Neurointervention in Pediatrics
From The Child's Doctor, Fall 2011
- Ali Shaibani, MD
- Director, Neurointerventional Service, Children's Memorial Hospital; Co-Director, Neurointerventional Surgery, Northwestern Memorial Hospital; Associate Professor of Radiology and Neurosurgery, Northwestern University Feinberg School of Medicine
- Disclosure: Dr. Shaibani refers to devices used in pediatric neurointervention that are approved in adults, but used off-label in children. He has no industry relationships to disclose.
Other Disclosure Information
At the conclusion of this activity, participants will be able to:
- Describe the role of neurointerventional techniques in the treatment of vascular diseases of the brain and spine
- Describe the role of neurointerventional techniques in the diagnosis and treatment of nonvascular diseases of the extracranial head, neck and spine
With the rapid advances in minimally invasive and image-guided surgical and interventional techniques, many conditions that would have been considered untreatable as recently as 10 years ago are now amenable to effective treatments with relatively low morbidity and mortality. Prime examples are pediatric neurovascular diseases, which now are either possible or safer to treat with rapid advances in neurointerventional techniques. With the advances in experience, techniques and devices, neurointerventional treatments that were previously only available for adults are now available for pediatric patients as well. The expertise for delivering such treatments tends to be concentrated in large pediatric specialty hospitals where larger volumes of patients with these relatively rare conditions are seen to provide adequate experience and quality outcomes. Given the relatively recent advances in these techniques, a review of neurointerventional treatments in pediatric patients is timely and helpful for pediatricians.
Interventional neuroradiology began as an outgrowth of diagnostic neuro-angiography. It has had a very rapid development in parallel with the advances in the development of better and more technically sophisticated fluoroscopic and angiographic equipment and devices such as catheters, microcatheters, stents, and embolic materials, all of which have been responsible for the explosion of minimally invasive image-guided treatments over the last 2 decades.
Early pioneers in minimally invasive and endovascular techniques were neurosurgeons such as Lussenhop in the 1960s, who described embolization of brain arteriovenous malformations (AVMs) by direct injection of silastic beads into cervical arteries, and Serbinenko in Russia who used latex balloons for treatment of brain aneurysms in the 1970s. Beginning in the 1980s, the field has been primarily advanced by neuroradiologists with special interest in endovascular treatment techniques. Guglielmi and Vinuela at UCLA developed the first detachable platinum coils in 1988 and the first patient was treated in 1990. The use of liquid embolics for treatment of AVMs was pioneered by several physicians, including Kerber at University of California, San Diego.
While the majority of practitioners come from a neuroradiology background, due to the increasingly multidisciplinary nature of the field, the name of the specialty and society was changed from interventional neuroradiology to neurointerventional surgery in 2007. Neurointerventional surgeons frequently interact with colleagues in neurosurgery, neurology, ENT, plastic surgery, and orthopedics, as well as the primary care pediatrician.
Advances in the field have allowed the minimally invasive treatment of neurovascular diseases in both adults and children. Examples include the endovascular treatment of intracranial aneurysms, as well as vein of Galen malformations in children.
Neurointerventional diagnostic procedures performed in children include diagnostic angiography for the evaluation of cervicocerebral and spinal vasculature.
- Cervicocerebral angiography is commonly performed for evaluation of possible cerebral vasculitis or other vasculopathies, Moya Moya disease, arterial dissections, as well as congenital and acquired arteriovenous malformations of the brain, head and neck, and spine.
- Image-guided biopsies of lesions of the head and neck, spinal column, discs, and paraspinous tissues are performed for the diagnosis of underlying neoplasm or infection.
- Image-guided lumbar punctures (LPs) are performed if traditional methods of obtaining cerebrospinal fluid for diagnostic testing have failed. LPs are performed using ultrasound in patients younger than 4 months and with fluoroscopy in patients older than 4 months. Large volume taps for symptom relief are performed in cases of idiopathic intracranial hypertension (pseudotumor cerebri) with measurement of opening pressures.
