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Y Fuchigami

Publications and source records attributed to Y Fuchigami.

18 recordsLinked to original sources
PubMed2001

A correlation between magnetic resonance imaging and electrophysiological findings in cervical spondylotic myelopathy.

STUDY DESIGN: Correlation between compressed spinal cords on magnetic resonance imaging (MRI) and electrophysiological findings in cervical spondylotic myelopathy patients. OBJECTIVE: To clarify the correlation between spinal-cord-evoked potentials and MRI measurements of compressed spinal cords in patients with cervical spondylotic myelopathy. SUMMARY OF BACKGROUND DATA: Compression of the spinal cord does not always cause clinical symptoms and it is difficult to infer the degree of dysfunction of the spinal cord from MRI findings. METHODS: Seventeen patients with cervical spondylotic myelopathy were examined with MRI and spinal-cord-evoked potentials before surgery. Using abnormality in spinal-cord-evoked potentials as indicators of spinal cord morphology, spinal-cord transverse area and compression ratios (central and 1/4-lateral) were measured on T1-weighted axial imaging. The correlations between these dimensions and electrophysiological findings were investigated. RESULTS: The mean preoperative transverse area of the spinal cord was 47.13 mm2. The mean preoperative central compression ratio of the spinal cord was 34.4%. The mean preoperative 1/4-lateral compression ratio of the spinal cord was 27.5%. A correlation (Spearman r=0.65, P < 0.01) was observed between the 1/4-lateral compression ratio of the spinal cord and the amplitude ratio of spinal-cord-evoked potentials after electric stimulation of the brain (Br(E)-SCEPs). CONCLUSIONS: The preoperative 1/4-lateral compression ratio of the spinal cord was found to reflect the degree of dysfunction of the corticospinal tracts.

Adult↗
PubMed2001

Endoscopic carpal tunnel release and nerve conduction studies.

We investigated the outcome of endoscopic carpal tunnel release (ECTR) for patients with carpal tunnel syndrome (CTS) in comparison with the results of preoperative nerve conduction studies. The compound muscle action potential (CMAP) of the abductor pollicis brevis muscle (APB) and the second lumbrical muscle (L2) was recorded following median nerve stimulation at the wrist. A total of 38 hands in 35 patients were classified into four categories. Hands with a similarly prolonged distal motor latency for the APB and L2 were classified as type I (n=25), while those with a more prolonged distal motor latency for the APB than for the L2 (>0.7 ms) were classified as type 2 (n=10). Hands with a CMAP for the APB, but not L2, were classified as type 3 (n=1), and hands with no CMAP for either the APB or L2 were classified as type 4 (n=2). After ECTR, all of the type 1 and 2 hands were improved. Patients with type 3 and type 4 hands did not show satisfactory improvement, which may have been due to anatomical variation of the recurrent motor branch of the median nerve.

Action Potentials↗
PubMed1998

New method to measure central motor conduction time using transcranial magnetic stimulation and T-response.

Measuring central motor conduction time (CMCT) is one of the useful methods to detect an impaired level of the spinal segment in cervical myelopathy patients. We modified a new technique to calculate the CMCT using tendon reflex latency (T-response) and investigated its accuracy. Motor-evoked potentials (MEPs) following transcranial stimulation were recorded in 19 patients with cervical myelopathy caused by a single level of spinal cord compression. CMCT was measured by subtracting the peripheral conduction time, which was calculated by using the T-response for the biceps brachii muscle (Biceps), the compound muscle action potentials (CMAPs) and the F-wave of the abductor digiti minimi muscle (ADM). In the control subjects, the mean value of CMCT of the Biceps and ADM was 3.8 and 7.0 ms, respectively. The accuracy of the determination of the CMCT for Biceps using T-response was investigated beforehand in the unilateral brachial plexus palsy patients and thoracic spinal cord myelopathy patients. The calculated CMCT (3.88+/-0.65 ms) for Biceps was close to the N2 latency (4.06+/-0.3 ms) of the evoked spinal cord potentials which were recorded from the epidural space on the C3-4 vertebral level following transcranial magnetic stimulation. The CMCT of both the Biceps and ADM was delayed in all cases of C1-2 cord compression. In patients with cord compression on the C3-4 level, two of four patients showed CMCT prolongation in Biceps. The prolongation of CMCT was observed only in ADM in patients with C4-5 or C5-6 cord compression. Measurement of the CMCT using T-responses was useful in proximal limb muscles. Comparison of the CMCT in Biceps and ADM could allow us to better detect the functional level diagnosis for compressive cervical myelopathy.

