Spinal extradural arteriovenous malformations with parenchymal drainage: venous drainage variability and implications in clinical manifestations.
OBJECTIVE
Although nontraumatic spinal arteriovenous malformations and fistulas (AVMs and AVFs) restricted to the epidural space are rare, they can lead to significant neurological morbidity. Careful diagnostic imaging is essential to their detection and the delineation of the pathological anatomy. Aggressive endovascular and open operative treatment can provide arrest and reversal of neurological deficits.


METHODS
The authors report on 6 cases of extradural AVMs/AVFs causing progressive myelopathy. Clinical findings, diagnostic evaluation, treatment, and outcome are discussed. Special consideration is given to the anatomy of the lesions and the operative techniques used to treat them. A review of the literature concerning extradural vascular malformations is also presented.


RESULTS
All 6 cases of extradural AVMs had an extradural fistulous location with intradural medullary venous drainage. These cases illustrate progressive myelopathy through cord venous congestion (hypertension) that can be caused by an extradural nidus or fistula. In 4 cases, a large epidural lake was identified on angiography. At surgery, the epidural lake was obliterated and medullary drainage interrupted. All patients had stabilization of their neurological deficits and successful obliteration of the AVM/AVF was obtained.


CONCLUSIONS
Extradural AVMs and AVFs are a poorly described entity with published clinical experience limited to sporadic case reports and small series. Although these lesions have a purely extradural location of arteriovenous shunting and early venous drainage, they can be responsible for acute and progressive neurological symptoms similar to those caused by their dural-based intradural counterparts. With careful imaging recognition of the pathological anatomy, surgical and endovascular techniques can be used for the treatment of extradural AVMs affording effective and durable obliteration with stabilization or reversal of neurological symptoms. Venous drainage directly correlates the pathologic mechanisms of presentation. Specific attention must be paid intraoperatively to the epidural lake common to both variants so that recurrence is avoided.
Clarke
Michelle J
MJ
Department of Neurologic Surgery, Mayo Clinic, Rochester, Minnesota 55905, USA. Clarke.michelle@mayo.edu
Patrick
Todd A
TA
White
J Bradley
JB
Cloft
Harry J
HJ
Krauss
William E
WE
Lindell
E P
EP
Piepgras
David G
DG
D000368:Aged; D001165:Arteriovenous Malformations / Q000150:complications / Q000628:therapy*; D020785:Central Nervous System Vascular Malformations / Q000150:complications / Q000628:therapy*; D004388:Dura Mater / Q000098:blood supply*; D004621:Embolization, Therapeutic / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D013116:Spinal Cord / Q000098:blood supply*