28 Cerebral Arteriovenous Malformation

Case 28 Cerebral Arteriovenous Malformation

Pascal M. Jabbour and Erol Veznedaroglu

Fig. 28.1 Computed tomography scan of the head showing a right basal ganglia bleed.

Fig. 28.2 Magnetic resonance imaging scan of the head showing a basal ganglia arteriovenous malformation.

Clinical Presentation

A 36-year-old woman presented to the emergency room for sudden onset of headaches and right hemiplegia.

Her medical and familial history was noncontributory.

Neurologic evaluation showed that the patient was awake, alert, and strength was 5/5 on the right; she was hemiplegic on the left, with right-sided gaze preference, anosognosia, and hemiasomatognosia.

Computed tomography (CT) scan is shown in Fig. 28.1; magnetic resonance imaging (MRI) scan of the head is shown in Fig. 28.2.

Questions

Considering the age of the patient, what is the most likely etiology of the bleed?
What is the next test to order?
What is the most common arteriovenous malformation (AVM) grading system used? And what is the patient’s grade?
What is the risk of rupture of an AVM and the lifetime cumulative risk for this patient?
What are the diff erent treatment options for this patient?
What are some important steps of AVM surgery?
What is normal perfusion pressure breakthrough and how is it treated?

Answers

Considering the age of the patient, what is the most likely etiology of the bleed?

Any intracerebral hemorrhage in a young patient without any past medical history should raise the suspicion of a vascular malformation.

What is the next test to order?

The CT of the head showed a basal ganglia bleed in a young patient; the next test to be ordered should be an imaging modality that is able to demonstrate any vascular abnormality, like a CT angiogram, MRI, or magnetic resonance angiography.

What is the most common AVM grading system used? And what is the patient’s grade?

The Spetzler–Martin grading system (Table 28.1).¹

The patient’s grade is 2 (size) + 1 (eloquence) + 1 (venous drainage) = 4
What is the risk of rupture of an AVM and the lifetime cumulative risk for this patient?
- The risk of rupture of this AVM is ~4% per year.²
- Risk is 1 (risk of not hemorrhaging) raised to the power of years left to live.
- In a 36-year-old patient, at an average life expectancy of 79 years, the years left to live can be calculated to be 43 years.
- Risk = 1 – (1 – risk of hemorrhage) ⁴³
- Risk = 1 – (0.96) ⁴³ = 83
- The patient has a lifetime risk of hemorrhage of 83%.
What are the diff erent treatment options for this patient?
- The diff erent options are^1,3,4
  - No intervention if the risk of intervening is higher than the natural history risk of the AVM rupturing.
  - Embolization in preparation for surgical resection
  - Embolization with the goal of reducing the volume of the AVM in preparation for radiosurgery
  - Surgery alone
  - Radiosurgery alone with possible volume fractionation
What are some important steps of AVM surgery?
- Furosemide + mannitol prior to dural opening
- Proximal temporary occlusion can be performed with aneurysm clips.
- Smaller vessels are occluded with AVM mini-clips.
- Large draining veins are clipped with large aneurysm clips.
- Do not commit on vessel occlusion until the vessel is seen to enter the AVM.
- “If it looks like it may be AVM, it probably is.”
- Difficult-to-control bleeding during this dissection is commonly an indication that the AVM–brain interface has been breached on the side of the AVM.
- As a safety measure, before taking the major draining vein, an aneurysm clip is placed across it for 10–15 minutes and dissect out in a diff erent area.
- Always obtain a postoperative angiogram and CT scan.⁵
What is normal perfusion pressure breakthrough and how is it treated?
- It is a disorder of autoregulation of the brain vasculature.
- May present with sudden onset of brain swelling and bleeding from multiple sites
- May be due to draining vein that was taken too soon
- Also occurs from raw normal brain surfaces, that have lost autoregulatory capacity
- Close inspection of the operative field will identify any residual AVM.
- Treatment
  - Elevation of the patient’s head
  - Administration of mannitol and furosemide
  - Barbiturate- or etomidate-induced coma
  - Hypotension may be beneficial.
  - Focal hypotension by means of proximal vessel occlusion with temporary clip⁵