Adult↗
PubMed1998

Correlation between spinal cord compression and abnormal patterns of median nerve somatosensory evoked potentials in compressive cervical myelopathy: comparison of surface and epidurally recorded responses.

To investigate the correlation between the level of spinal cord lesion and the abnormal pattern of median nerve somatosensory evoked potentials (SSEPs), evoked spinal cord potentials (ESCPs) were also recorded from the posterior epidural space intraoperatively in 18 patients with compressive cervical myelopathy. Levels of symptomatic spinal cord compression were determined by ESCP findings. Spinal N13 potential of the SSEPs was recorded from the surface of the posterior neck with anterior neck reference. Brainstem P14 and cortical N20 potential were recorded from the parietal scalp contralateral to the stimulated side. Spinal N13, P14, and N20 potentials were all normal when the ESCPs were abnormal at localized segmental region (C4-5 or C5-6 level alone). Spinal N13 potential was significantly attenuated in all of patients with abnormal ESCP findings at widespread segmental area of the median nerve territory. In four of these seven patients, brainstem P14 potential was also prolonged or diminished, but three patients showed normal P14 and N20 potentials. Isolated P14 abnormality with normal spinal N13 potential was characteristic in patients with abnormal ESCP at the C3-4 lesion. Although sensitivity of abnormal ESCP was higher than that of the SSEPs, abnormal patterns of spinal N13, P14 and N20 potentials following median nerve stimulation were useful in detecting not only the pathology (posterior horn and/or posterior column) but also symptomatic spinal compression level in compressive cervical myelopathy.

Adult↗
PubMed1998

Cortical motor neuron excitability during cutaneous silent period.

OBJECTIVE: To investigate cortical motor neuron excitability during cutaneous silent period (CSP), motor evoked potentials (MEPs) from abductor pollicis brevis following transcranial magnetic stimulation (TCM) were recorded with and without a conditioning of ipsilateral painful digital nerve electric stimulation. METHODS: MEPs following TCM were recorded with and without a conditioning stimulation at an interstimulus interval (ISI) from 0 ms to 100ms in 6 controls and four patients who had reduced pain sensation in unilateral upper limbs associated with cervical syringomyelia. In addition MEPs and evoked spinal cord potentials (ESCPs) from cervical epidural space following TCM with and without a conditioning stimulation were recorded in four patients with thoracic myelopathy. RESULTS: MEP amplitude was clearly attenuated by a conditioning stimulation at an ISI from 40 ms to 80 ms in controls (statistically significant at 60 ms). In patients with cervical syringomyelia, MEP amplitude was attenuated by a conditioning stimulation in asymptomatic hands similarly in controls but that was unchanged by a conditioning stimulation in the symptomatic hand with reduced pain sensation. In patients with thoracic myelopathy MEP amplitude was attenuated by conditioning stimulation similarly in controls, but ESCP amplitude was unchanged. CONCLUSIONS: We demonstrated that noxious cutaneous nerve stimulation suppressed spinal motor neurons but cortical motor neuron excitability was unchanged during CSP. In clinical practice, measurement of MEP suppression after noxious cutaneous nerve stimulation may provide useful information in patients with damaged pain related nerve fibers.

Adult↗
PubMed1997

Spatial distribution of corticospinal potentials following transcranial electric and magnetic stimulation in human spinal cord.

To investigate the spatial distribution of the human corticospinal tract in the spinal cord, evoked spinal cord potentials (ESCPs) following transcranial electrical and magnetic stimulation were recorded simultaneously from both the anterior and posterior epidural space in five anesthetized patients. One ESCP component following transcranial electrical stimulation (D-wave) and at least two ESCP components (initially D-wave and later I-wave) following transcranial magnetic stimulation were recorded in all subjects. The negative peak latency of all the potentials recorded from the posterior epidural space was the same as that recorded anteriorly. The amplitude ratio of the ESCP following electrical stimulation (posterior/anterior) was 1.10+/-0.12, while that of ESCPs following magnetic stimulation was 1.08+/-0.12 (N1) and 1.15+/-0.16 (N2). These results suggest that lateral corticospinal tract descending dorsolateral fasciculus in the spinal cord is main corticospinal pathway and spatial distribution of D and I-waves are similar in the human cervical cord.

