Biomedical subjects

Jen-Tse Chen

Publications and source records attributed to Jen-Tse Chen.

14 recordsLinked to original sources

PubMed2006

Hydrocephalus associated with Guillain-Barre syndrome.

A 68-year-old man developed progressive four-limb weakness and areflexia 17 days after an influenza vaccination. He was diagnosed with Guillain-Barre syndrome (GBS), and remained ventilator dependent and bed-bound for 3 months, despite plasmapheresis and immunoglobulin infusion. However, cognitive impairment, excessive daytime sleepiness, and motor disability were still present, even when he was no longer ventilator dependent. Brain computerized tomography scan and isotope cisternography was consistent with normal pressure hydrocephalus. His motor control and cognitive function recovered almost completely after insertion of a ventriculoperitoneal shunt. Although hydrocephalus is not frequently associated with GBS, our case report indicates that brain imaging is necessary in GBS patients whose cognitive functions deteriorates after disease onset.

Aged↗

PubMed2006

Mentalis muscle responses to median nerve stimulation.

Electrical stimulation may produce excitation or inhibition of the motor neurons, as represented the blink reflex and masseter silent period in response to trigeminal nerve stimulation. Clinically, a light touch on the palm may evoke a mentalis muscle response (MMR), i.e. a palmomental reflex. In this study, we attempted to characterize the MMR to median nerve stimulation. Electrical stimulation was applied at the median nerve with recordings at the mentalis muscles. An inhibition study was done with continuous stimuli during muscle contraction (I1 and I2 of MMRaverage). Excitation was done with a single shot during muscle relaxation (MMRsingle) or by continuous stimuli during muscle contraction (E1 and E2 of MMRaverage). The characteristic differences between MMRaverage and MMRsingle were as follows: earlier onset latencies of MMRaverage (MMRaverage < 45 ms; MMRsingle > 60 ms), and a lower amplitude of MMRaverage (MMRaverage < 50 microV; MMRsingle > 150 microV). The receptive field of MMRsingle was widespread over the body surface and that of MMRaverage was limited to the trigeminal, median and index digital nerves. Series of stimuli usually significantly decreased the amplitude of MMRsingle, as a phenomenon of habituation. On the other hand, it was difficult to evoke the earlier response (i.e. MMRaverage) without continuous stimuli and an average technique. MMRaverage had the components of both excitation (E) and inhibition (I); for example, E1-I1-E2-I2 or I1-E2-I2. E2 was the most consistent component. In patients with dorsal column dysfunction, median nerve stimulation could successfully elicit MMRsingle, but not MMRaverage. Contrarily, in patients with pain sensory loss, it was more difficult to reproduce MMRsingle than MMRaverage. It seemed that MMRaverage and MMRsingle did not have equivalents across the different modalities of stimulation.

Adult↗

PubMed2006

Neural correlates of Chinese word-appropriateness judgment: an MEG study.

To study the neural correlates of Chinese word-appropriateness judgment, we used 2-word phrases and corresponding meaningless pairs produced by replacing the second words (W2) with homophones. Fourteen right-handed healthy adults viewed word pairs randomly presented one word at a time, and judged the lexical appropriateness of the W2 for combining its preceding first word (W1) into a meaningful phrase. We measured magnetoencephalographic (MEG) responses to W1, appropriate W2, and inappropriate W2 stimuli. For each subject, multi-dipole analyses revealed sequential neuromagnetic activations which involved the bilateral visual cortices at approximately 100 milliseconds (ms), the bilateral occipitotemporal regions at approximately 190 ms, and the left temporal lobe at approximately 350 ms (M350) following stimuli. We found that the word appropriateness had no clear effect on the occipitotemporal activation to W2 stimuli, whereas the M350 activation to inappropriate W2 was greater than that to W1 or appropriate W2. In 8 of our subjects, we found an additional activation in the right temporal region, with a smaller amplitude as compared with the left M350. Our results suggest that the M350 activity reflects both lexical and semantic appropriateness assessment. The lateralized M350 strengths may be used to determine the language dominance hemisphere; and additionally, our 2-word contexture judgment paradigm can be applied in further research on the cortical processing of lexicon-semantic information in Chinese speakers.

Adult↗

PubMed2006

Multimodal evoked potentials in three siblings with mitochondrial disease.

Mitochondrial diseases are heterogeneous disorders affecting multiple systems. Here, we presented the findings of multimodal evoked potential (EP) studies of three siblings with a specific A8344G mutation of mitochondrial DNA. One of them had DM and another two had a history of encephalopathy. Visual EPs were abnormal in one patient and motor, somatosensory and brainstem auditory EPs were observed in all three patients. Our EP studies showed that the A8344G mutation of mitochondrial DNA involved multiple levels of the central nervous system even though there were no correlated symptoms. Therefore EP is an adjunct of methods to detect the functional disturbance and to screen the distribution of the involvement of the nervous system in mitochondrial diseases.

