primary angiitis of the central nervous system ( pacns ) was identified as a distinct clinical entity in adults in 1959 , and only recently now in children as a cause of childhood stroke .
the disease should be suspected in children presenting with newly acquired neurological or psychiatric deficits after exclusion of causes of secondary vasculitis .
we present a relapsing course of a young boy who was diagnosed as childhood pacns ( cpacns ) and was managed accordingly .
a 6-year - old boy presented with low - grade fever and frontal headache off and on for last 1 month .
the central nervous system ( cns ) examination revealed normal higher mental functions with palsy of right third cranial nerve and bilateral sixth cranial nerve .
investigations revealed normal hemoglobin and leukocyte count ; c - reactive protein ( crp ) was positive , and erythrocyte sedimentation rate ( esr ) was raised 34 mm/1 h. cerebrospinal fluid ( csf ) examination was normal .
the magnetic resonance imaging ( mri ) of the brain and spine was also normal .
the patient deteriorated on day 3 of hospitalization with seizures , altered sensorium , quadriparesis , and left upper motor neuron seventh nerve palsy .
repeat mri - angiography ( mra ) of the brain revealed block in the terminal right internal carotid artery ( ica ) , left ica , and bilateral posterior communicating artery ( pca ) suggestive of vasculitis with normal brain parenchyma and normal meninges [ figure 1a ] .
the workup for cause of vasculitis was noncontributory ( koch 's workup , procoagulants , anti - nuclear antibody , lupus anticoagulant , and viral serology ) , and serum complement was normal .
echocardiography was normal , and there was no evidence of systemic vasculitis . within 48 h of methylprednisolone ,
a diagnosis of idiopathic cns vasculitis was made , and the patient was started on oral prednisolone after five doses of methylprednisolone .
the patient was discharged with residual deficit of bilateral squint ( sixth nerve paresis ) with a plan to continue steroids for 6 weeks .
magnetic resonance imaging and angiography ( a ) initial scan : occlusion in the terminal right internal carotid artery and bilateral posterior communicating artery ; ( b ) follow - up after month : with thrombosis of the right internal carotid artery the patient presented after 1 month with fresh left twelfth nerve palsy and residual bilateral sixth nerve paresis . quadriparesis had resolved completely .
repeat mra of the brain revealed resolution of thrombosis and of thickening of the left ica and bilateral pca as compared to initial scan but persistent thrombosis of the right ica [ figure 1b ] .
the digital subtraction angiography of cranial vessels reported complete obliteration of right ica distal to carotid bifurcation with good collateral formation ; rest of brain vasculature was normal .
a diagnosis of medium vessel pacns ( mv - pacns ) was made . in light of partial response to steroids with features of steroid toxicity as evident on examination , the patient was shifted to azathioprine ( steroid - sparing drug ) as maintenance therapy .
the patient is currently recovering and has mild residual right sixth nerve and left twelfth nerve paresis at 1 year of follow - up , with resolution of cushingoid features .
primary angiitis of cns is a rare form of vasculitis with extremely low annual incidence of 24 cases per million patient - years .
the disease affects the small and medium size vessels of the brain resulting in lymphocytic infiltration of vessel walls with granulomatous differentiation ( granulomas are absent in childhood forms ) .
the diagnosis of pacns is challenging because of rarity of disease , unexplained etiology , varied clinical presentation , and lack of sensitive and specific tests .
the diagnosis of pacns should be suspected in any patient with multifocal or diffuse cns involvement with a remitting or progressive course .
laboratory tests which can exclude secondary causes of cns vasculitis [ as listed in table 1 ] should be undertaken before establishing a diagnosis of pacns .
the acute phase reactants may be raised , and csf abnormalities in the form of increased protein concentration or mild pleocytosis may be seen in majority though few studies have reported normal csf findings .
secondary causes of central nervous system angitis in children in cpacns , two distinct patterns can be recognized  small vessel pacns ( sv - pacns ) which presents with cognitive decline , seizures , and behavioral changes or mv - pacns where headache , hemiparesis , and other focal deficits are common manifestations .
 beading  or segmental narrowing in large , intermediate , or small arteries with interposed regions of ectasia or normal luminal architecture with collateral flow .
brain biopsy was initially considered as gold standard but carries a mortality risk of 3.7% .
it may be difficult to detect sv - pacns by angiography , where diagnosis is confirmed with a brain biopsy .
the mri with mra of the brain is a noninvasive and safer alternative diagnostic modality with good sensitivity ( 90%95% ) .
the abnormalities seen in subcortical white matter and deep gray matter are ischemic areas and infarcts with evidence of vasculitis .
the diagnosis of pacns is based on modified calabrese and mallek criteria which are a newly acquired focal or diffuse neurological or psychiatric symptom in a patient 18 years of age plus characteristic angiographic and/or histopathological features of cns angiitis , in the absence of an underlying systemic disorder that explains or mimics the features .
the treatment of pacns includes an induction phase and a maintenance phase . in general ,
cyclophosphamide pulses for 36 months may be used in conjunction with steroids to induce remission , but myelosuppression should be anticipated .
safer alternatives such as azathioprine , mycophenolate , and methotrexate are given as maintenance therapy .
mv - pacns has a more benign course and fewer relapses as compared to sv - pacns where relapse may occur in 25%30% patients .
the diagnosis of relapse rests on clinical presentation and supportive radiography ; acute phase reactants have little role .
thus , patients with sv - pacns need to be monitored for long and require immunosuppressive therapy for longer period ( 5 years ) as compared to mv - pacns where maintenance therapy for 23 years suffices .
. early identification of this condition helps to initiate appropriate immunosuppressive therapy which reduces chances of complications and mortality .
 childhood primary angiitis of the central nervous system ( cpacns ) is a rare and a potentially fatal cause of childhood stroke . 
 the disease poses a diagnostic dilemma for the clinicians due to overlapping and varied clinical manifestations such as headache , focal acute neurological deficits , cognitive impairment , or encephalopathy . 
 we report a young boy who presented with low - grade fever and headache but rapidly progressed to develop acute encephalopathy and quadriparesis with multiple cranial nerve palsies , masquerading as acute disseminated encephalomyelitis . 
 the neuroimaging was suggestive of vasculitis . 
 he was diagnosed as cpacns and recovered with immunosuppressive therapy . 
Introduction
Case Report
Discussion
Conclusion
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