Cerebral Cortex↗
PubMed1997

Effect of coil position and stimulus intensity in transcranial magnetic stimulation on human brain.

Evoked spinal cord potentials (ESCPs) from the cervical and high thoracic epidural space following transcranial magnetic stimulation were recorded from eight subjects in awake and anesthetized condition. Motor evoked potentials (MEPs) from the right abductor digiti minimi (ADM) and rectus femoris (RF) muscles were simultaneously recorded during voluntary contraction. The stimulus intensity was at 30% above the MEPs threshold of the ADM when the coil center was fixed on 10-20 international Cz position. In awake condition, multiple ESCP components (greater than 3) were recorded from the cervical epidural space but no or minimal components were recorded from the upper thoracic epidural space. When the coil was moved anteriorly so that the posterior edge of the coil was positioned on Cz, the amplitude of the first ESCP component was significantly increased (P < 0.02) and shortened (not significant) at cervical levels. In addition, several ESCP components were more evident at high thoracic levels. Although the amplitude of the ADM was not enhanced, that of the RF was enhanced. During general anesthesia with volatile anesthetics (sevoflurane), only the first component of the ESCPs (D-wave) was elicited. Its amplitude was enhanced (P < 0.02) when the coil edge was fixed on Cz, similar to results in awake condition. This enhancement of the first ESCP component was accompanied by enhancement of those recorded from the high thoracic epidural space. However the amplitude of D-wave was the same in the two different coil positions when the stimulus intensity was set a 100% of the output. These results suggest that at low stimulus intensity, positioning the coil edge on Cz is optimal in inducing D-wave effectively but at high stimulus intensity, D-wave generation can be achieved in either if the two different coil position.

Adult↗
PubMed1997

Coexisting peripheral nerve and cervical cord compression.

STUDY DESIGN: The authors investigated the clinical usefulness of recording motor evoked potentials after transcranial magnetic stimulation in coexisting peripheral nerve and cervical cord lesions. OBJECTIVE: To show that the measurement of central motor conduction time from the abductor policis brevis and the abductor digiti minimi can be used as a good screening method for double lesions involving peripheral nerves and the cervical cord. SUMMARY OF BACKGROUND DATA: Transcranial magnetic stimulation has been used in the diagnosis of compressive cervical myelopathy. This technique could be useful in the assessment of patients with an entrapment neuropathy and cervical myelopathy. METHODS: Motor evoked potentials after transcranial magnetic stimulation, compound muscle action potentials, and F waves after supramaximal peripheral nerve stimulation were recorded from the abductor policis brevis and the abductor digiti minimi. The central motor conduction time was calculated by subtracting the peripheral conduction time from the motor evoked potentials latency. RESULTS: Ten patients with coexisting peripheral nerve and cervical cord lesions were evaluated. Two patients did not show satisfactory improvement after the decompression of the entrapment lesions, and six patients had hyperreflexia of lower limbs. In seven of these patients, the central motor conduction time was prolonged an average of 2.5 standard deviation of the normal value. The remaining two patients had spinal cord compression due to the ossification of the posterior longitudinal ligament. The spinal cord compression was demonstrated by magnetic resonance imaging, but the central motor conduction time was normal. Subjective symptoms improved in these two patients after decompressive surgery at the entrapment site alone. CONCLUSIONS: Measurement of the central motor conduction time using motor evoked potentials is an ideal diagnostic approach for patients with coexisting entrapment neuropathy and cervical cord compression.

Carpal Tunnel Syndrome↗
PubMed1997

Experimental study on donor nerves for brachial plexus injury: comparison between the spinal accessory nerve and the intercostal nerve.

