Spinal contribution to CSF pressure lowering effect of mannitol in cats

OBJECTIVES

After application of hyperosmolar mannitol the cerebrospinal (CSF) pressure is usually lowered within 30 min but this effect cannot be explained either by changes in intracranial blood volume and flow or by changes in brain volume. We assume that this effect of mannitol my be consequence of CSF volume decrease primarily in the spinal CSF due to high compliance of the spinal dura.

METHODS

To explore such a possibility we planned to separate spinal and cerebral CSF. In chloralose anaesthetized cats dorsal laminectomy of C2 vertebrae was performed and a plastic semi ring was positioned extradurally separating cranial and spinal CSF. CSF pressures were recorded via cannulas positioned in lateral ventricle and lumbar subarachnoid space at L3 vertebrae, respectively.

RESULTS

After intravenous bolus of 20% mannitol (0.5 or 1.0 g/kg/ 3 min) in control animals without cervical stenosis, the fall of both ventricular and lumbar CSF pressures was equal over time. At 15 min after mannitol application in cats with cervical stenosis an slight increase of ventricular and a fall of lumbar CSF pressures were observed, while at 30 min a gradient of these pressures of 5.5 and 7 cm H2O at lower and higher dose of mannitol, respectively, were registered. However, after removal of cervical stenosis these gradients disappeared.

CONCLUSION

The observed changes of CSF pressures in spinal and intracranial space indicate that spinal subarachnoid space contributes a great deal to overall fall of CSF pressure and volume in the early period after mannitol application probably due to high compliance of the spinal dura.

Spinal stenosis: pathophysiology, clinical and radiologic classification

Stenosis is the narrowing of a hollow tube, in this case the central lumbar spinal canal, lateral recess, or foramen. Clinically, this narrowing produces neurovascular compression that may lead to pain. Lumbar spinal stenosis may be classified by etiology (for example, congenital or acquired) or by symptom complex (radiculopathy, neurogenic claudication, or mechanical back pain). Stenosis can also be classified radiographically, by the location of the stenosis (for example, central canal, lateral recess, or intervertebral foramen) or by the presence of deformity such as spondylolisthesis or scoliosis. Overlap occurs in these schemes of classification in that central stenosis with thecal sac compression typically leads to neurogenic claudication, whereas lateral recess compression is associated with compression of an individual nerve root and, therefore, radiculopathy. Because radiographic changes associated with stenosis are very common with aging, understanding the pathophysiology of lumbar spinal stenosis is critical in the assessment and management of related symptom complexes. Although symptoms may arise from narrowing of the spinal canal, not all patients with narrowing develop symptoms. The reason why some patients develop symptomatic stenosis and others do not is still unknown. Therefore, the term lumbar spinal stenosis refers not to the pathoanatomic finding of spinal canal narrowing, but rather to a clinical syndrome of lower extremity pain caused by mechanical compression on the neural elements or their blood supply.

The clinical syndrome associated with lumbar spinal stenosis

Lumbar spinal stenosis is well defined in patho-anatomical terms but its clinical features are heterogeneous. We carried out a comprehensive retrospective review of the clinical features, radiological changes and outcome of 75 patients with radiologically diagnosed lumbar spinal stenosis in order to define its clinical spectrum. The presenting complaints were of weakness, numbness/tingling, radicular pain and neurogenic claudication in almost equal proportions. The commonest symptom was numbness or tingling of the legs. Neurogenic claudication eventually occurred in only 61%. Ninety-three per cent showed abnormalities on neurological examination, but these were generally mild with reduced ankle jerks being commonest. Imaging of the lumbar spine showed that moderate to severe central spinal stenosis correlated with complaints of weakness and abnormal motor power on clinical examination. Patients were reviewed at a mean of 4 years after diagnosis and 65% had undergone surgical decompression; this was not a prospective comparison of different treatment modalities. Overall, a third of patients felt that their symptoms had improved while a quarter felt that they had worsened. More than half had satisfactory neurological function at the time of review. Thirty-nine per cent of those treated surgically, and 25% of those managed conservatively, reported improved symptoms. A poorer functional status at review correlated with complaints of motor weakness and associated comorbid disease. Degenerative lumbar stenosis is a clinically heterogeneous neurological disorder of the lower limbs in the elderly with variable longer-term outcome. A high index of suspicion is required and neuroimaging should be obtained to confirm the diagnosis.