Adult↗

PubMed2004

Hypotension due to interaction between lisinopril and tizanidine.

OBJECTIVE: To report a case in which significant hypotension occurred after initiation of tizanidine in a patient using the antihypertensive agent lisinopril. CASE SUMMARY: A 48-year-old woman was admitted due to cerebral hemorrhage at the midbrain and pons, with extension to the fourth ventricle. Consciousness disturbance (Glasgow coma scale 4) with a decerebrate posture improved 5 days after stroke onset. As the BP was fairly high, antihypertensive agents, including lisinopril, were initiated. Three weeks later, the decerebrate rigidity and high BP remained, and tizanidine was initiated to see whether the decrease in muscle tone could facilitate hypertension control and motor recovery. However, the BP dropped dramatically within 2 hours after the first dose of tizanidine. The tizanidine and all of the antihypertensive medications were withdrawn. Tizanidine was used again after her BP had stabilized, but did not produce similar problems. DISCUSSION: A similar event was reported in 2000. The reaction in our patient appeared after tizanidine initiation and improved after both lisinopril and tizanidine were discontinued. According to the Naranjo probability scale, this was classified as a possible drug interaction. This kind of reaction is seldom mentioned as occurring during co-administration with tizanidine. With its characteristics, tizanidine has the potential to compromise hemodynamic stability during concomitant angiotensin-converting enzyme inhibitor use. CONCLUSIONS: Based upon the literature review, the hypotension in this patient was possibly due to the interaction between tizanidine and lisinopril.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed2004

Effect of transcranial magnetic stimulation on bimanual movements.

Transcranial magnetic stimulation (TMS) of the motor cortex can interrupt voluntary contralateral rhythmic limb movements. Using the method of "resetting index" (RI), our study investigated the TMS effect on different types of bimanual movements. Six normal subjects participated. For unimanual movement, each subject tapped either the right or left index finger at a comfortable rate. For bimanual movement, index fingers of both hands tapped in the same (in-phase) direction or in the opposite (antiphase) direction. TMS was applied to each hemisphere separately at various intensities from 0.5 to 1.5 times motor threshold (MT). TMS interruption of rhythm was quantified by RI. For the unimanual movements, TMS disrupted both contralateral and ipsilateral rhythmic hand movements, although the effect was much less in the ipsilateral hand. For the bimanual in-phase task, TMS could simultaneously reset the rhythmic movements of both hands, but the effect on the contralateral hand was less and the effect on the ipsilateral hand was more compared with the unimanual tasks. Similar effects were seen from right and left hemisphere stimulation. TMS had little effect on the bimanual antiphase task. The equal effect of right and left hemisphere stimulation indicates that neither motor cortex is dominant for simple bimanual in-phase movement. The smaller influence of contralateral stimulation and the greater effect of ipsilateral stimulation during bimanual in-phase movement compared with unimanual movement suggest hemispheric coupling. The antiphase movements were resistant to TMS disruption, and this suggests that control of rhythm differs in the 2 tasks. TMS produced a transient asynchrony of movements on the 2 sides, indicating that both motor cortices might be downstream of the clocking command or that the clocking is a consequence of the 2 hemispheres communicating equally with each other.

Adult↗

PubMed2004

Guillain-Barré syndrome coexisting with pericarditis or nephrotic syndrome after influenza vaccination.

A 68-year-old woman and a 72-year-old man presented with distal weakness of the limbs and numbness following an influenza vaccination within 2 weeks. Moreover, Guillain-Barré syndrome (GBS) was diagnosed in two patients. Pericarditis was diagnosed in the first patient who also had precordial chest pain with referral to trapezius ridge, and nephrotic syndrome, was observed in the second patient who had leg edema and proteinuria. The relationship among GBS, pericarditis and nephrotic syndrome after an influenza vaccination is discussed.

Aged↗

PubMed2004

Prolonged central motor conduction time of lower limb muscle in spinocerebellar ataxia 6.

We investigated the function of corticospinal tract in spinocerebellar ataxia 6 (SCA6) by measuring the central motor conduction time (CMCT). Motor evoked potentials (MEP) of tibialis anterior (TA) muscle were elicited by magnetic stimulation to motor cortex and spinal cord in 9 SCA6 patients and 10 normal height- and age-matched subjects. CMCT in lower limb of SCA6 patients (18.1+/-1.9 ms) was significantly prolonged than that of the normal subjects (15.0+/-1.0 ms) ((p < 0.001). The prolonged CMCT was well correlated with the duration of disease (p = 0.005), but MEP amplitudes and stimulation intensities were not significantly different. These results indicate that the corticospinal tract function is also impaired and correlate with the disease duration in SCA6.

