Spinal vascular malformations consist of an abnormal connection between the normal arterial and venous pathways. These malformations do not benefit from intervening capillaries. As a result, venous pressure increases and the individual is predisposed to ischemia or haemorrhage.
The vascular lesions of the spinal cord are usually uncommon and may present with the progressive weakness. The spinal cord compression may be due to mass effect of the lesion expansion or haemorrhage or venous congestion.
Usually the initial investigation for any spinal cord lesion presenting with weakness of limbs is MRI of the spine. MRI may diagnose many lesions. But gold standard investigation for the diagnosis of vascular malformation of spine is spinal angiography.
3 common types of spinal vascular malformations are:
1. Cavernous malformations or Cavernous angiomas or Cavernomas
2. Arteriovenous malformations
3. Arteriovenous fistulas
Cavernous malformations are also known as cavernous angiomas or cavernomas. They constitute about 5% to 12% os spinal vascular malformations. They are aniographically occult , i.e., they may not be seen on angiography. They become symptomatic due to mass effect or due to haemorrhage. They are prone to repeated haemorrhage. So on MRI of the spine a mass occupying lesion may be seen inside the spinal cord hich is surrounded by a gliotic, hemosiderin rim. Patient may present with features of myelopathy due to recuuring hemorrhagic episodes.
Characteristics of intracerebral, brain stem and spinal cavernomas are almost similar.
So, here I have emphasized to describe spinal AVF & spinal AVM in detail.
About a century ago, In 1914, Charles Elsberg performed the first successful operation on a spinal cord malformation. In 1960s, Kendall and Loque used techniques of spinal angiography to define spinal AVMs . In 1977, Kendall and Loque treated these lesions with the less-invasive technique of directly ligating the fistula origin along the dural sleeve, with good results [Kendall].
Many ways have been proposed to describe and classify these vascular lesions of the spinal cord. But, my aim is to provide a simple yet comprehensive view of these lesions so that any neurosurgical trainee can comprehend the entire subject.
In 1992, Anson and Spetzler classified spinal cord vascular malformations into the following 4 categories:
Spinal malformations can also broadly be separated into 2 subgroups. Spinal vascular malformations can also be classified into 2 general groups. One group consists of the spinal dural fistulas (type 1), and the other group has intradural pathology (types 2-4).
Investigations
CT scanning may demonstrate dilated vessels in the thecal sac, but findings are usually normal. If a patient presents with symptoms of subarachnoid hemorrhage, CT scanning demonstrates blood in the spinal fluid.
Myelography findings, with or without CT, show dilated vessels in the intradural space. This imaging modality is very sensitive and shows these abnormalities in detail. This is an invasive procedure that requires injection of a contrast agent into the thecal sac. Postprocedure headaches are not uncommon.
MRI is a noninvasive imaging modality. The soft tissue and neural elements are visualized in detail with this technique. Dilated intradural vessels can be seen as flow voids or can be seen filling with contrast. Edema or hemorrhage in the spinal cord parenchyma can be assessed. The exact fistula site cannot be localized.
MRI of dural AVFs on the thoracolumbar junction usually shows serpiginous vessels in the intradural compartment, along with vasogenic edema in the spinal cord. Intradural vascular spinal malformations appear as lesions in the spinal parenchyma.
MRA or CTA are noninvasive modalities being used to identify any abnormal vessels. However, the resolution of these modalities is not to yet high enough.
Arteriography is the gold standard modality for visualizing arteriovenous malformations (AVMs). This is a dynamic study that allows visualization of the pathology in real time, allowing assessment of high-flow versus low-flow AVMs. In addition, the location of the fistula can be visualized. Arteriography is an invasive procedure that may cause morbidity such as spinal cord ischemia, cerebral vascular accident, and vascular dissection.
