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Spinal type I AVF


Introduction

Spinal dural arteriovenous fistulas (dAVFs) are the most common vascular lesion of the spinal cord, and they account for 70% of all AV shunts of the spine. Type I dAVFs are defined as an abnormal intradural low flow communication between a radiculomeningeal artery and a radicular vein (radiculomedullary vein) draining into the intradural venous plexus. In general, spinal vascular malformations encompass 3% to 4% of all intradural spinal cord masses. Men are affected five times more often than women, and the fistulous abnormality usually occupies the thoracolumbar region (80%). The mean age at the time of diagnosis is 55 to 60 years. This condition is usually underdiagnosed, in part because of its insidious neurological decline, which can cause acute, subacute, or chronic cord dysfunction, and also due to its challenging diagnosis. Congestion of the venous outflow of the spinal cord leads to mass effect and ischemia, resulting in progressive myelopathy that often mimics an anterior horn neurological disorder. Patients typically present with lower-extremity weakness (75%), pain (52%), and sensory disturbances (60%). Most of the patients will develop a stepwise progressive neurological deterioration. Spinal cord hemorrhage due to a dural AVF is a rare occurrence. Initial diagnosis is attained with magnetic resonance imaging (MRI) and MR angiography (MRA); however, definitive diagnosis requires spinal digital subtraction angiography (DSA) to appropriately categorize the condition and establish the extent of the disease. The progressive nature of the disorder and the necessity to halt and reverse the gradual neurological deterioration undoubtedly require timely intervention. Treatment should attain complete occlusion of the shunting zone and restore normal spinal cord perfusion and intravascular pressures. This can be achieved by either surgical obliteration or endovascular embolization.

Example case

  • Chief complaint: lower limb weakness and urinary incontinence

  • History of present illness: This is a 55-year-old male with progressive lower extremity weakness and new-onset urinary incontinence. He was referred after receiving a magnetic resonance imaging (MRI) report showing tortuous dorsal venous structures. Additionally, spinal angiogram demonstrated a feeding vessel from the left sacral artery ( Fig. 64.1 ).

    Fig. 64.1, Preoperative imaging. (A) Sagittal T2 image demonstrating abnormal vascularity extending along the thoracic and lumbar spinal canal with mild expansion with increased T2 signal and patchy enhancement in the distal thoracic cord extending from the inferior aspect of T8 to the conus. (B) Axial T2 image demonstrating cross-sectional increased T2 signal at the T10-T11 level. (C) Spinal angiogram showing dural arteriovenous fistula at the T11 segmental level, feeding vessel was a branch of the lateral sacral artery entering the left T10 neural foramen.

  • Medications: none

  • Allergies: not known

  • Past medical and surgical history: none

  • Family history: none

  • Social history: none

  • Physical examination: awake, alert, and oriented to person, place, and time; cranial nerves II–XII intact; bilateral deltoids/triceps/biceps 5/5; interossei 5/5; iliopsoas/knee flexion/knee extension 3/5, and dorsi and plantar flexion 4/5

  • Reflexes: 2+ in bilateral biceps/triceps/brachioradialis with negative Hoffman; 3+ in bilateral patella/ankle; two beats of clonus and positive Babinski; decreased sensation to light touch diffusely throughout bilateral lower extremities

  • Nicolas Dea, MD, MSc

  • Neurosurgery

  • Vancouver Spine Surgery Institute

  • Vancouver, Canada

  • Diego F Gómez MD MSc.

  • Neurosurgery

  • Fundación Santafe de Bogotá

  • Bogota, Colombia

  • Michael T. Lawton, MD

  • Fabio Frisoli, MD

  • Harrison Farber, MD

  • Neurosurgery

  • Barrow Neurological Institute

  • Phoenix, Arizona, United States

  • Jang Yoon, MD

  • Neurosurgery

  • University of Pennsylvania

  • Philadelphia, Pennsylvania, United States

Preoperative
Additional tests requested

  • Anesthesia evaluation

  • EMG/NCS/SSEP

  • Anesthesia evaluation

  • Complete spinal angiogram

  • Urological evaluation

  • MRI L-spine

  • MRI C- and L-spine

  • Spinal angiogram if edema present in cervical or lumbar spine

Surgical approach selected T10-T11 laminectomy and obliteration of spinal AV fistula T10-11 laminoplasty for obliteration of spinal AV fistula T10-11 laminectomy for obliteration of spinal AV fistula T10-11 laminectomy for obliteration of spinal AV fistula
Goal of surgery Disconnect fistula Disconnect fistula, eliminate venous congestion Disconnect fistula Disconnect fistula
Perioperative
Positioning Prone on Jackson table with pins Prone, no pins Prone on Jackson table Prone on Wilson frame on Jackson table
Surgical equipment Endovascular Fluoroscopy. Surgical microscope. IOM (MEP/SSEP) if cord feeder involved. Temporary clip.

