Table 2 A practical guide to relevant MRI findings
From: MRI of acute neck infections: evidence summary and pictorial review
Item | Useful sequences | Finding | Implications | Caveats |
|---|---|---|---|---|
Soft tissue edema | T2 Dixon (water) T1 Dixon post-Gd (water) | High signal against low signal background | In the setting of suspected neck infection, implies phlegmon/cellulitis Specific edema patterns (RPE, ME, SMSE, SLSE, VSE) indicate a more severe course of illness | Any type of inflammation (also non-infectious, such as post radiation treatment) can result in soft tissue edema |
Bone marrow edema | T1 SE T2 Dixon (water) T1 Dixon post-Gd (water) | Lowering of normal high fat signal on T1 High signal against low signal background in T1 post-Gd and T2 water images | Mandibular or maxillary edema usually suggests odontogenic infection Vertebral changes may suggest spinal origin of infection | Recent dental procedures and chronic osteomyelitis may cause non-specific edema Bone marrow changes are usually reactive, and not suggestive of frank osteomyelitis Spinal bone changes may be degenerative |
Abscesses | T1 SE T1 Dixon post-Gd (in-phase and water) DWI | Non-enhancing collection surrounded by tissue enhancement, with restricted diffusion (low ADC) | Low ADC in a non-enhancing collection suggests drainable abscess formation Exact localization important for guiding surgical approach | Purulent fluid may not be very T2 hyperintense Suppressed fat and non-enhancing fluid may look similarly hypointense in T1 post-Gd water images (be sure to check in-phase images as well) MRI is sensitive to even small abscesses that may be surgically insignificant Poorly enhancing, necrotic lymph nodes may mimic suppurative lymphadenitis (intranodal abscess) |
Complications | All | Mediastinal extension of abscesses Venous thrombosis Airway compromise | Urgent medical or surgical treatment of complications to minimize morbidity and mortality | Mediastinal edema alone does not necessarily imply descending mediastinitis or abscess, most often reactive non-suppurative edema Venous thrombosis may be difficult to diagnose on MRI Airway narrowing in MRI is non-specific and not predictive of need for airway support |