Vascular Malformations

Vascular malformations of the CNS comprise a heterogeneous group of abnormal vessel structures: arteriovenous malformations (AVMs), cavernous malformations, dural arteriovenous fistulas (DAVFs), venous angiomas (developmental venous anomalies), and capillary telangiectasias. Each has a distinct pathology, clinical presentation, and management. Some are surgical lesions; others are usually incidental and best left alone. Recognizing the pathologic distinction is critical because management decisions and patient counseling depend entirely on getting the diagnosis right. This page covers the major vascular malformations of the CNS.

Arteriovenous Malformation (AVM)

Pathology

A tangle of abnormal arteries and veins (the nidus) with direct arteriovenous shunting and NO intervening capillary bed. Features:

  • Feeding arteries: dilated, often arterialized walls with elastic lamina splitting.
  • Nidus: tangle of malformed vessels with mixed arterial and venous features; abnormal vessel walls with varying thickness and hyalinization.
  • Draining veins: dilated, arterialized due to high flow.
  • Intervening gliotic brain parenchyma, often with old hemorrhage (hemosiderin), reactive astrogliosis.

Clinical

  • Most common symptomatic vascular malformation.
  • Presents with: hemorrhage (~50% — ICH, SAH, or both), seizures, focal deficits, headache.
  • Annual bleeding risk ~2-4%; cumulative lifetime risk substantial.
  • Spetzler-Martin grading (size, location eloquence, venous drainage) predicts surgical risk.

Management

  • Embolization (often as adjunct).
  • Microsurgical resection.
  • Stereotactic radiosurgery (for small, deep, or surgically inaccessible).
  • Observation in selected patients (ARUBA trial showed observation may be reasonable in unruptured AVM, controversial).

Cavernous Malformation (Cavernoma, Cavernous Angioma)

Pathology

Cluster of dilated, thin-walled vascular channels lined by a single layer of endothelium, lacking smooth muscle and elastic tissue, without intervening brain parenchyma. Features:

  • Mulberry appearance grossly.
  • Channels filled with blood, often at various stages of organization.
  • Hemosiderin-laden macrophages and reactive gliosis at margins (chronic leakage).
  • NO normal brain tissue between channels.
  • Often associated with developmental venous anomaly.

Clinical

  • Presents with seizures, headache, focal deficits, or as incidental finding.
  • Annual hemorrhage risk ~0.5-2% (lower than AVM).
  • Familial form: CCM1 (KRIT1), CCM2 (MGC4607), CCM3 (PDCD10) genes; multiple lesions.
  • Sporadic: usually single.

Imaging

  • “Popcorn” or mulberry appearance on MRI.
  • Hemosiderin rim on T2 (low signal).
  • Mixed signal intensity reflecting blood at different stages.
  • SWI / GRE: low signal “blooming.”
  • Often associated DVA on contrast-enhanced imaging.

Management

  • Observation for asymptomatic.
  • Resection for symptomatic (seizures, hemorrhage, progressive deficit).
  • Stereotactic radiosurgery for surgically inaccessible (less effective than for AVM).

Developmental Venous Anomaly (DVA, Venous Angioma)

Pathology

Abnormal arrangement of normal-appearing venous channels — a tuft of medullary veins that drain through a single larger transparenchymal vein into a normal cortical or subependymal vein. The vein walls are histologically normal; brain parenchyma is interposed.

Clinical

  • Almost always incidental.
  • Very rarely a source of hemorrhage in pure form.
  • Often associated with cavernous malformation (the cavernoma is the real culprit when there’s a bleed).
  • Considered a normal variant of venous drainage in most cases.

Imaging

“Caput medusae” appearance with multiple small medullary veins converging on a single draining vein. Best on post-contrast T1 imaging.

Management

Leave alone. Disrupting a DVA can cause venous infarction in the territory it drains.

Capillary Telangiectasia

Pathology

Cluster of dilated capillaries with normal intervening brain parenchyma. Vessels resemble capillaries (thin walls, single layer endothelium) but enlarged.

Clinical

  • Usually incidental.
  • Most common location: pons.
  • Rarely symptomatic.
  • Very rare hemorrhage source.
  • Hereditary hemorrhagic telangiectasia (HHT) syndrome: multiple telangiectasias in brain, lung, GI, skin (Osler-Weber-Rendu).

Imaging

T2 slight hyperintensity; subtle enhancement on contrast. SWI: low signal due to slow flow / deoxyhemoglobin.

Dural Arteriovenous Fistula (DAVF)

Pathology

Abnormal connection between meningeal artery and dural venous sinus or cortical vein within the dura. No nidus (unlike AVM); typically a single fistulous point.

Clinical

  • Most common in older adults.
  • Acquired (often after sinus thrombosis, trauma, surgery, infection).
  • Symptoms depend on location and venous drainage pattern.
  • Cortical venous drainage (Cognard III-V, Borden II-III): high risk of intracranial hemorrhage and venous infarction; aggressive management.
  • Sinus drainage without cortical reflux: usually benign course.

Specific DAVFs

  • Transverse-sigmoid DAVF: pulsatile tinnitus.
  • Carotid-cavernous fistula: chemosis, proptosis, orbital bruit, ophthalmoplegia. Often traumatic.
  • Tentorial DAVF: high cortical reflux risk; aggressive.
  • Spinal DAVF: classic cause of progressive myelopathy in older men.

