66 Vein of Galen Malformation

Samer K. Elbabaa and Sten Solander

Clinical Presentation

A 1-month-old baby girl is referred to neurosurgery clinic for evaluation of enlarging head circumference since birth.

There is no history of seizures, lethargy, or vomiting.

Physical examination reveals a normal-looking baby girl, flatanterior fontanelle, mildly dilated scalp veins, and head circumference at the 75th percentile for age (it was at the 25th percentile at birth).

Initial head ultrasound shows normal-sized ventricles, but with dilated vascular structures.

Magnetic resonance imaging (MRI) of the brain is obtained and shown in Fig. 66.1.

Questions

Interpret the MRI findings.

What further diagnostic studies and workup would you like to obtain?

What is the most likely diagnosis?

Describe the incidence of this lesion.

What conditions do you need to evaluate when you consider your treatment options? Discuss your treatment options.

Interpret the provided cerebral angiogram images (Fig. 66.2)
You decide to proceed with endovascular treatment of the vascular lesion. What is the indication for treatment? What is the goal of the treatment? Does the age of presentation affect your treatment plan?
Interpret the provided postembolization angiogram images (Fig. 66.3).
How will you follow the patient after the treatment?
Provide a radiographic classification of this pathology.

Answers

Interpret the MRI findings.

MRI shows mildly dilated ventricles.
There is dilatation of the vein of Galen, straight sinus, and confluence of superior sagittal sinus and straight sinus.

What further diagnostic studies and workup would you like to obtain?

Pediatric cardiology consultation and echocardiogram to evaluate for congestive heart failure
Close monitoring of head circumference
Four-vessel angiogram and endovascular treatment in the same setting if there is clinical evidence of congestive heart failure, hydrocephalus, or change in neurologic status.

What is the most likely diagnosis?

Vein of Galen malformation (VOGM)