Spontaneously Stabilized Severe Dysplastic Spondylolisthesis without Operation

Surgical management is the accepted treatment choice for grade III or IV spondylolisthesis, and many satisfactory clinical and radiologic follow-up results have been reported. Very little, however, has been written about long-term results in preteenage patients in whom dysplastic spondylolisthesis has been treated nonoperatively, especially in those who have > or =50% displacement of the fifth lumbar vertebra on the sacrum. We report an unusual case of spontaneous stabilization of severe dysplastic spondylolisthesis in an 8-year-old girl who presented with grade III spondylolisthesis of L5-S1 and was followed up for >14 years in the absence of surgical intervention. On presentation, she complained of a restriction in forward bending and tightness of hamstrings, but she was undisturbed in her daily activities. Initial radiographs showed severe dysplastic spondylolisthesis; however, magnetic resonance imaging (MRI) performed at age 9 years showed that the amount of listhesis was much less than that seen in the initial radiograph. Routine radiographic follow-ups were chosen over early operative measures until she became a teenager. There was no change in the slip, and unusually a gradual ossification of the cartilaginous promontory of the S1 and the posterior lip of the L5 was observed. At 22 years old, the patient is asymptomatic and not conscious of her cosmetic appearance. Surgical treatment has generally been indicated for patients with grade III or IV spondylolisthesis, because slippage progression has been noted in most reported cases. However, MRI may be a tool for predicting which dysplastic spondylolisthesis cases are more likely to progress and therefore circumvent surgical intervention, while maintaining an excellent outcome.

[Blood flow changes of cauda equina in experimental lumbar spinal canal stenosis under dynamic burden]

OBJECTIVE

To study the changes of blood flow of the already-compressed cauda equina under dynamic burden, high frequency stimulation (HFS) and increased additional compression, and to clarify the mechanism of neurogenic intermittent claudication.

METHODS

Thirty SD rats were divided into 5 groups, 6 in each. All groups were operated with laminectomy of the fifth lumbar verfebra. One hour after the measurement of blood flow, in 4 experimental groups, the silicon sheets were inserted into the spinal canal of L4 and L6 to cause double level compression of cauda equina by 30%. Two hours after onset of compression, no dynamic burden was introduced to the subjects of the experimental group 1. Only HFS was introduced to the subjects of the experimental group 2 for 6 minutes. Both HFS and increased additional compression were introduced to the subjects of the experimental group 3 for 6 minutes. While only increased additional compression was introduced to the subjects of the experimental group 4 for 6 minutes. The subjects of control group only underwent laminectomy of the fifth lumbar vertebra and HFS 6 minutes. The blood flow of cauda equina was measured with laser Doppler flowmeter.

RESULTS

In the first 2 hours, there was no significant change of cauda equina blood flow in the control group. During the time of HFS, the blood flow increased significantly to 186.4% +/- 31.5% of initial value (P < 0.05). In the experimental group 1, there was no blood flow change during the period of dynamic burden(110.4% +/- 7.5%, P > 0.05). After introduction of dynamic burden, there was no blood flow changes in the experimental group 2 (111.6% +/- 17.6%, P > 0.05). The blood flow in the experimental group 3 decreased to 65.3% +/- 10.7% of initial value (P < 0.05); and the blood flow in the experimental group 4 decreased to 60.1% +/- 9.2% of initial value (P < 0.01). There was no significant difference between the experimental groups 3 and 4 (P > 0.05).

CONCLUSION

The results above show that during the period of increased impulse transmission, double level compression of cauda equina may limit the increase of blood flow, which may cause relative ischemia. If there is increased additional compression along with increased impulse transmission, the blood flow will decrease significantly, which will cause absolute ischemia.

Activation of extracellular signal-regulated protein kinase in dorsal horn neurons in the rat neuropathic intermittent claudication model

Extracellular signal-regulated protein kinase (ERK) is a mitogen-activated protein kinase (MAPK) that mediates several cellular responses to mitogenic and differentiation signals, and activation of ERK in dorsal horn neurons by noxious stimulation is known to contribute to pain hypersensitivity. In order to elucidate the pathophysiological mechanisms of the cauda equina syndrome, secondary to spinal canal stenosis, we evaluated walking dysfunction triggered by forced exercise and activation of ERK in the dorsal horn using a rat model of neuropathic intermittent claudication. Rats in the lumbar canal stenosis (LCS) group showed a shorter running distance from 1 to 14 days after surgery. Two minutes after running on the treadmill apparatus, phosphorylation of ERK was induced in neurons in the superficial laminae in the LCS group but not in the sham group, whereas there was no change in the deeper laminae. Intrathecal administration of the MAPK kinase inhibitor, U0126, 30 min before running, clearly increased the running distance, whereas there was no significant change in the vehicle control group 3 days after surgery. In addition, a prostaglandin E1 analog, OP-1206 alpha-CD, administered orally, improved the walking dysfunction, and further, inhibited activation of ERK following running 7 days after surgery. These findings suggest that intermittent claudication triggered by forced walking might affect the phosphorylation of ERK in the superficial laminae, possibly via transient (partial) ischemia of the spinal cord. ERK activation in the dorsal horn neurons may be involved in the transient pain in the neuropathic intermittent claudication model.

Clinical and radiologic features of lumbar spinal stenosis and disc herniation with neuropathic bladder

STUDY DESIGN

Clinical and radiologic findings of patients with lumbar spinal stenosis and lumbar disc herniation presenting with neuropathic bladder were prospectively analyzed.

OBJECTIVES

To study the relationship between the degree of cauda equina compression and prevalence of neuropathic bladder in patients with lumbar spinal stenosis and lumbar disc herniation.

