Young-Hoon Ryu

The homozygosity for 10-repeat allele at dopamine transporter gene and dopamine transporter density in Korean children with attention deficit hyperactivity disorder: relating to treatment response to methylphenidate

The symptoms of attention deficit hyperactivity disorder (ADHD) can be treated with methylphenidate (MPH), a potent blocker of dopamine transporter (DAT). The homozygosity of the 10-repeat allele at the DAT gene (DAT1) seems to be associated with a poor response to MPH in children with ADHD. In the present study, we investigated the association between DAT density using I-123-N-(3-iodopropen-2-yl)-2beta-carbomethoxy-3beta-(4-chlorophenyl)tropane [123I]IPT single photon emission computed tomography (SPECT)] and the homozygosity for 10-repeat allele at DAT1 and response to MPH in Korean children with ADHD. Eleven drug-naive children with ADHD were included in the study and treated with MPH for about 8 weeks. After the genotyping and SPECT were performed, we compared DAT density between ADHD children with and without the homozygosity for 10-repeat allele at DAT1 and investigated the correlation between the homozygosity for 10-repeat allele and response to MPH. ADHD children with 10/10 genotype (n=7) had a significantly greater increase of the DAT density in basal ganglia than the children without 10/10 genotype (n=4). We found that while only 28.6% (2/7) of the subject with 10/10 genotype showed good response to MPH treatment, 100% (4/4) of the subjects without 10/10 genotype showed good response to MPH treatment. Our findings support an association between homozygosity for 10-repeat allele at DAT1 and the DAT density assessed in vivo and correlation between the homozygosity for 10-repeat allele and poor response to MPH.

Dopamine transporter density of the basal ganglia assessed with [123I]IPT SPECT in drug-naive children with Tourette's disorder

There is evidence that abnormalities in the dopaminergic system involving the dopamine transporter (DAT) are involved in the pathophysiology of Tourettes disorder (TD) from previous studies using [(123)I]2beta-carbomethoxy-3-(4-iodophenyl)tropane ([(123)I]beta-CIT) and single photon emission tomography (SPECT). However, because those studies were performed in medicated adult patients with TD, we decided to compare DAT densities in nine drug-naive children with TD and eight normal children. The children with TD did not suffer from associated psychiatric problems such as obsessive-compulsive symptoms, attention deficit hyperactivity disorder, anxiety, depression and developmental difficulties. We performed brain SPECT 2 h after the intravenous administration of I-123N-(3-iodopropen-2-yl)-2beta-carbomethoxy-3beta-(4-chlorophenyl)tropane ([(123)I]IPT) and carried out both quantitative and qualitative analyses using the obtained SPECT data, which were reconstructed for the assessment of the specific/non-specific DAT binding ratio in the basal ganglia. We then investigated the correlation between the severity of tics in children with TD assessed with the Yale Global Tic Severity Scale (YGTSS) and the specific/non-specific DAT binding ratio of the basal ganglia. Drug-naive children with TD showed a significantly increased specific/non-specific DAT binding ratio in the basal ganglia compared with normal children that did not correlate significantly with the severity of tics. Our results with drug-naive children with TD between the ages of 6 and 12 may help to clarify previous findings concerning DAT binding in adult patients with TD and suggest that DAT densities may be associated directly with the pathophysiology of TD, regardless of disease progress or drug effect.

MRI of germinomas arising from the basal ganglia and thalamus.

Abstract We reviewed the MRI findings of germinomas originating from the basal ganglia, thalamus or deep white matter in 13 patients with 14 germinomas, excluding those in the suprasellar or pineal regions. Ten cases were confirmed as germinomas by stereotaxic biopsy, three by partial and one by total removal of the tumour. Analysis was focussed on the location and the signal characteristic of the tumour, haemorrhage, cysts within the tumour and any other associated findings. Thirteen of the tumours were in the basal ganglia and one in the thalamus. Haemorrhage was observed in seven patients, while twelve showed multiple cysts. Associated ipsilateral cerebral hemiatrophy was seen in three patients. The signal intensity of the parenchymal germinomas was heterogeneous on T1- and T2-weighted images due to haemorrhage, cysts and solid portions. We also report the MRI findings of germinomas in an early stage in two patients.

Perirolandic hypoperfusion on single-photon emission computed tomography in term infants with perinatal asphyxia: comparison with MRI and clinical findings

Abstract We describe the findings on single-photon emission computed tomography (SPECT) in patients with perinatal asphyxia at term, with perirolandic cortico-subcortical changes on MRI, and to correlate them with clinical features. SPECT of 7 patients was obtained after injection of 185–370 MBq of Tc-99m-ECD (ethyl cysteinate dimer). The patients had spastic quadriplegia (7/7) with perinatal asphyxia (6/7) at term (7/7). The results were correlated with the MRI findings. Hypoperfusion of the perirolandic cortex was clearly seen on SPECT in all patients, even in two with subtle changes on MRI. SPECT demonstrated a more extensive area of involvement than MRI, notably in the cerebellum (in 4), the thalamus (in 7) and basal ganglia (in 5), where MRI failed to show any abnormalities.