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acute spontaneous subdural hematoma ( sdh ) is very rare , and usually caused by tearing of the bridging veins in the subdural space369 ) .
the pathophysiology of spontaneous sdh includes rupture of the cortical artery or of the pial arteriovenous fistulae , an arteriovenous malformation ( avm ) , or intracranial aneurysm1269 ) . here
, we reported a very rare case of acute spontaneous sdh due to rupture of a tiny cortical avm that was pathologically shown to be an avm .
a 51-year - old man presented with a sudden onset of headache and gradually diminishing mentality . on neurological examination of the patient at admission time was semicomatous .
neurological examination showed glasgow coma scale ( gcs ) 5 , fixed light reflex , and dilatation of both pupils .
a computerized tomography ( ct ) of the brain depicted an acute sdh with severe midline shift in the right cerebral hemisphere ( fig .
however , we did not performed another imaging study , such as a ct angiography or conventional cerebral angiography .
laboratory findings , including blood analysis , blood cell counts and coagulation cascades , were normal .
the bone flap and the dura mater revealed no evidence of head trauma , such as , bone fracture or vascular abnormality . the subdural blood clot was removed and a tiny ( 5 mm sized ) aciniform mass with two connected engorged vessels was identified on parietal lobe ( fig .
after operation , mild neurologic deterioration with hemiparesis persisted , but his symptoms were considerably improved with a glasgow outcome scale 3 .
damage of bridging veins in the subdural space is the most common cause of acute and chronic sdh1 ) .
however , in the absence of trauma injury to the brain , spontaneous bleeding may occur due to ruptures of small cortical arteries or intracranial aneurysms , hypertensive cerebral hemorrhage , tumors , and hematologic disorders1269 ) .
drake3 ) concluded that the acute or subacute sdh could result from a small rent in a surface cortical artery torn from a dural attachment by the movement of brain .
kondziolka et al.6 ) suggested an aneurysm adherent to the arachnoid membrane might bleed directly into the subdural space or hemorrhage under high pressure and might lead to pia - arachnoid rupture and extravasation of blood into the subdural space .
mcdermott et al.9 ) described some anatomical situations that might predispose spontaneous rupture of a cortical artery , that is , rupture of a cortical artery at the bleeding origin of a fragile arterial twig or rupture of a small artery crossing the subdural space and connecting a cortical artery to the dura mater ( a bridging artery ) .
avms are vascular abnormalities composed of fistulous vessels between arteries and veins without a normal capillary bed .
mccormick et al.8 ) classified vascular malformations into five subgroups , namely , cavernous malformations , telangiectasia , varix , venous malformation , and avms .
the annual hemorrhagic risk posed by an avm is 2 - 3% , and the annual risk of fatality is 1%5 ) .
furthermore , avms are associated with a definite risk of neurologic deficit with or without a bleeding events .
other presenting symptoms include hydrocephalus , raised intracranial pressure , papilledema , ataxia , motor weakness , and impaired consciousness27 ) .
avms are most commonly located in the supratentorially , but are also encountered in cerebellar hemispheres and vermis7 ) .
almost cases with cranial avms , more than half of patients present with hemorrhage2 ) .
intraparenchymal hemorrhage is the most common , followed by intraventricular hemorrhage ( ivh ) and subarachnoid hemorrhage ( sah ) .
however , a presentation of sdh due to a ruptured cerebral avm is extremely rare .
in fact , only one case of acute posterior fossa sdh following ruptured cerebellar avm rupture has been previously reported2 ) .
these patients are suffering from the signs and symptoms of intraparenchymal hemorrhage , ivh and sah , because of almost avms are located in the subcortical area and triangular shape with the base toward the cerebral cortex and the apex toward the ventricular system .
however , in the present case , we encountered subdural bleeding through a hole in the cortical avm .
we thought the adhesion of the avm vessel to the arachnoid membrane and strain of arachnoid membrane could be led formation of sdh rather than sah or intraparenchymal hemorrhage . in the case of our patient ,
the pulsatile bleeding focus was at a hole on the wall of arterialized vein with an extraordinary morphology .
however , it should be noted a focus of bleeding in the operation field is not guaranteed in cases of acute spontaneous sdh , and thus , a close inspection of the cerebral cortex should be conducted intraoperatively in cases of acute spontaneous sdh without a traumatic history .
medical history and physical examination provide important diagnostic clue , but a confirmatory imaging study by ct , mri , and angiography is required . in our opinion , brain ct is the most valuable modality for determining treatment strategy in urgent situations , which often means , there is no time for other imaging studies .
however , when the situation permits , we recommend ct angiography in cases of acute spontaneous sdh without a definite trauma history .
an extravasation of contrast media from a cortical vessel is helpful for localizing the bleeding focus and detection of cortical avm .
we report an extremely rare case of acute spontaneous sdh due to rupture of a tiny cortical avm .
the ct angiography should be used to locate the bleeding focus on patients with spontaneous acute sdh without a definite traumatic history .
furthermore , a careful inspection of the brain cortex below the hematoma should be conducted during the surgery .
acute subdural hematoma ( sdh ) of arterial origin is rare , especially sdh associated with an arteriovenous malformation ( avm ) is extremely rare . 
 the authors report a case of acute spontaneous sdh due to rupture of a tiny cortical avm . a 51-year - old male presented with sudden onset headache and mentality deterioration without a history of trauma . 
 brain ct revealed a large volume acute sdh compressing the right cerebral hemisphere with subfalcine and tentorial herniation . 
 emergency decompressive craniectomy was performed to remove the hematoma and during surgery a small ( 5 mm sized ) conglomerated aciniform mass with two surrounding enlarged vessels was identified on the parietal cortex . after warm saline irrigation of the mass , active bleeding developed from a one of the vessel . 
 the bleeding was stopped by coagulation and the vessels were removed . 
 histopathological examination confirmed the lesion as an avm . 
 we concluded that a small cortical avm existed at this area , and that the cortical avm had caused the acute sdh . 
 follow up conventional angiography confirmed the absence of remnant avm or any other vascular abnormality . 
 this report demonstrates rupture of a cortical avm is worth considering when a patient presents with non - traumatic sdh without intracerebral hemorrhage or subarachnoid hemorrhage .