A 31-year-old woman in the 15th week of gestation suddenly lost consciousness and was transferred to our institution. She was in a deep coma with her left pupil dilated and right hemiplegia. Computed tomographic scans showed an intracerebral hemorrhage in the left basal ganglia extending to the temporal lobe and a small, enhanced mass above the APS [Figure 1a]. An endoscopic hematoma evacuation was promptly performed [Figure 1b]. She recovered consciousness and motor function soon after the operation. The fetal growth and development was also satisfactory. Angiograms showed a nidus, fed by the AChAs, the LSAs, and perforators from the A1 segment of the anterior cerebral artery, which drained into the basal vein of Rosenthal (BVR), the deep middle cerebral vein, and the anterior communicating vein. The maximum diameter of the nidus was 25 mm with an SM grade of 3 [Figure 1c and d]. Curative surgery was indicated because both she and her husband wanted her pregnancy to be continued to full term.
A bolus injection of rocuronium bromide (0.9 mg/kg) and propofol (2 mg/kg) was given before tracheal intubation. She received a continuous infusion of propofol (3-5 mg/kg/h) thereafter. An obstetrician monitored the fetal heartbeats. We performed an orbitozygomatic craniotomy and a partial temporal lobectomy to obtain a wide surgical field. A grid strip with 16 electrodes (Unique Medical, Tokyo, Japan) was inserted into the subdural space to facilitate electrical stimulation to the motor cortex (Neuropack X1, Nihon Koden, Tokyo, Japan). The filters were at 20 Hz and 3 kHz (low- and high-band passes, respectively). We confirmed the muscle action potentials from the contralateral thenar muscles. Intraoperatively, the motor cortex was stimulated at 2 mA above the threshold level. A monopolar anodal electrical stimulus with five pulses was applied. The frequency of the train pulse was 500 Hz, and the duration of each single pulse was 200 ms.
The internal carotid artery, the A1 segment of the anterior cerebral artery, and the M1 segment of the middle cerebral artery were all well exposed after widely opening the Sylvian fissure. More than 10 perforating arteries were found to feed the nidus in the APS adjacent to the M1 segment. There were four AChAs feeding the nidus, and the distal two were cut because the test occlusion for 5 min did not induce a depression of the motor evoked potential (MEP) [Figure 2a]. The proximal two AChAs were preserved because the amplitude decreased 1 min after clamping [Figure 2b]. A few A1 perforators were also cut after the test occlusion. The LSAs were clamped, one at a time, proximally to distally, with Sugita microclips (Mizuho Ika, Tokyo, Japan) and the MEP was measured at 1 and 5 min after the occlusion. The LSAs were cut when the amplitude was not decreased [Figure 2c]. An LSA branching from the most distal part of the M1 segment was preserved because the amplitude decreased 5 min after clamping [Figure 2d], even though there was no MEP depression at 1 min. The preserved LSA was revealed passing through the nidus [Figure 3a]. The nidus was lifted from the APS after all the arteries supplying the nidus were cut [Figure 3b]. We confirmed that the nidus was not stained by indocyanine green (ICG), and that there was a reflux of the ICG in the BVR [Figure 3c]. The nidus was finally removed after dividing the main drainer. The MEP was maintained at the time of dural closure [Figure 2e]. The fetal heart rate was maintained in the normal range (<80 bpm) throughout the procedure. A postoperative magnetic resonance image revealed small infarcts in the nonfunctional areas, which did not produce any additional symptoms. Pre [Figure 4a] and postoperative [Figure 4b] angiograms showing the AVM had completely disappeared, and two AChAs and one LSA were preserved. The patient successfully delivered a term neonate by cesarean section 122 days after the operation. She could take care of her baby herself, and the child developed normally. The mother, however, suffered dysgraphia due to initial intracerebral hemorrhage that remained 1 year after the onset.