SUMMARY OF BACKGROUND DATA

Bladder dysfunction has frequently been noted in patients with lumbar spinal stenosis and lumbar disc herniation. However, there have been few studies that have demonstrated the correlation between bladder function and the degree of stenotic compression of the cauda equina seen on radiologic findings in patients with lumbar spinal stenosis and lumbar disc herniation.

METHODS

Thirty-four patients admitted for treatment for lumbar spinal stenosis or lumbar disc herniation underwent urodynamic studies, and computed tomographic scans after myelography were obtained to determine the degree of cauda equina compression. The cross-sectional area and anteroposterior diameter of the dural sac were measured at their smallest transverse area.

RESULTS

Twenty (58.8%) of the 34 patients were diagnosed with positive neuropathic bladder. There was no significant difference in the cross-sectional area of dural sac between the patients with positive neuropathic bladder and with negative neuropathic bladder. However, the dural sac anteroposterior diameter in positive neuropathic bladder patients was significantly shorter than that in patients with negative neuropathic bladder. A critical size for the dural sac of patients with neuropathic bladder was revealed as 8 mm in this study.

CONCLUSIONS

The prevalence of neuropathic bladder is more significantly associated with dural sac anteroposterior diameter than with the cross-sectional area of dural sac. Therefore, dural sac anteroposterior diameter might be an important factor predicting the existence of neuropathic bladder.

Relationship between ambulation and obesity in older persons with and without low back pain

CONTEXT

For obese older persons, ambulation is both functionally important and a means of weight control. The relationship between weight and ambulation is not known in this population. Also, the extent to which pain interferes with ambulation is not studied.

OBJECTIVE

To examine the relationship between obesity and ambulation, and to determine the effect of pain and body mass index (BMI) on ambulation in older persons.

DESIGN, SETTING, AND PARTICIPANTS

Retrospective study of 82 older persons, ages 55-79 y, some with no back pain recruited from the community, others with back pain or spinal stenosis recruited from a magnetic resonance imaging (MRI) scanner as part of a larger university study of spinal stenosis.

OUTCOME MEASURES

Age, Visual Analog Scales for pain, BMI, patient diagnosis (no pain, mechanical back pain, and spinal stenosis), walking velocity and stride length on a 15-min laboratory ambulation test, and 1-week community ambulation measured with a pedometer (steps, distance, and energy expenditure).

RESULTS

BMI had a significant inverse relationship with ambulatory measurements in terms of the distance walked, steps taken, and walking velocity. Pain severity and pain category also had a significant inverse relationship with these measures. A negative correlation was observed between pain and obesity, although the relationship was statistically nonsignificant.

DISCUSSION

Obese older people walked less than the nonobese older people. Pain was associated with decreased ambulation. Clinicians who intend to encourage increased ambulation in older obese persons should consider possible barriers posed by musculoskeletal pain.

Treatment of lumbar spinal stenosis with epidural steroid injections: a retrospective outcome study

OBJECTIVE

To determine patient satisfaction, relief of pain, frequency of injections, change of function, and subsequent surgical rate in patients who received epidural steroid injections (ESIs) for the diagnosis of lumbar spinal stenosis (LSS).

DESIGN

Retrospective review conducted using a standard set of questions asked over the telephone, 6 to 36 months after the patient received an ESI.

SETTING

An outpatient spine center.

PARTICIPANTS

One hundred forty patients at or over the age of 55 years diagnosed with LSS who received ESI(s).

INTERVENTION

Transforaminal or caudal fluoroscopically guided ESIs with 60 to 100mg of triamcinalone in combination with local anesthetic or normal saline. Main outcome measures Duration and amount of pain relief, change in functional status, patient satisfaction, and surgical rate, assessed by a 5-item questionnaire.

RESULTS

Of the 140 participants, 32% reported more than 2 months of pain relief, 39% reported less than 2 months of pain relief, and 29% reported no relief from the injection(s). Twenty percent subsequently had surgery. Fifty-three percent reported improvement in their functional abilities. Seventy-four percent where at least somewhat satisfied with ESI as a form of treatment.

CONCLUSIONS

ESI is a reasonable treatment for LSS, providing one third of our patient population with sustained relief and more than half with sustained improvement in function.

Axial loading during MR imaging can influence treatment decision for symptomatic spinal stenosis

BACKGROUND AND PURPOSE

Previous studies have shown that axial loading can narrow the spinal canal. However, the clinical significance is unclear. The purpose of this study was to determine whether the narrowing of the spinal canal with axial loading during MR imaging could influence treatment decision for spinal stenosis.

METHODS

Two hundred patients with clinical symptoms of spinal stenosis underwent routine MR imaging and then immediately underwent axially loaded MR imaging. We selected 20 of these patients because they had narrowing of the spinal canal shown on the axially loaded images. Three experienced neurosurgeons evaluated these 20 patients based on clinical information and routine MR images. The same neurosurgeons were then asked for second treatment decisions based on the same clinical information but with axially loaded MR images.