Therapeutic interventions with embolization
Embolization refers to the occlusion of blood vessels using material delivered through endovascular catheters or, less commonly, using image-guided percutaneous access via a needle. There is a variety of material that can be used for embolization, including small, irregular or spherical particles made of polymers or acrylates, liquid sclerosants or non-sclerosing liquid embolics such as adhesive acrylates (medical superglue) and non-adhesive polymers such as ethylene vinyl alcohol copolymer. The type of embolic agent used depends on the type of lesion treated and the intention for treatment (ie, pre-operative embolization vs. definitive treatment for cure). Embolization is used for the following disease processes.
Congenital pial arteriovenous malformations of the brain: These are congenital shunts between pial arteries (arteries supplying the brain parenchyma) and veins. The exact cause of these lesions is unknown, but they represent an error in the embryologic development of the vasculature of the brain. The most common clinical manifestations of brain AVMs are usually headaches, hemorrhage or seizures, with less common manifestations being intracranial venous hypertension (with consequent hydrocephalus, headaches, or optic nerve ischemia). The most commonly used grading system for these lesions is the Spetzler Martin grading system, which assigns values based on size, location (eloquence of the part of the brain where the malformation is located) and the venous drainage (superficial vs. deep draining veins). The annual risk of bleeding depends on the grade of the lesion, the age of the patient and prior history of bleeding.
In children, given the large lifetime risk of hemorrhage, treatment is usually recommended in cases where the risk of treatment is acceptable. Treatment modalities in decreasing order of frequency include embolization followed by surgery, surgery alone, radiosurgery. Embolization alone is a viable treatment option in adults if a cure can be achieved, but because of the higher recurrence rate in children, surgical excision is usually recommended.
Dural arteriovenous shunts (DAVS): These lesions represent short circuits between dural arteries and the dural venous sinuses. These can be either acquired lesions or congenital. The most common congenital variety is the torcular DAVS where the arteriovenous connection is at the level of the confluence of the superior sagittal, transverse and straight sinuses.
The clinical presentation is due to intracranial venous hypertension (localized or generalized). Manifestations include hemorrhage, venous ischemia, hydrocephalus, loss of brain tissue, delayed neurological development, and enlarging head size among others. These can manifest clinically as headaches, seizures, and focal neurological deficits. The primary treatment modality for these malformations is endovascular embolization. See Case 1 A-D.
Vein of Galen malformations (VOGM): These malformations represent a subtype of pial brain AVMs where the “short circuit” is between deep perforating arteries and an enlarged vein of Galen (part of the deep venous system). The clinical manifestations are primarily due to the arteriovenous shunting and consequent venous hypertension. Often these malformations are picked up during fetal ultrasound. There are 3 main presentation patterns, reflecting primarily the degree of AV shunting:
- Presentation at or shortly after birth: These patients usually present with high-output cardiac failure due to the large amount of AV shunting. The prognosis of this population is usually guarded to poor even with embolization.
- Presentation between 6 months to 3 years: These patients usually present with enlarging head size (increased intracranial pressure in the setting of open fontanelles), hydrocephalus, dilated face and scalp veins (venous collaterals) and delayed neurological development. Untreated, the prognosis is poor. With treatment, they can have a very good prognosis.
- Presentation in late childhood/early teens: These patients often present with intracranial hemorrhage.
Because of the deep location of these malformations the primary treatment modality is embolization. These patients are managed in a multidisciplinary manner with involvement of neurointerventional physicians, as well as Neurosurgery and Neurology. The goal of treatment is to improve or normalize the intracranial venous pressures in order to prevent damage to the growing brain and allow for normal neurological development.
Extra-cranial vascular lesions of the head and neck: These lesions include arteriovenous malformations of the extracranial soft tissues, as well as neoplastic lesions such as juvenile nasopharyngeal angiofibromas (JNA), aneurysmal bone cysts, or other hypervascular tumors of the head and neck.
- Arteriovenous malformations: Embolization is usually the mainstay of treatment, although in certain cases it can be done as a pre-operative procedure to make the surgical resection safer and easier with less blood loss.
- JNA: This is an uncommon neoplasm of blood vessels and connective tissue, presenting almost exclusively in males. Embolization is performed pre-operatively to aid in the resection of the lesion.
