Cerebral arteriovenous malformation

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Cerebral arteriovenous malformation
Classification and external resources
ICD-10 Q28.2
ICD-9 747.81
OMIM 108010
DiseasesDB 2224
MedlinePlus 000779
eMedicine neuro/21
MeSH D002538

Cerebral arteriovenous malformation (AVM) is a malformed collection of blood vessels within the brain, characterized by tangle(s) of veins and arteries. While an arteriovenous malformation can occur elsewhere in the body, this article discusses malformations found in the brain.

Contents

[edit] Symptoms

The most frequently observed problems related to an AVM are headaches and seizures. These symptoms vary from extremely mild neurological events (e.g. unusual sensations) to uncontrolled tonic-clonic seizures. Moreover, AVMs in certain critical locations may stop the circulation of the cerebrospinal fluid, causing accumulation of the fluid within the skull and giving rise to a clinical condition called hydrocephalus.

Symptoms of bleeding within the brain (intracranial hemorrhage) include loss of consciousness, sudden and severe headache, nausea, vomiting, incontinence, and blurred vision, amongst others. Minor bleeding can occur with no noticeable symptoms. A stiff neck can occur as the result of increased pressure within the skull and irritation of the meninges. Impairments caused by local brain tissue damage on the bleed site are possible, including seizure, one-sided weakness (hemiparesis), a loss of touch sensation on one side of the body and deficits in language processing (aphasia). A variety of other symptoms can accompany this type of cerebrovascular accident.

Generally, intense headache, perhaps coincident with seizure or loss of bodily consciousness, is the first indication of a cerebral AVM. Estimates of the number of AVM-afflicted people in the United States range from 0.1% to 0.001%[1][2] of the population.

[edit] Diagnosis

An AVM diagnosis is established by neuroimaging studies. A computed tomography scan of the head (head CT) is usually performed—this can reveal the site of the bleed. More detailed pictures of the tangle of blood vessels that compose an AVM can be obtained by using radioactive reagents injected into the blood stream, then observed using a fluoroscope or Magnetic Resonance Imaging (MRI). A spinal tap (lumbar puncture) can be used to examine spinal fluid for red blood cells; this condition is indicative of leakage of blood from the bleeding vessels into the subarachnoid space. The best images of an AVM are obtained through cerebral angiography. This procedure involves using a catheter, threaded through an artery up to the head, to deliver a contrast agent into the AVM. As the contrast agent flows through the AVM structure, a sequence of X-ray images can be obtained to ascertain the size, shape and extent of that structure.

[edit] Pathophysiology

While the cause of AVMs remains unknown, the main risk is intracranial hemorrhage. This risk is difficult to quantify. Approximately 40% of cases with cerebral AVM are discovered through symptoms caused by sudden bleeding due to the fragility of abnormally-structured blood vessels in the brain. However, some patients may remain asymptomatic or have minor complaints due to the local effects of the tangle of vessels. If a rupture or bleeding incident occurs, the blood may penetrate either into the brain tissue (cerebral hemorrhage) or into the subarachnoid space, which is located between the sheaths (meninges) surrounding the brain (subarachnoid hemorrhage). Bleeding may also extend into the ventricular system (intraventricular hemorrhage). Cerebral hemorrhage appears to be most common. [3]

Once an AVM bleeds, the probability of rebleeding may increase. However, as long as the AVM is unruptured, the risk of hemorrhage may be relatively low.

AVMs that do not bleed may cause symptoms such as epileptic seizures, headaches, or fluctuating neurological symptoms. Many of them may even remain asymptomatic; at least 15% of AVMs are detected before they produce symptoms.[3]

[edit] Treatment

The treatment in the case of sudden bleeding is focused on restoration of vital function. Anticonvulsant medications such as phenytoin are often used to control seizure; medications or procedures may be employed to relieve intracranial pressure. Eventually, curative treatment may be required to prevent recurrent hemorrhage. However, any type of intervention may also carry a risk of creating a neurological deficit.