This is a dilatation of the median vein of the prosencephalon, which is a precursor of the vein of Galen, caused by an arteriovenous (AV) shunt from the choroidal arteries of the anterior and posterior circulation.¹
Describe the incidence of this lesion.
- The true incidence is unknown, but VOGM cases are rare.
- The reported incidence is less than 1% of cerebral vascular malformations.
- The first description of a VOGM was probably by Steinhill in the German pathology literature in 1895.²
What conditions do you need to evaluate when you consider your treatment options? Discuss your treatment options.
- It is important to understand that most conditions encountered in VOGM patients are related to the degree of AV shunting.
- Congestive heart failure (if present): Management by pediatric cardiologist is critical to evaluate the need of medical treatment (digoxin, diuretics, and ventilatory support). Emergency endovascular therapy may be necessary to reduce the AV shunt, which can improve the cardiac function.
- Ventriculomegaly: This results from the increased dural sinus pressures secondary to the AV shunting.
  - If the increase in head circumference seems too rapid or if the clinical follow-up period demonstrates a significant developmental delay, urgent embolization should be performed and ventricular shunting should be avoided.³
- Seizures (if present): There may be a need for antiepileptic therapy, likely phenobarbital in the neonatal period.
- Treatment options are discussed below.
  - Observation: Children with VOGM have a very poor prognosis if left untreated. An extensive clinical and anatomic evaluation is needed to determine the optimal timing of the treatment. A short period of observation may improve the outcome if clinically tolerated.
  - Surgical clipping: Surgical treatment was the best available therapeutic option before the era of endovascular treatment.
    - Different techniques for open microsurgical treatment of VOGM have been described.^2,4,5
    - Yasargil et al.⁴ emphasized the utility of a posterior interhemispheric approach in a sitting position.
    - The deep central fistulous communications that are characteristic for VOGM make them less amenable to excision than endovascular treatment.⁶
  - Endovascular embolization: Advances in endovascular techniques and imaging have helped us to understand the anatomy and pathophysiology of VOGM. They have also provided new treatment options with improved outcomes.
    - Ciricillo et al. in 1990 retrospectively compared the outcomes of both surgical and endovascular techniques in neonatal patients and concluded that endovascular options are far safer.⁷
    - Endovascular treatment has become the cornerstone for good outcomes in these challenging lesions.
    - Lasjaunias et al. reported a large series of 317 patients, 233 patients were treated with endovascular embolization from 1981 to 2002. The treatment method of choice was a transfemoral arterial approach to deliver glue at the fistulous zone. In their series, mortality rate after the embolization was 10%. Of the surviving patients, moderate to severe developmental delay was seen in 26% of patients; however, 74% were neurologically normal on follow-up.³
Interpret the provided cerebral angiogram images (Fig. 66.2).
- The images show aneurysmal dilatation of the median vein of the prosencephalon on both internal carotid and vertebral artery injections.
- The main arterial feeders are from the posterior choroidal arteries.
You decide to proceed with endovascular treatment of the vascular lesion. What is the indication for treatment? What is the goal of the treatment? Does the age of presentation affect your treatment plan?
- The indications for treatment include congestive heart failure, hydrocephalus, or neurologic symptoms.
- The primary goal of the treatment is to control the AV shunt. A staged embolization is generally recommended for neonates.
  - This provides preservation of the hydrovenous equilibrium.
  - Also, it limits the high renal exposure to contrast volumes.
  - Severe encephalomalacia and multiorgan failure are associated with poor prognosis, even with a technically successful embolization.
  - In infants, normal brain development should be preserved by endovascular exclusion of the fistula, if technically feasible.^3,8
- In 2006, Lasjaunias et al. summarized 20 years of experience in treatment of VOGM at Le Kremlin Bicetre, Paris, France, and emphasized the importance of a thorough analysis of neonatal patients with VOGM to best predict the degree of cerebral tissue impairment not evident on imaging.³
  - The VOGM neonatal score was developed by their group, which included cardiac, cerebral, respiratory, hepatic, and renal functions.
  - Their management decisions follow a strict protocol based on the neonatal score derived from the above information.³
Interpret the provided postembolization angiogram images (Fig. 66.3).
- The fistula has been obliterated by a combination of transarterial catheterization of the venous pouch with coil embolization, followed by glue injection in the feeding artery.
How will you follow the patients after treatment?
- Cardiac function by echocardiogram
- Head circumference
- Monitoring of ventricular size by head ultrasound or computed tomography scan
- Follow-up cerebral angiogram at 6 months post-treatment. If contrast hyperemia is demonstrated at 6 months, even without evidence of AV shunting, additional control angiograms are recommended at 1 and 2 years later.³
Provide a radiographic classification of this pathology.
- The most widely referenced angiographic classifications are those of Lasjaunias et al.^8,9,10 and Yasargil et al.^4,10
- Lasjaunias et al. angiographic classification includes true and secondary vein of Galen malformations.⁹
  - The true VOGM occurs because of a dysembryogenic event involving the median vein of the prosencephalon.
    - As a result, a fistulous connection develops between the choroidal arteries and the veins in the wall of the dilated vein of prosencephalon.
    - The deep venous system has a separate drainage pattern without communication with the fistula.
    - Further subcategories of true VOGM include the mural type, in which the fistula is in the wall of the vein (median vein of the prosencephalon) or the choroidal type, with drainage into tributary veins of the medial vein of the prosencephalon.
  - The secondary types of VOGM have adjacent arteriovenous malformation that drains selectively into the great vein of Galen.
    - These lesions are characteristically supplied by branches of the middle cerebral artery (thalamoperforating, lenticulostriate, or transsylvian branches), whereas the choroidal and mural true vein of Galen malformations are typically filled by choroidal and pericallosal vessels.⁹
- Yasargil et al. defined four types of VOGM lesions:
  - Type 1 is a simple small fistula involving branches from the pericallosal or posterior cerebral arteries.
  - Type 2 involves more feeding vessels from middle cerebral artery branches (thalamoperforating vessels).
  - Type 3 involves high-flow lesions with large numbers of fistulous connections from a wide range of feeding vessels.
  - Type 4 is a midline AVM with drainage into the vein of Galen (analogous to Lasjaunias’ secondary VOGM).¹⁰