Imaging CNS autoimmune and inflammatory disease
Amyloid related disease
This is the fifth lecture in a case based review of imaging of the brain and spine for autoimmune and inflammatory conditions. We will cover the MRI findings of some of the common conditions and some potential pitfalls and mimics.
This lecture covers three central nervous system (CNS) manifestations of amyloid disease: cerebral amyloid angiopathy (CAA), inflammatory amyloidosis, and amyloidomas. While the pathology is similar, the imaging manifestations are markedly different.
Cerebral amyloid angiopathy
Cerebral amyloid angiopathy is a small vessel vasculitis caused by deposition of amyloid beta in the walls of the vessels. The result is a vasculitis manifested by repeat hemorrhages, often in the periphery of the brain or at gray/white junctions, with relative sparing of areas often affected by hypertensive hemorrhage (such as the basal ganglia, thalamus, and pons). Patients are usually over 70 and may have progressive mental decline out of proportion for age. Imaging findings are most visible on gradient or susceptibility weighted T2 images, where you can see the sequelae of chronic hemorrhage. CAA is more common in patients with Alzheimer’s disease and Down’s syndrome, which are also amyloid related diseases.
Inflammatory amyloidosis is another intracranial manifestation of amyloid disease that may affect slightly younger patients. Imaging findings are similar in that small areas of microhemorrhage can be seen, but the major difference is in the amount of cerebral edema as best characterized on FLAIR and T2 weighted images. Patients with inflammatory amyloid may present with headache, altered mental status, or focal neurologic symptoms. It can be challenging to diagnose, particularly if areas of hemorrhage are not clearly seen, and biopsy may be required.
Amyloidomas are tumor-like conditions in which the patients often present with focal neurologic symptoms and an intracranial mass. It often has surrounding edema, but a key feature is its internal T2 hypointensity. On post-contrast imaging, it can mimic a high grade glioma or metastasis because it can enhance avidly. Often resection or biopsy is required because they look so tumor-like.
Summary and Conclusion
Amyloid related disease in the CNS is uncommon, with the most common manifestation a vasculopathy from amyloid deposition in vessels. If accompanied by edema and inflammation, it is called inflammatory amyloid. Masses of amyloid deposition within the brain are uncommon but in rare cases can mimic tumors. All of these disease can be hard to diagnose and can frequently require a biopsy.
The level of this lecture is appropriate for radiology residents, radiology fellows, and trainees in other specialties, such as neurology, who have an interest in neuroradiology or may see patients with CNS demyelinating or inflammatory conditions.