The Impact of Arteriovenous Malformation Radiosurgery on the Brain: From Morphology and Perfusion to Neurocognition

Computational Fractal-Based Analysis of Brain Arteriovenous Malformation Angioarchitecture

BACKGROUND:

Neuroimaging is the gold standard for diagnosis and follow-up of brain arteriovenous malformations (bAVMs), but no objective parameter has been validated for the assessment of the nidus angioarchitecture and for prognostication following treatment. The fractal dimension (FD), which is a mathematical parameter able to quantify the space-filling properties and roughness of natural objects, may be useful in quantifying the geometrical complexity of bAVMs nidus.

OBJECTIVE:

To propose FD as a neuroimaging biomarker of the nidus angioarchitecture, which might be related to radiosurgical outcome.

METHODS:

We retrospectively analyzed 54 patients who had undergone stereotactic radiosurgery for the treatment of bAVMs. The quantification of the geometric complexity of the vessels forming the nidus, imaged in magnetic resonance imaging, was assessed by means of the box-counting method to obtain the fractal dimension.

RESULTS:

FD was found to be significantly associated with the size (P = .03) and volume (P < .001) of the nidus, in addition to several angioarchitectural parameters. A nonsignificant association between clinical outcome and FD was observed (area under the curve, 0.637 [95% confidence interval, 0.49-0.79]), indicative of a potential inverse relationship between FD and bAVM obliteration.

CONCLUSION:

In our exploratory methodological research, we showed that the FD is an objective computer-aided parameter for quantifying the geometrical complexity and roughness of the bAVM nidus. The results suggest that more complex bAVM angioarchitecture, having higher FD values, might be related to decreased response to radiosurgery and that the FD of the bAVM nidus could be used as a morphometric neuroimaging biomarker.

Neuropsychological outcomes of stereotactic radiotherapy for cerebral arteriovenous malformations

To our knowledge, this is the first study to investigate cognitive outcome in patients with large or surgically inaccessible cerebral arteriovenous malformations (AVMs), who were treated with hypo-fractionated stereotactic radiotherapy (HSRT). A sample of 10 patients with AVMs was assessed up to 3.5 years post-HSRT. All patients were treated with HSRT to a total dose of 55 Gy in 11 fractions over a treatment period of 2.5 weeks. Neuropsychological assessments were given prior to radiotherapy and then at three time points following radiotherapy: 6 weeks, 6 months and 2.5-3.5 years post-treatment. The cognitive domains of attention, processing speed, learning, memory, semantic processing, naming, verbal fluency, visuospatial and executive function were assessed. Findings revealed that prior to radiotherapy the patient group was impaired in five of the nine cognitive domains. Post-treatment performances remained stable in the majority of domains; however, there was some fluctuation in semantic processing and memory performances. At 6 weeks post-treatment, a mild decrement was found in semantic processing ability; however, restoration to baseline levels was observed from 6 months onwards. At 2.5-3.5 years post-treatment, improvement was seen in the cohort's ability to remember new information when performances were compared with earlier time points. This study demonstrated improvements in memory several years after HSRT treatment. Further, this form of treatment was not associated with long-term, harmful cognitive side effects for these 10 patients encouraging further study of this treatment method. Further evaluation of the entire cohort is required to assess efficacy in terms of AVM obliteration and other potential side effects.

Peritherapeutic quantitative flow analysis of arteriovenous malformation on digital subtraction angiography

BACKGROUND

Digital subtraction angiography (DSA) provides detailed hemodynamic information. However, the imaging interpretation is mainly based on the physician's experience and observation. We aimed to quantitatively study the peritherapeutic blood flow changes of a cerebral arteriovenous malformation (AVM) treated by embolization using optical flow estimation on DSA.

METHODS

A 37-year-old woman with an AVM in the right frontal lobe of her brain was enrolled. The optical flow method with a pixel-by-pixel measurement was applied to determine the blood flow in brain vessels on anterior-posterior and lateral DSA views before and after embolization.

RESULTS

A return toward normalization of blood flow as a result of embolization was determined semiquantitatively on the posttherapeutic DSA.

CONCLUSIONS

Optical flow analysis on DSA illustrated the potential of quantifying intracranial blood flows in patients with cerebral vascular disorders and the therapeutic effects.

Neuropsychological effects of brain arteriovenous malformations

Brain arteriovenous malformations (AVM's) are developmental, chronic lesions that provide unique information about the human brain and can be a useful model for neuroscientists to study cerebral reorganization and hemodynamics. We review the neuroanatomy, epidemiology, natural history, imaging and treatment of brain AVMs, and provide a model with which to better understand neuropsychological functioning and brain reorganization. We suggest that future studies must exclude ruptured AVMs if they wish to further explain focal neurological/cognitive deficits associated with this neurovascular anomaly.

Neurovascular radiosurgery

SUMMARY

This article focuses on the treatment of neurovascular diseases, in particular brain arteriovenous malformations (BAVMs), with radiosurgery. The target group for this review is physicians who manage patients with neurovascular diseases, but are not actively engaged in radiosurgery. Radiosurgery for BAVMs is an established treatment with clearly defined risks and benefits. The efficacy of radiosurgery for dural arteriovenous shunts (DAVSs) is probably similar but the treatment has not yet gained the same acceptance. Radiosurgical treatment of cavernomas (cavernous hemangiomas) remains controversial. Well founded predictive models for BAVM radiosurgery show: * The probability of obliteration depends on the dose of radiation given to the periphery of the BAVM. * The risk of adverse radiation effects depends on the total dose of radiation, i.e. the amount of energy imparted into the tissue. The risk is greater in centrally located lesions. The risk of damage to brainstem nucleii and cranial nerves must be added to the risk predicted from current outcome models. * The risk of hemorrhage during the time span before obliteration depends on the BAVM volume, the dose of radiation to the periphery of the lesion and the age of the patient. Central location is a probably also a risk factor.