The spinal accessory nerve and intercostal nerves are widely used as donor nerves for neurotization in patients with brachial plexus injuries. However, the characteristic differences in reinnervation by the spinal accessory and intercostal nerves have not been investigated. The purpose of this study is to compare the resulting contractile properties of the biceps muscles following nerve-crossing procedures of spinal accessory nerve and intercostal nerves to the musculocutaneous nerves. In 10 beagle dogs, the spinal accessory nerve was used to reinnervate the left biceps muscle, and the second and third intercostal nerves were used to reinnervate the right biceps muscle. After 10 months, the reinnervated muscles were studied by measuring their force of contraction as well as by histochemical methods. Biceps muscles reinnervated by spinal accessory nerves (A transfers) acquired the properties of fast, fatigable muscles, whereas those reinnervated by intercostal nerves (IC transfers) acquired the properties of slow, fatigue-resistant muscles. Furthermore, histochemical studies showed that type II fibers were predominant in A transfers, whereas type I fibers were predominant in IC transfers. This study clearly demonstrates the differences between the spinal accessory nerve and intercostal nerves as donor nerves. This may lead us to select appropriate donor nerves for nerve-crossing procedures and free-muscle transfer depending on the desired functions to be reconstructed.

Accessory Nerve↗
PubMed1996

The effect of current direction induced by transcranial magnetic stimulation on the corticospinal excitability in human brain.

Evoked spinal cord potentials (ESCPs) from the cervical epidural space and motor evoked potentials (MEPs) from the hand muscles were recorded simultaneously in 6 subjects following transcranial magnetic stimulation in two different coil orientations on motor cortex. The onset latency of the MEPs was approximately 1 ms shorter when the induced current flowed in a latero-medial direction (L-M stimulation) on the motor cortex as compared to a postero-anterior direction (P-A stimulation). Hence, L-M stimulation elicited an earlier component of the ESCPs than that induced by P-A stimulation. During general anesthesia with Sevoflurane, only the first component of the ESCPs could be elicited routinely following L-M stimulation. In contrast, all components of the ESCPs were dramatically attenuated following P-A stimulation. Moreover, first component latency of the ESCPs induced by L-M stimulation was almost the same as that induced by transcranial anodal electrical stimulation. These results suggest that if the induced current following transcranial magnetic stimulation flows in a latero-medial direction on motor cortex, it preferentially stimulates the corticospinal tract non-synaptically (producing a D-wave). However, if the induced current flows in a postero-anterior direction, it preferentially stimulates the corticospinal tract trans-synaptically (producing I-waves). Therefore, the direction of magnetically induced current is crucial in determining corticospinal excitability in the human brain.

Adult↗
PubMed1996

Reconstruction of irreparable brachial plexus injuries with reinnervated free-muscle transfer. Case report.

The complete avulsion of the brachial plexus is a severe injury usually caused by high-energy trauma. Even with the advent of modern microsurgical techniques, many patients have been rendered severely handicapped following this injury. The authors present a new reconstructive procedure that uses a microsurgical reinnervated free-muscle transfer to return prehensile function to an upper limb that is completely paralyzed. Although the procedure is still preliminary, a successful case is briefly described.

Adult↗
PubMed1996

Effect of stimulus intensity and voluntary contraction on corticospinal potentials following transcranial magnetic stimulation.

Following magnetic transcranial stimulation, motor-evoked potentials (MEPs) from the abductor digiti minimi muscle, and evoked spinal cord potentials (ESCPs) from the cervical epidural space were recorded simultaneously in 9 subjects in the awake and anesthetized condition. In the awake condition, during voluntary contraction, one (n = 5) or two (n = 4) components of the ESCPs were elicited at the threshold stimulus intensity of the MEPs. As the stimulus intensity increased, an early response (n = 7) and multiple late components were recorded. The first component at high stimulus output (average 80%) preceded the small potentials elicited at threshold stimulus intensity. The latency of each component of the ESCPs during voluntary contraction was the same as that during the resting condition. In addition, the enhancement of amplitude of the ESCPs during voluntary contraction was not significant compared with that recorded at rest. During general anesthesia with volatile anesthetics, the first component of the ESCPs could be elicited at high stimulus intensity, but later components were markedly attenuated. In paired transcranial magnetic stimulation, the amplitude of this first potential following the test stimulus completely recovered within the 2 ms interstimulus interval. From these results, we hypothesized that the first component was generated non-synaptically (D-wave), but later components were generated transsynaptically (I-waves). Compound muscle action potentials (CMAPs) and F-waves also were recorded following supramaximal ulnar nerve stimulation at the wrist. Peripheral conduction time, which included synaptic delay in spinal motor neurons, was measured as follows (latency of CMAPs+ latency of F-wave + 1)/2 (ms). The central motor conduction time (CMCT) was measured by subtracting the peripheral conduction time from the onset latency of the MEP at high stimulus intensity in the awake state. During voluntary contraction, the calculated CMCT (4.9 +/- 1.0 ms) was the same as the onset latency of the second component of the ESCPs (I-wave, 4.3 +/- 0.2 ms) recorded from the C6-C6/7 epidural space. These results suggest that transcranial magnetic stimulation generates I-waves preferentially when the stimulus intensity was set at just the threshold level of the MEPs during voluntary contraction in the awake condition. At high stimulus intensity, transcranial magnetic stimulation can elicit both D- and I-waves, but most spinal cells require I-wave activation to fire. Facilitatory effects of voluntary contraction on the muscle response following transcranial magnetic stimulation mainly originates at a spinal level.

