Dural AV fistula

Plain CT and MR Axial T2w images show abnormal serpigenous vascular hyper density on CT and T2 flow voids on MRI marked in posterior fossa at the floor and along tentorial dura suggestive of dural AV fistula.
An associated abnormal dilatation of petrosal sinuses noted on MR Angio.

Dural arteriovenous fistula (DAVF)

Dural AVF, a rare, abnormal connectivity between arteries and veins, lies exclusively along dural covering of the brain or spinal cord, and referred accordingly as a cranial DAVF and spinal DAVF.
Cranial DAVF is supplied by branches of the carotid artery (external and internal carotid arteries) and possibly also by branches of the vertebral artery before these arteries penetrate the dura.
The fistula communications seen as serpigenous dilated vessels with T2 flow voids along dura overlying cererebral convexity and along tentorium. Frequently the blood flow in a DAVF is very high, and it may cause blood to flow in the opposite direction of normal over the brain's surface.

Commonly diagnosed in women over the age of 40 years. Unlike AVMs, which are thought to be present from birth, cranial DAVF most often develop later in life following hypoplasia or thrombosis of dural venous sinus particularly superior sagittal sinus.

Cranial DAVF may present with pulsatile tinnitus or pulsatile proptosis, impairment of vision and eye movement, isolated but persistent or progressive headache; hemorrhage
Unfortunately, the diagnosis may be missed or delayed because such lesions occur so rarely, CT may be normal and even in case of MRI, a common practise of inadequate sequences particularly screening protocols used for brain and spine.

Pathogenesis of Dural AV fistula:
Dural AV fistula are shunts between the meningeal arterial networks and the dural venous sinuses. Long standing dural sinus thrombosis result in obstruction in venous outflow which raises intra cranial venous sinus pressure. This venous hypertension leads to ischemia, followed by aberrant angiogenic activity along the Dura. CVT here is the primary event that result in venous hypertension and fistula. Sinus thrombosis may be the primary even as result of turbulent flow in the Dural venous sinus secondary to DAVFs.

Treatment:
Highly challenging, various line of management and materials are under debates.
Intra sinus stenting can relieve raised venous sinus pressure but may increase arteriovenous pressure gradient and shunt flow.
Arterial embolization of DAVF, without correction of venous hypertension can give rise to another fistula.
Intermittent carotid arterial compression.
Percutaneous intra arterial embolization using detachable balloons, isobutylcyanoacrylate, or polyvinyl alcohol particles.
Transvenous embolization with coils or liquid adhesives.
Surgical venous bypass using saphenous vein.
Gamma knife stereotactic surgery.

Similar Case: http://www.neuroradiologycases.com/2011/09/dural-arteriovenous-fistula-davf.html

Spinal Epidural Hematoma MRI

A 26 yo male with sudden onset backache and chest pain for last 2 days. An associated bilateral upper limb tingling numbness. Both lower limb weakness is of sudden onset and non progressive.

Power: Rt arm 4-5, Lt arm 4-5, Rt leg 0, Lt leg 0.

No history of trauma or any heavy weight lifting. 

BT CT PT and other related caugulation profile normal.

On admission MRI dorsal region spine done with contrast. 

MRI Findings: 

A focal posterior epidural lentiform shaped collection extending from C6-7 to D2-3 disc level

Collection is hypo intense on sagittal T2 images with low signal intensity 'blooming'on GRE. No significant enhancement within the collection on post contrast T1 and fat sat T1. Thin enhancement noted along the normal dura.

Significant cord compression with focal cord edema.

Imaging wise Diagnosis: Possible DDs given were as Epidural Hematoma more likely than Abscess.

Post operative findings:

Operated with C6-D3 Laminectomy, posterior epidural hematoma / blood clot evacuated with coagulation of dural AV fistula along left D2 root.

Final Diagnosis : Posterior epidural hematoma secondary to Spinal Dural AV Fistula - Malformation.

Discussion:

In this case possibility of Epidural hematoma is more likely due to sudden onset of symptoms clinically, low signal intensity of collection on T2w and T2*GRE, iso to hyper intensity on T1w images, non enhancing on post contrast on imaging, thought there no history of history of trauma and normal coagulation profile. So one should entertain a possibility of Hematoma for a spinal Epidural lesion as Epidural Hematoma can present without history of trauma and moreover blood has variable signal and enhancement pattern on MRI.

Spinal Epidural hematoma (EDH)

Extra vasation of blood into the epidural space of spine.

Imaging

MRI is best.

Typically lentiform shaped long segmental extra axial collection mass encasing or displacing cord or cauda equina.

Location anywhere along spinal canal, commonly in dorsal region. 

vertical extent variable depending upon severity of bleed, often multi segmental,rarely focal when associated with an adjacent fracture.

On CT, density on CT varies with age of hematoma high density in acute stage to low density in chronic. 

On MRI 

TIWI: Hypo-, iso- or hyperintense (depending on age)

T2WI: Inhomogeneous low (if acute), or high signal (if subacute) intensity.

T2* GRE: low signal.

T1 C+: None to marginal enhancement along the dural outling of collection. Avid enhancement if bleeding is active. 

DSA

Often negative. Rarely, may show AVM or vascular tumor as Source of bleeding. 

DDs

Epidural abscess: Usually vivid enhancement, associated osteomyelitis or paraspinous infection, constitutional signs like fever, pain, chills.

Epidural tumor: Typically quite focal, adjacent bone often involved, Lymphoma may simulate EDH, enhances vividly. 

Etiology

o Spontaneous in 1/3

• Pressure elevation in vertebral venous plexus due to minor exertion, like sit-ups with Valsalva.

• Chiropractic manipulation

o Therapeutic anticoagulation

• Coumadin

• Anti platelet agents

o Instrumentation

• Epidural anesthetic

• Nerve block

• Facet joint injection

• Lumbar puncture

o Vascular malformation

Clinical Presentation

Most common signs/symptoms are intense, knife-like pain.

Associated extremity weakness, sphincter disturbance

Age: 35-70 Gender: Male > Female

Treatment

o Surgical for significant cord compression is decompressive Laminectomy and evacuation of hematoma. 

o Non-surgical for minor neurological signs.

Dural AV Malformation / Fistula MRI

MRI Brain Axial FLAIR and coronal T2w images show an extra axial nodular T2 flow voids in right parasellar region, flow related signals on 3D TOF Noncontrast MR Angiography suggestive of a high flow vascular malformation. No direct communication with adjacent right ICA rules out ICA Aneurysm.
It seems to be a Dural Arterio Venous Malformation / Fistula, finding is noted incidentally as pt actually presented for a recent infarct involving cranial portion of right cerebellar hemisphere in superior cerebellar artery territory.