Primary CNS vasculitis of childhood is a serious but potentially reversible inflammatory brain disease. With early recognition of this rare condition, effective treatment can be instituted in a timely manner.
CNS vasculitis in children can occur as a primary disease that is isolated to the CNS or as a secondary manifestation of an underlying systemic condition. Although numerous systemic inflammatory diseases and infections have long been recognized as responsible for causing secondary CNS vasculitis, primary CNS vasculitis of childhood has only recently been described as a reversible inflammatory brain disease in case reports and case series. [1, 2, 3]
A newly acquired neurological deficit
Angiographic and/or histologic evidence of CNS vasculitis
The absence of a systemic condition associated with these findings
To date no diagnostic criteria for children are available; thus, the adult definition is applied in practice. [6, 7] There are 2 main diagnostic categories: large-medium vessel disease and small vessel disease.
The diagnosis of large-medium disease is based on magnetic resonance angiography and conventional angiography evidence of vasculitis in the CNS, in the absence of underlying systemic inflammatory disease.  Lesions typically conform to the territory defined by a particular arterial distribution.
Small vessel CNS vasculitis affects vessels smaller than those seen by magnetic resonance angiography and conventional angiography. Therefore, by definition, this condition has negative angiography findings.  Lesions can be multifocal and bilateral and tend not to conform to a distinct vascular distribution. The diagnosis is confirmed by brain biopsy findings.
Large-medium vessel disease has been further subdivided into progressive and nonprogressive groups, which are defined by evidence of disease progression on angiography findings 3 months after diagnosis. Nonprogressive large-medium vessel vasculitis shares many similarities with both postvaricella angiopathy and transient cerebral arteriopathy of childhood. A significant overlap in the presentation and imaging findings among these conditions is often observed. Studies are needed to define the differences in pathophysiology and treatment requirements for each clinical disorder and to determine whether these are, in fact, distinct disease entities.
Children with progressive large-medium vessel disease typically have neurocognitive dysfunction at presentation, multifocal lesions on MRI, and evidence of distal stenosis on angiography. 
The risk of progression in terms of new vascular lesions is considered to be low when the presentation consists of an isolated stroke and imaging reveals evidence of unilateral, proximal vessel stenosis.  However, the risk of recurrent stroke due to the initial vascular injury in the same distribution is thought to be significant. Decreasing the subsequent stroke risk is the rationale for treating these patients with immunosuppressive therapy. 
Because of the small of number of cases that have been described to date, estimating the frequency is not possible. As recognition of this condition increases, the number of cases that are diagnosed and treated appropriately also increases.
A small number of case reports have described fatalities resulting from this disease.  However, although the neurological compromise observed at initial presentation may be very grave and even life-threatening, most children survive. In the past, this condition may have gone unrecognized, meaning severe, refractory, and even fatal cases of status epilepticus or stroke in the pediatric population may have been attributable to undiagnosed primary CNS vasculitis. Practice guidelines to aid in the diagnosis of status epilepticus have been established. 
Morbidity is not uncommon, and includes a wide variety of diffuse and focal neurological deficits. Expectations for neurological improvement should be guided by the principal that although brain inflammation is reversible, ischemia is not. With early recognition and prompt treatment, including immunosuppression and anticoagulation when appropriate, the morbidity related to this disease can be greatly decreased. In current studies, good neurological outcome has been reported in 45% of patients with progressive large-medium vessel disease, in 31% of patients with nonprogressive large-medium vessel disease, and in 69% of patients with small vessel disease. [8, 13] Tools such as the Pediatric Stroke Outcome Measure can be used to quantify neurological deficits on serial clinical assessments.
No race predilection has yet been identified.
Currently, no evidence suggests that one sex is affected more frequently than the other.
This disease has been described in children as young as infancy and as old as adolescence. No peak in age distribution has been identified.
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