小児の脳動静脈奇形の特徴を踏まえた治療─いかに出血源を特定し，閉塞を確認し，そして経過観察するか─

抄録

Background: Arteriovenous malformations (AVMs) in the pediatric population exhibit clinical and pathological characteristics that are different from those in adults. Pediatric AVMs are more frequently associated with diffuse and small AVMs than adult AVMs, rendering it difficult to make a correct and prompt diagnosis in the acute phase of hemorrhage. Besides, AVMs in pediatric patients are correlated to a higher risk of recurrence. However, the optimal observation strategy for pediatric AVMs has not been well established.
Methods: A cohort of children aged 18 years or younger who had AVM and underwent treatment at our institution between 2008 and 2012 were included in the study. The characteristics investigated included initial clinical presentations, Spetzler-Martin grade, type of nidus (compact/diffuse/micro), timing of AVM detection, treatment methods, and outcome. In addition, the radiological modalities to confirm the obliteration and risks of residual or recurrence of AVMs were evaluated. To confirm the obliteration during surgery, we utilized the repetitive intraoperative indocyanine green-based videoangiography instead of intraoperative angiography.
Results: Twenty-three patients were included in this study. The initial presentation was hemorrhage in 22 patients. The numbers of cases classified as Spetzler-Martin grades I, II, III, and IV were 7, 13, 1, and 2, respectively. The type of nidus was compact in 10, micro-AVM in 7, and diffuse in 6. Among six patients whose angiography result on admission was negative, 5 had diffuse or micro-AVM. Fourteen patients had craniotomy, while 9 received stereotactic radiotherapy or gamma knife surgery. The favorable treatment outcome (modified Rankin Scale score of 0-2) was achieved in 91.3%. Except for one case of mortality immediately after surgery, no residual or recurrence was observed in the patients treated with craniotomy during the mean follow-up period of 3.7 years (0.4-10.5).
Conclusions: Pediatric AVMs should be treated with a deep understanding of their discrete characteristics. Although a high index of suspicion for AVM is essential in the treatment of cerebral hemorrhage in pediatric patients, failure of the initial angiography to reveal AVMs is not rare because nidi tend to be diffuse or small. The repetitive and aggressive search for AVMs by using angiography should be conducted after the mass effect is reduced. Our data suggest that intraoperative angiography is not mandatory to minimize the risk of residual AVM or recurrence. Indocyanine green-based videoangiography is effective especially for superficial diffuse or micro-AVMs. Considering the recurrence rate of pediatric AVMs is higher than that of adult AVMs, we advocate angiographical evaluation at 1-year follow-up after surgery, followed by magnetic resonance imaging until patients reach adulthood.