Biomedical subjects

N S Chu

Publications and source records attributed to N S Chu.

At least 55 records · Page 3Linked to original sources

PubMed1996

Recovery of finger sensibility and somatosensory evoked potentials following digit-to-digit replantation in man.

Recovery of finger sensation and digital nerve function following digit-to-digit replantation was studied in 14 patients by clinical sensory evaluation and somatosensory evoked potentials (SEP) to digital nerve stimulation. The mean interval between injury and surgery was 8 +/- 3h; that between surgery and study was 25 +/- 7 months. Sensory examination revealed a mild hypersensitivity to cold. Pinprick, touch and hot sensations had nearly complete recovery, while vibration and two-point discrimination were impaired. In digital SEPs from the replanted side, the N9 component was present and normal in 8 patients (57%), whereas the N13 and N20 components had prolonged latency with normal central conduction time. Absence of the N9 component appeared to correlate with a more proximal level of injury and poor surgical outcome. The present data indicate that sensory recovery of the replanted digits was in general satisfactory but incomplete, and that over half of the patients had normal digital nerve conduction.

Adolescent↗

PubMed1996

Recovery patterns of motor and somatosensory evoked potentials following treatment of vitamin B12 deficiency.

Motor and somatosensory pathway functions were studied using motor evoked potentials (MEPs), somatosensory evoked potentials (SEPs) and F-wave responses in a woman with vitamin B12 deficiency. Initial evaluation before treatment revealed: 1) prolongation of central motor conduction to both the upper and lower limbs, and prolongation of peripheral conduction to the lower limbs; 2) prolongation of central conduction time to median nerve stimulation and absence of cortical SEPs to tibial nerve stimulation; and 3) prolongation of F-wave responses to tibial and peroneal nerve stimulation. After 11 months of treatment with hydroxocobalamin, follow-up studies disclosed: 1) normalization of central motor conduction to the upper limbs, peripheral motor conduction to the lower limbs and improvement of central motor conduction to the lower limbs; 2) normalization of central conduction time to median nerve stimulation but persistent absence of cortical SEPs to tibial nerve stimulation; and 3) normalization of F-wave responses. These data suggest that both central and peripheral conductions of motor and somatosensory pathways may respond to hydroxocobalamin therapy, and that MEPs are useful in the early detection of central and peripheral motor pathway function recovery following treatment with vitamin B12 deficiency.

Adult↗

PubMed1995

Betel chewing increases the skin temperature: effects of atropine and propranolol.

Although betel chewing produces sweating, facial flush and a warm sensation of the body, objective documentation of the temperature effect has not been available. In this report, the skin temperature of the ear and forehead was recorded before and during betel chewing in healthy betel chewers. Betel chewing produced a mean temperature increase of 2 degrees C and 0.5 degree C, respectively, for the ear and forehead. This hyperthermic response was almost completely abolished by atropine and partially inhibited by propranolol. The present data suggest that both sympathetic and parasympathetic mechanisms are involved in the skin thermal response to betel chewing.

Areca↗

PubMed1995

Recovery of sensation and somatosensory evoked potentials following toe-to-digit transplantation in man.

Recovery of digital nerve function in 21 patients with toe-to-digit transplantation was evaluated by clinical sensory tests and somatosensory evoked potentials (SEPs) to median and digital nerve stimulation. The mean interval between injury and surgery was 7 months, and that between surgery and study was 31 months. The transplanted toes achieved a satisfactory but incomplete recovery in temperature (warm and cold), pinprick, touch, vibration, and two-point discrimination in that order. The overall sensory status of the transplanted toes appeared to be closer to normal toes than to normal fingers. In SEPs from the transplanted side, median N9, N13, and N20 components had normal latency but reduced amplitude, whereas digital N9 component was usually absent, but N13 and N20 components had prolonged latency and reduced amplitude. Transplantation performed within 1 month after injury prevented amplitude reduction in median SEPs and latency prolongation in digital SEPs. The SEP data suggest that timing of surgery was critical in preventing retrograde effect on the median nerve, and that recovery of digital nerve function was incomplete correlating with clinical sensory findings.

Adolescent↗

PubMed1995

Conduction study of digital nerve function recovery following toe-to-digit transplantation and a comparison with digit-to-digit replantation.

Recovery of digital nerve function following toe-to-digit transplantation was studied by nerve conduction in 16 patients, and a comparison was made with digit-to-digit replantation in 7 patients. For toe transplantation and digit replantation, the mean interval between injury and surgery was 7 months and 8 h, respectively, while the mean interval between surgery and study was 39 months and 25 months, respectively. Sensory nerve action potentials (NAPs) from digital nerve stimulation were recorded at the wrist and the elbow, whereas mixed NAPs from median nerve stimulation at the wrist were recorded at the elbow. Sensory NAPs from stimulation of the transplanted toe were detectable in 14 patients and showed reduced amplitude, prolonged latency, and slowed conduction velocity. There was retrograde amplitude reduction in the median nerve and in the proximal segment of the digital nerve. Sensory NAPs from the replanted digit were not different from those of the normal digit, nor was a retrograde effect observed. The present data indicate that digital nerve function recovery was incomplete in toe transplantation and nearly complete in digit replantation. The reasons for the differences in recovery following two types of nerve repair are discussed.

