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Biomedical subjects

W K Chong

Publications and source records attributed to W K Chong.

At least 37 records · Page 2Linked to original sources
PubMed2000

Diffusion and perfusion magnetic resonance imaging in childhood stroke.

Two magnetic resonance imaging techniques, diffusion and perfusion imaging, are being used increasingly for evaluation of pathophysiology of stroke. This article introduces these techniques and reports some initial studies using these approaches, together with conventional T2-weighted magnetic resonance imaging, for investigation of childhood stroke. It is shown that the combination of T2-weighted and diffusion images can provide information about the timing of stroke events in childhood, and perfusion imaging can detect abnormalities not visible by other magnetic resonance imaging techniques. These magnetic resonance methods therefore should play an important role in investigation of children with stroke and could be of particular value in studies of at-risk populations of children such as those with sickle cell disease.

Adolescent↗
PubMed2000

Hippocampal volume and everyday memory in children of very low birth weight.

Children born preterm and of very low birth weight have an increased incidence of learning difficulties, but little is known about the specific nature of their cognitive deficits and the underlying neuropathology. We hypothesized that their vulnerability to hypoxic, metabolic, and nutritional insults would lead to reduced hippocampal volumes and to deficits in memory because of the role of the hippocampus in this domain of cognition. Neuropsychological and magnetic resonance imaging methods were used to investigate this hypothesis in adolescents born preterm (< or = 30 wk gestation, n = 11) or full-term (n = 8). The preterm group had significantly smaller hippocampal volumes bilaterally, despite equivalent head size, and showed specific deficits in certain aspects of everyday memory, both on objective testing and as indicated by parental questionnaires. The preterm group also had a specific deficit in numeracy. The reduced hippocampal volumes and deficits in everyday memory have previously been unrecognized, but their prevalence in a group of neurologically normal children is striking.

Adolescent↗
PubMed1999

Development of a nurse-led sedation service for paediatric magnetic resonance imaging.

BACKGROUND: Children generally lie still enough for magnetic resonance imaging (MRI) only if they are asleep, either under sedation, which is deeper than conscious sedation, or under anaesthesia. Anaesthesia resources, however, are limited, and non-anaesthetists must use sedation frequently. Demand for MRI has increased and the failure of our sedation regimen led to an impractical demand for anaesthesia and unacceptable waiting times for scanning. We have therefore developed a nurse-led sedation service in a designated unit next to the scanner. This study assessed the safety and efficacy of this approach. METHODS: Children who required MRI were sedated in the unit by designated sedationist nurses, who used an oral drug regimen (according to weight and age from conception: weight <5 kg, 50 mg/kg chloral hydrate; 5-10 kg, 100 mg/kg chloral hydrate; 10-20 kg, 1 mg/kg temazepam plus 0.25 mg/kg droperidol; >20 kg temazepam and droperidol as directed by radiologist, maximum doses 20 mg and 5 mg respectively). Nurses checked patients for their suitability, charted and administered the drugs according to a protocol, and monitored the children throughout the sedation. We prospectively audited failure and complications of sedation. FINDINGS: During the 30 month study, there were 1155 sedations. 61 (5%) were unsuccessful, and there were no adverse events relating to the airway or breathing. After scanning had finished all children, in response to gently pinching the nose, could open their mouths to maintain their airway. INTERPRETATION: This study suggests that it is possible to have a nurse-led sedation service for MRI of children that is both successful and safe.

Anesthesia↗
PubMed1999

Somatomotor fMRI in the pre-surgical evaluation of a case of focal epilepsy.

A child with intractable partial epilepsy who was found to have a focal lesion in the motor cortex underwent detailed pre-surgical and intraoperative investigations which enabled curative surgery without morbidity by minimizing a targeted resection. The pre-surgical assessment included mapping motor cortical function with functional magnetic resonance imaging (fMRI). This was subsequently correlated with the results of pre-surgical and intraoperative invasive corticography.

