Benign+AVM

Arteriovenous malformations (AVM) occur in about 0.1% of the population (about 1/10th the incidence of intracranial aneurysms). 1  About 90% of AVMs are supratentorial lesions and 10% are in the posterior fossa. Brain AVMs account for 1-2% of all strokes, 3% of strokes in young adults, and 9% of subarachnoid hemorrhages. ||
 * **Epidemiology****:** || Erin
 * **Etiology:** || Spencer

The cause of arteriovenous malformation (AVM) in unknown. 2 ||
 * **Signs & Symptoms:** || Pablo

The signs and symptoms of Arteriovenous Malformations (AVM) depend on its location. In general the person may experience
 * Intracranial hemorrhage
 * Some may have focal or generalized seizures
 * Localized pain in the affected area
 * Difficulty with movement, speech and vision. 3 ||
 * **Diagnostic Procedures:** || Becky
 * Lab tests: hemoglobin/hematocrit, chemistry assay, coagulation parameters
 * Magnetic resonance angiography (MRA)
 * Computed tomography (CT )
 * Ultrasound
 * Angiography or Arteriography 4 ||
 * **Histology:** || Adam

Arteriovenous malformations are composed of intercommunicating arterial and venous structures. What gives them an identificable histology versus hemangiomas is the presence of nerve bundles. 5 ||
 * **Lymph node drainage:** || Megan

There is no lymph drainage in the brain due to the blood brain barrier. ||
 * **Metastatic spread:** || Kevin Tsai

Intra-cranial spread is most common but very rare. 6 ||
 * **Grading:** || Erin

The Spetzler-Martin AVM grading system is used for AVMs and gives a grade between 1 and 5. 7 The grade is used to estimate the risk of surgery for a patient with AVM based on the size, pattern of venous drainage, and eloquence of brain location. A grade 1 AVM would be considered small, superficial, and located in non-eloquent brain, and therefore a low risk for surgery. Grade 4 or 5 AVMs are large, deep, and adjacent to eloquent brain. Grade 6 is used to describe inoperable lesions. The following is a more detailed breakdown of the points given that make up the grade:

Size of AVM: Location: Venous Drainage:
 * Small (<3cm): 1
 * Medium (3-6cm): 2
 * Large (>6cm): 3
 * Noneloquent site: 0
 * Eloquent site: 1
 * Superficial: 0
 * Deep: 1 ||
 * **Staging:** || Spencer

Although there is a proven grading system for arteriovenous malformation, there is no known staging system that exists. ||
 * **Radiation side effects:** || Pablo

Some patients experience nausea, headaches and even seizures following the irradiation of Arteriovenous Malfomations (AVM). Hair loss is also a possible side effect of treatment. The area of the brain irradiated may experience long term side effects such as stroke like problems in months or even years following treatment. 8 ||
 * **Prognosis:** || Becky

The main prognostic factor is hemorrhage. If a patient has a hemorrhage, it could result in neurological damage or even death. ||
 * **Treatments:** || Adam

The best treatment option is surgical resection if possible, with a second treatment modality of endovascular embolization. AVMs respond to doses of 15 Gy or lower in some cases, but may doses of 20-25 Gy may result in a greater response. However, with the higher doses, there are increased odds of radiation-induced complications. 9 ||
 * **TD 5/5:** || Megan

AVMs are most commonly associated with the brain and the spinal cord. The idea with treatment of an AMV is to change the structure of the walls of the vessels causing the AVM. As the walls thicken, the vessels will close off, diminishing blood flow and decreasing the chance for other AVMs. A primary way to change the structure of these vessels is to administer radiation, either stereotactically or radiosurgically. For this reason, standard TD 5/5's for the brain and spinal cord area are useful. 10

Organs in which radiation lesions result in severe to fatal morbidity: 11

Back to Week 7
 * Brain: Infarction, necrosis 5000-6000 cGy
 * Retina: Blindness 5500 cGy
 * Cornea: Blindness 5000 cGy
 * Lens: Cataracts 500 cGy
 * Spinal cord: Infarction, necrosis 4500 cGy ||
 * **References:** || # UpToDate Website. Brain Arteriovenous Malformations. http://www.uptodate.com/contents/brain-arteriovenous-malformations. Accessed July 12, 2013.
 * 1) Arteriovenous Malformation. Medline Plus Web Site. [] . Accessed July 8, 2013.
 * 2) American Stroke Association. Web site. [] . Accessed July 09, 2013.
 * 3) Mayo Clinic Staff. Mayo Clinic Website. [] February 2011. Accessed July 3, 2013.
 * 4) Hemangioma Versus Arteriovenous Malformation. Archives of Pathology Web Site. http://www.archivesofpathology.org/doi/pdf/10.1043/1543-2165%282005%29129%5B772%3AHVVMPO%5D2.0.CO%3B2. Accessed July 13, 2013.
 * 5) Washington CM, Leaver D. //Principles and Practice of Radiation Therapy//. 2nd edition. St. Louis, MO: Mosby, Inc. 2004: 96.
 * 6) Boston Medical Center Website. Stroke & Cerebrovascular Center. http://www.bmc.org/stroke-cerebrovascular/services/AVM-Spetzler-Martin-Grading-Scale.htm. Accessed July 12, 2013.
 * 7) The Toronto Brain Vascular Malformation Study Group. Web site. [] . Accessed July 09, 2013.
 * 8) Chao KS, Perez CA, Brady LW. Radiation Oncology Management Decisions. 3rd edition. Philadelphia, PA: Lippincott Williams & Wilkins.
 * 9) The Toronto Brain Vascular Malformation Study Group website. [] . Accessed July 11, 2013.
 * 10) Washington CM, Leaver D. //Principles and Practice of Radiation Therapy//. 3rd ed. St. Louis, MO: Mosby-Elsevier; 2010. ||