Cerebral Parenchymal Arteriovenous Malformation (AVM)

Abstract

A 24-year-old male, presented with epilepsy, was treated with upfront (primary); Linac-based stereotactic radiosurgery (SRS) for left, frontal, parenchymal AVM. The target volume of 3.1 cc received a marginal dose of 25.6 Gy normalized to 80% isodose line. Serial post-SRS follow-up MRIs showed progressive reduction in the size of AVM nidus, coupled with perinidal high signal in T2 and FLAIR studies, denoting vasogenic edema. At 24 months post-SRS, MRI showed non-visualized AVM nidus and appearance of small focal ring-enhancing lesion at the site of prior AVM nidus, in T1 Gadolinium-enhanced study, denoting radiation necrosis. At 30 months post-SRS, conventional cerebral angiography documented complete obliteration of the AVM nidus. At 57 months post-SRS, MRI showed a large cystic lesion with a slightly enhancing rim at the site of prior AVM nidus, in T1 Gadolinium-enhanced study, denoting radiation-induced parenchymal changes with cyst formation. At last follow-up (81 months post-SRS), MRI showed regression in the size of the radiation-induced cyst and persistent surrounding vasogenic edema. Successful, uncomplicated SRS treatment was paralleled with control of seizures without anticonvulsant medications at the patient’s last clinical follow-up 96 months post-SRS.

• Demographics: Male; 24 years

• Initial Presentation: Epilepsy for 7 months before radiosurgery treatment

• Diagnosis: Cerebral parenchymal AVM

• Pre-radiosurgery Treatment: None

• Pre-radiosurgery Presentation: Epilepsy (generalized tonic-clonic seizures)

• Radiosurgery Treatment:

  Upfront (primary); Linac-based SRS for left, frontal, parenchymal AVM

• Radiosurgery Dosimetry:

  • Target volume: 3.1 cc

  • Marginal dose: 25.6 Gy

  • Marginal isodose: 80%

  • Maximum dose: 33.0 Gy

  • Minimum dose: 24.6 Gy

  • Average dose: 31.7 Gy

  • Number of isocenters: 1

• Follow-Up Period: 96 months post-SRS

• Clinical Outcome:

  • 6 months post-SRS: Persistent seizures with medications

  • 24 months post-SRS: Infrequent seizures with medications

  • 36 months post-SRS: Controlled seizures with medications

  • 96 months post-SRS: Sustainable control of seizures with medications

• Complications: None

• Radiological Outcome:

  • 6 months post-SRS (MRI): Slight decrease in size of AVM nidus

  • 12 months post-SRS (MRI):

    • Marked decrease in size of AVM nidus

    • Appearance of perinidal high signal in T2 and FLAIR studies, denoting vasogenic edema

  • 24 months post-SRS (MRI):

    • Non-visualized AVM nidus

    • Appearance of small focal ring enhancing lesion at the site of prior AVM nidus, in T1 Gadolinium-enhanced study, denoting radiation necrosis

    • Increased high signal, in T2 and FLAIR studies, surrounding the ring enhancing lesion at the site of prior AVM nidus

  • 30 months post-SRS (conventional angiography): Complete obliteration of AVM nidus

  • 57 months post-SRS (MRI):

    • Appearance of large cystic lesion with slightly enhancing rim at the site of prior AVM nidus, in T1 Gadolinium-enhanced study, denoting radiation-induced parenchymal changes with cyst formation

    • Markedly increased high signal in T2 and FLAIR studies around the radiation-induced large cyst

  • 81 months post-SRS (MRI):

    • Regression in size of the heterogeneously enhancing cystic lesion at the site of prior AVM nidus, in T1 Gadolinium-enhanced study

    • Persistent increased high signal in T2 and FLAIR studies around the residual small enhancing radiation-induced cyst

• Post-radiosurgery Treatment: Continued anti-convulsant medications