Arteriovenous malformations (AVMs) are a rare cause of cerebrovascular abnormality
with incidence of about 1 in 100,000 people per year and point prevalence of about
0.2%. AVMs are associated with serious complications such as intracranial haemorrhage
(2–4% a year, 16% and 29% at 10 and 20 years after diagnosis), seizures (10–30%),
focal neurologic deficits, and headaches. The management options are surveillance,
endovascular embolization, microsurgical excision and stereotactic radiosurgery (SRS).
In SRS Stereotactically focused high energy beams of photons induce progressive thrombosis
by fibro-intimal hyperplasia and subsequent luminal obliteration. These changes usually
take one to three years known as “latency period”. Complications are reported in 8%
of patients undergoing SRS, including radiographic parenchymal lesions, cranial nerve
deficits, seizures, headaches, and cyst formation.
Cyst formation is reported in about 1.2 % of patients undergoing SRS. While the exact
mechanism of post SRS cyst formation is unclear, it is hypothesized that it might
be due to damage to the blood brain barrier and increased vessel wall permeability.
Delayed cyst formation is reported with latency period between 3 and 10 years after
radiotherapy for treatment of cerebrovascular AVMs. However, cystic formation with
longer latency periods (in one case upto 17 years) after radiotherapy for other causes
such as nasopharyngeal cancers have been reported.
Here we report a case of delayed cyst formation after SRS for cerebrovascular AVM
with latency period of 20 years.