Iodine-123-Iomazenil SPECT Revealed Recovery of Neuronal Viability in Association with Improvement in Symptoms Following Treatment for Obstructive Hydrocephalus due to a Giant Posterior Cerebral Artery Aneurysm.

Abstract

Early and late images of ¹²³I-iomazenil (¹²³I-IMZ) single-photon emission computed tomography (SPECT) are considered to show cerebral blood flow and neuronal activity, respectively, and this modality may demonstrate temporal dysfunction of the frontal lobes in obstructive hydrocephalus. In this report, we examined ¹²³I-IMZ SPECT in a patient with chronic obstructive hydrocephalus owing to compression of the aqueduct by a partially thrombosed aneurysm of the left posterior cerebral artery for the first time. A woman aged 77 years presented with progression of cognitive decline, gait disturbance, and urinary incontinence. She had a medical history of epilepsy and subarachnoid hemorrhage due to a ruptured left posterior cerebral artery aneurysm, treated conservatively when she was age 56 years. Magnetic resonance imaging revealed a mass lesion in the pineal region, which showed a target sign with gadolinium-based contrast agents, causing obstructive hydrocephalus owing to compression of the cerebral aqueduct. A right vertebral angiogram confirmed the presence of a partially thrombosed giant aneurysm at the left posterior cerebral artery. To rule out the involvement of nonconvulsive status epilepticus in her pathology, we performed ¹²³I-IMZ SPECT, and both early and late images demonstrated low uptake in the bilateral frontal cortex. After surgical trapping of the parent artery and resection of the aneurysm, hydrocephalus was relieved, and the symptoms disappeared along with improvement in early and late ¹²³I-IMZ SPECT images. The findings in the present case indicate that ¹²³I-IMZ SPECT can detect reversible cerebral blood flow reduction and neuronal viability in the frontal lobes, which may affect the clinical manifestation of obstructive hydrocephalus.