RESULTS

Axial loading during MR imaging of the lumbar spine can influence neurosurgeons in their treatment decisions for symptomatic spinal stenosis. For this selected group of patients, all three neurosurgeons changed their treatment decision from conservative management to decompressive surgery for five patients when shown the axially loaded MR images. For two other patients, two neurosurgeons changed their treatment decisions, and for three additional patients, one neurosurgeon changed his treatment decision, all based on the axially loaded MR images. Treatment was not changed from surgical to medical management for any of the patients when shown the axially loaded images.

CONCLUSION

In selected patients with spinal stenosis and apparent narrowing of the spinal canal shown by axially loaded MR imaging, the additional information gained from this technique can influence experienced neurosurgeons in their treatment decisions.

An Interspinous Process Distractor (X STOP) for Lumbar Spinal Stenosis in Elderly Patients

BACKGROUND

Lumbar spinal stenosis (LSS) is often a position-dependent condition that is aggravated in extension and relieved in flexion.

METHODS

Ten consecutive elderly patients with LSS were assessed postoperatively by magnetic resonance imaging and the Swiss Spinal Stenosis Questionnaire. Cross-sectional areas of the dural sac and intervertebral foramina at the stenotic level were measured postoperatively and compared with the preoperative values.

RESULTS

Postoperatively the cross-sectional area of the dural sac increased 16.6 mm2 or 22.3% and intervertebral foramina increased 22 mm2 or 36.5%. The intervertebral angle and the posterior disc height changed significantly. Seventy percent of the patients were satisfied with the surgical outcome.

CONCLUSION

This new surgical method is effective in elderly LSS patients.

A predictive model for outcome after conservative decompression surgery for lumbar spinal stenosis

This study was designed to develop predictive models for surgical outcome based on information available prior to lumbar stenosis surgery. Forty patients underwent decompressive laminarthrectomy. Preop and 1-year postop evaluation included Waddell's nonorganic signs, CT scan, Waddell disability index, Oswestry low back pain disability questionnaire, low back outcome score (LBOS), visual analog scale (VAS) for pain intensity, and trunk strength testing. Statistical comparisons of data used adjusted error rates within families of predictors. Mathematical models were developed to predict outcome success using stepwise logistic regression and decision-tree methodologies (chi-squared automatic interaction detection, or CHAID). Successful outcome was defined as improvement in at least three of four criteria: VAS, LBOS, and reductions in claudication and leg pain. Exact logistic regression analysis resulted in a three-predictor model. This model was more accurate in predicting unsuccessful outcome (negative predictive value 75.0%) than in successful outcome (positive predictive value 69.6%). A CHAID model correctly classified 90.1% of successful outcomes (positive predictive value 85.7%, negative predictive value 100%). The use of conservative surgical decompression for lumbar stenosis can be recommended, as it demonstrated a success rate similar to that of more invasive techniques. Given its physiologic and biomechanical advantages, it can be recommended as the surgical method of choice in this indication. Underlying subclinical vascular factors may be involved in the complaints of spinal stenosis patients. Those factors should be investigated more thoroughly, as they may account for some of the failures of surgical relief. The CHAID decision tree appears to be a novel and useful tool for predicting the results of spinal stenosis surgery

The clinical use of dermatomal somatosensory evoked potentials in lumbosacral spinal stenosis

DSEPs provide clinicians with a safe, noninvasive technique useful in determining which patients with anatomic spinal stenosis have the added component of neurogenic compromise. Based on physiologic principles, level-by-level prolongation of DSEP latencies, reduction of amplitude, asymmetry, or a complete absence of response is associated with dysfunction in that particular afferent neurologic pathway. This dysfunction does not correspond to the exact level of stenosis noted on MRI because the rootlets in the lumbar and sacral regions pass through multiple spinal segments as they course rostrally through the spinal canal. Given that LSSS typically develops over time, the degree of abnormality likely would correspond to the physiologic slowing occurring in the multiple rootlets of the cauda equina. These recordings are not easy to perform and interpret, but when done correctly, they provide the best evidence for the type of neurophysiologic dysfunction in LSSS that responds favorably to surgical decompression. Similarly, DSEPs might provide a means of neurophysiologically monitoring clinically significant findings in a program of conservative management.

A prospective randomized multi-center study for the treatment of lumbar spinal stenosis with the X STOP interspinous implant: 1-year results

Patients suffering from neurogenic intermittent claudication secondary to lumbar spinal stenosis have historically been limited to a choice between a decompressive laminectomy with or without fusion or a regimen of non-operative therapies. The X STOP Interspinous Process Distraction System (St. Francis Medical Technologies, Concord, Calif.), a new interspinous implant for patients whose symptoms are exacerbated in extension and relieved in flexion, has been available in Europe since June 2002. This study reports the results from a prospective, randomized trial of the X STOP conducted at nine centers in the U.S. Two hundred patients were enrolled in the study and 191 were treated; 100 received the X STOP and 91 received non-operative therapy (NON OP) as a control. The Zurich Claudication Questionnaire (ZCQ) was the primary outcomes measurement. Validated for lumbar spinal stenosis patients, the ZCQ measures physical function, symptom severity, and patient satisfaction. Patients completed the ZCQ upon enrollment and at follow-up periods of 6 weeks, 6 months, and 1 year. Using the ZCQ criteria, at 6 weeks the success rate was 52% for X STOP patients and 10% for NON OP patients. At 6 months, the success rates were 52 and 9%, respectively, and at 1 year, 59 and 12%. The results of this prospective study indicate that the X STOP offers a significant improvement over non-operative therapies at 1 year with a success rate comparable to published reports for decompressive laminectomy, but with considerably lower morbidity.

