the cerebral abscess is a common central nervous system infection that can result from trauma , hematogenous spread , or spread from an adjacent infection such as otitis media or sinusitis . despite exhaustive searches ,
15 to 30% of abscesses are termed cryptogenic when no source of infection is identified20 ) . a distant infection focus that can cause brain abscesses
is a cardiac right to left shunt , which is related to patent foramen ovale15 ) , cyanotic cardiac disease15 ) or pulmonary arteriovenous malformation or fistula ( avf ) .
pulmonary avf is a rare congenital vascular malformation involving direct communication between the pulmonary artery and vein without an intervening capillary bed .
approximately 8095% of pulmonary avfs are associated with hereditary hemorrhagic telangiectasia ( hht ) , known as osler - weber - rendu syndrome5,8,9 ) .
the clinical triads of pulmonary avf is cyanosis , exertional dyspnea , and digital clubbing ; however , 56% of one large series were asymptomatic8 ) .
the most prominent central nervous system ( cns ) complications associated with pulmonary avfs are neurologic events , including transient ischemic attacks31 ) , recurrent stroke1,6,18,27 ) , brain abscesses , and seizures26 ) .
. we will focus on the cryptogenic brain abscess as developed by patients with idiopathic pulmonary avf , which may be detected only if we consider it may cause the brain abscess .
a 65-year - old woman was admitted with a 1-month history of headache and cognitive impairment that had become aggravated 10 days prior .
she showed impairment in orientation and judgment , but there were no lateralization signs of motor paralysis or cranial nerve deficits .
there was no history of diabetes mellitus , hypertension , lung disease or heart disease .
her blood pressure was 110/70 mmhg , pulse rate was 74/min , body temperature was 36.5c , and her respiration rate was 20 breaths / min .
erythrocyte sedimentation rate was 54 mm / h and c - reactive protein ( crp ) was 0.22 mg / l .
arterial blood gas analysis revealed a ph of 7.425 , pco2 of 42.5 mmhg , po2 of 90.4 mmhg , and an hco3 of 22.2 mmol / l on room air .
total cholesterol was 249 mg / dl and ldl - cholesterol was 172 mg / dl .
brain computed tomography ( ct ) showed a mass with perilesional edema on the right frontal lobe .
brain magnetic resonance ( mr ) imaging revealed a 43-cm ring enhanced mass in the right frontal lobe , which was associated with severe edema and midline shifting to the left side ( fig .
a chest x ray showed nodular infiltrations on the right mid - lung zone and the left upper and lower lung zones .
2 ) and antibiotics were maintained for 8 weeks . her past history gave no indication of exertional dyspnea or episodes of hemoptysis , melena , hematemesis , epistaxis or hematuria that might suggest underlying hht .
a 45-year - old woman presented with a 7-day history of a progressive left hemiparesis .
on admission , blood tests showed a hb of 13.4 g / dl , an hct of 39.6% , a white blood cell ( wbc ) count of 6290 cells/l , and a crp elevated to 2.62 mg / l .
diffusion mr imaging showed a diffusion - restricted ovoid mass on the right motor and sensory cortex measuring 1.50.9 cm that was surrounded by diffuse vasogenic perilesional edema ( fig .
3 ) . mr imaging and mr spectroscopy revealed an enhancing lesion involving the right motor and sensory cortex and increased lactate / lipid complex , which was compatible with a brain abscess .
a chest x ray did not suggest underlying lung disease . however , a chest ct revealed a pulmonary avf in the right upper lung ( fig .
the brain abscess progressed despite treatment with vancomycin and ceftriaxone , so it was removed via craniotomy and the pulmonary avf was embolized .
a 65-year - old woman was admitted with a 1-month history of headache and cognitive impairment that had become aggravated 10 days prior .
she showed impairment in orientation and judgment , but there were no lateralization signs of motor paralysis or cranial nerve deficits .
there was no history of diabetes mellitus , hypertension , lung disease or heart disease .
her blood pressure was 110/70 mmhg , pulse rate was 74/min , body temperature was 36.5c , and her respiration rate was 20 breaths / min .
erythrocyte sedimentation rate was 54 mm / h and c - reactive protein ( crp ) was 0.22 mg / l .
arterial blood gas analysis revealed a ph of 7.425 , pco2 of 42.5 mmhg , po2 of 90.4 mmhg , and an hco3 of 22.2 mmol / l on room air .
total cholesterol was 249 mg / dl and ldl - cholesterol was 172 mg / dl .
brain computed tomography ( ct ) showed a mass with perilesional edema on the right frontal lobe .
brain magnetic resonance ( mr ) imaging revealed a 43-cm ring enhanced mass in the right frontal lobe , which was associated with severe edema and midline shifting to the left side ( fig .
a chest x ray showed nodular infiltrations on the right mid - lung zone and the left upper and lower lung zones .
2 ) and antibiotics were maintained for 8 weeks . her past history gave no indication of exertional dyspnea or episodes of hemoptysis , melena , hematemesis , epistaxis or hematuria that might suggest underlying hht .
a 45-year - old woman presented with a 7-day history of a progressive left hemiparesis .
, blood tests showed a hb of 13.4 g / dl , an hct of 39.6% , a white blood cell ( wbc ) count of 6290 cells/l , and a crp elevated to 2.62 mg / l .
diffusion mr imaging showed a diffusion - restricted ovoid mass on the right motor and sensory cortex measuring 1.50.9 cm that was surrounded by diffuse vasogenic perilesional edema ( fig .
