====== Vermian Arteriovenous Malformation ======

Arteriovenous Malformation of the [[Vermis]] lies in the midline and may be on the [[tentorial]] surface or on the [[suboccipital]] surface. 

Superior and inferior, divided by the [[horizontal fissure]].

see [[Superior vermian arteriovenous malformation]].

===== Clinical features =====

Intracranial hemorrhage was the presenting symptom in 73% of the cases and recurrent bleeding episodes occurred in 60%
((Samson D, Batjer H. Arteriovenous malformations of the cerebellar vermis.
Neurosurgery. 1985 Mar;16(3):341-9. PubMed PMID: 3982613.
)).

===== Diagnosis =====
Computed tomographic scans demonstrated the site of the malformation in 80% and documented the presence of intracerebral bleeding in all posthemorrhage patients. 

Angiography revealed two consistent patterns of arterial supply depending on the involvement by the malformation of the superior inferior cerebellar vermis
((Samson D, Batjer H. Arteriovenous malformations of the cerebellar vermis.
Neurosurgery. 1985 Mar;16(3):341-9. PubMed PMID: 3982613.
)).

===== Treatment =====

Vermian AVMs were typically resected through torcular craniotomies (89%), improving access to the superior vermian surface, relative to the standard subocciptial craniotomy, by removing the ledge of overhanging bone and lift the transverse sinuses with tacking sutures on the dural flap. 
----
[[Vermian Arteriovenous Malformation]]s are located in the midline and exposed with a [[torcular craniotomy]] to gain access to both the [[suboccipital]] and [[tentorial]] surfaces. The suboccipital part of the   - vermis ([[tuber]], [[pyramid]], [[uvula]], and [[nodule]]) is superficial and easily accessed, but the tentorial part ([[culmen]], [[declive]] and [[folium]]) is deep and requires [[subarachnoid]] dissection to open the supracerebellar-infratentorial plane. The ascending slope of the tentorial part of the vermis requires significant neck flexion when positioning the head, tucking the chin two finger breadths from the [[manubrium]] in the prone position to align the tentorium vertically. Alternatively, small AVMs at the apex of the vermis or anteriorly in the [[quadrigeminal cistern]] can be approached with the patient in the [[sitting position]], which allows gravity to retract the cerebellum and open the supracerebellar-infratentorial plane. Vermian AVMs attract bilateral feeding arteries, with superior vermian AVMs supplied by [[superior cerebellar artery]] SCAs and inferior vermian AVMs supplied by [[PICA]]s. 



===== Case series =====
Fifteen cerebellar vermian arteriovenous malformations were surgically treated over a 7-year period. Intracranial hemorrhage was the presenting symptom in 73% of the cases and recurrent bleeding episodes occurred in 60%. Computed tomographic scans demonstrated the site of the malformation in 80% and documented the presence of intracerebral bleeding in all posthemorrhage patients. Angiography revealed two consistent patterns of arterial supply depending on the involvement by the malformation of the superior inferior cerebellar vermis. All lesions were surgically removed via a midline suboccipital posterior fossa microsurgical approach. Intraventricular extension of arteriovenous malformation was common, often in association with the [[choroid plexus]] of the [[fourth ventricle]]. Immediate postoperative angiography was used to document arteriovenous malformation removal. Three instances of unsuspected residual malformation were documented and required reexploration. The total operative mortality was 7%, and the neurological morbidity was 21%
((Samson D, Batjer H. Arteriovenous malformations of the cerebellar vermis.
Neurosurgery. 1985 Mar;16(3):341-9. PubMed PMID: 3982613.
)).