Case study
Iomazenil hyperfixation in single photon emission computed tomography study of malformations of cortical development during infancy

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Abstract

We present 2 cases of malformations of cortical development and early onset epilepsy. The first case is of a patient with left hemimegalencephaly who developed focal epilepsy at the age of 2 days and cluster spasms at 1.5 months. After left functional hemispherectomy, seizures originated from the contralateral hemisphere, which had shown normal signals in the preoperative magnetic resonance imaging study. The second case is of a patient with lissencephaly, caused by a missense mutation in the doublecortin gene, who developed West syndrome at the age of 5 months. In both the cases, 123I-iomazenil single photon emission computed tomography performed during infancy showed significant hyperfixation in the dysplastic lesions. This finding indicates the immaturity of the affected neurons and a gamma-aminobutyric acidergic involvement in epileptogenesis associated with malformations of cortical development during infancy.

Introduction

Malformation of cortical development (MCD) is one of the major causes of intractable childhood epilepsy.1 Defects in some processes of corticogenesis, including migration, proliferation, or differentiation of neurons, can cause diverse types of MCDs. Here, we report 2 cases of patients with severe MCD and early onset epilepsy, who underwent 123I-iomazenil single photon emission computed tomography (SPECT) during infancy. Neither of the patients had received benzodiazepines around the time of the SPECT scans.

Section snippets

Case 1

The patient was a boy with left hemimegalencephaly. His detailed clinical history, including seizure development associated with functional hemispherectomy, has been previously reported.2 He experienced seizures consisting of motion arrest, apnoea, and facial cyanosis at the age of 2 days. Magnetic resonance imaging (MRI) revealed enlargement of and cortical dysplasia in the left cerebral hemisphere (Fig. 1A). The right hemisphere appeared to be normal, except for the slightly blurred

Discussion

In both the patients with severe MCD, 123I-iomazenil SPECT demonstrated abnormal hyperfixation in the lesions during early infancy. During normal development of the brain, postnatal neuronal maturation occurs early in the occipital and central regions and later in the frontal region. This development is corroborated by a synchronous progression of myelination and an increase in regional cerebral blood flow, which can be detected by MRI and SPECT. The images of the control infants in this study

Acknowledgement

We are deeply grateful to Dr. Mitsuhiro Kato, at the department of pediatrics, Yamagata University School of Medicine, for the genetic analysis of the doublecortin gene.

None of the authors has any conflict of interest to disclose.

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