Avm: Symptoms, Types, Causes and Treatment

Arteriovenous malformations (AVMs) are complex vascular anomalies that can occur anywhere in the body, but are most commonly found in the brain, spinal cord, and peripheral tissues. They represent a direct, abnormal connection between arteries and veins, bypassing the capillary system. This unique vascular architecture predisposes individuals to a range of symptoms, complications, and intricate medical challenges. Understanding AVMs—how they present, their types, what causes them, and how they are treated—is essential for both patients and clinicians. This article provides an in-depth, evidence-based overview of AVMs, drawing on the latest research and clinical experience.

Symptoms of Avm

AVMs can remain silent for years, but when they do cause symptoms, these can be sudden, dramatic, or subtle and misleading. The manifestations depend on the AVM’s location, size, and the blood flow dynamics within the malformation.

Symptom	Description	Common Sites	Sources
Hemorrhage	Sudden bleeding, often intracranial	Brain, spinal cord	3 4 18
Seizures	Convulsions or abnormal movements	Brain	3 4 5
Headache	Chronic or acute	Brain	3 4
Focal Deficits	Weakness, numbness, vision/speech loss	Brain, spinal cord	1 2 5
Steal Phenomenon	Hypoperfusion symptoms	Brain, periphery	1 5
High Output Failure	Heart overload	Large or visceral AVMs	12
Incidental	No symptoms, found on imaging	Any	3 4 18

Table 1: Key Symptoms of AVM

Common Presenting Symptoms

AVMs most often come to clinical attention due to hemorrhage—particularly in the brain—resulting in sudden neurological deterioration or even death. Roughly half of cerebral AVM cases are first discovered after an intracranial hemorrhage, often in young adults 3 4 18. Seizures are another frequent mode of presentation, especially with AVMs in cortical regions of the brain. Persistent or severe headaches can signal the presence of a cerebral AVM, but these are less specific.

Focal Neurological Deficits

Depending on the AVM’s location, patients may develop specific deficits:

• Motor weakness or paralysis (hemiparesis)
• Speech disturbances (aphasia)
• Visual field defects
• Sensory disturbances

Such symptoms often reflect the territory of the brain affected by the AVM’s blood flow or by secondary effects like venous congestion, not just its anatomical location 1 2 5.

Steal Phenomenon

Some AVMs create a "steal" phenomenon, where blood is diverted away from normal brain or spinal cord tissue, leading to transient or fluctuating neurological symptoms. This can cause confusion, cognitive disturbances, or transient ischemic attacks 1 5.

High-Output Cardiac Failure

Large AVMs—especially in the liver or lungs—can burden the heart, leading to high-output cardiac failure, particularly in infants or in patients with multiple or very large lesions 12.

Asymptomatic (Incidental) AVMs

With the increasing use of advanced imaging, more AVMs are detected before symptoms occur. These incidental findings raise complex questions about the risks and benefits of intervention 3 4 18.

Types of Avm

AVMs span a spectrum of anatomical locations and vascular architectures, each with distinct clinical implications and therapeutic strategies.

Type	Location	Key Feature	Sources
Cerebral AVM	Brain	Risk of hemorrhage, seizures	3 4 18
Dural AVM	Dura mater (brain)	Venous hypertension, cranial nerve symptoms	1 2
Spinal AVM	Spinal cord	Motor/sensory deficits	6 7
Peripheral AVM	Limbs, skin, organs	Tissue destruction, overgrowth	8 9 10
Capillary malformation-AVM (CM-AVM)	Skin, multiple	Multifocal, genetic links	11

Table 2: Main Types of AVM

Cerebral (Brain) AVMs

These are the most studied and clinically significant AVMs. They are often congenital and may not cause symptoms until adolescence or adulthood. Cerebral AVMs carry a significant risk of hemorrhagic stroke and can produce seizures, headaches, and neurological deficits 3 4 18.

Dural AVMs

Located within the dura mater (the brain’s outer covering), these malformations produce symptoms through venous hypertension, arterial steal, or even cranial nerve dysfunction. They have different patterns of venous drainage and can present with unique neurological signs, depending on their specific location and drainage pathway 1 2.

Spinal AVMs

Spinal AVMs can be classified into several types:

• Type I: Dural AV fistula
• Type II: Glomus (intramedullary) AVM
• Type III: Juvenile AVM
• Type IV: Perimedullary AV fistula

These affect the spinal cord or its coverings, often causing progressive neurological deficits, pain, or even sudden paralysis 6 7.

Peripheral and Visceral AVMs

These AVMs occur outside the central nervous system, often in the limbs, skin, or organs like the liver. They can lead to tissue destruction, disfigurement, bleeding, or high-output cardiac failure if large enough. Peripheral AVMs are also classified by their angiographic appearance, which guides treatment 8 9 10.

Capillary Malformation-AVM (CM-AVM)

This form features both capillary malformations and AVMs, often in multiple sites, and is associated with inherited genetic mutations. It can mimic hereditary hemorrhagic telangiectasia (HHT) in its presentation 11.

Causes of Avm

The underlying causes of AVMs are a fascinating blend of genetics, developmental biology, and sometimes environmental triggers.

