There are four type of vascular malformations.
1. Developmental venous anomalies (DVAs) or venous angiomas
These lesions are characterized by medullary veins (“caput medusae”) that are arranged in a radial manner, draining in a central dilated superficial or deep vein of the parenchyma.
Histology
Microscopically, these DVAs are formed by normal vessels and in rare situations there are hyalinisation or thickening of the wall (degenerative changes).
Common sites
These lesions are, usually, supratentorial and appear most frequently in the frontal lobe. Diencephalon, brainstem and spinal cord don’t present this type of pathology.
Clinical Presentation
In general, DVAs are benign lesion and rarely they are diagnosed in presence of:
- Seizures
- Headache
- Neurological deficits
- Hemorrhage
Pathophysiological correlations
Note that clinical manifestations are variable and could be classifiable in relation to the pathophysiology of the lesion:
Mechanical compression on intracranial structures:
- Hydrocephalus
- Brainstem deficits
- Hemifacial spasm
- Tinnitus
- Trigeminal neuralgia
Flow-related symptoms:
- Increased flow (arteriovenous malformation draining through a DVA causing a intraventricular/parenchymal hemorrhage or a venous infarction with headache, coma, neurological deficit and seizures;
- Restricted outflow (both anatomical obstruction and physiologic obstruction), in both cases there are headache, neurological deficits, altered cognition and seizures.
Diagnosis and Treatment
Cerebral angiography (gold standard), CT scan, MRI, MRA (Magnetic Resonance Angiography)
The treatment is usually conservative. Surgery is indicated in case of hemorrhage or if seizures.
2. Capillary teleangectasias
Capillary teleangectasias are usually multiple lesions found in middle cerebellar peduncles, pons and dentate nuclei.
Teleangectasia is a term referred to small and dilated capillaries.
Histology
The surrounding brain presents micro-hemorrhage or gliosis. Probably, this lesions are the early stage in the process of development of cavernous malformation.
Clinical Presentation
Normally these lesions are silent and are found incidentally.
Occasionally they present:
Diagnosis and Treatment
MRI is the gold-standard for the identification of these lesions. They present as black dots of hypointensity on T1 and T2.
Surgery is generally not indicated.
Angiography
Angiographically, it is possible to make a differential diagnosis with DVAs: capillary teleangectasias can be identified in late arterial or early capillary phase, conversely, DVAs are identified in the venous phase.
3. Cavernous malformations (CM) or cavernous angiomas or cavernous hemangiomas or cavernomas.
Macroscopically, CMs are “mulberry” lesions with swollen purplish clusters. The diameter is between 2 mm to several centimeters.
Microscopically, CMs are composed of capillaries with thin wall, simple endothelial lining and thin fibrous adventitia. Note that typically there is absence of both elastic fibers and smooth muscle.
The cerebrum is the most frequent location (70-90%), usually these lesions are subcortical and located both in the peri-rolandic and temporal areas.
Histology
Due to hemorrhages, the surrounding tissue presents gliosis and hemosiderin laden associated to the presence of dilated capillaries (resembling capillary teleangectasias). This last feature supports to the hypothesis that capillary teleangectasias and cavernous malformations are two types of AVM probably originating from a common abnormality.
Note that in larger lesions it is possible to identify calcification, ossification and inflammation.
In 25% of cases, cavernomas are located in the posterior fossa (pons and cerebellar hemispheres)
Etiology
Familiar (characterized by some mutations in genes):
- CCM1 - Frequent in Hispanic Americans;
- CCM2 - Frequent in Non-Hispanic Americans;
- CCM3 - Frequent in Non-Hispanic Americans.
Sporadic
Epidemiology
Cavernomas occurs with 1:1 ratio in male and female population. The mean age is 30-40 years old. In women, hemorrhage and neurological deficits are most present.
Cavernomas associated with DVAs are more prone to cause hemorrhage than those not associated with DVAs.
Clinical Presentation
Symptoms and signs are specific on the basis of the location of CMs.
Supratentorial CMs
- Seizures
- Hemorrhage
- Neurological deficits
Infratentorial CMs
- Hemorrhage
- Neurological deficits
- Cranial neuropathies and long tract signs (if the brainstem is involved, worse prognosis)
Pathophysiological correlations
Note that seizures and neurological deficits are caused by both mass effect with compromise of the circulation and by microhemorrhage with subcortical hemosiderin deposition.
Diagnosis
CMs are “angiographycally occult” because the blood flow through these lesions is extremely slow. So, MRI is the best technique to detect them.
