Keisuke Takahashi

Epidural pressure measurements. Relationship between epidural pressure and posture in patients with lumbar spinal stenosis

Study Design The relationship between epidural pressure and lumbar posture was assessed in patients with lumbar spinal stenosis. Objectives This study was performed to assess the relationship between epdural pressure and lumbar posture in patients with lumbar spinal stenosis. Methods The study was performed on 10 patients who had cauda equina symptoms at the L4–L5 level. The catheter transducer was inserted into the epidural space through L5-S1 interlaminar space and placed at the L4–L5 disc level. This transducer was connected with an amplifier and a recorder. Epidural pressure was continuously measured in various postures. Results Local epidural pressure at the stenotic level was low in lying and sitting postures, and high in standing postures. Pressure was increased with extension, but decreased with flexion. The highest pressure was 116.7±38.4 mm Hg in standing with extension. Conclusion Epidural pressure was significantly related to posture. These pressure changes correlated with the development of cauda equina symptoms. The increase of epidural pressure by posture may induce compression of the cauda equina. These pressure changes may explain the postural dependency in eliciting symptoms.

Changes in epidural pressure during walking in patients with lumbar spinal stenosis

Study Design This study was done to assess the pathophysiology of neurogenic intermittent claudication by measuring the epidural pressure at walking. Objectives Changes in epidural pressure during walking in patients with neurogenic intermittent claudication and in normal individuals were analyzed. Summary of Background Data Neurogenic intermittent claudication may be caused by compression of the nerve roots or may be a result of nerve root ischemia. The exact pathogenesis of neurogenic intermittent claudication is uncertain. Methods Local epidural pressure changes at the stenotic level during walking were analyzed in 12 patients with lumbar spinal stenosis and seven normal individuals. A flexible pressure transducer was inserted into the epidural space and placed at the L4-L5 level. The epidural pressure was monitored continuously during walking. The pattern of the pressure change was assessed by gait analysis using a foot switch. Results The pressure was changed during walking. The pressure had a wave pattern of increase and decrease, and this pattern was repeated during walking. Intermittent pressure increase was seen about 90 times per minute while walking at a velocity of 2 km/h. An increase in epidural pressure occurred at the double-supporting phase in each gait cycle. Conclusions The pressure was high in spinal stenosis and low in normal individuals. The increase of epidural pressure at simple walking was higher than walking with lumbar flexion. Intermittent compression to the nerve roots during walking may be cause of neurogenic intermittent claudication.

Nerve root pressure in lumbar disc herniation.

STUDY DESIGN The contact pressure between the nerve root and lumbar disc herniation was measured and compared with clinical features. OBJECTIVE To assess levels of actual compression to the nerve root in clinical cases. SUMMARY OF BACKGROUND DATA Actual levels of pressure to the nerve root of lumbar disc herniation in clinical cases is unknown. METHODS The study was performed on 34 patients who had lumbar disc herniation. All of them had been treated by open discectomy. After laminotomy, nerve root pressure was measured by inserting a transducer between the nerve root and the disc herniation. The magnitude of pressure was compared with clinical features. RESULTS Nerve root pressures before discectomy were varied from 7 mm Hg to 256 mm Hg (mean, 53 mm Hg). After discectomy, the contact pressure was 0 mm Hg in all cases. There were no significant correlations between the magnitude of nerve root pressure and limits to the degree of straight leg raising, duration of symptoms, and age of the patients. However, the magnitude of the pressure in patients with neurologic deficits and trunk list was significantly higher than in the absence of these findings. CONCLUSIONS The contact pressure exerted by lumbar disc herniation on the nerve roots was recorded during surgical intervention, and the mean pressure was 53 mm Hg. The magnitude of nerve root pressure was not correlated with the degree of straight leg raising, but with the severity of neurologic deficits.

A rapid transport route between the epidural space and the intraneural capillaries of the nerve roots.