Adolescent↗
PubMed1999

Cerebral tissue water spin-spin relaxation times in human neonates at 2.4 tesla: methodology and the effects of maturation.

Using a 4-echo spin-echo sequence, cerebral T2 was measured in specific anatomic regions in eleven healthy newborn infants, whose gestational plus postnatal ages (GPAs) lay between 37 and 42 weeks. For a region in the pons, T2 was 141+/-9 ms (mean +/- standard deviation), and no significant dependence upon GPA was seen. In the thalamus mean T2 was 136+/-13 ms, and T2 demonstrated a significant negative linear dependence upon age (r = 0.690; p < 0.02). In periventricular and frontal regions, mean T2 were 217+/-33, and 228+/-32 ms respectively, and more marked negative linear correlations with age were observed (r = 0.833; p < 0.001 and r = 0.722; p < 0.02). For these regions, the rate of T2 decrease with age appeared to be related to known patterns of myelination. For the parietal region studied, mean T2 was 204+/-34 ms, no significant dependence upon GPA being seen. T2 shows promise as an objective measure of cerebral development in the perinatal period.

Brain↗
PubMed1999

Conventional cerebral angiography in children with ischemic stroke.

A retrospective review of conventional cerebral angiograms of 46 children with ischemic stroke was undertaken. Comparison was made with findings on magnetic resonance imaging and magnetic resonance angiography where available. Thirty-six children (78%) underwent magnetic resonance angiography in addition to conventional cerebral angiography. Seven patients had normal cerebral angiograms. Magnetic resonance angiography was diagnostic in 25 of 28 patients with large vessel occlusion, stenosis, or moya-moya syndrome. Conventional angiography was abnormal in four of nine patients with a normal magnetic resonance angiography. All patients with normal conventional angiograms also had normal magnetic resonance angiograms. Conventional angiography, either diagnostic or yielding further information, altered management in five patients with arterial dissection, one patient with large vessel occlusion, one patient with large vessel stenosis, and four patients with arteritis. On the basis of this experience, a clinical algorithm for the use of conventional cerebral angiography in the investigation of ischemic stroke in children is proposed.

Adolescent↗
PubMed1999

Lesion volume, lesion location, and outcome after middle cerebral artery territory stroke.

AIM: To investigate the relation between lesion volume, lesion location, and clinical outcome in children with infarction in the territory of the middle cerebral artery (MCA). PATIENTS AND METHODS: Children with MCA territory infarcts were selected retrospectively from a database of children with ischaemic stroke. Lesion volumes were expressed as a percentage of the supratentorial intracranial volume and were categorised as "small", "moderate", or "large". Lesion location was categorised as cortical or purely subcortical. Outcome was ascertained by parental questionnaire and was categorised as "good" or "poor". RESULTS: 38 patients were identified (median age 6 years); 21 patients had lesions that involved cortical tissue. Outcome was good in 12 cases and poor in 26 cases (including 2 children who died). Although there was no significant effect of lesion size or lesion location on outcome for the group as a whole, all children who had infarcted more than 10% of intracranial volume had a poor outcome. Of note, some children with small subcortical lesions had pronounced residual deficits. CONCLUSIONS: Although the outcome after a small infarct in the MCA territory is variable and unpredictable, infarction of more than 10% of intracranial volume is universally associated with a poor outcome. Characterisation of lesion volume and topography might be helpful in identification of such children for participation in future trials of treatments for acute stroke.

Adolescent↗
PubMed1999

Safety and efficacy of a new oral contrast agent for sonography: a phase II trial.

