F wave studies of neurogenic intermittent claudication in lumbar spinal stenosis

Recovery pattern after decompression of central lumbar spinal stenosis: a prospective observational cohort study

BACKGROUND

Detailed preoperative information is associated with superior outcomes. We aimed to describe the recovery pattern after decompression of central lumbar spinal stenosis (CLSS).

METHODS

50 patients aged 51-85 years who underwent decompression without fusion due to CLSS were followed from before to after surgery (post-op day 1, 7, and 14). Back and leg pain were evaluated using the Numeric Rating Scale (NRS; 0 = no pain 0, 10 = worst pain) and quality of life using the EuroQol-5D index (0 = death, 1 = best), and EQ-5D-visual analogue scale (VAS; 0 = worst, 100 = best).

RESULTS

NRS leg pain was reduced from preoperative to first postoperative day by 5.2 (6.1, 4.3) (mean (95%CI)], and NRS back pain from postoperative day 1-7 by 0.6 (1.2, 0.03) and from day 7 to 14 by 0.7 (1.3, 0.2)]. In contrast, EQ-5D index increased from preoperative to first postoperative day by 0.09 (0.06, 0.13) and from day 1 to 7 by 0.05 (0.02,0.08), and EQ-5D VAS from preoperative to first postoperative day by 13.7 (9.1, 18.3) and from day 1 to 7 by 6.0 (2.0, 10.0). After two weeks, 51% of the patients had improved above the minimal clinically important difference (MCID) in back pain and 71% in leg pain.

CONCLUSIONS

Patients scheduled for decompression due to CLSS should be informed that improvement in leg pain and quality of life in general can be expected within one day of surgery, that quality of life improves a little further in the first postoperative week, and that back pain improves in the first 2 postoperative weeks. In most patients, decompression without fusion due to CLSS seems to achieve clinically relevant improvement within 2 weeks.

Evaluation of dynamic F wave parameters before and after physical activity in normal population

Objectives

F wave is one of the nerve conduction studies, mainly used to study the proximal pathway of peripheral nerves. One of its applications is dynamic assessment, i.e., before and after physical activity, when symptoms develop in some patients. Best to our knowledge, few studies evaluate normal dynamic F wave values in healthy individuals. This study aims to determine and compare normal values of several parameters of Compound Muscle Action Potential (CMAP) and F waves of tibial nerves dynamically before and after physical activity in the lower extremities of 34 normal subjects. These parameters were recorded before and after 15 min of continuous walking at intervals of 1, 5, and 10 min after the end of physical activity.

Results

Normal values of CMAP onset latency and amplitude, minimum, maximum, and mean latency of 10 F waves, F chronodispersion, and F persistence were dynamically collected before and during 10 min after physical activity in three phases. Some of the parameters showed significant changes (P < 0.05). Although physical activity showed statistically significant effects on some CMAP and F wave parameters (especially F chronodispersion) in normal subjects, none of them exceeded the normal clinical values introduced in the literature.

Peripheral nerve adaptations to 10 days of horizontal bed rest in healthy young adult males

Space analogs, such as bed rest, are used to reproduce microgravity-induced morphological and physiological changes and can be used as clinical models of prolonged inactivity. Nevertheless, nonuniform decreases in muscle mass and function have been frequently reported, and peripheral nerve adaptations have been poorly studied, although some of these mechanisms may be explained. Ten young healthy males (18-33 yr) underwent 10 days of horizontal bed rest. Peripheral neurophysiological assessments were performed bilaterally for the dominant (DL) and nondominant upper and lower limbs (N-DL) on the 1st and 10th day of bed rest, including ultrasound of the median, deep peroneal nerve (DPN), and common fibular nerve (CFN) , as well as a complete nerve conduction study (NCS) of the upper and lower limbs. Consistently, reduced F waves, suggesting peripheral nerve dysfunction, of both the peroneal (DL: P = 0.005, N-DL: P = 0.013) and tibial nerves (DL: P = 0.037, N-DL: P = 0.005) were found bilaterally, whereas no changes were observed in nerve ultrasound or other parameters of the NCS of both the upper and lower limbs. In these young healthy males, only the F waves, known to respond to postural changes, were significantly affected by short-term bed rest. These preliminary results suggest that during simulated microgravity, most changes occur at the muscle or central nervous system level. Since the assessment of F waves is common in clinical neurophysiological examinations, caution should be used when testing individuals after prolonged immobility.

Unilateral repetitive tibial nerve stimulation improves neurogenic claudication and bilateral F-wave conduction in central lumbar spinal stenosis

BACKGROUND

Repetitive electrical nerve stimulation of the lower limb may improve neurogenic claudication in patients with lumbar spinal stenosis (LSS) as originally described by Tamaki et al. We tested if this neuromodulation technique affects the F-wave conduction on both sides to explore the underlying physiologic mechanisms.