A new method to measure caudal motor conduction time using magnetic stimulation

Although central motor conduction time (CMCT) has been used for the diagnosis of lumbosacral spinal stenosis (LSSS), its diagnostic value is limited due to the short length of the involved segment compared to the long length of the total conduction distance. To overcome this, we introduce a new method to measure the caudal motor conduction time (caudal MCT) using magnetic stimulation. Magnetic stimulation was applied to the vertex and the T12 and S1 spinous processes for transcortical, thoracic, and sacral stimulation, respectively, and compound muscle action potentials were recorded simultaneously from the rectus abdominis (RA) and the right and left abductor hallucis (AH) muscles using three channels. CMCT was calculated by the latency difference in the AH response between transcortical and sacral stimulation, and between transcortical and thoracic stimulation for RA. Caudal MCT was calculated by subtracting CMCT for RA from that for AH. Caudal MCT was delayed in patients with LSSS compared to normal persons. We suggest that measuring caudal MCT may be useful for the diagnosis of LSSS, but its diagnostic sensitivity and specificity requires prospective study.

[Changes of neural electrophysiology properties of cauda equina in experimental lumbar spinal canal stenosis under dynamic burden]

OBJECTIVE

To study the changes of neural electrophysiology properties of cauda equina under double level compression and dynamic burdens, and to clarify the mechanisms of intermittent neurogenic claudication.

METHODS

Thirty SD rats were divided into 5 groups (6 in each group). The laminectomy of L5 was performed in control group. In the experimental groups, the silicon sheets were inserted into the spinal canal of L4 and L6 to cause double level compression of cauda equina by 30%. Two hours after onset of compression, no dynamic burden was introduced in experimental group 1. Only high frequency stimulation(HFS) was introduced for 6 minutes in experimental group 2. Both HFS and additional increased compression were introduced for 6 minutes in experimental group 3. While only additional increased compression was introduced for 6 minutes in experimental group 4. After 6 minutes of dynamic burdens, all were returned to the status of static compression for another 30 minutes and then electrical examination was made.

RESULTS

After 2 hours of compression, motor and sensory nerve conduction velocity (NCV) of all the four experimental groups decreased significantly (P < 0.05), but there was no significant difference between them. There was no significant change in the control group. There was no significant change of NCV in experimental group 1 during the last 30 minutes of experiment. NCV in the other three experimental groups decreased after introduction of dynamic burdens, especially in the experimental group 3.

CONCLUSION

The above results showed that NCV of cauda equina decreased significantly under dynamic burdens during static compression. Two kinds of dynamic burdens introduced at the same time can cause more profound change than a single one.

Effects of orally administered OP-1206 alpha-CD with loxoprofen-Na on walking dysfunction in the rat neuropathic intermittent claudication model

An orally active prostaglandin E1 analogue, OP-1206 alpha-CD improves walking dysfunction in the rat spinal stenosis model. Loxoprofen-Na, a non-steroidal anti-inflammatory drug, is used to relieve chronic pain in patients with lumbar spinal canal stenosis. To determine whether the OP-1206 alpha-CD in combination with loxoprofen-Na could induce a greater therapeutical effect on walking dysfunction and spinal cord blood flow (SCBF) than OP-1206 alpha-CD treatment alone after chronic spinal stenosis in the rat. Spinal stenosis was induced by placing two pieces of silicon rubber strips in the lumbar (L4 and L6) epidural space of rats. After surgery, walking function was measured using a treadmill apparatus and SCBF was measured using a laser-Doppler flow meter. Drugs were administered orally twice a day for 11 days from the day 3 post-surgery. OP-1206 alpha-CD elicited a significant improvement of walking dysfunction on days 7 and 14 post-surgery and significantly increased spinal cord blood flow on day 15, whereas walking dysfunction and SCBF of rats treated with loxoprofen-Na alone remained unchanged. Combined treatment of OP-1206 alpha-CD with loxoprofen-Na did not provide additive therapeutical effect. These results suggest that a significant improvement seen after OP-1206 alpha-CD treatment is primarily mediated by improvement of the local spinal cord blood flow. This effect is not ameliorated or potentiated by a combined treatment with loxoprofen-Na.

