arteriovenous malformations ( avms ) present with hemorrhage , seizures , headache or focal neurological deficits .
cysts associated with avms are uncommon , and are usually a sequelae of stereotactic radiosurgery or after a hemorrhage .
untreated and unruptured avms with large cysts are uncommon , with only five cases reported in literature , and one in the pediatric population .
we describe a case of an untreated and unruptured avm in the right parietal lobe , which was associated with a large cyst .
an 8-year - old boy presented with history of generalized tonic clonic seizures for the last 2 years . there was no history of sudden onset headache or neurological deficits , suggestive of bleed . on examination , there were no focal neurological deficits .
an mri was performed , which showed a nidus , seen as flow voids , in the medial parietal lobe on the right side with a large cystic area abutting it posteriorly .
this was hyperintense on t2-weighted images and inverted completely on flair images [ figure 1a and b ] .
a digital subtraction angiogram was subsequently performed , which showed the nidus was receiving arterial feeders from the pericallosal branches of the right anterior cerebral artery and draining into the superior sagittal sinus via cortical veins [ figure 1c and d ] .
( a and b ) sagittal t2-weighted ( a ) and axial flair ( b ) mr images showing the avm nidus anteriorly and medially with the large cystic component posteriorly located in the right medial parietal lobe .
( c and d ) digital subtraction angiogram images in ap and lateral planes showing the nidus receiving arterial feeders from the pericallosal branches of the right anterior cerebral artery .
( e and f ) post - operative angiograms in ap and lateral planes showing complete excision with non - visualization of the nidus on right ica injection various treatment options were discussed , and the patient was offered surgical excision of the avm as the first choice .
the avm nidus and the draining vein was seen on the surface , and below that , there was a large cyst containing about 30 ml of clear fluid .
histological examination of the nidus showed abnormal arterial and venous channels , and the cyst wall had numerous thin - walled vascular channels containing hemosiderin in the fibrous tissue .
a post - operative angiogram was done on post - operative day two , which showed complete excision of the nidus [ figure 1e and f ] .
his post - operative stay in the hospital was uneventful , and was discharged on the third post - operative day . at 6-month follow - up , patient is neurologically normal , and is seizure - free on a single anti - epileptic drug .
avms associated with cyst without undergoing radiosurgery are extremely rare . in previously reported literature of 5 cases , there were 2 females and 3 males , with age between 14 and 38 years .
our patient is the youngest case of this type of association , and is only the second patient in pediatric age group reported in the literature [ table 1 ] .
three of the patients presented with seizures , 1 with headache and 1 with a focal neurological deficit in the form of a superior quadrantanopia . in 4 of the 5 patients ,
the avms were located in the temporal lobe and 1 was located in the parietal lobe .
cysts accompanying avms have been attributed to cavity formation secondary to liquefaction of the hematoma , which forms due to the bleeding in the avm .
the cases reported in literature had no history to suggest any previous episode of hemorrhage , and neither had received stereotactic radio surgery . in our case as well , there was no history suggestive of bleed or previous radiation treatment .
multiple hemorrhages in a long period and exudation of fluid from part of the avm have been suggested as the etiology for cyst formation .
reported the histology of the cyst wall and showed numerous thin - walled vascular channels and deposits in fibrous tissue , which are also seen in the membrane of the giant cysts associated with cavernous angiomas .
hence , they suggest that a capsule forms around the minor hemorrhage from the avm resulting in the cyst and repeated subclinical hemorrhages from the neovascular channels of the cyst wall result in the growth of the cyst .
itakura et al . , have propounded the theory of gradual exudation of fluid into the surrounding parenchyma resulting in cyst formation . in the present patient ,
the fluid in the cyst was clear , without any xanthochromia or hemorrhage , and the characteristic of the fluid was similar to csf on imaging .
the histology too showed no evidence of hemorrhage or slit  like cavities in the cyst wall .
hence , we are in concurrence with this theory of gradual exudation of fluid causing the cyst associated with the avm .
these can occur secondary to microhemorrhages or exudation of fluid from the part of the avm .
 cysts associated with arteriovenous malformations ( avms ) are either secondary to hemorrhage or after radiosurgery . 
 untreated and unruptured avms with large cysts are rare . 
 we here describe a child with medial parietal avm associated with cyst , without any history of hemorrhage or radiosurgery . surgical excision led to cure for the patient . 
Introduction
Case Report
Discussion
Conclusions