Spinal MRI is first-line screening method to detect spinal vascular malformations. If a spinal vascular malformation is still suspected, digital subtraction angiography (DSA) must be performed to display the very small vessels of the spinal cord. As DSA is an invasive procedure, an MR angiography (MRA) or CT angiography (CTA) can be used to determine the spinal cord level of the feeding artery.
Treatment of SVMs
The ideal treatment of spinal vascular malformation is to obliterate the nidus without damaging the spinal vascular blood supply and spinal cord. It may be achieved with open surgery, endovascular methods, or a combination of both. Stereotactic radiosurgery is a newer modality of treatment.
The present surgical treatment options include open surgical ligation or resection of the malformation, endovascular occlusion, spinal radiation, or a combination of these techniques.
Surgical excision is the mainstay of treatment of cavernomas.
Dural arteriovenous fistulas (AVFs), type 1, can be treated with either open or endovascular ligation. Both techniques yield excellent results, with occlusion rates reported as higher than 80%. The benefit of the endovascular technique is that it is less invasive. If the patient has multiple sites of fistula formation, open ligation is more appropriate because all feeding vessels may be ligated under direct vision. Open surgery is necessary if the arterial feeding vessel is impossible to access because of tortuous vascular anatomy or if the vessel supplies blood to healthy regions of the spinal cord [Özkan, Lin, Signorelli, Clark, Kirsch, Maimon]
Intradural AVMs (types 2-4) are typically best treated with endovascular surgery and, if required, open surgery and resection.
Treatment options are dictated by the location of the lesion, the patient's medical condition, and the risk-versus-benefit ratio. The most important factor in determining treatment options is the presence of intramedullary or extramedullary shunting. Malformations that are subpial in location are less likely to be cured. These are usually supplied by subcommissural branches of the anterior spinal artery (ASA). Lesions on the surface of the spinal cord that are supplied by circumferential branches of the ASA may be safely treated with either embolization or surgery.
The new generation of liquid embolic material and microcatheters has made interventional treatment of spinal AVMs safer, with better results [Warakaulle , Corkill].The goal of any intervention is to eliminate the shunt. Microcatheterization is of paramount necessity in achieving effective results. Delivery of embolic material to the nidus of the lesion reduces the arteriovenous malformation (AVM) and reduces the risk of inadvertent embolization of normal vessels.
When preoperative embolization is planned, polyvinyl alcohol microparticles (PVAs) are a reasonable choice of embolic material. They are also useful for embolization of type 2 AVMs. The advantages of PVA are that embolization may be performed at a more proximal location and that the size of particle can be determined depending on the size of the lesion and its collaterals. The goal of treatment with either agent is to provide distal occlusion of the nidus. Proximal occlusion results in collateral reconstitution, with little hope of cure.
Procedure is done under general anesthesia and neurophysiologic monitoring. Somatosensory-evoked potentials (SSEPs) help in assessing spinal cord function. Motor-evoked potentials (MEPs) are also useful when a spinal AVM is supplied by the ASA.
References
The vascular lesions of the spinal cord are usually uncommon and may present with the progressive weakness. The spinal cord compression may be due to mass effect of the lesion expansion or haemorrhage or venous congestion.
Usually the initial investigation for any spinal cord lesion presenting with weakness of limbs is MRI of the spine. MRI may diagnose many lesions. But gold standard investigation for the diagnosis of vascular malformation of spine is spinal angiography.
3 common types of spinal vascular malformations are:
1. Cavernous malformations or Cavernous angiomas or Cavernomas
2. Arteriovenous malformations
3. Arteriovenous fistulas
Cavernous malformations are also known as cavernous angiomas or cavernomas. They constitute about 5% to 12% os spinal vascular malformations. They are aniographically occult , i.e., they may not be seen on angiography. They become symptomatic due to mass effect or due to haemorrhage. They are prone to repeated haemorrhage. So on MRI of the spine a mass occupying lesion may be seen inside the spinal cord hich is surrounded by a gliotic, hemosiderin rim. Patient may present with features of myelopathy due to recuuring hemorrhagic episodes.