METHODS

We studied a total of 26 LSS patients, assigning 16 to a study group receiving repetitive tibial nerve stimulation at the ankle (RTNS) on one leg, and 10 to a group without RTNS. RTNS conditioning consisted of a 0.3-ms duration square-wave pulse with an intensity 20% above the motor threshold, delivered at a rate of 5 Hz for 5 min. All patients underwent the walking test and the F-wave and M-wave studies for the tibial nerve on both sides twice; once as the baseline, and once after either the 5-min RTNS or 5-min rest.

RESULTS

Compared to the baselines, a 5-min RTNS increased claudication distance (176 ± 96 m vs 329 ± 133 m; p = 0.0004) and slightly but significantly shortened F-wave minimal onset latency (i.e., increased F-wave conduction velocity) not only on the side receiving RTNS (50.7 ± 4.0 ms vs 49.2 ± 4.2 ms; p = 0.00081) but also on the contralateral side (50.1 ± 4.6 ms vs 47.9 ± 4.2 ms; p = 0.011). A 5-min rest in the group not receiving RTNS neither had a significant change on claudication distance nor on any F-wave measurements. The M response remained unchanged in both groups.

CONCLUSIONS

The present study verified a beneficial effect of unilaterally applied RTNS of a mild intensity on neurogenic claudication and bilateral F-wave conduction. Our F-wave data suggest that this type of neuromodulation could be best explained by an RTNS-induced widespread sympathetic tone reduction with vasodilation, which partially counters a walking-induced further decline in nerve blood flow in LSS patients who already have ischemic cauda equina.

Lumbar spinal stenosis: syndrome, diagnostics and treatment

Lumbar spinal stenosis (LSS) comprises narrowing of the spinal canal with subsequent neural compression, and is frequently associated with symptoms of neurogenic claudication. To establish a diagnosis of LSS, clinical history, physical examination results and radiological changes all need to be considered. Patients who exhibit mild to moderate symptoms of LSS should undergo multimodal conservative treatment, such as patient education, pain medication, delordosing physiotherapy and epidural injections. In patients with severe symptoms, surgery is indicated if conservative treatment proves ineffective after 3-6 months. Clinically relevant motor deficits or symptoms of cauda equina syndrome remain absolute indications for surgery. The first randomized, prospective studies have provided class I-II evidence that supports a more rapid and profound decline of LSS symptoms after decompressive surgery than with conservative therapy. In the absence of a valid paraclinical diagnostic marker, however, more evidence-based data are needed to identify those patients for whom the benefit of surgery would outweigh the risk of developing complications. In this Review, we briefly survey the underlying pathophysiology and clinical appearance of LSS, and explore the available diagnostic and therapeutic options, with particular emphasis on neuroradiological findings and outcome predictors.

Assessment and management of neurogenic claudication associated with lumbar spinal stenosis in a UK primary care musculoskeletal service: a survey of current practice among physiotherapists

Background

Neurogenic claudication (NC) is the clinical syndrome commonly associated with lumbar spinal stenosis (LSS). Non-surgical management is recommended as initial treatment, but little is known about current practice in relation to the assessment and management of these patients in the non-surgical setting.

Methods

We conducted a questionnaire survey of physiotherapists in a large UK primary care musculoskeletal service which provides a city-wide multidisciplinary assessment and treatment facility for patients with spinal and other musculoskeletal problems. Data on therapists' recognition and management of patients with NC and LSS were collected.

Results

Fifty out of 54 therapists completed questionnaires, and all but one of these identified a clearly recognised posture-related clinical syndrome of NC. Almost all respondents (48: 96%) reported the routine use of physiotherapy treatments. In particular, advice and education (49: 98%) along with an exercise programme (47: 94%) incorporating flexion-based exercises (41: 82%) and trunk muscle stabilising exercises (35: 70%) were favoured.

Conclusion

Musculoskeletal physiotherapy clinicians in this survey recognised a clear clinical syndrome of NC, based on the findings of posture-dependent symptoms. Most therapists reported the routine use of flexion-based exercise, reflecting recommendations in the literature which are based on theoretical benefits, but for which trial evidence is lacking. There is a need for research evidence to guide the choice of physiotherapy treatments.

Clinical usefulness of assessing lumbar somatosensory evoked potentials in lumbar spinal stenosis

Object

The aim of this retrospective study was to evaluate the clinical usefulness of assessing lumbar somatosensory evoked potentials (SSEPs) in central lumbar spinal stenosis (LSS).

Methods

The latencies of lumbar SSEPs were recorded in 40 patients with central LSS, including 16 men and 24 women. The mean age of the patients was 67.3 ± 7.4 years. The diagnosis was LSS in 23 cases and LSS associated with degenerative spondylolisthesis in 17 cases. The average duration of symptoms was 43.8 ± 51.2 months. Twenty-two cases had bilateral and 18 cases had unilateral leg symptoms. Thirty-seven cases were associated with neurogenic intermittent claudication and the mean walking distance of patients with this condition was 246.8 ± 232.7 m. The mean Japanese Orthopedic Association scale score, as well as the visual analog scale (VAS) scores of low-back pain, leg pain, and numbness, were 16.5 ± 3.5, 6.0 ± 2.5, 6.9 ± 2.1, and 7.8 ± 2.2, respectively. The minimal cross-sectional area of the dural sac on MR imaging was 0.44 ± 0.21 cm2. Thirty-nine cases of cervical spondylotic myelopathy without lumbar and peripheral neuropathy were chosen as the control group.