Study Design The possibility of epidurally applied substances reaching the intraneural capillaries of the spinal nerve roots and cauda equina was assessed in the pig sacrococcygeal spine. Methods The presence of Evans blue-labelled albumin in intraneural capillaries after epidural applicaton for 1, 10, or 30 minutes was studied with fluorescence microscopy. Ink angiography was used to determine whether there were any direct communicating vessels between the epidural vien plexus and the intraneural capillaries. Results Evans blue-labelled albumin was present in the intraneural capillaries 1 minute after epidural application. Microangiography demonstrated small venules that connected the epidural vein plexus and the intraneural capillaries. Conclusions The results of this study demonstrated a rapid transport route between the epidural space and the intraneural capillaries. The results suggest that nucleus pulposus material, as well as epidurally applied substances, such as local anesthetic drugs or epidurally injected corticosteroids, may have a rapid, direct transport route to the axons of the spinal nerve roots. The demonstrated transport route also may be related to the mechanisms behind epidural anesthesia and spinal nerve root infiltration.

Postural changes of the dural sac in the lumbar spines of asymptomatic individuals using positional stand-up magnetic resonance imaging.

Study Design. Positional magnetic resonance imaging (MRI) study of control subjects. Objectives. To determine dimensional changes in the lumbar dural sac as a function of posture, and to establish changes between the supine, erect and seated positions. Summary of Background Data. Studies using computerized tomography and MRI were done to determine the mechanical effects on the lumbar spinal canal in the different positions. There has been no consecutive study, however, in which normal individuals were investigated for positional changes of the dural sac, including true standing position. Methods. Thirty-two male asymptomatic volunteers were recruited. The examination was performed using a new MRI system. All subjects were examined with sagittal T2 and axial T1-weighted spin-echo images. The subjects were studied in the supine, standing, and sitting positions. The measurements were made using OSIRIS software (Digital Imaging Unit University Hospital of Geneva, Geneva, Switzerland). On axial images, dural sac cross-sectional area and anteroposterior (AP) dural sac diameter were measured at the level of the L3/4, L4/5, and L5/S1 discs. On midsagittal images, AP dural sac diameter and the upper-endplate angles of L1 and S1 were measured. Results. We found a disc degeneration or disc protrusion in 41% (12/29) of the subjects, but there was no obvious compression of the dural sac. Depending on the postures, the mean dural sac cross-sectional area and AP dural sac diameter changed. At all levels, mean dural sac cross-sectional area in the supine position was significantly smaller than in other postures. The dural area decreased most at the L5/S1 level due to positional change from standing to supine. The largest dural area at the L5/S1 level was in sitting extended. AP dural sac diameter on axial and midsagittal images showed a similar tendency. Conclusions. A significant posture-dependent difference of the dural sac cross-sectional area at the level of intervertebral disc in asymptomatic volunteers has been demonstrated. When the posture changed from supine to standing position, lumbar dural sac volume expanded by the increased pressure of cerebrospinal fluid, and the dural sac cross-sectional area increased. The smallest values were found in the supine position.

The length of the cervical cord: effects of postural changes in healthy volunteers using positional magnetic resonance imaging.

Study Design. The length of the cervical cord in healthy volunteers was measured in the supine and erect position using positional magnetic resonance imaging (MRI). Objective. To assess the relationship between the length of the cervical cord and cervical posture in healthy volunteers. Summary of Background Data. A number of detailed descriptions of the normal morphologic features of the cervical cord have been published. However, to our knowledge, there is no report to compare the relationship between the length of the cervical cord and cervical posture in healthy volunteers using positional MRI. Methods. This study was performed on 20 healthy volunteers using positional MRI. The subjects were studied in the supine and erect positions. The recumbent series consisted of 3 positions: neutral, flexion, and extension. The erect series consisted of 3 positions: neutral, flexion, and extension. On the midsagittal image, the length of the cervical cord from C1 to C7 was measured at the anterior, middle, and posterior line. The angle of the lower-endplate of C2 and C7 was measured. The results were compared with each series. Results. In the recumbent and erect series, the mean length of the cervical cord in flexion was longer than in neutral and extension at the anterior, middle, and posterior line. There were significant differences between the length of the cervical cord in flexion, neutral, and extension. The mean length of the cervical cord in extension was shorter than in neutral and flexion at the anterior, middle, and posterior line. There were significant differences between length of the cervical cord in extension, neutral, and flexion. Conclusions. We found posture-dependent differences of the length of the cervical cord in the recumbent and erect series. These results may be important when assessing the dynamic factor in cervical spondylotic myelopathy.