Characteristics of intracerebral, brain stem and spinal cavernomas are almost similar.
So, here I have emphasized to describe spinal AVF & spinal AVM in detail.
About a century ago, In 1914, Charles Elsberg performed the first successful operation on a spinal cord malformation. In 1960s, Kendall and Loque used techniques of spinal angiography to define spinal AVMs . In 1977, Kendall and Loque treated these lesions with the less-invasive technique of directly ligating the fistula origin along the dural sleeve, with good results [Kendall].
Many ways have been proposed to describe and classify these vascular lesions of the spinal cord. But, my aim is to provide a simple yet comprehensive view of these lesions so that any neurosurgical trainee can comprehend the entire subject.
In 1992, Anson and Spetzler classified spinal cord vascular malformations into the following 4 categories:
Type 1: This dural AVF is the most common type of
malformation, accounting for 70% of all spinal vascular malformations
[Patsalides et al ]. These fistulas are created when a radiculomeningeal artery
feeds directly into a radicular vein, usually near the spinal nerve root. Dural
AVFs are most commonly found in the thoracolumbar region [ Krings]. Patients
with type 1 malformations become symptomatic because the AVF creates venous
congestion and hypertension, resulting in hypoperfusion, hypoxia, and edema of
the spinal cord. Due to the slow-flow nature of type 1 AVFs, hemorrhage rarely
occurs. Most dural AVFs are believed to occur spontaneously, but the exact
etiology is still unknown [Krings].
Type I lesions are most frequently found in men between the
fifth and eighth decades of life and patients with AVFs are typically older than 40 years. Symptoms increase
over an extended period of months to years and include progressive weakness of
the legs and concurrent bowel or bladder difficulties. Typically, pain is
located in the distal posterior thoracic region over the spine, without a
significant radicular component. However, painful radiculopathy may be present.
Activity or a change in position may exacerbate symptoms in the thoracic or
lumbar region and can result in thoracic spinal cord venous congestion and
lower-extremity weakness.
These
lesions can be mistakenly diagnosed as spinal stenosis and neurogenic
claudication. Foix-Alajouanine syndrome is an extreme form of spinal dural AVF
that affects a minority of patients. These patients present with a rapidly
progressive myelopathy due to venous thrombosis from spinal venous stasis.
Type 2: ( also referred to as a glomus AVM or racemosum ) type 2
malformations are high flow lesions located within the spinal cord. This Glomus AVM consists of a tightly compacted group of arterial and venous
vessels (nidus) inside a short segment of the spinal cord. Multiple feeding
vessels from the anterior spinal artery and/or the posterior spinal circulation
typically supply these AVMs. The abnormal vessels are intramedullary in
location, although superficial nidus compartments can reach the subarachnoid
space [Krings]. Type 2 AVMs are the most commonly encountered intramedullary
vascular malformations, representing about 20% of all spinal vascular
malformations. These lesions usually present in younger patients with acute
neurologic deterioration secondary to their location, which is usually the
dorsal cervicomedullary region. The mortality rate related to type 2
malformation is reported at 17.6%. After initial hemorrhage, the rebleed rate
is 10% within the first month and 40% within the first year.
Type 3: These malformations are arteriovenous abnormalities
of the spinal cord parenchyma fed by multiple vessels. These juvenile
malformations are extensive lesions with abnormal vessels that can be both
intramedullary and extramedullary in location. These lesions are typically
found in young adults and children.
Type 4: Also known as pial AVFs, these malformations are
intradural extramedullary AVFs on the surface of the cord that result from a
direct communication between a spinal artery and a spinal vein without an
interposed vascular network. They are usually seen in patients who are between
their third and sixth decade of life.
Spinal malformations can also broadly be separated into 2 subgroups. Spinal vascular malformations can also be classified into 2 general groups. One group consists of the spinal dural fistulas (type 1), and the other group has intradural pathology (types 2-4).