Cause	Mechanism	Associated AVM Type	Sources
Congenital	Developmental vascular error	All types	3 4 12
Genetic Mutations	RASA1, EPHB4, MAP2K1, etc.	CM-AVM, extracranial AVMs	10 11 13
Sporadic Somatic	Mosaic RAS/MAPK pathway mutations	Brain/peripheral AVM	10 13
Environmental	Trauma, wounds (trigger in predisposed)	Any, especially in HHT	9 12

Table 3: Main Causes of AVM

Congenital Origins

Most AVMs are thought to arise from developmental errors during vascular formation, typically in embryogenesis. This leads to a persistent abnormal connection between arteries and veins that bypasses the normal capillary bed 3 4 12.

Genetic Factors

Hereditary Hemorrhagic Telangiectasia (HHT)

A well-known inherited disorder (HHT) predisposes to AVMs in multiple organs. Mutations in genes such as ENG (endoglin), ACVRL1, and EPHB4 disrupt normal vascular development, leading to AVMs and other vascular anomalies 11 12.

Capillary Malformation-AVM Syndromes

Germline mutations in RASA1 and EPHB4 have been identified in CM-AVM1 and CM-AVM2, respectively, which are characterized by multifocal capillary malformations with associated AVMs 11.

Somatic Mutations

Recent research has uncovered that many sporadic AVMs are caused by somatic mosaic mutations—alterations in genes of the RAS/MAPK pathway (including KRAS, NRAS, BRAF, and MAP2K1)—that arise after conception and are present only in the affected tissue 10 13. These mutations drive abnormal endothelial cell signaling, proliferation, and vessel formation.

Environmental and Secondary Causes

While most AVMs are congenital, environmental factors such as trauma or localized wounds may trigger AVM formation in genetically susceptible individuals or exacerbate an existing malformation 9 12.

Treatment of Avm

Managing AVMs is complex and tailored to the individual, depending on type, location, size, symptoms, and risk of complications. Treatments aim to eliminate the AVM or reduce its risks, often requiring a multidisciplinary approach.

Treatment	Approach/Goal	Typical Use	Sources
Microsurgery	Surgical removal	Accessible brain/spinal AVMs	4 15 16 18
Endovascular	Embolization (arterial/venous)	Cerebral, spinal, peripheral AVMs	8 15 17 18
Radiosurgery	Targeted radiation	Small/deep brain AVMs	4 15 16 18
Multimodality	Combo of above	Complex/high-grade AVMs	15 16 18
Observation	No intervention	Asymptomatic, high-risk AVMs	14 18
Pharmacologic	Targeted therapies (experimental)	Genetic/somatic mutation-driven AVMs	10 13

Table 4: Main Treatment Approaches for AVM

Microsurgical Resection

For accessible AVMs, especially in the brain or spinal cord, surgical removal can be curative. Microsurgery is often preferred for small, low-grade lesions with accessible locations. However, surgery carries risks of neurological deficit, especially in eloquent brain regions 4 15 16 18.

Endovascular Embolization

This minimally invasive technique involves threading a catheter into the AVM’s vessels and injecting materials (such as glue, coils, or ethanol) to block abnormal blood flow. Embolization can be curative for some peripheral, spinal, and select brain AVMs, or used as an adjunct to surgery or radiosurgery 8 15 17 18. Transvenous embolization is an emerging technique with promising results 17.

Radiosurgery

Radiosurgery (e.g., Gamma Knife) delivers focused radiation to the AVM, causing gradual vessel closure over months to years. This is best suited for small, deep-seated brain AVMs not easily reached by surgery. Obliteration rates are highest for small lesions, but treatment effects are delayed 4 15 16 18.

Multimodality Therapy

Many AVMs, especially larger or more complex ones, require a combination of treatments—surgery, embolization, and radiosurgery—to optimize cure rates and minimize complications. This approach has improved outcomes in both pediatric and adult populations 15 16.

Observation and Conservative Management

For high-grade AVMs (large, deep, or in eloquent locations), the risks of intervention may outweigh the benefits. In these cases, careful observation and management of symptoms is recommended. Partial treatment may not reduce hemorrhage risk and could even worsen outcomes 14 18.

Pharmacologic and Targeted Therapies

Recent discoveries of molecular drivers (such as MAP2K1, KRAS, BRAF mutations) have opened the door for targeted therapies using drugs like MEK1 or BRAF inhibitors—already in use for some cancers. Early studies and animal models show promise, especially for previously untreatable or recurrent AVMs 10 13.

Conclusion

AVMs are intricate vascular anomalies with diverse presentations, causes, and management strategies. Understanding the nuances of their symptoms, types, and underlying biology is crucial for optimizing care and improving outcomes.

Key Points:

• AVMs may present with hemorrhage, seizures, neurological deficits, or remain asymptomatic.
• They can occur in the brain, spinal cord, peripheral tissues, or as part of genetic syndromes.
• Most AVMs are congenital, with both germline and somatic genetic mutations playing key roles.
• Treatment is individualized, ranging from observation to surgery, embolization, radiosurgery, and—emerging—targeted pharmacologic therapies.
• Multidisciplinary teams and ongoing research are central to advancing AVM care.

By staying informed of the latest advances and tailoring approaches to each case, clinicians offer hope for safer, more effective AVM management.