Cervical spine stenosis and possible vitamin K deficiency embryopathy in an unusual case of chondrodysplasia punctata and an updated classification system

We describe in this paper a patient with brachytelephalangic chondrodysplasia punctata (BCDP) who has multiple serious medical problems and striking physical abnormalities. These include cervical spine stenosis with resultant quadriplegia, severe nasal hypoplasia, and brachytelephalangy. Radiographs taken shortly after birth demonstrated extensive epiphyseal and vertebral stippling, and distal phalangeal hypoplasia. The pregnancy was complicated by maternal intestinal obstruction due to a small bowel carcinoma and probable malabsorption. The severity of the phenotype in this case may have been influenced by these maternal factors particularly vitamin K deficiency.

Onset and recovery of hyperalgesia and hyperexcitability of sensory neurons following intervertebral foramen volume reduction and restoration

OBJECTIVE

To investigate the relationships between L4 and L5 intervertebral foramen (IVF) stenosis (IVFS), as well as the restoration and onset and recovery of behavioral hyperalgesia and alterations in primary sensory neuron excitability.

METHODS

IVFS was produced by surgically implanting stainless steel rods unilaterally into the intervertebral foramen at L4 and L5. The insertion of a stainless steel rod in the IVF caused IVF volume reduction, which mimics IVFS. The rods were kept for up to 14 weeks in 16 rats and 2 to 4 weeks in another 32 rats. Rod withdrawal was expected to restore the IVF volume. The rods were withdrawn in 20 rats on the 7th day and in another 20 rats on the 14th day, postoperatively. Two additional groups of control rats received no surgery or sham operation. Behavioral hyperalgesia was evidenced by the significantly decreased threshold and shortened latency of foot withdrawal to mechanical and thermal stimulation of the plantar surface. Electrophysiological intracellular recordings were obtained in vitro from L4 and/or L5 dorsal root ganglia (DRG).

RESULTS

The IVFS rats exhibited a rapid-onset (</=1 day), long-lasting (10-11 weeks), mechanical, and thermal hyperalgesia. DRG neurons in each category, large-sized, medium-sized, and small-sized, from IVFS rats were more excitable than those from control rats, evaluated by the significantly decreased threshold current and action potential threshold and increased number of discharges evoked by depolarizing current and incidence of spontaneous activity. IVF volume restoration significantly reduced behavioral hyperalgesia and the increased excitability of DRG neurons. In contrast, sham surgery produced no behavioral or electrophysiological changes in the ganglion neurons.

CONCLUSION

The present study demonstrates that hyperalgesia and hyperexcitability of the primary sensory neurons can be induced following the IVF volume reduction produced by insertion of a stainless steel rod and mostly relieved by the rod withdrawal. The recovery of excitability of DRG cells to normal levels is associated with the abatement of hyperalgesia. These results support the hypothesis that increased excitability of DRG neurons is associated with the generation and maintenance of hyperalgesia and suggest that relief of the IVF stenosis, which could compress all of the normal constituents within the IVF (ie, DRG, nerve root, blood and lymph vessels, adipose, etc.), may help to alleviate chronic pain in humans.

Influence of graded facetectomy and laminectomy on spinal biomechanics

Facetectomy and laminectomy are techniques for decompressing lumbosacral spinal stenosis. Resections of posterior bony or ligamentous parts normally lead to a decrease in stability. The degree of instability depends on the extent of resection, the loading situation and the condition of the intervertebral discs. The correlation between these parameters is not well understood. In order to investigate how these parameters relate to one another, a three-dimensional, non-linear finite element model of the lumbosacral spine was created. Intersegmental rotations, intradiscal pressures, stresses, strains and forces in the facet joints were calculated while simulating an intact spine as well as different extents of resection (left and bilateral hemifacetectomy, hemilaminectomy and bilateral laminectomy, two-level laminectomy), disc conditions (intact and degenerated) and loading situations (pure moment loads, standing and forward bending). The results of the modelling showed that a unilateral hemifacetectomy increases intersegmental rotation for the loading situation of axial rotation. Expanding the resection to bilateral hemifacetectomy increases intersegmental rotation even more, while further resection up to a bilateral laminectomy has only a minor additional effect. Hemilaminectomy and laminectomy only differ in their effect for ventriflexion and muscle-supported forward bending. Two-level laminectomy increases the intersegmental rotation only for standing. Degenerated discs result in smaller intersegmental rotations and higher disc stresses at the respective levels. Decompression procedures affect the examined biomechanical parameters less markedly in degenerated than in intact discs. Resection of posterior bony or ligamentous elements has a stronger influence on the amount than on the distribution of stresses and deformations in a disc. It has only a minor effect on the biomechanical behaviour of the adjacent region. Spinal stability is decreased after a laminectomy for forward bending, and after a two-level laminectomy for standing. For axial rotation, spinal stability is decreased even after a hemifacetectomy. Patients should therefore avoid excessive axial rotation after such a treatment.

Square cervical laminoplasty incorporating spinous process: surgical technique

BACKGROUND

We have used a laminoplasty technique in multilevel cervical canal stenosis that incorporates spinous process in the neural arch and does not require free graft or foreign material.

METHODS

In this technique, laminae and spinous processes were used to enlarge stenotic cervical spinal canal. Three patients (mean age 34.6 years) formed the study group with a mean follow-up period of 24.6 months. Postoperative computed tomography (CT) and lateral radiographs were used to assess results in terms of bony union, canal diameter, and alignment of cervical spine.

