Spinal Vascular Malformations

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Spinal Vascular Malformations

• Sohail Bajammal
• February 2, 2009

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Acknowledgement

• Dr. Aleksa Cenic

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Outline

• Embryology
• Anatomy
• Classification
• Clinical presentation
• Treatment

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Embryology ofthe Spinal Vascular Network

• 4 stages
• Congenital theory of AVMs
• 20 of patients with intradural AVMs have other
  associated congenital vascular malformations
  intracranial AVMs, cerebral aneurysm, vascular
  agenesis, hemangioblastoma, Rendu-Osler-Weber
  syndrome, Klippel-Trenaunay-Weber syndrome
• Present in younger patients
• Distributed throughout the entire spinal axis

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Stage I Primitive Segmental Stage

• Week 2-3 gestation
• 31 pairs of segmental vessels originate from
  paired dorsal aortas ? grow toward the neural
  tube along the developing nerve roots
• Segmental vessels divide into ventral dorsal
  branches and form capillary networks on the
  ventrolateral surface of the neural tube
• These networks develop into paired primitive
  ventral arterial tracts, the precursors of the
  anterior spinal artery

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Stage II Initial Stage

• Week 3-6 gestation
• Development of the dorsal arterial anastomosis
• Longitudinal venous channels develop on both
  ventral and dorsal spinal cord surfaces
• These channels expand and give rise to
  interconnected capillary network
• AVM theoretically happens during this stage

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Stage III Transitional Stage

• 6th week 4th month gestation
• Formation of the adult pattern of vascular supply
• The primitive ventral longitudinal arterial
  tracts fuse and the number of segmental arteries
  is reduced
• By 10 weeks, adult patterns are present

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Stage IV Terminal Stage

• After 4th month
• Maturation and increased tortuosity of the major
  spinal cord vessels

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Adult Anatomy
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Arterial Anatomy

• Anterior spinal artery
• arises from the fusion of a contribution from
  each of the vertebral arteries
• supplies the ventral 2/3 of the cord
• narrows as it descends but reinforced by blood
  vessels at some segmental levels
• Paired posterior spinal arteries
• run the length of the spine
• supply the posterior 1/3 of the cord

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Arterial Anatomy

• At each segmental level a dorsal ramus of the
  segmental artery enters the intervertebral
  foramen and gives rise to 3 branches
• Dural branch to dura
• Radicular branch to nerve root
• Medullary branch
• Augments the flow to the anterior spinal artery
• During the 3rd stage of fetal development, most
  of the medullary branches involute ? distal
  portion of the cord relatively ischemic
• Somewhere between T8 L2, especially on the
  left the medullary branch does not involute and
  becomes the artery of Adamkiewicz

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Venous Anatomy

• Coronal venous plexus
• A plexus on the cord surface
• Formed by coalescence and anastomosis of radial
  veins
• Epidural venous plexus
• At segmental levels, medullary veins leave the
  coronal plexus and exit the intervertebral
  foramen to join the epidural plexus
• The plexus communicates with the venous sinuses
  of the cranial dura
• It drains into the ascending lumbar veins and the
  azygous venous system

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Spinal Vascular MalformationsTerminology

• Definition abnormalities of the arteries or
  veins surrounding the spinal column, spinal cord,
  and nerve roots
• AV fistula (AVF) direct communication between
  artery vein
• AV malformations (AVMs) multiple complex
  communications
• Nidus the core of an AVM that appears
  angiographically and anatomically as a
  conglomeration of vessels because of the
  superimposition of arteries and veins.

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Spetzler et al. Modified classification of spinal
cord vascular lesions. J Neurosurg (Spine 2)
2002.
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Incidence

• Rare cause of neurologic dysfunction
• 5 of all intraspinal pathology
• Occur throughout the spine
• Affect any age group, majority 30-50
• Better diagnosis and management with improved
  techniques of spinal angiography, MRI, MRA and
  endovascular surgery

OToole and McCormick. Chapter 83 Vascular
Malformations of the Spinal Cord. Rothman-Simeone
The Spine. 5th Edition
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Clinical Presentation

• Haemorrhage
• Myelopathy
• Radiculopathy
• Back pain

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Pathophysiology of Symptoms

• Depends on the type of the AVM
• High-flow
• Ischemia
• Hemorrhage
• Slow-flow
• Venous congestion
• Mechanical compression of the spinal cord and
  roots

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Classification

• Many exist
• Most common 4 types based on the location and
  angioarchitecture
• Anatomical intradural vs extradural
• Presence or absence of AV shunts
• Recent Spetzler 2002

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4 Types

• Type I Dural AV Fistula
• Type II Glomus AVMs
• Type III Juvenile AVMs
• Type IV Intradural AV Fistula

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Type I (Dural AV Fistula)

• The most common type
• 60 of spinal AVF/AVM
• Single AV connection within the dura of the nerve
  root sheath
• Results in dilated arterialized coronal venous
  plexus

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Type I
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Type 1
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Pathophysiology of Type 1

• Slow-flow ? Intradural venous hypertension ?
  progressive spinal cord ischemia
• Exercise (elevated intraspinal venous pressure) ?
  reversible ischemic symptoms
• Venous hypertension may be exacerbated by
  structural changes in the veins
• Venous thrombosis ? acute exacerbation

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Clinical Presentation Type 1

• Mean age 50yr
• Men 4 times more common
• Majority thoracic and thoracolumbar
• Symptoms insidious back and leg pain, mild
  sensorimotor dysfunction (like spinal stenosis)
• Signs mixed UMNL and LMNL and patchy sensory
  loss.

