Transient Symptomatic Downregulation of Cortical Neurotransmitter Receptor Function Due to Cerebral Hyperperfusion after Arterial Bypass Surgery for a Patient with Ischemic Moyamoya Disease

Abstract

Cerebral hyperperfusion syndrome following arterial bypass surgery is known as a surgical complication of moyamoya disease (MMD). How cerebral hyperperfusion affects neural function and causes neurological deficits remains unknown. We report here a case with cerebral hyperperfusion syndrome after arterial bypass surgery for ischemic MMD. Chronological changes of brain perfusion and central benzodiazepine receptor biding potential were observed using single-photon emission computed tomography. A 20-year-old woman with ischemic MMD underwent arterial bypass surgery. Six days later, cerebral hyperperfusion syndrome developed. During this syndrome, contralateral-to-ipsilateral cerebellar asymmetry of blood flow and a decrease in central benzodiazepine receptor binding potential in the area with hyperperfusion were observed. Four months later, these two findings resolved and a neurological examination revealed no abnormal signs. Cerebral hyperperfusion after arterial bypass surgery for ischemic MMD may lead to transient, reversible reduction of cerebral metabolism and downregulation of cortical neurotransmitter receptor function, resulting in transient neurological deficits.

Keywords: arterial bypass surgery; downregulation; hyperperfusion; moyamoya disease; neurotransmitter receptor.

Fig. 1.

Diffusion-weighted magnetic resonance image at the day when motor aphasia and right hemiparesis newly developed shows no ischemic cerebral lesions (left). Magnetic resonance angiography performed simultaneously demonstrates a patent superficial temporal artery-middle cerebral artery anastomosis (right).

Fig. 2.

Brain perfusion single-photon emission computed tomography (SPECT) images with ¹²³I-N-isopropyl-p-iodoamphetamine. At 7 days before surgery, blood flow is lower in the left cerebral hemisphere than in the right cerebral hemisphere (left). New neurological deficits, such as motor aphasia and right hemiparesis developed 6 days after surgery. During development of these deficits (2 days after the onset), blood flow is prominently increased in the left pre-motor area and blood flow in the right cerebellar hemisphere is decreased relative to blood flow in the left cerebellar hemisphere (middle). On the 4th postoperative month when a neurological examination revealed no abnormal signs, increased blood flow in the left pre-motor area and contralateral-to-ipsilateral cerebellar asymmetry of blood flow disappear (right).

Fig. 3.

Central benzodiazepine receptor biding potential SPECT images with ¹²³I-iomazenil. At 5 days before surgery, central benzodiazepine receptor biding potential is slightly lower in the left cerebral hemisphere than in the right cerebral hemisphere (left). During development of new postoperative neurological deficits (4 days after the onset), central benzodiazepine receptor biding potential is prominently decreased in the left frontal lobe (middle). On the 4th postoperative month, the decrease in central benzodiazepine receptor biding potential in the left frontal lobe disappears (right).