- Aneurysmal bone cysts: Embolization is performed usually as a pre-operative measure as these lesions are usually very vascular and occasionally associated with AV shunting. More recent reports have demonstrated good results with percutaneous treatment of these lesions with sclerosing agents.
- Venous and venolymphatic malformations (including cystic hygroma) of the head and neck: These lesions are treated with sclerotherapy, often in conjunction with colleagues in Interventional Radiology.
Spine interventions with embolization: Vascular malformations involving the spinal column and/or cord in children are primarily congenital. There are several classification schemes for these malformations, primarily based on the arterial system involved. These malformations can involve the paraspinous soft tissues, the vertebral bodies, dura, epidural arteries and veins, as well as the spinal cord and nerve roots. Generally speaking, the long-term prognosis of malformations involving the medullary (spinal cord) arteries and/or veins is poor. The most commonly used classification scheme is listed below:
- Type I: These are usually acquired lesions consisting of a fistulous connection between a radicular artery (supplying a nerve root) and a radiculomedullary or radiculopial vein. Due to the arterioveous shunting, flow in the vein becomes reversed, towards the spinal cord. These are almost exclusively seen in adults.
- Type II: These are glomus congenital AVMs involving the substance of the spinal cord. They can be located anywhere along the spinal cord. They usually present early in life (first and second decades) and the most common mode of presentation is hemorrhage, either intra-medullary, subarachnoid or both. The natural history of these lesions is poor. Treatment is generally difficult because of the sensitive location of such lesions within the cord substance. Embolization can be used to decrease the degree of AV shunting through the lesion for palliation of symptoms. It also can be used to treat/occlude aneurysms associated with the nidus of the AVM or afferent arteries. Embolization can be a pre-operative adjunct and used, although rarely, for cure. Stereotactic radiation (cyberknife) has recently been performed with some efficacy.
- Type III: These are also known as a metameric AVM. The malformation involves multiple derivatives of the metamere, including the soft tissues, bone, dura, and cord. The pathophysiology, presentation and treatment strategies are similar to the type II. Treatment is aimed at the symptomatic part of the malformation (usually the cord component).
- Type IV: These are also known as a pial AV fistula. There are 3 subtypes depending on the degree of arteriovenous shunting. Subtypes A and B are low and medium flow respectively. They are most commonly located close to or at the level of the conus medullaris. Subtype C has the highest flow and is more often cervical in position. See Case 2 A-C. These lesions also present earlier in life, although presentation in early adulthood or middle age can also occur. They either occur spontaneously or can also be associated with hereditary hemorrhagic telangiectasias. Treatment for subtypes B and C is primarily endovascular, while subtype A lesions are treated primarily surgically.
- Other: AV shunts can occur in the epidural and paraspinous locations as well. Their clinical manifestations are most commonly related to the pattern of venous drainage. If the medullary (spinal cord) veins are involved it may result in venous hypertension and cord ischemia. In general, the primary mode of treatment for these lesions is endovascular.
For vascular lesions of the spinal column such as aneurysmal bone cysts (ABCs), aggressive hemangiomas and hypervascular metastases, embolization is usually performed as a pre-operative measure in order to decrease blood loss and make the surgery safer and faster. In inoperable cases of ABCs or hemangiomas, embolization can result in a durable involution and healing of the lesion.
Percutaneous spinal interventions
The following are the most commonly performed needle-based percutaneous interventions.
Intralesional steroid injections: In the setting of a painful vertebral pathologic fracture where EG (eosinophilic granuloma) is suspected, direct intra-lesional injection of steroids can be performed at the same time as image-guided biopsy if the cytopathology preliminary report supports the diagnosis. The intra-lesional steroids provide symptom relief and can accelerate lesion involution and bony healing.
Percutaneous injection of polymethyl-methacrylate (PMMA) or sclerosant: Percutaneous injection of PMMA can be performed as primary treatment for symptomatic hemangiomas without surgical indication. There are increasing data demonstrating good response to the intra-lesional injection of sclerosants for ABCs in locations where surgical treatment may be too risky or morbid.
