Biomedical subjects

Kwong-Kum Liao

Publications and source records attributed to Kwong-Kum Liao.

At least 19 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

Dimensional complexity of neuromagnetic activity reduced during finger movement of greater difficulty.

OBJECTIVE: We investigated the variation in dimensionality (D2) of neuromagnetic activity over the primary sensorimotor cortex (SM1) in healthy adults performing motor tasks of different difficulty. METHODS: Magnetoencephalography (MEG) was used to record neuromagnetic activity during self-paced, brisk unimanual finger extension at a rate of 1 and 2 Hz using the index finger of the dominant and non-dominant hands in 16 healthy subjects. Motor task difficulty was rated by the relative difference in time measurement between 1 and 2 Hz finger movements of both hands. The relative difference in dimensionality of SM1 activity was calculated by subtracting the D2 value in 2 Hz movement from that in 1 Hz one within subjects. RESULTS: Simple regression analyses show a significantly negative relationship between the relative dimensional complexity and the relative motor task difficulty in the contralateral SM1 for the left- (p<0.05), but not the right- (p=0.447) hand movement. CONCLUSIONS: The present data suggest that a motor task of greater difficulty may engender a reduction of simultaneously active quasi-independent neuronal generators in the contralateral SM1 underpinned by stronger neuronal connectivity of a relatively low dimensionality. SIGNIFICANCE: The decrease in dimensional complexity of MEG activity associated with a motor task of greater difficulty gives new insights to motor control strategy.

Adult↗

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

Effects of cognitive demands on postmovement motor cortical deactivation.

Postmovement beta-rebounds induced by different intermovement intervals were investigated using magnetoencephalography in 14 healthy participants to test the hypothesis that postmovement motor cortical deactivation over the primary motor cortex depends on movement-related cognitive demands. Shorter latency and lower amplitude in postmovement beta-rebounds over the contralateral primary motor cortex were noted in the short-movement interval movement (repetitive finger lifting). Greater latency span of postmovement beta-rebounds jittering using single-trial analysis in the long-movement interval movement (discrete finger lifting) was observed. The study elucidates that the temporal interval between two adjacent movements reflecting different degrees of cognitive demands can affect postmovement motor cortical deactivation in terms of postmovement beta-rebounds latency and amplitude, and latency span of postmovement beta-rebounds jittering. Postmovement motor cortical deactivation can reflect cognitive demands in addition to motor and somatosensory processing.

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↗

PubMed2005

Differential generators for N20m and P35m responses to median nerve stimulation.

To study the spatial and behavioral dynamics of cortical sources for N20m and P35m at varying stimulus intensities, we measured neuromagnetic cortical responses to left electric median nerve stimulation at the wrist in 17 male healthy adults. The stimulus intensity levels were individually determined according to sensory threshold (ST) for perceiving electric pulses. Using equivalent current dipole (ECD) modeling, we analyzed the peak latencies, amplitudes, and locations of ECDs from 14 subjects for N20m and P35m elicited at 2 ST, 3 ST, and 4 ST. Compared with N20m, P35m was localized 3.3 +/- 0.6 mm more superiorly at 2-4 ST, and 2.9 +/- 1.2 mm more medially at 3-4 ST. Superimposed over subjects' own MR images, N20m ECDs were localized in the area of 3b contralateral to stimulus side in all 17 subjects at 3 ST, whereas P35m ECDs were localized either in the postcentral (in 14 subjects) or in the precentral areas (in 3 subjects). We found no clear correlation between N20m and P35m in terms of peak latencies as well as the corresponding growth of activation strengths along with stepwise increase in stimulus intensity. Our results imply that the two early SEF components, N20m and P35m, have differential cortical generators, with distinctive neurophysiological behaviors in response to varying stimulus intensity levels.

Adult↗

PubMed2005

Hemispheric balance in coding speech and non-speech sounds in Chinese participants.

To study the role of neuromagnetic auditory approximately 100-ms responses (N100m) in phonetic processing, we recorded N100m in 24 right-handed Chinese participants using a whole-head neuromagnetometer. The stimuli included vowel /a/ and consonant-vowels /ba/ and /da/, spoken by one Chinese speaker, and a 1-kHz tone. N100m to tones was larger in the right hemisphere, whereas that to speech sounds was bilaterally similar. The amplitude ratio of speech to non-speech N100m was larger in the left hemisphere. N100m dipoles in the left hemisphere were approximately 2 mm more anterior for speech than for tone stimuli. The results suggest that N100m reflects both acoustics and phonetic processing. Moreover, the ratio of speech to non-speech activation in individual hemispheres may be useful for language lateralization.

Acoustic Stimulation↗

PubMed2005

Optimal check size and reversal rate to elicit pattern-reversal MEG responses.