RESULTS

All patients noted some improvement in both sensory and motor functions. The average increase in sagittal diameter of cervical spinal canal was 4.2 mm, and decrease in range of motion (ROM) was 13.2 degrees. Bony fusions at the gutters were seen after 6 months.

CONCLUSION

This new technique of cervical laminoplasty is safe, effective, relatively easy, and avoids complications related to free grafts or metallic or nonmetallic foreign materials used in other techniques

[Operative results and prognosis of thoracic spinal stenosis]

OBJECTIVE

To discuss the clinical properties, operative results of thoracic spinal stenosis and factors correlating with prognosis.

METHODS

From September 1992 to January 2001, 16 patients who suffered from thoracic spinal stenosis caused by degeneration, ossified ligamentum flavum, diffuse idiopathic hyperostosis and trauma, were decompressed by operation. The operative method was selected according to the compressed position of spinal cord. All patients were followed up 6 months to 9 years. The pain severity, ambulatory status and paraplegia index were compared between before operation and after operation. The correlation between prognosis and ages, the length of stenosis and the duration of disease was studied.

RESULTS

The results of Wilcoxon Signed Ranks Test show significant difference in pain severity, ambulatory status and paraplegia index between before operation and after operation (P < 0.01). The results of partial correlation analyzing show that only the duration of disease was correlated with paraplegia index (P < 0.05).

CONCLUSION

Thoracic spinal stenosis frequently develops in the lower-thoracic segments in middle and old aged men. Decompression by operation early can achieve a good clinical result. Duration of disease affects the prognosis.

L5-S1 segment survivorship and clinical outcome analysis after L4-L5 isolated fusion

STUDY DESIGN

A retrospective investigation of the L5-S1 motion segment after an isolated L4-L5 posterior lumbar fusion.

OBJECTIVE

To determine the survivorship of the L5-S1 segment in patients undergoing L4-L5 fusion and to identify the correlation between radiographic degeneration and clinical outcome at this level.

SUMMARY OF BACKGROUND DATA

There is current controversy regarding future degeneration of the L5-S1 segment following single-segment fusion at L4-L5. There are no long-term studies that look at L5-S1 after L4-L5 fusion to assess the rate of degeneration at this adjacent segment and the functional clinical outcome of the patient.

METHODS

Thirty-two consecutive patients (average age 56.4 years, range 27-77 years) having isolated L4-L5 posterior spinal fusion for instability or stenosis by a single surgeon were included in this study. There were 25 females and 7 males with an average follow-up of 7.3 years (range 2.3-12.4 years). A survivorship analysis was performed to determine the degeneration at the adjacent L5-S1 segment. Radiographs were analyzed for arthritic degeneration at that level. At the time of the L4-L5 index procedure, the L5-S1 disc spaces were graded on a 4-point scale for degeneration. Questionnaires were submitted by mail, and telephone interviews were conducted by one of the authors to determine the current level of patient function.

RESULTS

Of the total 32 patients assessed, 31 (97%) had no evidence of symptomatic degeneration at L5-S1 requiring additional decompression or fusion. One patient had clinical symptoms that required a foraminotomy and laminotomy at L5-S1, but none of the patients required any further fusion. Although there was a trend of progression of the arthritic grade at L5-S1 from preoperative to postoperative examination, there was no correlation between preoperative arthritic grade versus further degeneration. The discs showed progression of degeneration from an average score of 2.28 before surgery to a score of 2.49 after surgery at the last follow-up.

CONCLUSION

There appears to be no need to routinely include the L5-S1 segment when performing a posterior lumbar fusion for patients with instability or stenosis at L4-L5 if no symptoms are attributed to the lumbosacral level. At an average of 7.3 years, there was neither increased symptomatic disc degeneration nor symptoms necessitating the need for an L5-S1 fusion.

Lumbar spinal stenosis: surgical considerations

Spinal stenosis is an acquired or congenital narrowing of the spinal or nerve-root canals. Surgical treatment is often effective. Acquired spinal stenosis most commonly occurs in those with degenerative disk disease and arthritic facets. If the degenerative process stabilizes and there is adequate room to accommodate the neural contents, symptomatic patients become asymptomatic. Residual stability after decompression must be assessed in patients having multilevel decompression. Fusion maybe indicated. In women with osteoporosis coexisting with degenerative scoliosis and spinal stenosis, decompression for concave nerve-root compression and fusion are necessary. Spinal fusion is not indicated in patients with lumbar spinal stenosis having unilateral decompression for lateral stenosis. Patients with central-mixed stenosis may not need fusion. Patients with spinal stenosis after laminectomies and diskectomies had better results when arthrodesis was done in conjunction with repeated decompression. Arthrodesis with instrumentation and decompression is recommended for patients with degenerative spondylolisthesis.