Lumbar Paraspinal Myonecrosis After Abdominal Vascular Surgery : A Case Report

Study Design. Case report. Objectives. Lumbar paraspinal myonecrosis after abdominal vascular surgery. Summary of Background Data. Lumbar paraspinal myonecrosis does not appear to have been reported previously. Methods. A patient who had severe back pain after abdominal vascular surgery was observed with computed tomographic scans and histologic examination of a specimen obtained in open biopsy. Results. Computed tomographic scans of the lumbar region demonstrated muscle swelling of the unilateral paraspinal compartment. Histologic examinations of affected muscle revealed fresh ischemic necrosis. A compartmental syndrome was considered from the patient’s clinical presentation and radiographic and histologic features. An accompanying secondary infection led to an extensive abscess in the paraspinal compartment. The patient resumed active daily life after aggressive débridements of infected and necrotic muscles. Conclusions. A compartmental syndrome in the paraspinal muscle should be kept in mind as a potential cause of acute back pain especially after abdominal vascular surgery.

Biomechanical aspects of the cervical cord: effects of postural changes in healthy volunteers using positional magnetic resonance imaging.

Study Design The area in cross-sectional view of the cervical cord (ACSCC) at each disc levels was measured in supine and erect positions using positional magnetic resonance imaging (pMRI). Objectives To assess the relationship between ACSCC and cervical posture in healthy volunteers using pMRI. Summary of Background Data There have been few detailed descriptions of the normal morphologic features of the cervical cord. However, there is no report to compare the relationship between ACSCC and cervical posture in healthy volunteers. Methods The study was performed on 20 healthy volunteers. The subjects were studied with pMRI in the supine and erect positions. The recumbent series and the erect series consist of 3 positions each: neutral, flexion and extension. On axial images, ACSCC was measured at the C2/3, C3/4, C4/5, C5/6, and C6/7 disc levels. On midsagittal image, the angle of the lower-endplate of C2 and C7 was measured. The results were compared between each series. Results In the recumbent and erect series, ACSCC was larger in extension than in neutral and flexion at all levels. There were significant differences between ACSCC in extension, neutral and flexion. ACSCC was smaller in flexion than in neutral and extension at all levels. There were significant differences between ACSCC in flexion, neutral and extension. Conclusions We found posture-dependent differences of ACSCC in the recumbent and erect series. These results may be valuable for identifying a dynamic factor in patients with cervical spondylotic myelopathy.

Effects of peripheral nerve stimulation on the blood flow of the spinal cord and the nerve root

Hemodynamic changes In the spinal cord and the nerve root caused by electrical sciatic nerve stimulation In anesthetized dogs were measured with a thermal diffusion method. The electrical stimulation Increased the blood flow of the stimulated spinal cord and the nerve root. The conditions of stimulation giving the maximum increase of blood flow were different for the spinal cord and the nerve root. Strong stimulation at a high frequency of 50 to 100 Hz was effective for Increasing the blood flow. In the spinal cord, an increase of the local metabolic rate appeared to be important for the blood flow increase. In the nerve root, the sympathetic nerves may have an important effect In the blood flow increase.

Quantitative analysis of edema in the dorsal nerve roots induced by acute mechanical compression.

Study Design. Edema in the dorsal nerve roots caused by acute compression was assessed quantitatively in the lumbar spine of the adult dog. Objective. To establish quantitative evaluation of edema in the dorsal nerve roots and to observe changes after acute compression with time. Summary of Background Data. Mechanical compression induces an increase in microvascular permeability of the endoneurial capillaries and results in intraneural edema. However, there are no quantitative studies on edema in the nerve roots. Methods. The seventh lumbar nerve root was compressed with a 60‐g force clip for 10 minutes. The nerve roots were removed immediately and at 24 hours, 1 week, and 3 weeks after compression. Nerve roots from the control and the sham groups were also obtained. Before removing the nerve roots, Evans blue albumin was injected intravenously. Changes in edema were examined using fluorescence microscopy. Evans blue albumin emits a bright red fluorescence. The relative red fluorescent area was calculated using computer image analysis, and the data were used to indicate the degree of edema. Results. In the compressed segment, edema was most pronounced just after decompression and reduced in nerves removed at 24 hours. In nerves removed at 1 week, edema was pronounced but was reduced at 3 weeks. In the segments closest to the spinal cord, edema was seen after 1 week and was significant after 3 weeks. In the segments closest to the dorsal root ganglion, edema was not detected at any time. Conclusion. In the dorsal nerve roots the degree and the area of edema changed with time elapsed after acute compression. The degree of edema 24 hours after decompression was one third the degree immediately after decompression. These results show that edema induced by mechanical compression can recover after decompression.