Adult↗
PubMed1988

Effect of desynchronized inputs on compound sensory and muscle action potentials.

Stimulation of the second (S1) or third (S2) digit elicits a median sensory potential at the wrist. Similarly, a shock applied to the median (Sm) or ulnar (Su) nerve at the wrist evokes a sensory potential of the fourth digit and a muscle potential over the thenar eminence. Hence, a concomitant application of S1 and S2 or Sm and Su with varying interstimulus intervals simulates the effect of desynchronized inputs. In 10 hands, a shift in latency on the order of 1 msec between S1 and S2 or Sm and Su caused a major reduction in sensory potential by as much as 30-40% but little change in muscle action potential. A latency difference slightly less than one-half the total duration of unit discharge maximized the phase cancellation between the two components and consequently the loss of area under the waveform.

Action Potentials↗
PubMed1988

Changes of short latency somatosensory evoked potential in sleep.

We studied how the first negative waves (frontal 'N18' and parietal 'N20') of median somatosensory evoked potentials (SEP) change from waking to sleep in 9 healthy volunteers. Frontal and parietal responses in awake subjects showed multiple fast frequency potentials (FFP) over the ascending and descending phases of the slow negative waves. The main frontal FFP consisted of N16, P17, N18, P18, N19 and P20, with an additional small FFP, n15, over the ascending phase of N16. The parietal FFP included 3 major peaks (N15, P18 and N20) and 3 small FFP (n17, n19 and n20). Frontal FFP, except for n15, were markedly attenuated or totally disappeared in stage II sleep. Only a few FFP were identified in stage IV. The FFP returned in REM sleep, but amplitude was smaller than the waking state. Parietal FFP were also attenuated in NREM and recovered in REM sleep, but these changes were less prominent compared to those of frontal FFP. Latencies of frontal P20 and parietal N20 were prolonged in NREM sleep with greater prolongation of P20 than N20. These returned to waking values in REM sleep. These findings suggest that the frontal and parietal major negative peaks ('N18' and 'N20') consist of multiple physioanatomical substrates mediated through complex thalamocortical projection systems, and that the FFP are closely related to the sleep-wake mechanism possibly reflected by mutual interaction between cortex and the thalamic reticular system.

Adult↗
PubMedDate not supplied

Stationary potentials after median nerve stimulation: changes with arm position.

We previously reported the presence of stationary negative potentials (N3, N6, N9) over the arm ipsilateral to the side of median nerve stimulation. In this study, we examined the effect of different arm positions upon these stationary peaks in 12 normal subjects. When arm position was changed from elbow extended to elbow flexed 90 degrees, we recorded a new negative peak, N4. The peak latency of N4 corresponded to the traveling impulse reaching the distal biceps brachii. With the elbow flexed, N3, N6 and N9 peak latencies significantly shortened compared to those recorded with the arm in the usual elbow extended position. In contrast, with the arm abducted at the shoulder, N6 and N9 latencies were significantly prolonged while N3 remained unchanged. Corresponding latency shifts were also observed in the bipolarly recorded traveling impulse. We consider 2 possible factors for N4 enhancement by elbow flexion. One is the change in conducting volume surrounding the nerve, i.e., increased muscle bulk of biceps brachii. The other is the change in axial orientation of the propagating nerve impulse by 90 degrees. We also propose that the latency shifts of the stationary potential as well as of a traveling wave can be attributed primarily to relaxation or stretching of the nerve trunk with change in arm position.

Adult↗