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Natural History of Type 1

• Inevitable progression of symptoms
• Episodes of acute worsening
• e.g., Foix-Alajouanine syndrome
• If untreated wheelchair dependence within 6mo to
  3 years after symptom onset
• Preoperative neurologic status is the most
  important predictor of post-treatment outcomes.
• Median time from symptom onset to diagnosis 15
  to 23 months.

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Type II (Glomus AVMs)

• Analogous to intracranial AVMs
• Tightly packed nidus of dysmorphic arteries and
  veins in direct communication w/o capillary bed
  over a short segment of the spinal cord
• The nidus may be completely or partially
  intramedullary
• Usually at the cervicothoracic junction

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Pathophysiology of Type II

• Vascular steal mechanism High-flow lesion AVM
  nidus acts as a low-resistance sump siphoning
  blood away from the surrounding normal spinal
  cord
• Dysmorphic vessels susceptible to hemorrhage
• Mass effect myelopathy or radiculopathy

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Clinical Presentation of Type II

• Childhood or adult years
• Acute presentation from subarachnoid or
  intramedullary hemorrhage is most common
• Acute onset of severe neck or back pain coup de
  poignard approximates the level of AVM
  typically the first symptom of AVM hemorrhage

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Type III (Juvenile AVMs)

• Arise in single or multiple adjacent somites ?
  thus intradural and extradural, may involve soft
  tissue and bone in addition to the cord
• Diffuse shunts with normal spinal cord existing
  between loops of abnormal vessels
• No distinct nidus
• Metameric tissue derived from the entire somite

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Type IV (Intradural AVF)

• Direct connection between an intradural artery
  and vein in the subarachnoid space without a
  definable nidus
• Usually ventral, involves the anterior spinal
  artery
• Sub classified small, medium, large

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Pathophysiology of Type III IV

• High-flow lesions
• Vascular steal/ischemia
• Hemorrhage
• Mass effect

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Type V

• Type III lesions outside the spinal cord and
  dural (i.e., not truly metameric)

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Diagnosis

• MRI and MR angiography (MRA) useful for the
  initial screening of AVMs. Permit more targeted
  selective angiography
• Selective spinal angiography gold standard for
  definitive diagnosis and characterization

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Treatment

• Goal total obliteration or excision of the
  abnormal shunt
• If only partially reduce the shunt or address
  proximal feeders only ? recurrence

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General Considerations of Surgical Treatment

• Majority of AVMs are dorsal or dorsolateral ?
  standard posterior laminectomy of appropriate
  number of levels
• Neuromonitoring SSEPs MEPs
• Wide laminectomy
• Dural opening with preservation of arachnoid

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General Considerations of Endovascular Treatment

• Continues to evolve
• Advances in catheter technology, image resolution
  and embolization materials
• Neuromonitoring and pharmacologic intra-arterial
  provocative testing (amobarbital and lidocaine)
• Either primary or adjunctive role depending on
  the type of AVMs expertise
• Procedure of choice for type III
• Type I IV attempts of embolization, if failed
  ? surgery. Some authors prefer surgery as first
  line
• Type II surgery remains the gold standard

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Type I
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Treatment of Type 1

• Historically, stripping of the long dorsal vein ?
  poor outcomes b/c removal of normal cord venous
  drainage
• Now, excision of the dural fistula
• Two-level hemilaminectomy and partial medial
  facetectomy to expose the dural root sleeve and
  foramen
• Paramedian longitudinal dural incision exposes
  the intradural nerve root and initial segment of
  draining vein
• Several mm of the feeding radicular artery and
  intradural draining vein, cauterized, divided and
  excised along with a small window of dura on the
  root sleeve.

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Outcomes of Type 1 Treatment

• Neurologic improvement or stabilization in 70 to
  99. Motor and gait disturbances improve to a
  greater degree than sensory or sacral deficits
• Surgery produces 98 fistula obliteration rate,
  endovascular embolization produces 25 to 66
  obliteration rate.

OToole and McCormick. Chapter 83 Vascular
Malformations of the Spinal Cord. Rothman-Simeone
The Spine. 5th Edition
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Type II
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Treatment of Type II

• Preoperative endovascular embolization to shrink
  the size
• Surgical excision
• Interruption of the feeding arteries first
• If mainly intramedullary, midline myelotomy

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Type III
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Treatment of Type III

• The most difficult to treat
• They penetrate the spinal cord
• Do not have well-defined margins (intramedullary,
  intradural-extramedullary, extradural) over many
  spinal segments
• Generally unresectable. Palliative treatment with
  endovascular embolization, and/or surgery

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Type IV
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Treatment of Type IV

• Depends on the size and complexity
• Small surgical ligation is definitive
• Posterior (or posterolateral) or anterior
  approach
• Usually needs spinal instrumentation
• Medium and large endovascular embolization
  preferred as primary treatment or preopeative
  adjunct

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Thanks
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Credits

• Images from
• Spetzler et al
• OToole and McCormick
• Oldfield