An aneurysm occurs when part of an artery wall weakens, allowing it to balloon out or widen abnormally. Aneurysm can be caused by head trauma, an infection or another medical condition, such as Moyamoya disease. As with adults, most aneurysms in children do not cause symptoms and are never detected unless they rupture. If an aneurysm ruptures, it can be life-threatening.

An arteriovenous malformation (AVM) is a complex tangle of abnormal connections between arteries and veins that is present at birth. It can raise a person’s blood pressure, and over time can reduce blood supply to surrounding skin and tissues. AVMs can increase a person’s risk of having a stroke or brain aneurysm.

An arteriovenous fistula is an abnormal connection between an artery and a vein. It can be something a person is born with, or it can result from disease or a traumatic injury.

An arterial dissection is a tear in the inner lining of an artery. It usually develops suddenly. Arterial dissection can be associated with an injury or an existing medical condition (such as Bow hunter’s disease).

A cavernous malformation (CVM), also called a cavernoma, cavernous angioma or cavernous hemangioma, is a condition in which clusters of blood vessels in the brain or spinal cord form abnormally, creating “caverns” filled with slow-moving blood. Some CVMs cause no symptoms, but larger ones may cause seizures, headaches and impaired speech or vision.

CVMs can be found anywhere in the body, and can cause significant bleeding problems in the brain or spinal cord. These malformations can also be attached to an important “normal” vein that the brain and spinal cord need to function normally. Some CVMs can be identified by a genetic abnormality.

Hereditary hemorrhagic telangiectasia (HHT) is a genetic disorder that causes malformed blood vessels. It can lead to bleeding in multiple organs of the body. HHT is also known as Osler-Weber-Rendu syndrome.

Some vascular conditions, such as arteriovenous malformation, Moyamoya disease and stroke, can cause movement disorders. Symptoms include involuntary movements such as tremors, dystonia (sustained muscle contractions) and others.

Moyamoya disease is a rare but very serious condition in which one or both of the internal carotid arteries (located in the front of the neck) become narrower over time. This causes blood flow to slow down, increasing a child’s risk of developing a blood clot. Tiny blood vessels form around the blocked artery as the body attempts to restore normal blood flow. The Japanese word “moyamoya” means “puff of smoke” — which is what the tiny blood vessels look like on an imaging test.

If left untreated, Moyamoya disease can cause multiple strokes, leaving brief or permanent weakness, or mental decline. 

Moyamoya syndrome is a rare occurrence in which Moyamoya disease and another related condition are present. Some of these related conditions include sickle cell disease, Down syndrome, Alagille, PHACE, neurofibromatosis and cancer. Radiation therapy can also lead to Moyamoya disease.

Neurofibromatosis (NF) is a set of genetic disorders of the nervous system. It causes tumors to form in the brain, spinal cord and nerves.  

NF1 is the most common type of neurofibromatosis, affecting one in 3,000 people. NF1 can be characterized by changes in skin pigment, tumors, bone abnormalities and learning disabilities. 

NF2 is a separate genetic disorder characterized by tumors of the eighth cranial nerves and other nerves. It can result in hearing loss and other complications.

Schwannomatosis is a rare form of NF. Patients with schwannomatosis develop multiple schwannomas (Schwann cell tumors) on cranial, spinal and peripheral nerves, without other signs of NF1 or NF2. These tumors are often limited to a single segment of the body.

A pseudoaneurysm occurs when the vessel wall is injured and blood flow through the vessel is disrupted or even cut off. Blood collects outside the artery and a clot (thrombosis) forms. This condition is usually caused by some kind of trauma to the artery. In contrast, a true aneurysm is usually caused by a defect that has been present since birth, or by some kind of disease process.

A pseudotumor, also called idiopathic intracranial hypertension, occurs when pressure inside the skull increases for an unknown reason. Symptoms mimic a brain tumor, but no tumor is present. Symptoms can include headaches behind the eyes, ringing in the ears, nausea, vomiting or dizziness, and others.

Sinus pericranii is a rare disorder in which veins on the outside of the scalp are abnormally connected to veins in an area of the brain called the dural sinuses. Dural sinuses play a role in blood circulation in the brain. The most visible symptom of sinus pericranii is a swollen mass on the scalp. The condition sometimes occurs along with other medical problems, such as developmental delays and macroencephaly (an abnormally large head in infants).

Sinus thrombosis occurs when a blood clot forms in the brain’s venous sinuses. This can prevent blood from draining out of the brain. As a result, blood cells may break and leak blood into the brain tissue. This causes a hemorrhage. Symptoms of hemorrhage may include headache, abnormal vision, seizures, and weakness of the face and limbs on one side of the body.

A stroke occurs when blood flow to the brain stops because of a clot (ischemic stroke) or because a blood vessel ruptures (hemorrhagic stroke). 

Blood carries oxygen and other nutrients to the body’s cells and organs. When it cannot reach the brain for more than three minutes, brain cells begin to die. The brain cells continue to die for as long as they are deprived of oxygen.

The main types of stroke (in children and adults) are:

• Ischemic stroke
• Transient ischemic attack (TIA)
• Hemorrhagic stroke

Sometimes stroke can occur when a child has a heart disorder, lymphoma (cancer of the immune system and white blood cells) or other serious medical condition.

Learn More About Childhood Stroke

Sturge-Weber syndrome (SWS) is a rare condition in which abnormal blood vessels grow on the brain’s surface. This can lead to seizures, developmental delays, glaucoma and weakness or paralysis on one side of the body. Babies with SWS are born with a port-wine stain birthmark, usually on the face. 

The most common types of head, neck and spine tumors in children are gliomas and medulloblastomas.

Head, neck and spine tumors may be benign or malignant. The medical team “grades” these tumors to indicate how serious they are. Low-grade tumors (I and II) tend to grow slowly, and high-grade tumors (III and IV) are fast-growing, malignant and spread into healthy brain tissue.

Vein of Galen malformation (VOGM) is a rare type of arteriovenous malformation (AVM) deep in the brain. It occurs when blood from cerebral arteries rushes too quickly into a large vein called the vein of Galen. The blood flows away from the brain instead of toward it. This puts pressure on the heart and lungs and can lead to heart failure or pulmonary hypertension, a type of high blood pressure that affects arteries in the lungs and in the heart. VOGM occurs during early prenatal development and is often visible on a prenatal ultrasound. It must be treated soon after birth.

Venous malformations consist of malformed veins that do not work properly. They can occur anywhere in the body, including the skin, soft tissues, muscles and internal organs. Venous malformations typically grow slowly, but they can grow quickly as well.