Results

The latencies of lumbar SSEPs in patients with LSS and in the control group were 23.0 ± 2.0 ms and 21.6 ± 1.9 ms, respectively. There was a statistically significant difference between the LSS and control groups (p < 0.05). The latency of lumbar SSEPs was significant correlated with the VAS score of leg numbness (p < 0.05). The latency of lumbar SSEPs in LSS was clearly delayed when the VAS score of leg numbness was ≥ 8 (p < 0.05).

Conclusions

Lumbar SSEPs are able to detect neurological deficit in the lumbar area effectively, and they can reflect part of the subjective severity of sensory disturbance (numbness) in LSS. Both lumbar SSEPs and VAS scores of leg numbness may be useful for clinical evaluation in patients with LSS.

Routine electrodiagnosis and a multiparameter technique in lumbosacral radiculopathies

OBJECTIVE

This study compares Routine nerve conductions studies (NCS)/needle electromyography (nEMG) with a multiparameter recording method (NC-stat; NeuroMetrix Inc., Waltham, MA, USA) in patients with lumbosacral radiculopathies (LSR).

METHODS

Charts from 34 consecutive patients with a clinical history and/or examination consistent with an LSR were retrospectively reviewed. All underwent both Routine NCS/nEMG studies and NC-stat EDX. NC-stat testing included peroneal and posterior tibial nerve distal motor latencies and amplitudes and F-wave analysis. Twenty-eight patients had magnetic resonance imaging of the lumbosacral spine, and two had post-myelogram computerized tomography scan.

RESULTS

In the 24 patients with abnormal routine NCS/nEMG, NC-stat EDX was abnormal in 22. Raw agreement values between specific abnormal Routine and NC-stat EDX parameters ranged from 065 to 0.76. NC-stat amplitude and F-wave data provide reasonable electrodiagnostic 'rule in, rule out' information for LSR. Routine and NC-stat EDX had comparable positive and negative likelihood ratios with radiographic findings based on blinded neuroradiological evaluation. This included good 'stand alone' values for NC-stat F-wave and compound muscle action potential (CMAP) amplitude abnormalities in patients with spinal stenosis.

CONCLUSIONS

This report supports the value of multiparameter clinical neurophysiological evaluations in patients with LSR including CMAPs and F-waves.

Inward currents induced by ischemia in rat spinal cord dorsal horn neurons

Hypoxia and ischemia occur in the spinal cord when blood vessels of the spinal cord are compressed under pathological conditions such as spinal stenosis, tumors, and traumatic spinal injury. Here by using spinal cord slice preparations and patch-clamp recordings we investigated the influence of an ischemia-simulating medium on dorsal horn neurons in deep lamina, a region that plays a significant role in sensory hypersensitivity and pathological pain. We found that the ischemia-simulating medium induced large inward currents in dorsal horn neurons recorded. The onset of the ischemia-induced inward currents was age-dependent, being onset earlier in older animals. Increases of sensory input by the stimulation of afferent fibers with electrical impulses or by capsaicin significantly speeded up the onset of the ischemia-induced inward currents. The ischemia-induced inward currents were abolished by the glutamate receptor antagonists CNQX (20 μM) and APV (50 μM). The ischemia-induced inward currents were also substantially inhibited by the glutamate transporter inhibitor TBOA (100 μM). Our results suggest that ischemia caused reversal operation of glutamate transporters, leading to the release of glutamate via glutamate transporters and the subsequent activation of glutamate receptors in the spinal dorsal horn neurons.

Lumbale Spinalkanalstenose

Lumbal spinal stenosis is gaining more and more clinical relevance because of changing population structure and increasing demand on lifequality in the elderly. Current treatment recommendations are based on clinical experience, expert opinions and single studies rather than on proven evidence. The radiologic degree of stenosis does not correlate with the patients' clinical situation. It is not the main factor indicating surgery but rather the typical history and spinal claudication. Symptomatic patients with light to moderate complaints should undergo multimodal conservative treatment. Epidural injections, delordosating physiotherapy and medication are useful. In patients with severe symptomatic stenosis surgery is indicated after a conservative treatment of 3 months. Relevant pareses or a cauda equina syndrome are absolute indications for surgery. The general aim is to decompress sufficiently while maintaining or restoring segmental stability. A laminectomy is not necessarily required. In patients with accompanying degenerative Meyerding grade I-II spondylolisthesis or instability in functional radiographs, fusion or dynamic stabilisation are recommended in addition to decompression, depending on the patient's age and activity level.