Action Potentials↗

PubMed1995

Mitochondrial encephalomyopathies: CT and MRI findings and correlations with clinical features.

Seven patients (3 men, 4 women; age 15-48 years) from 6 families with mitochondrial encephalomyopathies were studied. There were 4 patients with mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) and 3 patients with myoclonus epilepsy and ragged-red fibers (MERRF). The clinical course was variable in both MELAS and MERRF patients. Interestingly, one MERRF patient had putaminal hemorrhage with left hemiplegia. In MELAS patients, brain computed tomography (CT) revealed cerebral hypodensity lesions affecting all four lobes and relative sparing of the basal ganglia and the thalamus. The CT of MERRF patients showed cerebral and cerebellar cortical atrophies in two and ventricular dilatation in one. During the recovery stages, magnetic resonance images (MRI) revealed subcortical white matter lesions in two MELAS patients and one MERRF patient. These subcortical white matter lesions were most prominent in the paraventricular areas. The present data indicate that in MELAS the hypodense lesions tend to affect the cerebral hemisphere and to spare the subcortical gray matter. Furthermore, the involvement of the paraventricular white matter may occur in both MELAS and MERRF.

Adolescent↗

PubMed1995

Distribution and clinical expression of the tRNA(Lys) mutation in mitochondrial DNA in MERRF syndrome.

The distribution and clinical expression of mutant mtDNA with an A-to-G transition at the 8,344th nucleotide position in the tRNA(Lys) gene were studied in different tissues of the probands and relatives in a Taiwanese family with myoclonic epilepsy with ragged-red fibers (MERRF) syndrome. The proportions of mutant mtDNA were 89% to 95% for muscles and 78% to 99% for blood cells in the symptomatic probands except for one who had no mutant mtDNA in the muscles. In asymptomatic maternal relatives, these were 1% to 80% for muscles and 54% to 78% for blood cells. However, there was a lack of correlation between the clinical severity and the proportion of mutant mtDNA. Furthermore, among the maternal relatives studied, some asymptomatic family members had proportions of mutant mtDNA > 80% in muscles and > 53% in blood cells. Although these findings may suggest a threshold effect of mtDNA in MERRF syndrome, clinical manifestations are difficult to predict from the proportions of mutant mtDNA at the tRNA(Lys) gene only.

Adolescent↗

PubMed1995

Effect of betel chewing on RR interval variation.

Betel chewing in man often produces palpitations, sweating, facial flushing and a warm sensation in the body. These observations suggest that betel chewing may affect the autonomic nervous system. To examine this, the RR interval variation (RRIV) was studied to determine if betel chewing might affect parasympathetic function. Three experimental groups of people consumed a betel nut preparation, betel quid and chewing gum, respectively. Recordings of RRIV were made before and during chewing. When one or two betel nut preparations were consumed, the main effect was a cardioacceleratory response. With increasing consumption of betel nut preparation, there was a reduction in RRIV, particularly during deep breathing. Consumption of betel quid or chewing gum had no effect on RRIV. The effect of betel chewing was dose-dependent. Consumption of a small amount caused cardioacceleratory response suggesting a sympathetic activation, while consumption of a large amount reduced RRIV, suggesting involvement of the parasympathetic function.

Adult↗

PubMed1994

Myoclonic epilepsy with ragged-red fibers (MERRF) syndrome: report of a Chinese family with mitochondrial DNA point mutation in tRNA(Lys) gene.

We report myoclonic epilepsy with ragged-red fibers (MERRF) syndrome in a Chinese family with confirmed mitochondrial DNA point mutation. Six members of the family including the grandmother, two siblings, and three grandchildren were affected. Among them, action myoclonus was seen in five; short stature, muscle weakness, and mental retardation in four; lactic acidosis, hearing impairment, and ataxia in two; and seizures in one. Muscle biopsy from two affected siblings revealed ragged-red fibers and abundant subsarcolemmal mitochondria with paracrystalline inclusions. Pedigree analysis suggests a maternal transmission. Analysis of mitochondrial DNA showed a point mutation from A to G at the 8344th nucleotide position located in the tRNA(Lys) gene. To our knowledge, this is the first report of MERRF syndrome with such genetic defect from a Chinese family. The present and previous reports support the notion that mitochondrial DNA point mutation at the 8344th nucleotide position is the most common cause of MERRF syndrome.

Adult↗

PubMed1994

Retrograde effects of digital nerve severance on somatosensory evoked potentials in man.

To determine if retrograde conduction changes might occur long after injury of the most distal peripheral nerves, short-latency somatosensory evoked potentials (SEPs) to median or ulnar nerve stimulation at the wrist were studied in 10 subjects who had sustained traumatic digit amputation 4 months to 15 years previously. SEPs were recorded from Erb's point (N9), the cervical region (N13), and the contralateral scalp hand area (N20). While N9 latency was slightly delayed or not affected, the amplitude was either markedly reduced or undetectable. For N13 and N20 components, latency prolongation and amplitude reduction were mild to moderate, but the central conduction time (N13-N20) remained normal. The present data indicate that even the most distal nerve injury may have profound long-term retrograde effects on parental nerve function which are presumed mainly due to an axonopathy.

