Amyloidosis of the Brain
The Common Vein Copyright 2010
Amyloidosis is a disorder in which diseases occur due to the extracellular deposition of insoluble polymeric protein fibrils in the body. Many neurodegenerative diseases, remarkably Alzheimer’s, are secondary to amyloidosis.
The name amyloid was introduced by the pathologist Virchow in 1854, when he thought such deposits were cellulose-like.
The mechanisms of fibril formation are unknown in its most part, but the mechanism includes the formation of interactions between trans beta sheet and certain proteins named amyloid precursor proteins, leading to the formation of multimers and polymers. Eventually, these become insoluble and deposit in tissues.
It results in organ dysfunction, because there will be an uptake of the amyloid precursors from cells, which can be fundamental for the normal function of cells.
Many types of amyloidosis exist, a classification is based upon the protein deposited. A type of this – Beta – is associated with cerebral amyloid angiopathy. It results in deposition of amyloid in the media and adventitia of small vessels, mostly in the meninges, cortex, and cortical penetrating vessels.
Patients present with seizures, and focal cerebral symptoms, and possibly coming with an encephalopathic picture. There can be a rapid progressive dementia. Often, multiple TIA’s are present.
The diagnosis is made with microscopic examination of biopsies; the extracellular amyloid deposits can be identified by Congo red staining and viewed with polarized light, due to its birefringence.
Radiologically, the MRI can show large subcortical patches of T2 signal change, suggesting edema. IC hemorrhages are frequent, mostly single lobar hemorrhage superficially located, with or without extension to the subarachnoid and intraventricular spaces.
This disorder has no known treatment at the time. Complications are treated accordingly.