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Biomedical subjects

Wui K Chong

Publications and source records attributed to Wui K Chong.

7 recordsLinked to original sources
PubMed2006

Magnetic resonance imaging of neonatal encephalopathy at 4.7 tesla: initial experiences.

OBJECTIVES: The goals were to develop safe 4.7-T MRI examination protocols for newborn infants and to explore the advantages of this field strength in neonatal encephalopathy. METHODS: Nine ventilated newborn infants with moderate or severe encephalopathy were studied at 4.7 T, with ethical approval and informed parental consent. The custom-made, 4.7-T-compatible, neonatal patient management system included acoustic noise protection and physiologic monitoring. An adult head coil was used. Acquisition parameters for T2-weighted fast spin echo MRI and a variety of T1-weighted methods were adapted for MRI of neonatal brain at 4.7 T. The pulse sequences used had a radiofrequency specific absorption rate of <2 W/kg. RESULTS: Physiologic measures were normal throughout each scan. T2-weighted fast spin echo imaging provided better anatomic resolution and gray/white matter contrast than typically obtained at 1.5 T; T1-weighted images were less impressive. CONCLUSIONS: With appropriate safety precautions, MRI of newborn infants undergoing intensive care is as feasible at 4.7 T as it is at 1.5 T; our initial studies produced T2-weighted fast spin echo images with more detail than commonly obtained at 1.5 T. Although T1-weighted images were not adequately informative, additional pulse sequence optimization may be advantageous. A smaller neonatal head coil should also permit greater flexibility in acquisition parameters and even more anatomic resolution and tissue contrast. In neonatal encephalopathy, interpretation of the T2-weighted pathologic detail in combination with comprehensive neurodevelopmental follow-up should improve prognostic accuracy and enable more patient-specific therapeutic interventions. In addition, more precise relationships between structural changes and functional impairment may be defined.

Brain Diseases↗
PubMed2006

Frameshift mutation in GJA12 leading to nystagmus, spastic ataxia and CNS dys-/demyelination.

Mutations in GJA12 have been shown to cause Pelizaeus-Merzbacher-like disease (PMLD). We present two additional patients from one family carrying a homozygous frameshift mutation in GJA12. Both presented initially with nystagmus. The older girl developed ataxia first, then progressive spastic ataxia. The younger boy suffered from severe sensory neuropathy. Magnetic resonance imaging (MRI) of both children showed progressive demyelination in addition to dysmyelination, and also characteristic brainstem abnormalities. In children with nystagmus, ataxia and dysmyelination, mutation analysis of GJA12 should be considered early, especially if inheritance is autosomal recessive.

Ataxia↗
PubMed2005

Three or more copies of the proteolipid protein gene PLP1 cause severe Pelizaeus-Merzbacher disease.

We describe five boys from different families with an atypically severe form of Pelizaeus-Merzbacher disease (PMD) who have three, and in one case, five copies of the proteolipid protein (PLP1) gene. This is the first report of more than two copies of PLP1 in PMD patients and clearly demonstrates that severe clinical symptoms are associated with increased PLP1 gene dosage. Previously, duplications, deletions and mutations of the PLP1 gene were reported to give rise to this X-linked disorder. Patients with PLP1 duplication are usually classified as having either classical or transitional PMD rather than the more rare severe connatal form. The clinical symptoms of the five patients in this study included lack of stable head control and severe mental retardation, with three having severe paroxysmal disorder and two dying before the first year of life. Gene dosage was determined using interphase FISH (fluorescence in situ hybridization) and the novel approach of multiple ligation probe amplification (MLPA). We found FISH unreliable for dosage detection above the level of a duplication and MLPA to be more accurate in determination of specific copy number. Our finding that three or more copies of the gene give rise to a more severe phenotype is in agreement with observations in transgenic mice where severity of disease increased with Plp1 gene dosage and level of overexpression. The patient with five copies of PLP1 was not more affected than those with a triplication, suggesting that there is possibly a limit to the level of severity or that other genetic factors influence the phenotype. It highlights the significance of PLP1 dosage in CNS myelinogenesis as well as the importance of accurate determination of PLP1 gene copy number in the diagnosis of PMD and carrier detection.

Brain↗
PubMed2005

Taylor-type focal cortical dysplasia in infants: some MRI lesions almost disappear with maturation of myelination.

Identification of focal cortical dysplasia (FCD) on magnetic resonance (MR) images of young children with refractory focal epilepsy is important, as surgical resection may offer improvement of seizure control and subsequent developmental progress. However, the MR appearances of malformations of cortical development may change during brain maturation. We report 4 children with refractory focal epilepsy, whose MR images in infancy showed localized cortical and subcortical signal abnormalities (hypointense on T(2)-weighted and hyperintense on T(1)-weighted images), suggestive of abnormal cortical development. The visibility of these lesions was significantly reduced on later MR images. Subtle blurring of the gray-white matter junction in these areas was the only indicator of cortical abnormality in 3 patients, which was recognized only after comparison with earlier images. Taylor-type FCD was subsequently confirmed in all patients, following surgical cortical resection of the lesions. MR images performed early within the first year of life in children with epilepsy are important to identify areas of FCD. The appearances of FCD on later scans can be very subtle escaping recognition, and conclusions may be misleading with respect to diagnosis and appropriateness of surgical treatment.

Age Factors↗
PubMed2003

Cortical anomalies associated with visuospatial processing deficits.

Children born preterm provide a fruitful population for studying structure-function relationships because they often have specific functional deficits in the context of normal neurological status. We selected a group of preterm adolescents with deficits in judgment of line orientation. Despite their very low birth weight, all were neurologically normal with no consistent abnormalities on conventional magnetic resonance imaging. However, voxel-based morphometric analysis of their magnetic resonance imaging scans showed areas of decreased gray matter and increased white matter most prominently in right ventral extrastriate cortex, close to an area previously implicated in the line orientation task. We suggest that these anomalies of cortical architecture relate to impaired performance on the line orientation task.

Adolescent↗
PubMed2003

Sonographic features of benign thyroid nodules: interobserver reliability and overlap with malignancy.

OBJECTIVE: To prospectively determine the sonographic findings of nodular hyperplasia of the thyroid, to compare these with reported findings associated with malignancy, and to assess interobserver reliability. METHODS: Seventy thyroid nodules were scanned, and then biopsies of the nodules were performed under sonographic guidance with fine-needle cytologic analysis; in all cases images were reviewed by 2 experienced radiologists without knowledge of clinical outcome. Findings reported associated with malignancy were specifically assessed. Interobserver agreement between the expert and secondary readers for each finding was calculated by the kappa or weighted kappa statistic and the Fisher exact test of independence. RESULTS: There were 68 benign and 2 malignant nodules in a population of 63 female and 7 male patients. The mean benign nodule size was 2.9 cm; 60% were solid; 54% were hypoechoic; 59% were microlobulated or macrolobulated; 47% had central vascularity; 24% contained calcifications; and 82% were elliptical in shape. There was very good interobserver reliability for the presence of calcium (kappa = 0.91) and good agreement for the presence and location of vascularity (kappa = 0.75) and the amount of cystic components (kappa = 0.62; all P < .01). CONCLUSIONS: Sixty-nine percent of benign nodules had at least 1 finding reported previously as associated with malignancy. The interobserver reliability of the sonographic findings was good to very good for 3 of the 5 findings assessed.

Biopsy, Fine-Needle↗