Central Nervous System Vasculitis (CNS Vasculitis)
CNS Vasculitis refers to inflammation of the arteries supplying the brain. Each artery is a laminated tube. The wall of the artery is made up of many different components, such as connective tissue, smooth muscle, skin-like tissue called endothelium, and many others. Sometimes, part of the artery wall becomes inflamed, which can lead to swelling of the wall. This expansion or swelling of the artery wall can secondarily narrow the lumen of the artery, through which blood flows into the brain. If the narrowing is severe enough, there may not be enough blood flow to the brain and the patient may start to experience symptoms of stroke. Finally, the artery can close altogether.
There are many different kinds of vasculidites (inflammations of vessels). Some affect arteries as large as the aorta (Takayasu’s arteritis), while others involve medium vessels (temporal arteritis). Most cases of CNS vasculitis occur as a part of autoimmune or inflammatory disorders, such as Systemic Lupus Erythematosus, dermatomyositis, Rhematoid Arthritis, Wegner’s Granulomatosis, or Behçet’s disease, or as part of bacterial/vrial infection, and affect even smaller vessels. Another cause is Primary Angiitis of the CNS (PACNS), a condition of isolated CNS vascular inflammation in absence of systemic disease.
It is with medium and small vessels disease that cerebral angiography is concerned. The walls of these arteries are normally very thin – too small to be seen on modern MRI and CT machines to the extent necessary to make a diagnosis of CNS vasculitis. In these cases, an angiogram may be required. The angiogram cannot depict the wall of the vessel either. However, it can visualize in exquisite detail the lumen (inside channel) of the artery. An irregularity or narrowing of this channel, in the right location and clinical setting, can be a sign of an artery wall inflammation, and help to either rule in (diagnose) or rule out (exclude) the possibility of CNS vasculitis. Unfortunately, the angiogram, though more sensitive than CT or MRI, is still not a perfect test for CNS vasculitis. This is because the angiogram is not able to evaluate the actual place of disease, which is the wall of the artery. The “gold standard” – meaning definitive – testfor this is an actual biopsy, where a surgeon removes a piece of brain with its arteries so as to evaluate them under a microscope. Needless to say, this procedure is a last resort, when it is absolutely essential to answer the question and no answer came from any other test. This is why a cerebral angiogram is still sometimes necessary to evaluate for CNS vasculitis.
In this angiogram, one can see areas of narrowing and dilatation in several different arteries (white arrows). This picture, by itself, is not diagnostic of CNS vasculitis. However, in the context of the patient’s symptoms and neurolgic findings, the possibility of CNS vasculitis was raised and confirmed on this angiogram:
Following a course of treatment, repeat angiography shows complete resolution of the abnormalities