  • IOM (MEP/SSEP)

  • Fluoroscopy

  • Ultrasound

  • Surgical microscope

  • Miniclips

  • IOM (MEP/SSEP)

  • Fluoroscopy

  • Surgical microscope with ICG

  • IOM (MEP/SSEP)

  • Fluoroscopy

  • Surgical microscope with ICG

  • Dural sealant

Medications None Steroids, Maintain MAP Steroids, Maintain MAP >75 None
Anatomical considerations Spinal cord feeders Spinal cord, veins Spinal cord, nerve roots, posterior spinal artery, artery of Adamkiewicz, dentate ligaments Thoracic spinal cord, en passage spinal arteries and veins
Complications feared with approach chosen Spinal cord infarct Spinal cord infarct, hemorrhage Spinal cord injury, nerve root injury, spinal cord infarct Incomplete disconnection, presence of multiple fistulas
Intraoperative
Anesthesia General General General General
Exposure T10-T11 T10-11 T10-T11 T10-T11
Levels decompressed T10-T11 T10-11 T10-T11 T10-T11
Levels fused None None None None
Surgical narrative Position prone, xray localisation. midline incision. T10-t11 laminectomy centered on the t10 foramen. midline durotomy and tenting sutures. identify culprit vessels. if doubt about cord feeder use IOM and temporary clip. Temporary decrease MAP and monitor for any change. If pre-op angio confirms that there is no spinal cord feeder involved then just localised abnormal vessel. Then take vessel at its intradural entrance. Note change of color of arterialized veins. Watertight dural closure. No drain. Bed rest × 24h. Position prone, 3D fluoroscopy to localize level, midline incision where neuroradiology demarcated shunt, subperiosteal dissection exposing posterior elements, two-level laminoplasty, ultrasound to identify tortuous vein, midline dural opening and tenting sutures, identify arterialized medullar vein under microscope usually near the entrance of the dorsal root, disconnect fistula immediate at entrance using min-clips, monitor SSEP/MEP if clip reversal is needed, pay attention to the change in color of arterialized vein, watertight dural closure with fibrin sealant, laminoplasty with titanium plates, layered closure with no drain Position prone, skin incision localized with fluoroscopy, surgical dissection carried out in the midline, expose lamina of correct level and confirm with fluoroscopy, laminectomy, dura is opened and tacked up under microscopic visualization, dorsal nerve roots followed to the root sleeve to identify the radiculomedullary artery, dentate ligaments may be cut to gently rotate the spinal cord, ICG videoangiography and microdissection to identify fistulous point, place clip on vein as close to the fistula as possible, fistula is cauterized and then divided sharply, ICG used to confirm obliteration of the fistula and preservation of normal vasculature, dura is closed with dural sealant, closure in layers Position prone, confirm fistulous location on spinal angiogram, count levels in both anterior-posterior and lateral, midline incision from T10 to T11, expose posterior elements, preserve posterior tension band and facet complexes, reconfirm level with fluoroscopy, open dura, tack up dura, identify fistulous point with surgical microscope, confirm location with ICG injected intravenously, place aneurysm clip on abnormal arterial feeder near fistulous point, look for change in color in venous drainage, confirm obliteration with ICG, disconnect fistulous point with bipolar and microscissors, final ICG, watertight dural closure with dural sealant, closure in layers, bed rest until next day
Complication avoidance Ensure good level with fluoroscopy. Alternatively, radiology can leave a coil for localisation during diagnostic spinal angiogram. Ensure no spinal cord feeder involved in the fistula. If any doubt use temporary clip and IOM. Ensure only one vessel contributing to the fistula. Watertight closure with dural sealant. 3D fluoroscopy to help localize level, laminoplasty, ultrasound to identify tortuous vein, disconnect fistula at dural entrance, monitor SSEP/MEP if clip reversal is needed, pay attention to the change in color of arterialized vein Follow nerve roots to the root sleeve to identify radiculomedullary artery, cut dentate ligaments to rotate spinal cord, ICG video angiography, place clip on vein as close to fistula as possible to avoid venous aneurysm Count in both anteroposterior and lateral, preserve posterior tension brand and facet complexes, ICG to evaluate fistula and confirm disconnection
Postoperative
Admission Floor ICU ICU ICU
Postoperative complications feared Spinal cord infarct. CSF leak. Epidural hematoma. Spinal cord/nerve root injury Spinal cord/nerve root injury, spinal infarct, CSF leak Residual fistula, pseudomeningocele, wrong level surgery
Anticipated length of stay 2-3 days 2 days 2–3 days 3–5 days
Follow-up testing

  • Intraprocedural angiogram MRI 2 month post-op. If residual tortuous vein, no change in cord signal change or no clinical improvement: follow-up angiogram.

Spinal angiogram within 48 hours

  • Spinal angiogram during hospitalization after surgery

  • MRI T-spine 6 months after surgery

  • Standing T- and L-spine x-rays 6 weeks after surgery

  • MRI T- and L-spine 12 weeks, 1 year, 2 years after surgery

  • Repeat spinal angiogram if needed

Bracing None None None None
Follow-up visits 2 months after surgery 2 weeks after surgery 10–14 days, 6 weeks, 6 months after surgery 2 weeks, 6 weeks, 3 months, 6 months, 12 months, 24 months after surgery
AV , Arteriovenous; CSF , cerebrospinal fluid; EMG , electromyogram; ICG , indocyanine green; ICU , intensive care unit; IOM , intraoperative monitoring; MAP , mean arterial pressure; MEP , motor evoked potential; MRI , magnetic resonance imaging; NCS , nerve conduction study; SSEP , somatosensory evoked potential.

Differential diagnosis

  • ▪

    Radicular arteriovenous malformations

  • ▪

    Epidural arteriovenous shunts

  • ▪

    Polyneuropathy

  • ▪

    Degenerative disk disease

  • ▪

    Spinal tumors

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