a 75-year - old man with a slightly increased serum creatinine level had developed proteinuria and hypertension in 2000 . in 2007 , he noticed a gradually progressive hearing loss and repeated bloody nasal discharge resulting from a refractory sinusitis . initial laboratory findings revealed elevated serine proteinase 3-anti - neutrophil cytoplasmic antibody ( pr3-anca ; 26.2 eu ) , blood urea nitrogen ( 35 mg / dl ) , and serum creatinine ( 1.62 mg / dl ) levels . because of these combined findings , he was diagnosed as having granulomatosis with polyangiitis ( gpa ) according to the american college of rheumatology 1990 criteria for gpa and watts algorithm [ 1 , 2 ] . the birmingham vasculitis activity score 2003 was 6 . because of the low disease activity , the slow progression and the advanced age , we did not initiate immunosuppressive therapy at this time . in october 2008 , he developed fever lasting for several days . laboratory data were as follows : c - reactive protein 11.91 mg / dl , pr3-anca 49.1 u / ml , fibrinogen 752 mg / dl , d - dimer 1.7 g / ml , and urinary protein 0.27 g / day . activated partial thromboplastin time , prothrombin time and fibrin degradation product were within the respective normal range . although we administered meropenem ( 2.0 g / day for 1 week ) , vancomycin ( 500 mg / day for 17 days ) and itraconazole ( 200 mg / day for 20 days ) , the fever and c - reactive protein level did not decrease . on day 12 of admission a brain mri revealed a mass lesion in the right frontal lobe and hypertrophic mucosa in the paranasal sinuses ( fig . 1a ) in addition to a thickened and strongly enhanced dura mater surrounding the mass lesion ( fig . however , he rapidly developed left hemiparesis and deterioration of consciousness [ glasgow coma scale ( gcs ) : e1v2m4 ] . a brain ct revealed that the parenchymal mass lesion had enlarged and the mucous effusion was invading the posterior wall of the right frontal sinus . due to an impending transtentorial herniation , a decompressive hemicraniectomy and partial right frontal lobectomy were performed , which moderately improved his consciousness ( gcs : e2v3m4 ) . after the surgery , he developed bloody sputa , and a chest ct revealed an infiltrative shadow in both lungs . the biopsied brain material from the surgery revealed a granulomatous inflammation with geographic necrosis and multinucleated giant cells in the perivascular area of the thickened dura mater and leptomeninges ( fig . small vessels in the meninges were involved in the granulomatous lesions , and the lumens of the veins were often occluded . in the cerebral cortices and the white matter in these areas , hemorrhagic infarction was widely observed . after treatment with prednisolone ( 20 mg / day ) and azathioprine ( 40 mg / day ) , the disturbance of consciousness substantially improved ( gcs : e4v3m5 ) , and the epistaxis stopped . this study was conducted with the approval of the ethics committee of niigata university graduate school of medical and dental sciences . cns involvement such as pachymeningitis and cerebrovascular events is uncommon in gpa , reported in only 28% of cases [ 3 , 4 ] . we previously clarified that leptomeningeal and parenchymal involvement in the brain were significantly more common in pr3-anca - positive hypertrophic pachymeningitis compared to myeloperoxidase anti - neutrophil cytoplasmic antibody - positive and idiopathic hypertrophic pachymeningitis in a study of 36 patients ( including this case ) . based on the study , mri findings showed an enhancement of both the pachymeninges and leptomeninges . moreover , the present case had the extension of the mass lesion with the granulomatous inflammation , and the venous obstruction resulted in severe edema and hemorrhagic infarction . emergency decompressive craniectomy and partial lobectomy for cerebral infarction with gpa likely contributed to our patient 's survival . to our knowledge , this is the first report successfully managed with surgical decompressive craniectomy .
central nervous system ( cns ) involvement , such as pachymeningitis and/or cerebrovascular events , is rare in patients with granulomatosis with polyangiitis ( gpa ) . 
 furthermore , the details of pathological examinations of cases have rarely been described . 
 we describe a case of gpa that manifested as an isolated paranasal sinus disease that invaded the subarachnoid space and caused a hemorrhagic venous infarction . 
 we also describe the pathological characteristics of the biopsied brain material from the successful decompressive craniectomy . 
 in particular , granulomatous inflammation with geographic necrosis and multinucleated giant cells were observed in the perivascular area of the thickened dura mater and leptomeninges . 
 small vessels in the meninges were involved in the granulomatous lesions , and the lumens of the veins were often occluded . in the cerebral cortices and white matter in these areas , 
 hemorrhagic infarction was widely observed . 
 we suggest that our findings represent a novel mechanism of cns involvement in gpa . 
 moreover , we believe that the emergency decompressive craniectomy and partial lobectomy for the cerebral infarction in this patient with gpa likely contributed to his survival .