Adolescent↗

PubMed1994

Manganism and idiopathic parkinsonism: similarities and differences.

From the comparison we have made between PD and manganism, we draw the following conclusions: 1. There are similarities between PD and manganism, notably the presence of (a) generalized bradykinesia and (b) widespread rigidity. 2. There are also dissimilarities between PD and manganism, notably the following in manganism: (a) less-frequent resting tremor, (b) more frequent dystonia, (c) a particular propensity to fall backward, (d) failure to achieve a sustained therapeutic response to levodopa, and (e) failure to detect a reduction in fluorodopa uptake by PET. Further studies are likely to yield more discriminants between PD and manganism. For example, PET with raclopride may be useful in early cases of manganism, and MRI may be helpful in patients with advanced manganism.

Brain↗

PubMed1994

Levodopa failure in chronic manganism.

We report a placebo-controlled study of levodopa in four patients with extrapyramidal deficits caused by chronic manganese intoxication. Their parkinsonism and dystonia had progressed slowly over a period of 5 years after they left the site of exposure. Initially the patients appeared to respond to levodopa in open observations, but this apparent benefit was not sustained. This short-term, double-blind study indicates that their parkinsonism and dystonia failed to respond to levodopa.

Adult↗

PubMed1994

Carotid duplex and transcranial color-coded sonography in evaluation of carotid-cavernous sinus fistulas.

We performed carotid duplex and transcranial color-coded sonography in three patients with traumatic and one patient with spontaneous carotid-cavernous fistulas. High flow and low resistance were detected by carotid Doppler imaging in the extracranial internal carotid artery in three cases and in the external carotid artery in one case. The fistula could be demonstrated directly as heterogenous color flashes with turbulent flow by transcranial color-coded sonography through the orbital or temporal window. The transorbital approach showed that the ophthalmic venous flow was normal or to-and-fro bidirectional in patients without proptosis and was retrograde, away from the cavernous sinus with arteriolization in patients with proptosis. Combination of carotid duplex and transcranial color-coded sonography provides a noninvasive method for more accurate hemodynamic study of cerebral circulation and direct imaging of CCF.

Adult↗

PubMed1994

Pure cheiro-oral syndrome due to a small pontine hematoma: report of a case and review of the literature.

Cheiro-oral syndrome is frequently associated with other neurologic deficits; its pure form is rare. We report a 60-year-old man with pure cheiro-oral syndrome due to a small hematoma located in the ventral tegmentum of the right upper pons. His sensory disturbance remained unchanged during a follow-up period of 16 months. Review of the literature suggests that the pons is the most frequent site of lesions in pure cheiro-oral syndrome.

Cerebral Hemorrhage↗

PubMed1994

Effects of betel chewing on electroencephalographic activity: spectral analysis and topographic mapping.

The effect of betel chewing on the electroencephalographic (EEG) activity of 52 betel users was studied by spectral analysis and topographic mapping before and during betel chewing. Betel chewing increased both alpha and beta activities but decreased theta activity. These effects were most prominent for beta rhythm. Topographic mapping revealed that altered spectral rhythms were restricted to the occipital areas for the alpha band but were more widespread for both theta and beta bands. The present data suggest that betel chewing causes EEG changes associated with a state of arousal and to a lesser degree a state of relaxation.

Adult↗

PubMed1994

Effect of betel chewing on performance reaction time.

To test the validity of claims by users that betel chewing heightens alertness and improves motor responses, the effect of betel chewing on simple and choice reaction times (SRT and CRT) was investigated in habitual users. Control consisted of chewing gum and practice groups. Both SRT and CRT were correlated with age. In the SRT task, reaction times were not different among the three groups studied. In the CRT task, only betel and chewing gum groups showed a significant shortening of reaction time, but the betel group had a higher degree of statistical significance in this effect. It is concluded that shortening of CRT from betel chewing is probably partly due to chewing itself and partly due to a cholinergic arousal mechanism.

Adult↗

PubMed1994

Blink reflex in Wilson's disease.

Blink reflex and brainstem auditory evoked potential (BAEP) were studied in 10 patients with Wilson's disease (WD) and 10 family members. In blink reflex, R1 and R2 latencies as well as R2 duration were prolonged in the patient group, but not in the family group. In BAEP, latencies of peaks III and V and interpeaks I-III, III-V and I-V were also delayed only in the patient group. These data suggest that blink reflex abnormalities in WD are different from other movement disorders and are mainly due to brainstem dysfunction.

Adolescent↗

PubMed1994

Sympathetic skin responses to betel chewing.

The sympathetic skin response of habitual betel users was studied to determine the effect of betel chewing on sympathetic function. Sympathetic skin response was recorded from the hand by stimulation of the contralateral median nerve at the wrist. While the response latency remained unchanged, the response amplitude showed a progressive reduction during chewing and a gradual recovery after chewing. The present data suggest that betel chewing probably affects sympathetic function through a cholinergic action at the central generator sites.

Adult↗