Percutaneous spinal injections for pain management: The neurointerventional team works jointly with the Anesthesia team to provide a program for diagnosis and treatment of discogenic pain or pain related to spondylolysis. Procedures include epidural, nerve root and facet joint injections with anesthetics and local steroids.
Intra-cranial hypotension: Intra-cranial hypotension due to spinal leakage of CSF is increasingly being recognized and diagnosed as an uncommon but potentially dangerous and treatable condition. Potential causes of CSF leakage include trauma, iatrogenic (post LP or spinal anesthesia or post-operative), connective tissue abnormality (Ehlers-Danlos or Marfan syndrome) or idiopathic. Patients present with positional headaches as well as non-specific complaints such as fatigue, muffled hearing, double vision and occasionally radicular pain. The diagnosis is usually made by history and supportive diagnostic finding on imaging (MRI: dural thickening and enhancement, inferior displacement of the cerebellar tonsils) and a low opening pressure with LP. The location of the leak is usually determined by MR or CT myelography of the spine. Treatment most often consists of fluoroscopically guided injection of autologous blood or fibrin glue within the epidural space at the suspected level of the dural tear/leak.
Endovascular stroke intervention for embolic/ischemic stroke is becoming relatively commonplace in adults, but its use in the pediatric population is by comparison rare. This is multifactorial, including a relative paucity of clinical trials in children, as well as the fact that the presentation in children is often atypical in comparison with adults, consequently delaying the diagnosis. In selected cases presenting within the correct time windows (up to 8 hours in the anterior circulation, up to 24 hours in the basilar artery), endovascular treatment can be offered to patients in consultation with Pediatric Neurology.
Dural sinus thrombosis
Patients presenting with dural sinus thrombosis are usually placed on anti-coagulation with either low molecular weight heparin or unfractionated heparin. Patients who fail traditional treatment, either by demonstrating neurological worsening or progression of thrombosis, can be treated effectively with catheter-based mechanical and chemical thrombolysis. The dural sinuses are accessed by a trans-femoral trans-venous approach. The thrombus is then treated using direct administration of TPA over 12-24 hours, often combined with mechanical clot maceration and/or rheolytic thrombectomy. In general, endovascular treatment is usually successful unless the thrombus is greater than 3 weeks old, in which case it has become fibrotic and organized and is usually much less responsive to the treatments listed above.
Intra-arterial chemotherapy for treatment of retinoblastoma
Abramson and Gobin in New York have published pioneering work in the treatment of advanced retinoblastomas by using super-selective targeted delivery of chemotherapeutic agents to the affected eye using neurointerventional techniques. This treatment has shown excellent results in obtaining cures and precluding the need for enucleation especially in children with bilateral disease. A treatment program for delivering this exciting new therapy to patients in the Chicago area has recently been developed via a multidisciplinary collaboration with the Pediatric Ophthalmology and Oncology departments at Children’s Memorial Hospital.
Pediatric neurointerventional treatments and procedures have advanced rapidly over the last 2 decades due to advances in knowledge, equipment and techniques that have taken place in the adult neurointerventional discipline. Due to the relative rarity of serious neurovascular diseases, such as brain AVMs, these patients are best managed by multi-disciplinary groups of physicians, including the neurointerventional surgeon, at tertiary pediatric hospitals where the requisite volume and experience exist. The same treatments and procedures available in adults are available to pediatric patients at many of these experienced tertiary care pediatric hospitals. Neurointerventional techniques play either a complementary role to existing surgical treatment paradigms by making them safer, easier or feasible, or a role as an alternative treatment with decreased morbidity and increased efficacy.
For Further Reading
[1.] Alvarez H, Garcia Monaco R, Rodesch G, et.al. Vein of Galen aneurysmal malformations. Neuroimaging Clinics of North America 2007 May;17(2):189-206.
[2.] Cullen S, Krings T, Ozanne A, et.al. Diagnosis and endovascular treatment of pediatric spinal arteriovenous shunts. Neuroimaging Clinics of North America 2007 May;17(2):207-221.
[3.] Niimi Y, Song JK, Berenstein A. Current endovascular management of maxillofacial vascular malformations. Neuroimaging Clinics of North America 2007 May;17(2):223-237.