Rare Subtype of Venous-Predominant Parenchymal Arteriovenous Malformation (AVM)

Abstract

An 18-year-old male, who had two previous attacks of subarachnoid hemorrhage, presented asymptomatic and neurologically intact, after complete recovery from hemorrhage-associated severe headache. He was treated with upfront (primary); Linac-based SRS for right, frontal, large, diffuse, rare subtype of venous-predominant, parenchymal AVM, mimicking atypical arterialized developmental venous anomaly (DVA). The target volume of 12.5 cc received a marginal dose of 25.0 Gy normalized to 80% isodose line. The maximum dose to optic chiasm was 15.8 Gy. At 3 months post-SRS, the patient experienced moderate headache and vomiting, which resolved gradually over couple months with steroid and diuretic medications. Serial post-SRS follow-up imaging showed progressive reduction in the size of AVM nidus till its non-visualization at 11 months post-SRS. The follow-up images also showed perinidal high signal in T2 and FLAIR studies, denoting vasogenic edema, and perinidal large heterogeneously enhancing lesion, in T1 Gadolinium-enhanced study, denoting radiation-induced parenchymal changes. At last radiological follow-up (55 months post-SRS), conventional cerebral angiography documented complete obliteration of AVM nidus. The radiosurgery treatment was successful, and the patient was neurologically intact throughout the entire follow-up period of 64 months post-SRS.

• Demographics: Male; 18 years

• Initial Presentation: Hemorrhage (subarachnoid), which occurred twice; at 8 months and 1 month before radiosurgery treatment

• Diagnosis: A rare subtype of venous-predominant parenchymal AVM, mimicking atypical arterialized developmental venous anomaly (DVA)

• Pre-radiosurgery Treatment: None

• Pre-radiosurgery Presentation: Asymptomatic and neurologically intact, after complete recovery from severe hemorrhage-associated headache

• Radiosurgery Treatment:

  Upfront (primary); Linac-based SRS for right, frontal, large, diffuse, venous-predominant, parenchymal AVM

• Radiosurgery Dosimetry:

  • Target volume: 12.5 cc

  • Marginal dose: 25.0 Gy

  • Marginal isodose: 80%

  • Maximum dose: 33.0 Gy

  • Minimum dose: 14.5 Gy

  • Average dose: 30.0 Gy

  • Number of isocenters: 1

  • Maximum dose to optic chiasm: 15.8 Gy

• Follow-Up Period: 64 months post-SRS

• Clinical Outcome:

  • 3 months post-SRS: Experienced moderate headache and vomiting; started medications (steroids, diuretics)

  • 5 months post-SRS: Improving headache and vomiting with gradual tapering of medications

  • 7 months post-SRS: Recurrence of severe headache and vomiting; restarted medications (steroids, diuretics)

  • 8 months post-SRS: Complete resolution of headache and vomiting; stopped medications

  • 12 months post-SRS: Asymptomatic and neurologically intact

  • 64 months post-SRS: Sustainable asymptomatic and intact neurological status

• Complications: None

• Radiological Outcome:

  • 3 months post-SRS (CT):

    • Slight decrease in size of AVM nidus

    • Diffuse right frontal perinidal hypodensity, denoting severe vasogenic edema with focal mass effect and midline shift

  • 7 months post-SRS (MRI):

    • Marked decrease in size of AVM nidus

    • Diffuse right frontal perinidal high signal in T2 study, denoting marked vasogenic edema

    • Appearance of right frontal perinidal large heterogeneously enhancing lesion, in T1 Gadolinium-enhanced study, denoting radiation-induced parenchymal changes

  • 8 months post-SRS (CT):

    • Much more decrease in size of AVM nidus

    • Decreased right frontal perinidal hypodense vasogenic edema

  • 9 months post-SRS (CTA):

    • Non-visualized AVM nidus

    • Persistent slightly dilated draining deep venous system

  • 11 months post-SRS (CT):

    • Non-visualized AVM nidus

    • Markedly decreased right frontal perinidal hypodense vasogenic edema

  • 12 months post-SRS (CTA):

    • Non-visualized AVM nidus

    • Evident decrease in number and size of draining deep veins

  • 55 months post-SRS (Conventional angiography): Complete nidus obliteration

• Post-radiosurgery Treatment: None