Adult↗

PubMed2004

Subtle brain dysfunction in treated 6-pyruvoyl-tetrahydropterin synthase deficiency: relationship to motor tasks and neurophysiological tests.

6-Pyruvoyl-tetrahydropterin synthase (6PTPS) deficiency is a major cause of biopterin deficiency. 6PTPS patients usually have an elevated serum phenylalanine level, a deficiency of neurotransmitters (serotonin and dopamine), and neurological symptoms, if without treatment. We herein investigated the possibility of neurological dysfunction in early-treated patients. In the study, 12 early-treated 6PTPS patients were studied. Their auditory simple reaction time, movement rhythm variation (MRV), somatosensory evoked potentials to median nerve stimulation, and hand muscle responses to transcranial magnetic stimulation, were measured. MRV is a test of repetitive voluntary movements, and was used with and without auditory cues at 0.3 Hz. The 6PTPS patients had an increased motor threshold but normal motor and sensory central conduction times. They performed very well in simple reactions (6PTPS 208.4+/-16.7 ms, control 200.3+/-11.7 ms, p=0.18), but not in continuous tasks. The continuous performance tests showed that MRV had increased in the 6PTPS patients (with cues: 6PTPS 7.35+/-0.94, control 5.47+/-0.80, p<0.0001; without cues: 6PTPS 9.87+/-1.44, control 6.59+/-0.68, p<0.0001). Without cues, MRV had increased in both the 6PTPS and control groups, but more significantly in the 6PTPS patients (6PTPS 2.51+/-0.97, control 1.25+/-0.42; p=0.0001). Our findings indicate that early-treated 6PTPS patients have subtle neurological dysfunctions. They may not maintain movement rhythm as well as normal subjects, even with external cues. Hence, MRV is a good method to assess motor control.

Acoustic Stimulation↗

PubMed2004

Transcranial magnetic stimulation in patients with transient ischemic attacks.

BACKGROUND: By definition, transient ischemic attacks (TIAs) do not leave a neurological deficit beyond 24 hours after onset. However, a subgroup of TIA patients is characterized by persistent perfusion defect on single photon emission computed tomogram or infarction on brain computerized tomogram and magnetic resonance imaging. Here, we applied transcranial magnetic stimulation (TMS) to study whether TIA could produce persistent subclinical dysfunction for more than 24 hours. METHODS: The study included 23 TIA patients who had the criteria of hand weakness as one of their clinical manifestations. TMS was done twice in each TIA patient. The first time was during the period of 24-48 hours after onset and the second 7 days after onset. We studied the cortical motor threshold, the latencies and the amplitudes of the motor evoked potentials, the central motor conduction time, and the cortical silent period at the intensity of 1.5 times motor threshold with maximal voluntary isometric contraction. The recording was at the first dorsal interosseous muscle. RESULTS: There was no significant difference between the whole group of TIA patients and normal control. However, in the subgroup of TIA patients who had hand weakness more than 1 hour, they had increased motor threshold and prolonged cortical silent period during the first test. Both improved 1 week after onset. On the contrary, in TIA patients who had hand weakness less than 1 hour, their data were all within normal limits during the first and the second studies. CONCLUSIONS: Our results indicate that the motor function of TMS study will recover to full if the motor symptoms subside within 1 hour in TIA patients. Subclinical motor deficits may persist in TIA patients who have motor symptoms more than 1 hour.

Aged↗

PubMed2003

Differential effects of stimulus intensity on peripheral and neuromagnetic cortical responses to median nerve stimulation.

To study the differential effects of tactile stimulus intensity on cortical and peripheral responses, we measured neuromagnetic cortical responses, compound muscle action potentials (CMAP), sensory nerve action potentials (SNAP), and the subjective estimation of tactile magnitude to electric median nerve stimulation at the wrist in 13 male healthy adults. The sensory perception threshold (ST) for electric pulses at wrist skin was determined and then various levels of stimulus intensity (1 approximately 6 ST) were given to each subject. At 1 ST, only the P50m components of the primary somatosensory (SI) cortical responses were recorded. The second somatosensory (SII) cortical responses were saturated at 2 ST, while the SI responses reached maximum at 3 ST equivalent to the subjective threshold intensity for "strong" tactility. The CMAP and SNAP were maximum at 4-5 ST. At 2 ST, >70% of maximum SI responses were produced, whereas only <40% of maximum CMAP or SNAP responses were obtained. We concluded that the stimulus intensities for activating or saturating somatosensory cortical responses were lower than those for CMAP and SNAP. The differential intensity effects on cortical and peripheral responses suggest a polysynaptic organization underlying the central amplification for somatosensory cortical activation. The optimal intensity levels for producing maximum SI and SII responses were 3 and 2 ST, respectively. Compared with the SII, the SI plays a crucial role in the coding of the tactile stimulus intensity.