Imaging

Spinal angiography (gold standard for confirming and characterizing); MRI with venography; CT angiography. Look for prominent vessels on cord surface (spinal DAVF) or abnormal dural enhancement (cranial DAVF).

Management

  • Endovascular embolization (first-line for most).
  • Surgical disconnection of fistulous point.
  • Stereotactic radiosurgery for selected cases.
  • Untreated, cortical venous drainage carries high stroke/hemorrhage risk.

Spinal Vascular Malformations

  • Spinal AVM (intramedullary or extramedullary): nidus within or on cord; presents with hemorrhage or progressive myelopathy.
  • Spinal DAVF: most common spinal vascular malformation; classic in older men; progressive myelopathy from venous hypertension; cord T2 hyperintensity + flow voids on surface; treatable with embolization or surgery.
  • Spinal cavernous malformation: intramedullary cavernoma; recurrent hemorrhage; surgical resection often required.

Sturge-Weber Syndrome

Leptomeningeal capillary-venous angioma with overlying port-wine stain in the trigeminal distribution. Features:

  • Leptomeningeal vascular malformation (often parieto-occipital).
  • Underlying cortical atrophy and calcifications (“tram-track” on imaging).
  • Seizures (often refractory).
  • Hemiparesis, visual field defects.
  • Port-wine stain in V1 distribution.
  • GNAQ somatic mutation (most cases).

Surgery (lobectomy or hemispherectomy) for refractory seizures.

Hereditary Hemorrhagic Telangiectasia (HHT, Osler-Weber-Rendu)

Autosomal dominant; ENG, ACVRL1 genes. Multiple telangiectasias and AVMs in:

  • CNS (brain AVMs, spinal AVMs).
  • Lung (pulmonary AVMs — paradoxical embolism source).
  • GI tract (bleeding).
  • Skin and mucous membranes.
  • Liver.

Brain AVMs in HHT are often multiple and small. Screening is recommended.

🔍 Did You Know?

The classical spinal dural arteriovenous fistula (DAVF) is the most often missed spinal vascular malformation — and the most rewarding to recognize. The typical patient is an older man (often 50s-70s) who presents with slowly progressive lower extremity weakness, sensory disturbance, and bladder dysfunction over months to years. The differential is broad — cervical spondylotic myelopathy, multiple sclerosis, normal-pressure hydrocephalus, B12 deficiency — and the diagnosis is often delayed for one to two years on average. The mechanism is venous hypertension: an abnormal connection between a radicular artery and a radicular vein at a single dural site (usually thoracolumbar) raises pressure throughout the cord’s venous system, leading to chronic cord ischemia. The MRI findings are characteristic but easily overlooked: T2 hyperintensity in the central cord (cord edema) often extending over many segments, with prominent serpiginous flow voids on the cord surface (the dilated arterialized veins). Recognition matters because treatment is curative or markedly improves the patient — embolization or surgical disconnection of the fistula site stops the progression and often produces dramatic recovery. The lesson: any older man with progressive paraparesis and bladder dysfunction without an obvious cause deserves a careful look at the cord MRI for flow voids on the cord surface, and if present, urgent spinal angiography. The diagnosis transforms outcomes when caught.

Pitfalls and Pearls

  • AVM: tangle of arteries + veins with no intervening capillary bed. Hemorrhage, seizures, deficits.
  • Cavernous malformation (cavernoma): cluster of thin-walled channels; mulberry / popcorn appearance on MRI; hemosiderin rim.
  • DVA: caput medusae; almost always incidental; leave alone.
  • Capillary telangiectasia: incidental, often pontine; rarely symptomatic.
  • DAVF: especially cortical venous drainage → hemorrhage risk; emergency management.
  • Carotid-cavernous fistula: chemosis + proptosis + ophthalmoplegia + bruit.
  • Spinal DAVF: progressive myelopathy in older men; flow voids on cord surface; embolization/surgery curative.
  • Spetzler-Martin grade: AVM surgical risk (size, eloquence, drainage).
  • ARUBA trial: unruptured AVM observation may be reasonable; controversial.
  • Sturge-Weber: leptomeningeal angioma + port-wine stain + seizures + cortical calcifications.
  • HHT: multiple telangiectasias and AVMs; pulmonary AVMs → paradoxical embolism risk.
  • Cavernoma + associated DVA: do not disrupt the DVA when removing the cavernoma.
  • Familial cavernoma: CCM1/2/3 genes; multiple lesions; suspect with multiple cavernomas.

References

  1. Love S, Budka H, Ironside JW, Perry A, eds. Greenfield’s Neuropathology. 9th ed. CRC Press; 2015.
  2. Mohr JP, Parides MK, Stapf C, et al. Medical management with or without interventional therapy for unruptured brain arteriovenous malformations (ARUBA). Lancet. 2014;383(9917):614-621.
  3. Spetzler RF, Martin NA. A proposed grading system for arteriovenous malformations. J Neurosurg. 1986;65(4):476-483.
  4. Awad IA, Polster SP. Cavernous angiomas: deconstructing a neurosurgical disease. J Neurosurg. 2019;131(1):1-13.
  5. Krings T, Geibprasert S. Spinal dural arteriovenous fistulas. AJNR Am J Neuroradiol. 2009;30(4):639-648.
  6. Faughnan ME, Mager JJ, Hetts SW, et al. Second international guidelines for the diagnosis and management of hereditary hemorrhagic telangiectasia. Ann Intern Med. 2020;173(12):989-1001.