**8.4 Embolization**

A rapidly evolving technique uses embolic agents such as silk, Histoacryl with Lipiodol and Onyx and delivery systems such as balloons with calibrated leaks, flow-guided micro-catheters and over-the-wire micro-catheters (**Figure 6**). It was used initially as an adjunct to microsurgery or radiosurgery; nowadays in selected cases, embolization is a sole treatment modality. By embolization less than 5% of cAVMs are cured.

Embolization can be an effective adjunct to radiosurgery and surgery. Embolization prior to radiosurgery is used to reduce the nidus size of large brain AVMs as the large AVMs have a lower cure rate with radiosurgery alone. Embolization prior to surgery is employed to reduce blood loss and to occlude

**Figure 6.** *Embolization process.* vessels that may be difficult to control during surgery [29]. Pre-embolization steroids and anti-epileptic medications should be started; the procedure is done under general anesthesia. The aims of cAVM embolization could be curative or palliative, and it could be partial prior to the radio- or microscopic surgery. Careful analyses of angiographic information including size, eloquent location, deep versus superficial venous drainage and vascular anatomy/number of feeders are considered for the suitability for embolization of cAVMs.

The cAVM embolization can be complicated into partial occlusion, intracranial hemorrhage, brain ischemia, glueing of micro-catheter or perfusion pressure breakthrough syndrome. Perfusion pressure breakthrough syndrome occurs in approximately 5% of the patients, thought to be related to the loss of autoregulation causing oedema or hemorrhages in the surrounding normal brain tissues [30]. The successful cAVM embolization occurs in 10–40% of the patients and may have to be done in the multiple settings.

To summarize the treatment of cAVMs, the following factors have to be considered: the patient's age and anatomic and vascular morphology of the cAVM.

#### **8.5 Patient's age**

It is an important factor in the decision to treat cAVMs. Those with a longer life expectancy will accrue a higher lifetime risk of hemorrhage. Accordingly therapy is recommended for children and young adults, whereas the older cAVM patients with shorter life expectancies may be managed more conservatively. The cumulative risk of hemorrhage in cAVM patients can be calculated by the formula [31]: Lifetime risk of hemorrhage = 1 – (1 − P) × N (N is the expected years of life remaining, and P is the annual probability of hemorrhage). Another simpler formula is as follows: [32] Lifetime risk of hemorrhage = 105 - patient's age in years.

#### **8.6 cAVM location**

cAVM in eloquent brain territories presents a challenge for risk assessment. Significant clinical morbidity is likely to result if a surgical complication occurs as well as if the cAVM ruptures. Such patients may be more likely to be considered for radiosurgery.

#### **8.7 Deep venous drainage**

Deep venous drainage is a risk factor for surgical complications as well as for AVM rupture. If the lesion is otherwise amenable for treatment, radiosurgery may be the best option.

#### **8.8 The cAVM size**

Larger lesions are more difficult to treat but are not clearly at higher risk of bleeding than smaller lesions. cAVMs greater than 6 cm are managed conservatively. In patients with large lesions, the endovascular treatments may be useful to reduce the size of the aneurysm, if the vascular anatomy is determined to be amenable to this approach.

#### **8.9 Associated aneurysm**

The treatment of aneurysms associated with AVMs varies depending on aneurysm location and diameter [33]. When believed to be the source of hemorrhage,


*Cerebral Arteriovenous Malformation from Classification to the Management DOI: http://dx.doi.org/10.5772/intechopen.86659*

#### **Table 10.**

*Factors for selecting the modalities of therapy in cAVM patients [34].*

aneurysms are generally treated with surgery or endovascular therapy, depending on their location and size, according to the expertise of the available experienced clinicians. Aneurysms associated with unruptured cAVMs do not necessarily require treatment, depending on their size and other anatomic features.

Spetzler-Martin grading scale: Spetzler-Martin grading scale classifies surgical risk of removing cAVM according to its size, location and the presence of deep venous drainage. According to S-M grading, surgery is the modality of choice for grade I and II lesions, with radiosurgery as an alternative for small lesions based on location or other vascular anatomic features, while grade IV and V lesions are generally managed conservatively. S-M Supp grading gives a cut-off scale of 6 for operability of cAVM, and it is also a better predictor for post-cAVM excision neurological outcome. Hafez et al. [34] nicely described that apart from the S-M Supp grading, perforates play an important role in cAVM patient's outcome (**Table 10**) [35].

#### **9. Conclusion**

Cerebral arteriovenous malformations are rare and 10 times less frequent than the cerebral aneurysms. cAVMs are rare in the posterior fossa and account for 33% of intracerebral hemorrhage in young patients. They are classified by four different ways, but the commonly used classifications are Spetzler-Martin grading and supplementary Spetzler-Martin grading, as they also help in deciding the therapeutic approach. But it is not much useful in dealing the posterior fossa cAVMs. cAVMs can complicate into the formation of flow-related aneurysms and, according to their locations in relation to the cAVM, are classified into intranidal, distal, proximal or unrelated aneurysms. Angio-structure of cAVM is the direct connection between arterial and venous circulations without any intervening capillary network, and this makes cAVM high in flow and pressure structure at the risk of rapture.

The common presentation of cAVM is with intracerebral hemorrhage, with convulsions and rarely with focal neurological deficit. The most commonly used imaging modality for the diagnosis of cAVMs is computerized tomography. MRI scan has a unique sensitivity for the detection of remote hemorrhage, and conventional catheter cerebral angiography remained a gold standard in diagnosis of cAVMs. Multidisciplinary team approach is the best for management of cAVM patients. The surgical excision of cAVM gives definitive therapy in cAVM patients, radiosurgery is curative in selected cAVM patients and cerebral angiographic embolization is

rarely a sole therapy and usually in combination with surgical therapy. The medical therapies of cAVM are anticonvulsants and steroids. While taking a therapeutic decision for cAVMs, it is of vital importance to consider the patient's age, location, deep venous drainage, size of cAVMs and the presence of the associated aneurysms. The associated aneurysms must be secured before the interventions for cAVMs.