In the U.S., surgical removal of the blood vessels involved (craniotomy) is the preferred curative treatment for most types of AVM. While this surgery results in an immediate, complete removal of the AVM, risks exist depending on the size and the location of the malformation.

Radiation treatment (radiosurgery) has been widely used on smaller AVMs with considerable success. The Gamma Knife, developed by Swedish physician Lars Leksell, is one apparatus used in radiosurgery to precisely apply a controlled radiation dosage to the volume of the brain occupied by the AVM. While this treatment is non-invasive, two to three years may pass before the complete effects are known. Complete occlusion of the AVM may or may not occur, and 8%-10% of patients develop long term neurological symptoms after radiation.[citation needed]

Embolization, that is, occlusion of blood vessels with coils or particles or glue introduced by a radiographically guided catheter, is frequently used as an adjunct to either surgery or radiation treatment. However, embolization alone is rarely successful in completely blocking blood flow through the AVM.

The benefit of invasive treatment for unruptured AVMs has never been proven, as the risk of intervention may be as high as the spontaneous bleeding risk. An international study is currently under way to determine the best therapy for patients with unruptured AVMs (ARUBA—A Randomized Trial of Unruptured Brain AVMs [1]).[4]

[edit] Epidemiology

The annual new detection rate incidence of AVMs is about one in 100,000 people; the prevalence of AVMs in the population is estimated between 10 and 20 per 100,000 people.[5](incidence) of AVMs is about one in 100,000 people; the prevalence of AVMs in the population is estimated between 10 and 20 per 100,000 people.[5]

[edit] Vein of Galen aneurismal malformations

[edit] Pathophysiology

Vein of Galen aneurysmal malformations (VGAM) and vein of Galen aneurysmal dilations (VGAD), which are the most frequent arteriovenous malformations in infants and fetuses.[6][verification needed] VGAM consisted of a tangled mass of dilated vessels supplied by an enlarged artery.[7] The malformation increases greatly in size with age, although the mechanism of the increase is unknown [7]. Dilation of the great cerebral vein of Galen is a secondary result of the force of arterial blood either directly from an artery via an arteriovenous fistula or by way of a tributary vein that receives the blood directly from an artery.[6][7] There is usually a venous anomaly downstream from the draining vein that, together with the high blood flow into the great cerebral vein of Galen causes its dilation.[8] The right sided cardiac chambers and pulmonary arteries also develop mild to severe dilation.[9]

Five patterns of Galenic arteriovenous malformations have been described:

Pattern 1: Many vessels, including anterior cerebral arteries, thalamic perforating arteries, and superior cerebellar arteries discharge into the vein of Galen.[10]
Pattern 2: A single posterior choroidal artery drains into the vein of Galen.[10]
Pattern 3: One or both posterior choroidal and one or both anterior cerebral arteries drain directly into the Galenic system.[10]
Pattern 4: An angiomatous network of posterior choroidal and thalamic perforating arteries enter the Vein of Galen directly.[10]
Pattern 5: A high flow arteriovenous malformation in the right inferior frontal lobe drains via the inferior sagittal sinus and pericallosal vein into the Vein of Galen.[8]

These malformations develop in utero by the persistence of fistulae between primitive pia arachnoidal arteries and plial veins that cross each other at right angles.[8] 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.[8]

[edit] Effects of vein of Galen aneurysmal malformations

Malformations often lead to cardiac failure, cranial bruits (pattern 1), hydrocephaly, and subarachnoid hemorrhage in neonates.[8] The heart failure is due to the size of the arteriovenous shunt that can steal 80% or more of the cardiac output, with large volumes of blood under high pressure returning to the right heart and pulmonary circulation and sinus venosus atrial septal defects.[8][9] It is also the most common cause of death in such patients.[12]

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.

