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Most evidence on moyamoya comes from Japan, where the condition is most common, and from long-term surgical series. The main randomized trial was in adults who had bled. Different questions have different evidence:

QuestionMain sourceWhat it shows
How is moyamoya diagnosed?Revised Japanese diagnostic criteriaThe vascular pattern required, and that one-sided disease qualifies
Does bypass prevent rebleeding?JAM trial, adults after hemorrhageFewer rebleeds after direct bypass
How do children do after surgery?Boston pediatric seriesLong-term independence and few late strokes after indirect surgery
What happens without symptoms?AMORE registry, Japanese adultsAn annual stroke risk of about 1.4% per person

Diagnosis and guidelines

The diagnostic criteria were revised in Japan in 2021 and accept disease affecting only one side1. The European Stroke Organisation guideline of 2023 distinguishes graded recommendations from expert consensus; for many questions about ischemic disease, children and surgical technique, the evidence is very uncertain2. The Japanese management guidance uses its own grading3, and the American Heart Association has summarized its scientific statement on moyamoya in adults4.

Adults after hemorrhage: the JAM trial

The Japan Adult Moyamoya trial randomly assigned 80 adults who had bled within the previous year to bilateral direct bypass (42) or conservative care (38), and followed them for five years. Serious adverse events occurred in 14.3% of the surgical group and 34.2% of the conservative group, and rebleeding in 11.9% against 31.6%. The authors describe the results as statistically marginal but supportive of bypass to prevent rebleeding5.

Children: long-term results

A Boston series followed 59 children and young adults (aged 21 or under) more than 20 years after indirect surgery called pial synangiosis. Of 55 with follow-up, 45 were living independently; one had a late stroke and six had died, four of whom had previously had radiation to the head6. The series has no untreated comparison group.

Adults without symptoms: AMORE

The Asymptomatic Moyamoya Registry followed 103 Japanese adults with no history of stroke or mini-stroke for five years. Seven strokes occurred, six of them hemorrhages, an annual risk of 1.4% per person and 1.0% per affected hemisphere7. The study observed patients without assigning treatment, so it can't show whether preventive surgery would help.

Patient information

MedlinePlus explains the condition and its genetics8, and the US Centers for Disease Control and Prevention describes the warning signs of stroke9.

References

  1. Kuroda S et al. Neurologia medico-chirurgica. 2022;62:307–312. doi:10.2176/jns-nmc.2022-0072. Source ↩
  2. Bersano A et al. European Stroke Journal. 2023;8:55–84. doi:10.1177/23969873221144089. Corrected March 2023. Source ↩
  3. Fujimura M et al. Neurologia medico-chirurgica. 2022;62:165–170. doi:10.2176/jns-nmc.2021-0382. Source ↩
  4. American Heart Association. Top Things to Know: Adult Moyamoya Disease and Syndrome. 23 August 2023. Statement doi:10.1161/STR.0000000000000443. Source ↩
  5. Miyamoto S et al. Stroke. 2014;45:1415–1421. doi:10.1161/STROKEAHA.113.004386. PubMed ↩
  6. Riordan CP et al. Journal of Neurosurgery: Pediatrics. 2019;23:586–592. doi:10.3171/2019.1.PEDS18457. PubMed ↩
  7. Kuroda S et al. Stroke. 2023;54:1494–1504. doi:10.1161/STROKEAHA.122.041932. PubMed ↩
  8. US National Library of Medicine. MedlinePlus Genetics: Moyamoya disease. Webpage. Source ↩
  9. US Centers for Disease Control and Prevention. Signs and Symptoms of Stroke. 19 May 2026. Source ↩