Head MRI
- “Popcorn” pattern of variable intensity because of the presence of different blood products;
- Dark hemosiderin peripheral ring if an hemorrhage occurred (not infrequently silent).
Head CT
It reveals an hyperdense and irregular mass with calcifications.
4. Arteriovenous malformations (AVMs)
These are the most dangerous congenital vascular malformation because, potentially, they cause massive hemorrhage and intractable epilepsy.
Epidemiology
AVMs are present in 0,1% of the population.
Most of them (90%) are supratentorial lesions and 10% are infratentorial.
In 91% of cases they are single lesion.
Stroke incidence
Brain AVMs cause 1-2% of strokes, 3% of strokes in young adults and 9% of SAH.
Physiopathology
The architecture of AVMs is typical: there is a direct communication between artery and vein without the presence of capillary.
Multiple arteries and veins can be involved.
A vascular communication of this type lead to the development of a high flow phenomena:
- The development of aneurysms both in the afferent and efferent sides. Aneuerysm can lead to bleeding;
- Arterialisation of venous side Note that both the aneurysm and the variation of blood flow are responsible of symptoms and signs.
Clinical Presentation
High incidence between 10 and 40 years old.
Major onset symptoms are:
- Intracranial hemorrhage (41-79%), more frequent in children;
- Seizures (11-33%), typically focal with secondary generalization, are more frequent if AVM is cortical, large, multiple and superficially-drained;
- Headache;
- Focal neurological deficit are uncommon, it can be caused by vascular steal syndrome (due to abnormal blood flow), mass effect, hemorrhage or seizures.
Factors influencing symptoms
Important factors influencing symptom intensity:
- Age
- AVM Location
- Size
- Vascular features
Diagnosis
CT, MRA (Magnetic Resonance Angiography), Angiography.
Head CT
With contrast administration. The contrast enhance the AVM, but in case of intraparenchymal hemorrhage/intracranial hypertension, a minor evidence of AVM quote can occur.
Head MRI
Dark flow in T1 and T2. It’s important also for the follow up.
Angiography
It gives information about:
- Anatomical structure of AVMs;
- Presence of flow-related complication (aneurysms);
- Bloodflow state (critical for evaluation of endovascular treatment).
Treatment
- Surgery - Surgical risk is quantified by Speztler-Ponce score, derived by Spetzler-Martin scale;
- Stereotactic radiosurgery;
- Endovascular embolisation.
References
McCormick WF. The pathology of vascular ("arteriovenous") malformations. J Neurosurg 1966; 24:807.
Kondziolka D et al. The natural history of cerebral cavernous malformations. J Neurosurg 1995; 83:820.
Madder P et al. Development of a cavernous malformation of the brain. Am J Neuroradiol 1998; 19:1141.
Peebles TR et al. Intracranial developmental venous anomalies: diagnosis using CT angiography. J Comput Assist Tomogr 1997; 21:582.
Kamezawa T et al. Clinical implications of associated venous drainage in patients with cavernous malformation. J Neurosurg 2005; 102:24.
Del Curling O Jr et al. An analysis of the natural history of cavernous angiomas. J Neurosurg 1991; 75:702.
Robinson JR et al. Natural history of the cavernous angioma. J Neurosurg 1991; 75:709.
Alba T et al. Natural history of intracranial cavernous malformations. J Neurosurg 1995; 83:56.
Zimmerman RS et al. Cavernous malformations of the brain stem. J Neurosurg 1991; 75:32.
Tian KB et.al. Clinical course of untreated thalamic cavernous malformations: hemorrhage risk and neurological outcomes. J Neurosurg. 2016 Nov 11:1-12.
Ellis JA et.al. Arteriovenous malformations and headache. J Clin Neurosci. 2016 Jan;23:38-43
Gross BA et.al. Cerebral cavernous malformations: natural history and clinical management. Expert Rev Neurother. 2015;15(7):771-7.
Klostranec JM et.al. Neuroimaging of cerebral cavernous malformations. J Neurosurg Sci. 2015 Sep;59(3):221-35.
Petr O et.al. Brainstem cavernous malformations. J Neurosurg Sci. 2015 Sep;59(3):271-82.
Authors
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Federico Nicolosi, MD
Neurosurgeon
University of Milan
"Spedali Civili" Hospital Brescia (Italy)
Scientific Team - UpSurgeOn
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Giorgio Saraceno, MS
Medical Student
University of Brescia (Italy)
Scientific Team UpSurgeOn
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