[edit] Diagnosis

Testing for a malformed vein of Galen is indicated when a patient has heart failure which has no obvious cause.[13] Diagnosis is generally achieved by signs such as cranial bruits and symptoms such as expanded facial veins.[8] The vein of Galen can be visualized using ultrasound or doppler.[8] A malformed Great Cerebral Vein will be noticeably enlarged. Ultrasound is a particularly useful tool for vein of Galen malformations because so many cases occur in infancy and ultrasound can make diagnoses prenatally. Many cases are diagnosed only during autopsy as congestive heart failure occurs very early.[10]

[edit] Treatment

Treatment depends on the anatomy of the malformation as determined by angiography or Magnetic Resonance Imaging (MRI).[8]

[edit] 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, surgery is needed to clip the fistulous tract[8] or to ligate the arteries feeding into the Vein of Galen, thereby reducing the blood flow into the vein.[10] 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.[14] The young age of many patients, the complex vascular anatomy, and the sensitive location of the Vein of Galen offer considerable challenges to surgeons.[15] Another treatment option is Radiotherapy. Radiotherapy, also called radiosurgery, involves the use of focused beams to damage the blood vessel.[14] 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.[14]

[edit] 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.[14] Endovascular treatments involve delivering drugs, balloons, or coils to the site of the malformation through blood vessels via catheters.[14] 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.[9] 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. [16] 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.[16] When none of these procedures are viable, shunting can be used to ameliorate the pressure inside the varix.[8] Seizures usually are managed with antiepileptic medications.[17]

[edit] Complications

The complications that are usually associated with vein of Galen malformations are usually intracranial hemorrhages.[18] Over half the patients with VGAM have a malformation that cannot be corrected. Patients frequently die in the neonatal period or in early infancy.[9]

[edit] Sociological Impacts

Vein of Galen malformations are devastating complications. Studies have shown that 77% of untreated cases result in mortality.[15] Even after surgical treatment, the mortality rate remains as high as 39.4%.[15] Most cases occur during infancy when the mortality rates are at their highest. Vein of Galen malformations are a relatively unknown affliction, attributed to the rareness of the malformations. Therefore, when a child is diagnosed with a faulty Great Cerebral Vein of Galen, most parents know little to nothing about what they are dealing with. To counteract this, support sites have been created which offer information, advice, and a community of support to the afflicted ([2], [3]).

