Abstracts

Rationale: Moyamoya disease (MMD) involves progressive steno-occlusive changes in the internal carotid arteries and main branches with compensatory formation of a fine vascular network from the lenticulostriate arteries. Moyamoya syndrome (MMS) is the same phenomenon occurring unilaterally. As such, it may be an earlier stage of MMD. Moyamoya is typcally seen in patients with sickle cell disease (SCD), down syndrome (DS), neurofibromatosis (NF). Encephaloduroarteriosynangiosis (EDAS) and encephalomyoarteriosynangiosis (EMAS) are surgical revascularization techniques which aim to improve cerebral perfusion and decrease the risk for stroke. However, these procedures themselves may have peri-operative complication including cerebral ischemia or hyperperfusion injury. Use of clinical monitoring tools to assess for peri-operative risks have not been defined. Easily accessible, intraoperative electroencephalography is one such tool but it is not consistently utilized during this procedure. We describe our experience with EEG monitoring during revascularization.Methods: Between Sept 2011 and May 2015, we prospectively performed intra-operative EEG recordings during all surgical revascularizations performed at Children’s Hospital of Alabama. The 10-10 electrode placement was used with omission of several electrodes (predominantly temporal) to accommodate for surgical incision. Clinical history, and neuroimaging studies were recorded.Results: Ten patients with MMD underwent staged bilateral revascularization & 6 with MMS had ipsilateral procedures only, Table 1. In the MMD cohort, 10/20 procedures had intermittent bilateral delta/theta slowing with attenuation and loss of faster frequencies. Two patients had a concomitant decrease in mean arterial pressure (MAP) to 59 -62 range in both hemispheres. Both the EEG and MAP changes were typically maximal during synangiosis itself. 1of these 4 patients with no prior history of seizures had 4 stereotyped electrographic seizures during synangiosis with a concomitant MAP decrease from 100 to 90. In the MMS cohort, four patients had intermittent bilateral slowing, maximal in the contralateral hemisphere in 3. MAP decreased to low 60s in 1 patient with bilateral slowing. EEG results are summarized in Table 2. When persistent slowing was seen, MAP was increased to >70 & neuroprotective doses of propofol were administered. Post-operative complications included a stroke in 1 patient with MMD 2 weeks after surgery. No other neurologic complications were seen.Conclusions: Contralateral and ipsilateral slowing was seen in the majority of patients. This was associated with a decrease in MAP in some. Though the mechanisms involved need further study, we hypothesize that the EEG findings may be secondary to impaired cerebrovascular autoregulation in these patients. Further studies on MAP parameters that optimize autoregulation in MMD/MMS may further define the role of intra-operative monitoring tools such as electroencephalography.