OBJECTIVE: To determine the impact of check size and interstimulus interval (ISI) on neuromagnetic visual cortical responses. METHODS: We recorded visual evoked fields to pattern-reversal stimulation with central occlusion in ten subjects. The -100 ms magnetic activation (P100m) was analyzed by single dipole modeling. RESULTS: With 1 s ISI, P100m strengths increased as check size increased from 15' up to 120' of visual arc, and larger checks elicited less P100m activation. With 120' checks, we found no P100m attenuation as ISI decreased from 4 s to 0.16 s. P100m sources around the calcarine sulcus did not vary with check size or ISI. CONCLUSIONS: The magnitude of cortical activation during visual contrast processing is check size-dependent and the 120' checks are optimum for future studies on neuromagnetic visual cortical functions using central-occluded stimulation. The corresponding neuronal activation demonstrated a short refractory period less than 0.16 s. We also found significantly overlapping cortical representation areas for different check sizes or ISIs.

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

Spinal cord repair with acidic fibroblast growth factor as a treatment for a patient with chronic paraplegia.

STUDY DESIGN: We present a case of a patient with chronic paraplegia with a complete spinal cord gap resulting from a stabbing injury 4 years ago recovering after an innovative surgical strategy. OBJECTIVES: To demonstrate the clinical outcome of surgical repair with sural nerve graft with fibrin glue containing acidic fibroblast growth factor in a patient with chronic spinal cord injury. SUMMARY OF BACKGROUND DATA: Spinal cord injury usually causes permanent disability, and there had been not effective surgical technique to obtain satisfactory functional motor recovery, particularly in chronic patients. Previous studies have revealed that acidic fibroblast growth factor could promote axonal regeneration and reduce neuronal death in adult rats with spinal cord injury. METHODS: The spinal cord gap at T11 level was bridged with 4 sural nerve grafts that redirected specific pathways from white to gray matter. The grafted area was stabilized with fibrin glue containing acidic fibroblast growth factor. RESULTS: Before the operation, the paraplegia was identified as ASIA-C, with a motor score for the right and left legs of 12 and 0, respectively, a pinprick score of 77, and 77 on a light touch of left side limbs. His functional status improved from being wheelchair-bound to being able to ambulate independently with a walker 2-and-a-half years after surgery. At this stage, paraplegia was ASIA-D, with motor scores for the right and left legs of 15 and 12, respectively, 86 for a pinprick, and 86 for a light touch of left side limbs. CONCLUSIONS: This case demonstrated significant motor recovery attained in a patient with chronic paraplegia following a repair surgery with nerve graft and growth factor.

Adult↗

PubMed2004

Congenital insensitivity to pain with anhidrosis in Taiwan: a morphometric and genetic study.

Congenital insensitivity to pain with anhidrosis (CIPA) is characterized by insensitivity to pain, anhidrosis, recurrent hyperpyrexia, mild mental retardation, and self-mutilating behavior. We report 2 brothers, aged 20 and 18 years, who suffered from phenotypes of CIPA. Both brothers had a branch site mutation in intron 7 (IVS7-33 T-->A) of the neurotrophic tyrosine kinase receptor type 1 gene. The electrophysiological studies showed no significant abnormal findings in sensory evoked potentials, motor evoked potentials to transcranial magnetic stimulation, or heart rate variations; sympathetic skin responses were absent. Morphometric study of their sural nerve histopathology revealed normal myelinated fiber density, 8,082 fibers/mm2 and 5,637 fibers/mm2 (normal 6,141 +/- 421); decreased unmyelinated fiber density, 2,537 fibers/mm2 and 2,211 fibers/mm2 (normal 28,578 +/- 8,669); increased axon size, 4.41 +/- 1.59 microm and 5.33 +/- 1.48 microm (normal 3.73 +/- 1.45), and increased axon diameter (A)/myelin thickness (M) ratio (A/M), 3.47 +/- 1.42 and 2.70 +/- 1.07 (normal 2.49 +/- 0.93). Scatterplot analysis of the G ratio (axon diameter:fiber diameter) did not show consistent results in the relationship between axon size and myelin thickness. In conclusion, the neuropathy of our CIPA patients included a marked reduction of small myelinated and unmyelinated fibers and a relatively increased axon size. This is the first CIPA family encountered in Taiwan.

Adolescent↗

PubMed2004

Presence of spinocerebellar ataxia type 2 gene mutation in a patient with apparently sporadic Parkinson's disease: clinical implications.

Among 242 patients with apparently sporadic Parkinson's disease, a 70-year-old man with a CAG repeat number of 37 in the SCA2 gene was identified. He has remained responsive to levodopa 14 years after onset and has had no overt signs suggesting cerebellar dysfunction. Although it is not possible to confirm if this patient has a de novo mutation of the SCA2 gene, this genetic defect seems to be contributing to his parkinsonian features and further supports the concept that apparently sporadic, late-onset, levodopa-responsive Parkinson's disease may have multiple causes.

Aged↗

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↗