Richard Jackson, MD
Moyamoya disease is one of those rare diseases that we come across infrequently and are uncertain what to do about when we do. The syndromic disease is easily recognizable, and the work-up largely revolves around ruling out secondary moyamoya syndrome from an identifiable cause that can be modified. Primary moyamoya vasculopathy has remained a surgical disease due to lack of understanding of its etiology.
I was excited to see Hu Yin et al. had collected a large cohort of 506 patients with primary moyamoya disease and attempted to stratify them radiographically into who would respond best to treatment. The group used Gao et al.’s CT-Perfusion scale system of stages of pre-infarction in moyamoya disease (MMD) to explore perfusion differences in pre-surgical intervention with direct or combined bypass techniques and to explore the perfusion difference between hemorrhagic and ischemic patients.
The study was approved by the ethics committee at Beijing Tiantan hospital and enrolled 506 patients after screening 696. Inclusion criteria were diagnosis by DSA or MRA, CT-perfusion before surgery, and surgical intervention with direct or combined bypass surgery. Stage of disease was categorized by the Suzuki criteria. Patients with identifiable causes, no pre-operative CT-perfusion, and follow-up <12 months were excluded. There were 155 patients with ICH, 168 patients with ischemic strokes, and 183 with other symptoms classified as headache, seizure, or TIA. Neuroradiologists had at least 5 years’ experience, underwent CT-perfusion training and performed independent readings of each case. Hemispheres were evaluated independently, but if both were affected, the cerebellum was used as a perfusion control.
Results reported as Stage 1 hypoperfusion (TTP delay only) had the highest improvement ratio of pre-surgical to post-surgical mRS, and normal perfusion the lowest. A decreasing benefit of improvement was noted from Stage 1 (TTP delay only) to Stage 4 (abnormal MTT, TTP, rCBF, rCBV). However, there were much lower numbers of patients in both the ischemic and hemorrhagic Stage 1 disease with <10% in the Stage 1 and >20% in all other stages. Stage 3 had the highest rates of evaluation with 242 in the ischemic group but only 66 in the hemorrhagic group.
In the Discussion, the authors conclude that their novel scale of pre-infarction period found that the hemispheres with normal perfusion in the hemorrhagic group were more common than the ischemic group. However, a limitation in the study might be that the numbers were low with 140 ischemic patients and 89 hemorrhagic. Other limitations were the semi-quantitative scale, the low numbers, and limitation of the intervention to direct and combined bypass technique.
Despite the limitations, it is exciting to see a large group of these patients be evaluated with an objective scale for post-surgical outcomes and some data to guide treatment for this disease, even though most of us only see this rare disease infrequently.