3 ) . mr imaging and mr spectroscopy revealed an enhancing lesion involving the right motor and sensory cortex and increased lactate / lipid complex , which was compatible with a brain abscess .
however , a chest ct revealed a pulmonary avf in the right upper lung ( fig .
the brain abscess progressed despite treatment with vancomycin and ceftriaxone , so it was removed via craniotomy and the pulmonary avf was embolized .
cryptogenic brain abscesses can occur due to rare diseases that are not addressed in routine clinical practice .
congenital cyanotic heart disease3 ) , patent foramen ovale12,15 ) , thoracic infection19 ) or asymptomatic dental infections7 ) are commonly associated with cerebral abscesses .
idiopathic asymptomatic pulmonary avfs are also a cause of brain abscess , especially recurrent brain abscess ( table 1 ) .
the incidence of idiopathic pulmonary avf - related cns complications is between 19 and 59 % 11,25,29 ) .
associated neurological events included migraine , transient ischemic attack , stroke , abscess , and seizure17,26,30 ) .
the incidence of brain abscess in patients with a pulmonary avf is around 1 to 5%8 ) .
the most likely mechanism for these neurological events is a paradoxical embolism across the pulmonary avf or across a coexisting cerebral arteriovenous malformation in patients with hht17 ) .
the pulmonary capillary bed acts as a filter that removes small thrombi and bacteria as they enter the bloodstream , even during daily activities such as oral hygiene . in a pulmonary avf
, the pulmonary capillary bed is bypassed , providing a direct right to left shunt that depends on the diameter of the feeding artery . as a consequence
, patients may develop paradoxical emboli that present as a transient ischemic attack , stroke , or brain abscess5 ) .
the fundamental defect that we found was a right - to - left shunt from the pulmonary artery to the pulmonary vein , and the degree of shunting determines the clinical effects .
if shunting is minimal , cyanotic symptoms are usually absent . if the right - to - left shunt is greater than 20% of the systemic cardiac output , or if there is reduction of hemoglobin by more than 50
g / l , the patient will have obvious cyanosis , clubbing , and polycythemia17 ) .
the characteristic findings of cyanosis , clubbing and an extra - cardiac murmur do not always accompany pulmonary avf , and diagnosis may be difficult .
a review of the mayo clinic experience suggested a morbidity of 2633% and mortality of 816% in untreated patients with pulmonary avf26 ) .
the international guidelines for the management of pulmonary avf in hht recommends that treatments should be applied to all adults with avfs and children with symptomatic pulmonary avfs .
the decision to treat in asymptomatic children ( no dyspnea , no exercise intolerance , no growth delay , no cyanosis or clubbing , no previous complication ) should be made on a case - by - case basis .
the selection of pulmonary avfs for embolization is based on feeding artery diameter , generally 3 mm or greater10 ) . a literature review ( table 1 )
indicates that idiopathic pulmonary avfs can cause brain abscess in patients as young as 18 years old . based on these reported series
, 10 of 13 patients did not have pulmonary avf - related symptoms until the brain abscess developed .
idiopathic pulmonary avfs are more frequently solitary , around 80% , compared with that of hht ( < 40%)30 ) .
it means idiopathic pulmonary avfs are less likely to be associated with large right - to - left shunt , this might in part explain why patients with idiopathic pavms might have a lower frequency of cyanosis and polycythemia .
also , previous hht series have shown an association between number of pulmonary avfs and cerebral abscess risk22 ) .
this might explain why idiopathic pulmonary avfs are associated with a lower frequency of cerebral abscess than in hht .
the organisms in the brain abscess were not consistent but most frequently isolated ones were streptococci genus .
6 cases out of 13 did not reveal an organism at all . if young adults without a premorbid history present with a brain abscess , pulmonary problems must be evaluated .
this report highlights the need to consider pulmonary avf as an etiology of cerebral abscess when routine investigations fail to detect a source .
 brain abscess commonly occurs secondary to an adjacent infection ( mostly in the middle ear or paranasal sinuses ) or due to hematogenous spread from a distant infection or trauma . 
 pulmonary arteriovenous fistulas ( avfs ) are abnormal direct communications between the pulmonary artery and vein . 
 we present two cases of brain abscess associated with asymptomatic pulmonary avf . 
 a 65-year - old woman was admitted with a headache and cognitive impairment that aggravated 10 days prior . 
 an magnetic resonance ( mr ) imaging revealed a brain abscess with severe edema in the right frontal lobe . 
 we performed a craniotomy and abscess removal . 
 bacteriological culture proved negative . 
 her chest computed tomography ( ct ) showed multiple avfs . 
 therapeutic embolization of multiple pulmonary avfs was performed and antibiotics were administered for 8 weeks . a 45-year - old woman presented with a 7-day history of progressive left hemiparesis . 
 she had no remarkable past medical history or family history . on admission , 
 blood examination showed a white blood cell count of 6290 cells / ul and a high sensitive c - reactive protein of 2.62 mg / l . 
 ct and mr imaging with mr spectroscopy revealed an enhancing lesion involving the right motor and sensory cortex with marked perilesional edema that suggested a brain abscess . 
 a chest ct revealed a pulmonary avf in the right upper lung . 
 the pulmonary avf was obliterated with embolization . 
 there needs to consider pulmonary avf as an etiology of cerebral abscess when routine investigations fail to detect a source . 
INTRODUCTION
CASE REPORT
Case 1
Case 2
DISCUSSION
CONCLUSION