Investigations
CT scanning may demonstrate dilated vessels in the thecal sac, but findings are usually normal. If a patient presents with symptoms of subarachnoid hemorrhage, CT scanning demonstrates blood in the spinal fluid.
Myelography findings, with or without CT, show dilated vessels in the intradural space. This imaging modality is very sensitive and shows these abnormalities in detail. This is an invasive procedure that requires injection of a contrast agent into the thecal sac. Postprocedure headaches are not uncommon.
MRI is a noninvasive imaging modality. The soft tissue and neural elements are visualized in detail with this technique. Dilated intradural vessels can be seen as flow voids or can be seen filling with contrast. Edema or hemorrhage in the spinal cord parenchyma can be assessed. The exact fistula site cannot be localized.
MRI of dural AVFs on the thoracolumbar junction usually shows serpiginous vessels in the intradural compartment, along with vasogenic edema in the spinal cord. Intradural vascular spinal malformations appear as lesions in the spinal parenchyma.
MRA or CTA are noninvasive modalities being used to identify any abnormal vessels. However, the resolution of these modalities is not to yet high enough.
Arteriography is the gold standard modality for visualizing arteriovenous malformations (AVMs). This is a dynamic study that allows visualization of the pathology in real time, allowing assessment of high-flow versus low-flow AVMs. In addition, the location of the fistula can be visualized. Arteriography is an invasive procedure that may cause morbidity such as spinal cord ischemia, cerebral vascular accident, and vascular dissection.
Spinal MRI is first-line screening method to detect spinal vascular malformations. If a spinal vascular malformation is still suspected, digital subtraction angiography (DSA) must be performed to display the very small vessels of the spinal cord. As DSA is an invasive procedure, an MR angiography (MRA) or CT angiography (CTA) can be used to determine the spinal cord level of the feeding artery.
Treatment of SVMs
The ideal treatment of spinal vascular malformation is to obliterate the nidus without damaging the spinal vascular blood supply and spinal cord. It may be achieved with open surgery, endovascular methods, or a combination of both. Stereotactic radiosurgery is a newer modality of treatment.
The present surgical treatment options include open surgical ligation or resection of the malformation, endovascular occlusion, spinal radiation, or a combination of these techniques.
Surgical excision is the mainstay of treatment of cavernomas.
Dural arteriovenous fistulas (AVFs), type 1, can be treated with either open or endovascular ligation. Both techniques yield excellent results, with occlusion rates reported as higher than 80%. The benefit of the endovascular technique is that it is less invasive. If the patient has multiple sites of fistula formation, open ligation is more appropriate because all feeding vessels may be ligated under direct vision. Open surgery is necessary if the arterial feeding vessel is impossible to access because of tortuous vascular anatomy or if the vessel supplies blood to healthy regions of the spinal cord [Özkan, Lin, Signorelli, Clark, Kirsch, Maimon]
Intradural AVMs (types 2-4) are typically best treated with endovascular surgery and, if required, open surgery and resection.
Treatment options are dictated by the location of the lesion, the patient's medical condition, and the risk-versus-benefit ratio. The most important factor in determining treatment options is the presence of intramedullary or extramedullary shunting. Malformations that are subpial in location are less likely to be cured. These are usually supplied by subcommissural branches of the anterior spinal artery (ASA). Lesions on the surface of the spinal cord that are supplied by circumferential branches of the ASA may be safely treated with either embolization or surgery.
The new generation of liquid embolic material and microcatheters has made interventional treatment of spinal AVMs safer, with better results [Warakaulle , Corkill].The goal of any intervention is to eliminate the shunt. Microcatheterization is of paramount necessity in achieving effective results. Delivery of embolic material to the nidus of the lesion reduces the arteriovenous malformation (AVM) and reduces the risk of inadvertent embolization of normal vessels.