Action Potentials↗

PubMed2003

Prolonged cortical relay time of long latency reflex and central motor conduction in patients with spinocerebellar ataxia type 6.

OBJECTIVE: Spinocerebellar ataxia type 6 (SCA6) is a neurodegenerative disorder characterized by a slowly progressive ataxia and dysarthria. Anatomically. SCA6 was said to affect only the cerebellum. However, ithasbeen argued that SCA6 may involve widespread regions of the brain. This study was designed to investigate the electrophysiological functions of the central nervous system in patients affected with SCA6. METHODS: Nine patients with SCA6 and 10 normal, age-matched control subjects were included in the study. The motor evoked potentials, somatosensory evoked potentials, and long latency reflex (LLR) of the hand muscle were measured to evaluate the functions of the central nervous system. RESULTS: Significantly delayed LLR, as well as prolonged cortical relay time (CRT) and central motor conduction time (CMCT) of the hand muscle, were noted in the patients with SCA6. CONCLUSIONS: The prolongation of CMCT andCRT suggested that SCA6 disturbed the functions of the corticospinal tract and the transcortical polysynaptic pathways from the sensory to motorcortices. It seems likely that the CNS dysfunction caused by SCA6 is not limited to the structures that are anatomically abnormal. Furthermore, the prolongation of CMCT alone does not seem to suffice to differentiate between various types of autosomal dominant cerebellar ataxias. Molecular analysis is indispensable for the diagnosis of different genetic types of SCA.

Adult↗

PubMed2003

Using electrodiagnostic machine to study movement rhythm variation.

BACKGROUND: Hand movement constitutes the most common daily activities in our life. Hand dexterity is often impaired in patients with neurological disease. We developed an adjunct method, based upon the electrodiagnostic software, for study of motor control and hand dexterity. METHODS: Thirty-two normal subjects, 2 stroke patients and 2 Parkinson patients were included in the study. All of them were right-handed, and were asked to pace rhythmic finger tapping at a comfortable rate without cue or any external stimuli. A trigger kit was designed to transform the finger tapping. After using the triggering mode and adjusting the sweep speed, 2 tapping signals were simultaneously displayed on the screen. The first signal was the triggering potential, and the variation in timing of the second signal represented the variation in timing of the inter-response interval. Twenty sweeps were recorded, superimposed and measured on the screen. Movement rhythm variation (MRV) was defined as b/a x 100 (b = [maximal interval of finger tapping - minimal interval of finger tapping]; a = [maximal interval of finger tapping + minimal interval of finger tapping]/2). Each subject started with right hand and then left hand. RESULTS: MRV measurement showed excellent intrarater (r = 0.97) and interrater (r = 0.97) reliability. In normal right-handed subjects, the MRV was better in right hand than in left hand (right 16.5 +/- 4.1% and left 21.0 +/- 7.6%; p < 0.05). The MRV improved in stroke patients along with the recovery and improved in Parkinson patients after levodopa treatment. CONCLUSIONS: MRV was a good method to provide quantitative data for assessment of hand dexterity. Our study also showed the potential role of MRV in motor control study.

Adult↗

PubMedDate not supplied

Transcranial magnetic stimulation after conditioning stimulation in two adrenomyeloneuropathy patients: delayed but facilitated motor-evoked potentials.

Two male patients were diagnosed with adrenomyeloneuropathy. Their chief problems were progressive spastic paraparesis, sensory impairment, hyperpigmentation and testis atrophy. Transcranial magnetic stimulation (TMS) does not easily elicit motor-evoked potentials (MEPs) in patients with a central nervous system dysfunction, even though a few methods, such as contraction of the target muscles and the Jendrassik maneuver (JM), are used in the attempt to facilitate them. In these two patients, we used a conditioning method (prior electrical stimulation over the cutaneous nerve of the left index finger) in order to facilitate MEPs, elicited by TMS, in the left tibialis anterior muscle. In patient 1, facilitation of MEPs was present at conditioning-test (C-T) intervals in the range 60-220 ms, with the maximal MEP recorded at C-T 160 ms; in patient 2, it occurred in the C-T interval range 110-140 ms, with the maximal MEP recorded at C-T 130 ms. By means of conditioning electrical stimulation, we can facilitate MEPs elicited by TMS in those subjects in whom MEPs are minimal or difficult to elicit even using the conventional JM or muscle contraction. The facilitation of MEPs by conditioning stimuli allowed us not only to assess central motor conduction time, but also to demonstrate the preserved continuity of the corticospinal tract in these two patients.

Adrenoleukodystrophy↗