[edit] Famous sufferers

[edit] Fictional characters

[edit] References

  1. ^ "Columbia Weill Cornell Neuroscience Centers". http://www.nypneuro.org/healthinfo/stroke.html. Retrieved 2007-09-20. 
  2. ^ avms at NINDS
  3. ^ a b Al-Shahi R, Warlow C (October 2001). "A systematic review of the frequency and prognosis of arteriovenous malformations of the brain in adults". Brain : a journal of neurology 124 (Pt 10): 1900–26. PMID 11571210. http://brain.oxfordjournals.org/cgi/content/full/124/10/1900. 
  4. ^ Hartmann A, Mast H, Choi JH, Stapf C, Mohr JP (2007). "Treatment of arteriovenous malformations of the brain". Current neurology and neuroscience reports 7 (1): 28–34. doi:10.1007/s11910-007-0018-2. PMID 17217851. 
  5. ^ a b Berman MF, Sciacca RR, Pile-Spellman J, Stapf C, Connolly ES Jr, Mohr JP, Young WL. (August 2000). "[uid The epidemiology of brain arteriovenous malformations.]". Neurosurgery (Pt 47): 389-96. PMID 10942012. http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=DetailsSearch&Term=10942012[uid]. 
  6. ^ a b O'Brien M; Schechter M (September 1970). "Arteriovenous malformations involving the Galenic system" (pdf). The American Journal of Roentgenology, Radium Therapy, and Nuclear Medicine 110 (1): 50–55. ISSN 0002-9580. PMID 5459527. http://www.ajronline.org/cgi/reprint/110/1/50.pdf. Retrieved October 25, 2009. 
  7. ^ a b c Takashima S; Becker LE (May 1980). "Neuropathology of cerebral arteriovenous malformations in children". Journal of Neurology, Neurosurgery, and Psychiatry 43 (5): 380–385. ISSN 0022-3050. PMID 7420086. PMC 490562. http://jnnp.bmj.com/cgi/content/abstract/43/5/380. Retrieved October 25, 2009. 
  8. ^ a b c d e f g h i j k Nicholson AA; Hourihan MD, Hayward C (December 1989). "Arteriovenous malformations involving the vein of Galen". Archives of Disease in Childhood 64 (12): 1653-1655. ISSN 0003-9888. PMID 2696431. 
  9. ^ a b c d McElhinney DB; Halbach VV, Silverman NH, Dowd CF, Hanley FL (June 1998). "Congenital cardiac anomalies with vein of Galen malformations in infants". Archives of disease in childhood. Fetal and neonatal edition 78 (6): 548-551. ISSN 1359-2998. PMID 9713012. 
  10. ^ a b c d e f Hoffman HJ; Chuang S, Hendrick EB, Humphreys RP (September 1982). "Aneurysms of the vein of Galen. Experience at The Hospital for Sick Children, Toronto". Journal of Neurosurgery 57 (3): 316-322. ISSN 0022-3085. PMID 7097326. 
  11. ^ Padget DH (May 1956). "The cranial venous system in man in reference to development, adult configuration, and relation to the arteries". The American journal of anatomy 98 (3): 307-355. ISSN 0002-9106. PMID 13362118. 
  12. ^ Johnston IH; Whittle IR, Besser M, Morgan MK (May 1987). "Vein of Galen malformation: diagnosis and management.". Neurosurgery 20 (5): 747-758. ISSN 0148-396X. PMID 3601022. 
  13. ^ "Vein of Galen Abnormalities". Duke University. http://www.dukehealth.org/services/cerebrovascular_center/treatments/vein_of_galen_abnormalitie. Retrieved December 6 2009. 
  14. ^ a b c d e The Arteriovenous Malformation Study Group (June 10, 1999). "Arteriovenous Malformations of the Brain in Adults". New England Journal of Medicine 340 (23): 1812-1818. ISSN 0028-4793. PMID 10362826. http://content.nejm.org/cgi/content/short/340/23/1812. Retrieved October 27, 2009. 
  15. ^ a b c Alexander, Michael J.; Spetzler, Robert F. (October 2005). Pediatric Neurovascular Disease: Surgical, Endovascular, and Medical Management. New York: Thieme Medical Publishers. ISBN 9781588903686. 
  16. ^ a b >Ciricillo, S.F.; SCHMIDT K.G., SILVERMAN N.H., HIESHIMA G.B., HIGASHIDA R.T., HALBACH V.V., EDWARDS M.S.B (1990). "Serial Ultrasonographic Evaluation of Neonatal Vein of Galen Malformations to Assess the Efficacy of Interventional Neuroradiological Procedures.". Neurosurgery (Baltimore) 27 (4): 544-548. ISSN 0148-396. 
  17. ^ Chatterjee, S. (May 22 2009). "Antiepileptic drugs". Molecules of the Millenium. Indian Journal of Pharmacology. http://medind.nic.in/ibi/t01/i3/ibit01i3p229.pdf. Retrieved December 6 2009. 
  18. ^ >Meyers PM; Halbach VV, Phatouros CP, Dowd CF, Malek AM, Lempert TE, Lefler JE, Higashida RT (2000 month = June). "Hemorrhagic complications in vein of Galen malformations.". Annals of Neurology 47 (6): 748-755. 

[edit] External links

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Congenital vascular defects (Q25-Q28, 747)
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Great veins
Arteriovenous malformation
Cerebral arteriovenous malformation
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