Associated conditions

Non-developmental syndromes also directly or indirectly affect the Great Cerebral Vein of Galen, although they are extremely rare. These include superior vena cava syndrome (SVCS), and thrombosis of the lateral sinus, superior sagittal sinus, internal jugular vein, or of the Great Cerebral Vein of Galen itself.^{[citation needed]}

Classification

Five patterns of Galenic arteriovenous malformations have been described:

These malformations develop in utero by the persistence of fistulae between primitive pia arachnoidal arteries and pial veins that cross each other at right angles.^[4] Because the primitive Galenic system and the primitive choroidal system lie close together, an arteriovenous malformation involving the primitive choroidal system will inevitably involve the Galenic vein.^[11] Larger arteriovenous shunts correlate with greater hemodynamic effects and earlier symptom onset; small arteriovenous shunts correlate with greater local mass effect causing progressive neurological impairment.^[4]

Surgical

Head circumference measurements should be obtained regularly and monitored carefully to detect hydrocephalus. Neurosurgical procedures to relieve hydrocephalus are important. A ventriculoperitoneal shunt may be required in some infants. A pediatric cardiologist should be consulted to manage high-output failure, if present. Often patients need to be intubated. In most cases, the fistulous arteries feeding into the Vein of Galen must be blocked, thereby reducing the blood flow into the vein.^[10] Open surgery has a high morbidity and mortality. Recent advances over the past few decades have made endovascular embolization the preferred method of treatment. These treatments are preferred because they offer little threat to the surrounding brain tissue. However, there have been several reported cases of arteriovenous malformations recurring.^[12] The young age of many patients, the complex vascular anatomy, and the sensitive location of the Vein of Galen offer considerable challenges to surgeons.^[13] Another treatment option is Radiotherapy. Radiotherapy, also called radiosurgery, involves the use of focused beams to damage the blood vessel.^[12] Radiotherapy is often not pursued as a treatment because the effects of the procedure can take months or years and there is risk of damaging adjacent brain tissue.^[12]

Medical care

Surgery is not always an option when the anatomy of the malformation creates too much of a risk. Recent improvements in endovascular procedures have made many cases, which were not surgically accessible, treatable.^[12] Endovascular treatments involve delivering drugs, balloons, or coils to the site of the malformation through blood vessels via catheters.^[12] These treatments work by limiting blood flow through the vein. There is, however, still risk of complications from endovascular treatments. The wall of the vein can be damaged during the procedure and, in some cases, the emboli can become dislodged and travel through the vascular system.^[5] Two-dimensional echocardiography with color-flow imaging and pulsed Doppler ultrasound was used to evaluate one fetus and five neonates with a Vein of Galen malformation.^[14] Color-flow imaging and pulsed Doppler ultrasonography provided anatomical and pathophysiological information regarding cardiac hemodynamics and intracranial blood flow; with the patient's clinical status, these methods provided a reliable, noninvasive means to evaluate the effectiveness of therapy and the need for further treatment in neonates with Vein of Galen malformations.^[14] When none of these procedures are viable, shunting can be used to ameliorate the pressure inside the varix.^[4] Seizures usually are managed with antiepileptic medications.^[15]