OBJECTIVE: Our purpose was to study the safety and efficacy of a new orally administered sonographic contrast agent in patients with suspected upper abdominal disorders. SUBJECTS AND METHODS: Ninety-nine patients with signs or symptoms suggestive of upper abdominal disorders were enrolled in a prospective range-of-dose phase II clinical trial at six sites; sonograms of 93 patients were evaluated for efficacy. Patients underwent upper abdominal sonography before and after receiving a randomized dose of the contrast agent (200, 400, 600, 800, or 1000 ml). Safety was monitored by physical examination and laboratory testing. The primary efficacy parameter was additional information provided by the contrast agent when comparing unenhanced and contrast-enhanced sonography. RESULTS: Of the 14 adverse events in 11 patients, only five, which included mild diarrhea and nausea, were considered related to the contrast agent. In 83 of 93 patients, additional information was obtained from the contrast-enhanced images. Visualization of anatomy was improved as follows: the stomach, in 82% of patients; the duodenum, in 63% of patients; the pancreatic head and body, in 61% of patients; and the pancreatic tail, in 67% of patients. CONCLUSION: SonoRx is a safe and well-tolerated contrast agent that improves the sonographic evaluation of the upper abdomen, with significant improvement in imaging the stomach, duodenum, and pancreas.

Abdomen↗
PubMed1999

Sturge-Weber syndrome: cerebral haemodynamics during seizure activity.

The aim of this study was to examine the haemodynamic response to seizures in three infants with Sturge-Weber syndrome by measuring regional cerebral blood flow using transcranial Doppler sonography and 99mTc HMPAO SPECT. Time-locked video/digital EEG recording was carried out for ictal studies. MRI was performed in all subjects. SPECT showed hemispheric hypoperfusion interictally in all three patients and also ictally in one of the three; a small region of hyperperfusion was seen on the same ictal scan in the latter, ie. the patient with interictal and ictal hypoperfusion. In the two older children middle cerebral artery velocity (MCAV) was reduced by between 29 and 62% in the middle cerebral artery of the predominantly affected hemisphere compared with the contralateral side. During seizures, increases of 6 to 30% in MCAV were recorded for the clinically seizing hemisphere compared with 24 to 170% for the contralateral side in four of the seizures recorded. In one infant, MCAV fell bilaterally during a seizure that generalized (-18 and -43% in the predominantly affected and contralateral side respectively). Sequential recordings in one infant suggested that, with time, the haemodynamic response to seizures of the unaffected hemisphere may decrease. These findings suggest that the venous malformation in SWS is associated with an impairment of the cerebral haemodynamic response to seizure activity.

Cerebral Cortex↗
PubMed1999

Neonatal diabetes mellitus and cerebellar hypoplasia/agenesis: report of a new recessive syndrome.

Classical neonatal diabetes mellitus is defined as hyperglycaemia occurring within the first six weeks of life in term infants. Cerebellar agenesis is rare. We report three cases of neonatal diabetes mellitus, cerebellar hypoplasia/agenesis, and dysmorphism occurring within a highly consanguineous family. This constellation of abnormalities has not previously been described. Two of these cases are sisters and the third case is a female first cousin. The pattern of inheritance suggests this is a previously undescribed autosomal recessive disorder. Prenatal diagnosis of the condition in this family was possible by demonstration of the absence of the cerebellum and severe IUGR.

Cerebellum↗
PubMed1999

Quantitative MR diffusion mapping and cyclosporine-induced neurotoxicity.

Apparent diffusion coefficient maps of two patients with cyclosporine-induced neurotoxicity showed areas of increased diffusion that corresponded to the characteristic regions of signal change on routine T2-weighted sequences. The majority of lesions subsequently resolved without residual T2 or diffusion signal alteration. These findings suggest that, in our patients, the neurotoxic effects of cyclosporine resulted in a partially reversible extravasation of fluid into the cerebral interstitium and were not associated with acute ischemia.

Anemia, Sickle Cell↗
PubMed1998

Labyrinthine involvement in Langerhans' cell histiocytosis.

