title: Radiation-induced moyamoya syndrome.
abstract: OBJECTIVE
  The moyamoya syndrome is an uncommon late complication after radiotherapy (RT).
  
  
  METHODS
  A PubMed search of English-language articles, with radiation, radiotherapy, and moyamoya syndrome used as search key words, yielded 33 articles from 1967 to 2002.
  
  
  RESULTS
  The series included 54 patients with a median age at initial RT of 3.8 years (range, 0.4 to 47). Age at RT was less than 5 years in 56.3%, 5 to 10 years in 22.9%, 11 to 20 years in 8.3%, 21 to 30 years in 6.3%, 31 to 40 years in 2.1%, and 41 to 50 years in 4.2%. Fourteen of 54 patients (25.9%) were diagnosed with neurofibromatosis type 1 (NF-1). The most common tumor treated with RT was low-grade glioma in 37 tumors (68.5%) of which 29 were optic-pathway glioma. The average RT dose was 46.5 Gy (range, 22-120 Gy). For NF-1-positive patients, the average RT dose was 46.5 Gy, and for NF-1-negative patients, it was 58.1 Gy. The median latent period for development of moyamoya syndrome was 40 months after RT (range, 4-240). Radiation-induced moyamoya syndrome occurred in 27.7% of patients by 2 years, 53.2% of patients by 4 years, 74.5% of patients by 6 years, and 95.7% of patients by 12 years after RT.
  
  
  CONCLUSIONS
  Patients who received RT to the parasellar region at a young age (<5 years) are the most susceptible to moyamoya syndrome. The incidence for moyamoya syndrome continues to increase with time, with half of cases occurring within 4 years of RT and 95% of cases occurring within 12 years. Patients with NF-1 have a lower radiation-dose threshold for development of moyamoya syndrome.
authors.affiliation: Department of Radiology, Division of Radiation Oncology, Baylor College of Medicine, Methodist Hospital, Houston, TX 77030, USA.
authors.forename: Snehal S
authors.initials: SS
authors.lastname: Desai
authors.forename: Arnold C
authors.initials: AC
authors.lastname: Paulino
authors.forename: Wei Y
authors.initials: WY
authors.lastname: Mai
authors.forename: Bin S
authors.initials: BS
authors.lastname: Teh
mesh_terms: D000704:Analysis of Variance; D005260:Female; D006801:Humans; D008297:Male; D009072:Moyamoya Disease / Q000209:etiology*; D011878:Radiotherapy / Q000009:adverse effects*; D011879:Radiotherapy Dosage