Title: Spinal Vascular Malformations
1Spinal Vascular Malformations
- Sohail Bajammal
- February 2, 2009
2Acknowledgement
3Outline
- Embryology
- Anatomy
- Classification
- Clinical presentation
- Treatment
4Embryology 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
5Stage 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
6Stage 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
7Stage 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
8Stage IV Terminal Stage
- After 4th month
- Maturation and increased tortuosity of the major
spinal cord vessels
9Adult Anatomy
10 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
11Arterial 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
12Venous 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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14Spinal 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.
15Spetzler et al. Modified classification of spinal
cord vascular lesions. J Neurosurg (Spine 2)
2002.
16Incidence
- 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
17Clinical Presentation
- Haemorrhage
- Myelopathy
- Radiculopathy
- Back pain
18Pathophysiology 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
19Classification
- 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
204 Types
- Type I Dural AV Fistula
- Type II Glomus AVMs
- Type III Juvenile AVMs
- Type IV Intradural AV Fistula
21Type 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
22Type I
23Type 1
24Pathophysiology 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
25Clinical 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.
26Natural 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.
27Type 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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29Pathophysiology 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
30Clinical 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
31Type 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
32Type 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
33Pathophysiology of Type III IV
- High-flow lesions
- Vascular steal/ischemia
- Hemorrhage
- Mass effect
34Type V
- Type III lesions outside the spinal cord and
dural (i.e., not truly metameric)
35Diagnosis
- 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
36Treatment
- Goal total obliteration or excision of the
abnormal shunt - If only partially reduce the shunt or address
proximal feeders only ? recurrence
37General 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
38General 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
39Type I
40Treatment 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.
41Outcomes 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
42Type II
43Treatment of Type II
- Preoperative endovascular embolization to shrink
the size - Surgical excision
- Interruption of the feeding arteries first
- If mainly intramedullary, midline myelotomy
44Type III
45Treatment 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
46Type IV
47Treatment 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
48Thanks
49Credits
- Images from
- Spetzler et al
- OToole and McCormick
- Oldfield