BACKGROUND: Langerhans' cell histiocytosis, a rare condition caused by the proliferation of abnormal Langerhans' cells ('LCH cells') and an accompanying granulomatous infiltrate, can affect several organs including the ear. External and middle ear involvement are common with a reported incidence as high as 61%. The bony labyrinth is resistant to erosion by the granulation tissue, thereby protecting the cochlea and vestibular structures. Probably for this reason, involvement of the inner ear is rare, with few case reports in the literature. PATIENTS: We report two girls, one with bilateral and the other with unilateral mastoid involvement, in whom there was invasion of the labyrinth. The first girl had 'single system' LCH affecting only bone and developed an acute hearing loss due to invasion of the cochlea, while the second had both bone and skin involvement and labyrinthine involvement was diagnosed on imaging prior to the onset of labyrinthine symptoms. CONCLUSION: Inner ear involvement can lead to permanent deafness, which may be prevented by early institution of treatment. Threatened inner ear involvement requires urgent systemic medical therapy with steroids, possibly combined with chemotherapy.

Child, Preschool↗
PubMed1998

Familial congenital saccade initiation failure and isolated cerebellar vermis hypoplasia.

The underlying lesion in congenital saccade initiation failure (c-SIF) ('congenital ocular motor apraxia', 'Cogan's apraxia') is uncertain. Often no abnormality can be found, yet in others a midline cerebellar abnormality has often been reported. We examined this cerebellar association in a brother and sister. In addition to standard ophthalmological and neurological examinations, both siblings underwent ocular motor testing and neuroradiological investigations including CT and MRI. Both siblings exhibited the typical signs of c-SIF, including headthrusting, synkinetic blinking, missed-nystagmus quick phases, mild developmental delay, and speech difficulties. CT and MRI revealed cerebellar vermis hypoplasia in the brother, but appeared normal in the sister. No other neuroradiological abnormalities were detected. These cases highlight the wide variability in the association of vermis abnormalities with c-SIF, despite the inheritance and similar clinical manifestations. They show that either: (1) the vermis is causal in saccade triggering, but that c-SIF may result from very subtle damage that is beyond MRI resolution in some cases; or (2) that a vermis abnormality per se is not causative but only a marker of another subtle abnormality, either structural or possibly biochemical.

Apraxias↗
PubMed1998

Neuroimaging in children with congenital disorders of the peripheral visual system.

The study investigates the neurological substrate in children with congenital disorders of the peripheral visual system (CDPVS), i.e. disorders of the anterior visual pathways and the globe. The design is retrospective; brain MRI and/or CT scans were traced and reviewed for 79 of 254 children with CDPVS on our database. The neuroradiological findings were considered in the context of degree of visual impairment (profound [PVI] and severe [SVI]), developmental outcome (setback and non-setback), and mode of imaging (MRI and CT). Scans were abnormal in 40 of 79 (51%) children; 23 of 40 (58%) had more than one lesion; and in some children lesions not previously reported were found. The number of abnormalities per child was significantly higher in the PVI than the SVI group (P<0.05); the level of significance varied according to the method of scanning (MRI, P<0.001; CT, ns). Seven children were known to have had developmental setback; significantly more brain abnormalities per child were found in the group with setbacks than in the group without (P<0.001). Eighty-six percent (24 of 28) of MRI compared with 38% (22 of 58) of CT scans were abnormal. MRI detected more lesions per child than CT (P< 0.001). Thus, a significant amount of brain pathology occurs in children with CDPVS. The number of lesions varies directly with degree of visual impairment and both correlate with developmental outcome. As brain pathology will be only one of many factors influencing developmental progress in visually impaired children, prospective multifactorial studies of the CDPVS population, which include MRI studies of the neurological substrate, will be required to clarify the latter.

Brain↗
PubMed1998

Acquired spinal cord lesion associated with os odontoideum causing deterioration in dystonic cerebral palsy: case report and review of the literature.

A boy with a dystonic quadriparesis presented with acquired paralysis, spasticity, and a feeding disorder. Spinal MRI revealed a cervical cord lesion and os odontoideum. Excessive movement of the neck, leading to failure of ossification of the dens and then to cervical cord trauma was the likely mechanism. The poor outcome of this subject is described, emphasising the need to pay careful attention to neurological changes in children with extrapyramidal cerebral palsy, who may be at particular risk of cord pathology. The management issues are discussed.

Atrophy↗