When preoperative embolization is planned, polyvinyl alcohol microparticles (PVAs) are a reasonable choice of embolic material. They are also useful for embolization of type 2 AVMs. The advantages of PVA are that embolization may be performed at a more proximal location and that the size of particle can be determined depending on the size of the lesion and its collaterals. The goal of treatment with either agent is to provide distal occlusion of the nidus. Proximal occlusion results in collateral reconstitution, with little hope of cure.
Procedure is done under general anesthesia and neurophysiologic monitoring. Somatosensory-evoked potentials (SSEPs) help in assessing spinal cord function. Motor-evoked potentials (MEPs) are also useful when a spinal AVM is supplied by the ASA.
References
- Harrop JS. Vascular malformations of the spinal cord.
- Anson JA, Spetzler RF. Interventional neuroradiology for spinal pathology. Clin Neurosurg. 1992. 39:388-417.
- Patsalides A, Santillan A, Knopman J, et al. Endovascular management of spinal dural arteriovenous fistulas. J NeuroIntervent Surg. 2010. 3(1):80-84.
- Krings T. Vascular Malformations of the Spine and Spinal Cord : Anatomy, Classification, Treatment. Klin Neuroradiol. 2010 Feb 28.
- Özkan N, Kreitschmann-Andermahr I, Goerike SL, Wrede KH, Kleist B, Stein KP, et al. Single center experience with treatment of spinal dural arteriovenous fistulas. Neurosurg Rev. 2015 Oct. 38 (4):683-92.
- Kendall BE, Loque V. Spinal epidural angiomatous malformations draining into intrathecal veins. Neuroradiology. 1977. 13:181-189.
- Aadland TD, Thielen KR, Kaufmann TJ, et al. 3D C-arm conebeam CT angiography as an adjunct in the precise anatomic characterization of spinal dural arteriovenous fistulas. AJNR Am J Neuroradiol. 2010 Mar. 31(3):476-80.
- Lin N, Smith ER, Scott RM, Orbach DB. Safety of neuroangiography and embolization in children: complication analysis of 697 consecutive procedures in 394 patients. J Neurosurg Pediatr. 2015 Oct. 16 (4):432-8.
- Signorelli F, Della Pepa GM, Sabatino G, Marchese E, Maira G, Puca A, et al. Diagnosis and management of dural arteriovenous fistulas: a 10 years single-center experience. Clin Neurol Neurosurg. 2015 Jan. 128:123-9.
- Clark S, Powell G, Kandasamy J, Lee M, Nahser H, Pigott T. Spinal dural arteriovenous fistulas--presentation, management and outcome in a single neurosurgical institution. Br J Neurosurg. 2013 Aug. 27 (4):465-70.
- Kirsch M, Berg-Dammer E, Musahl C, Bäzner H, Kühne D, Henkes H. Endovascular management of spinal dural arteriovenous fistulas in 78 patients. Neuroradiology. 2013 Feb. 55 (3):337-43.
- Warakaulle DR, Aviv RI, Niemann D, Molyneux AJ, Byrne JV, Teddy P. Embolisation of spinal dural arteriovenous fistulae with Onyx. Neuroradiology. 2003 Feb. 45(2):110-2.
- Corkill RA, Mitsos AP, Molyneux AJ. Embolization of spinal intramedullary arteriovenous malformations using the liquid embolic agent, Onyx: a single-center experience in a series of 17 patients. J Neurosurg Spine. 2007 Nov. 7(5):478-85.
- Veznedaroglu E, Nelson PK, Jabbour PM, Rosenwasser RH. Endovascular treatment of spinal cord arteriovenous malformations. Neurosurgery. 2006 Nov. 59(5 Suppl 3):S202-9; discussion S3-13.
- Schuette AJ, Cawley CM, Barrow DL. Indocyanine green videoangiography in the management of dural arteriovenous fistulae. Neurosurgery. 2010 Sep. 67(3):658-62; discussion 662.
- Bridwell KH, DeWald RL. The textbook of Spinal Surgery , 3rd ed. ( Wolters Kluwer/ Lippincott, Williams & Wilkins, 2011.
