INFECTIOUS AND NONINFECTIOUS INFLAMMATORY DISORDERS: VASCULITIS INCLUDING ARTERITIS, THROMBOPHLEBITIS, AND VASCULAR THROMBOSIS
- Venous and arterial disease is an important conduit of inflammatory disease spread in the head and neck.
- Venous and arterial structures are frequently secondarily involved in head and neck pathology, and their involvement may be the most crucial feature of the disease.
- Some of the most disastrous functional outcomes can be the result of vascular complications, especially with regard to the eye and brain.
- Computed tomographic angiography, and to a lesser extent magnetic resonance imaging, magnetic resonance angiography, diffusion-weighted imaging, and susceptibility-weighted imaging, have replaced catheter angiography for initial screening for possible vascular abnormalities related to inflammation.
- While an excellent tool for vascular pathology, ultrasound has only a very limited role to play in these diseases, as it does not show the full extent and nature of disease and/or related findings.
VENOUS INFLAMMATION, INFECTIONS, AND OCCLUSION
Venous thrombosis or thrombophlebitis may complicate or be the source of an inflammatory process in the head and neck region.1 In general, the involved vessel or sinus contains clot and varying degrees of perivascular inflammation induced by causative pathology that somehow irritates the endothelium and starts the clotting cascade.
Causative pathology initiating venous disease is most frequently in the sinuses and mastoid. Two common examples are sigmoid sinus thrombosis secondary to mastoiditis and jugular vein thrombophlebitis related to indwelling catheters. Other sources include the pharynx, such as Lemierre tonsillogenic venous thrombosis (Fig. 15.1), sinus infections, and occasionally the skin (Fig. 15.2).
Septic thrombophlebitis is an important route of spread of infectious disease from the extracranial head and neck structures to the intracranial compartment.2,3 Such spread may be via transdiploic vessels to the skull, epidural space, subdural space, subarachnoid space, and brain (Fig. 15.3). Either bland or septic involvement of the cavernous sinus, other major dural sinuses, and cortical veins is possible. Any or all of these vascular structures may be simultaneously involved (Fig. 15.4). Intracranial involvement due to such vascular spread is often close to the inciting infection but can be fairly remote (Fig. 15.2).4
The rate of clot lysis and restoration of flow depends on the causative condition and the treatment of the original inciting condition.
Contrast-enhanced computed tomography (CECT) will show the clotted vessel or sinus to be obviously occluded compared to normally patent enhancing vessels with flowing blood (Figs. 15.1, 1.15, and 2.15).3,5,6 Typically, the occluded vessel or venous sinus lumen appears to be homogeneously fluid density, and its wall often enhances (Fig. 15.5). There may be varying degrees of surrounding edema/inflammation. Rarely, morphology similar to that of an abscess will be present and strongly suggest suppurative thrombophlebitis (Fig. 15.6). In the neck, retropharyngeal and peripharyngeal edema is frequently present (Fig. 15.7).
On magnetic resonance imaging (MRI), the normal flow void as seen on spin echo (SE) images or loss of flow-related enhancement as seen on gradient echo (GE) images will be absent, and the vessel lumen will be filled with material that is of variable intensity on T1-weighted (T1W) images and T2-weighted (T2W) images depending on the age of the clot (Fig. 15.8).6,7 Flow-related enhancement may be mistaken for clot, and a combination of flow-sensitive GE and standard T1W and T2W images in at least two different planes may be necessary to differentiate flow-related artifact from clot. Magnetic resonance (MR) venography is an excellent adjunctive method to confirm the diagnosis that is usually strongly suspected on the anatomic, non–flow-related images. Susceptibility-weighted techniques can be used to improve on time-of-flight MR venography and produce extraordinary images of the manifestations of relatively small vessel venous disease in the brain. Diffusion-weighted images are used in conjunction with the anatomic and flow-related imaging to determine the effects of vascular occlusion on the brain and may help determine whether intervention is likely to improve the situation (Fig. 15.9)