Yasunori Fuchigami

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.

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

&NA; 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. (Plast. Reconstr. Surg. 100: 900, 1997.)

Cutaneous silent period in syringomyelia

Painful cutaneous nerve stimulation can suppress measured. F waves over 100 mV in peak-to-peak amplitude were considered significant. electromyographic activity in voluntarily contracting muscle.3–5,10,11 This phenomenon is designated the cuMotor evoked potentials (MEPs) following transcranial magnetic stimulation were recorded from the taneous silent period (CSP). In the present study we investigated a clinical application of CSP in syringoAPB during 30% of maximal contraction. The center of a round coil 14 cm in diameter (Magstim, Whitmyelia associated with Chiari I malformation, where the loss of pain sensation is the most common early land, UK, Model 200) was held over the vertex. Induced current was applied to target motor cortex in neurologic sign.7,8 a posteroanterior direction. The stimulus intensity was set at 30% above the threshold of the MEPs. MATERIALS AND METHODS Somatosensory evoked potentials (SSEPs) followFive male patients (mean age 18 years) with cervical ing median nerve stimulation at the wrist were resyringomyelia were studied. Dysesthesias and recorded. Spinal responses were recorded with active duced pain sensation were the only symptoms in all electrodes placed over the spinous process of the patients. Fifteen healthy subjects (12 men, 3 women; sixth cervical vertebra (Cv6) and reference electrodes mean age, 32 years) were studied as controls. The placed above the thyroid cartilage.9 Peripheral nerve experimental procedure was explained and informed potentials from Erb’s point were recorded with the consent was obtained. same reference. Cortical responses were recorded Several CSPs following index finger stimulation from the parietal scalp with both ears connected as were recorded from the abductor pollicis brevis a reference (A1 1 A2). (APB) using self-adhesive electrodes over the belly All potentials except for SSEPs were recorded and tendon. Electrical stimuli were applied randomly with a bandpass filter between 20 Hz and 5 kHz. from ring electrodes using 0.5 ms square pulses at 10 SSEPs were filtered between 20 Hz and 3 kHz. The times the sensory threshold. The degree of isometric parameters of all the responses were expressed as contraction was maintained at about 30% of maximean 6 SD. mum using an audiovisual biofeedback system. From sagittal and axial T1and T2-weighted magCompound muscle action potentials (CMAPs) netic resonance imaging (MRI), the location and and F waves following supramaximal stimulation to laterality of the syrinxes was confirmed. the median nerve at the wrist were recorded. Onset latency and baseline-to-negative peak amplitude of RESULTS CMAPs were measured. The persistence and shortest latency for F waves among 20 responses also were Controls. The onset and duration of CSPs were 74.7 6 8.1 ms and 44.9 6 10.6 ms, respectively. CMAPs latency and amplitude were 3.5 6 0.3 ms and 7.2 6 2.8 mV, respectively. F-wave latency was 26.8 6 2.2 ms with 40.3 6 10.5% persistence. MEPs *Correspondence to: Dr. K. Kaneko latency and amplitude (peak-to-peak) were 19.5 6 CCC 0148-639X/97/070884-03  1997 John Wiley & Sons, Inc. 1.5 ms and 4.0 6 2.5 mV, respectively. For SSEPs,

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.

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.

Compound Muscle Action Potentials Under Dynamic Stress in Lumbar Spinal Canal Stenosis

Intermittent claudication is one of the characteristic symptoms in lumbar spinal canal stenosis. We recorded compound muscle action potentials (CMAPs) from the extensor digiti brevi (EDB) and the abductor hallucis (AH) before and after dynamic stress elicited by cauda equina electrical stimulation or transcranial magnetic stimulation. In 12 cases of 25 patients, the amplitudes of the CMAPs from the EDB or the AH elicited by cauda equina electrical stimulation decreased transiently, and recovered to the status of the control gradually within 5 min. In four cases of six patients, the amplitudes of the CMAPs elicited by transcranial magnetic stimulation decreased temporarily, and recovered to the status of the control within six minutes. It was suggested that a rapidly reversible physiological block by ischemia on the chronic injured cauda equina was the cause of the neurogenic intermittent claudication.