 diskitis with adjacent osteomyelitis and psoas myositis.
Fig. 25.2 Psoas abscess. (a) Axial T2W image at the L4 level in a 3-year-old girl with fever and back pain shows heterogeneous edema and fluid in the right psoas muscle (red arrow) and asymmetric thickening of the right ventrolateral epidural space (red arrowhead). (b) Axial T1W plus contrast image with fat saturation shows enhancement of the edematous areas, consistent with myositis, with focal hypoenhancing areas (red arrows) representing psoas abscess. There is solid enhancement of the thickened right ventrolateral epidural space (red arrowhead), representing an epidural phlegmon.
Fig. 25.3 Epidural abscess. Axial computed tomographic image at the C7 level in a 9-year-old boy with fever and neck pain shows a multiloculated abscess in the paraspinous musculature (red arrow). There is an epidural component along the left aspect of the central canal that has a peripheral rim of enhancement and central hypoenhancement, representing an epidural abscess (red arrowhead).

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May 28, 2020 | Posted by in NEUROLOGICAL IMAGING | Comments Off on 25 Infection and Inflammatory Conditions

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