Clinical and psychofunctional measures of conservative decompression surgery for lumbar spinal stenosis: a prospective cohort study

Less invasive decompressive surgery has emerged as a logical surgical treatment alternative to wide decompression of spinal stenosis. The clinical outcomes of such conservative surgical treatment, however, are not well known. The aim of the study was to evaluate short-term psychometric and functional outcomes after conservative decompressive surgery for lumbar canal stenosis. Forty patients had a lumbar laminectomy procedure, which preserved the integrity of the neural arches, facet joints and most muscle attachments. Pre-operative clinical evaluation of the patients included: Waddell's non-organic signs (NOS) performed by an independent surgeon observer; three self-report questionnaires--the Waddell Disability Index (WDI), the Oswestry Low Back Pain Disability Questionnaire (ODI), and the Low Back Outcome Score (LBOS); and a general questionnaire that included a visual analog pain intensity scale (VAS). Post-operative clinical evaluations and questionnaires were obtained in 36 subjects (mean age 59.8 years) after a 1.7-year follow-up (range 1-2.6 years). Pre-operative versus post-operative statistical comparisons of the data were performed using adjusted error rates within families of predictors. Successful surgical outcome was defined as an improvement in at least three of the following four criteria: self-reported pain on a VAS, self-reported functional status measured by LBOS, reduction of pain during walking and reduction of leg pain. At follow-up, there was a statistically significant improvement in VAS pain intensity, ODI, WDI, and LBOS. Patients classified as having mixed stenosis had a higher incidence of continuous pain symptoms in comparison with acquired stenosis, but there was no differential improvement with treatment depending upon stenosis classification and/or number of operative levels. Overall, 58% (21/36) of patients met the successful surgical outcome criteria, including 14 subjects who met all four success criteria. Based upon a stringent definition of successful surgical outcome, the results of a conservative laminectomy were as good as those of more aggressive decompressive procedures presented in the literature. Our findings indicate that, even in a highly organic disorder such as spinal stenosis, illness behavior plays an important role in predicting surgical outcome.

Impact of somatosensory evoked potential monitoring on cervical surgery

Controversy still exists about the necessity of somatosensory evoked potential (SSEP) monitoring during cervical surgery. The purpose of this prospective study is to determine the impact of SSEP monitoring on anterior cervical surgery. Intraoperative SSEP monitoring was performed in 100 patients treated by an anterior cervical approach. The patients were divided into three groups according to their preoperative clinical condition. Somatosensory evoked potential monitoring was performed during five stages of the procedure: M1, after the induction of anesthesia; M2, during positioning; M3, during distraction of the intervertebral space; M4, throughout decompression; and M5, during graft placement. Normal SSEPs were obtained during M1 from all the patients in group 2. Pathologic SSEPs were recorded at M1 in 45 patients from group 1. No SSEPs were recorded at M1 in six patients in group 3. A deterioration of the SSEPs was observed in 35 patients during M2. Deteriorated SSEPs were observed during M3 in 14 patients. No deterioration of the SSEPs was recorded during M4. Intraoperative SSEP monitoring is easy to perform and helps to increase safety during anterior cervical surgery. Critical phases of the surgical procedure were identified and the surgical strategy was modified as a result of this study.

Differential diagnostics in patients with mild lumbar spinal stenosis: the contributions and limits of various tests

Lumbar spinal stenosis (LSS) and diabetic polyneuropathy are common ailments of older age. Many people suffer from both at the same time. In such patients it may sometimes be difficult to separate signs and symptoms that could be attributed to either disease. This study evaluates the contributions and limits of various tests, especially the exercise treadmill test (ETT) and electrophysiological examination, in the diagnostics of patients with mild LSS. Twenty-nine patients with mild LSS documented by computed tomography (CT) participated in this study. Sixteen of the patients had neurogenic claudication (LSS NC+), and 13 patients did not (LSS NC-). Patients with LSS were compared with a group of 24 patients with diabetic polyneuropathy and 25 healthy volunteers. The distance covered, the time spent walking and the reasons for preliminary termination of the ETT were evaluated in all groups. Initial electrophysiological examination included electromyography (EMG) from the upper and lower extremities and motor evoked potentials (MEPs) to the lower extremities. LSS NC+ patients covered a significantly shorter distance and the time spent walking was significantly shorter than in LSS NC- patients and in the two control groups. The main reason for preliminary termination of the ETT was the development of NC in 67% of the LSS NC+ patients. In contrast, no LSS NC- patient and none from the control groups revealed NC, but 31% of LSS NC- patients were not able to finish the ETT for other reasons (e.g. dyspnoea). Electrophysiological parameters evaluated from the upper extremities distinguished diabetic patients from LSS patients. The latencies of the tibial F-wave, soleus H-reflex and spinal MEP response reliably distinguished healthy volunteers from diabetic patients and LSS patients, and particularly LSS patients from diabetic patients. The chronodispersion of the tibial F-wave distinguished LSS NC+ patients from the other groups. The results of the study show that electrophysiological examination contributes to the differential diagnostics between mild lumbar spinal stenosis and diabetic polyneuropathy. The contribution of electrophysiological methods in verification of NC in LSS patients is limited (chronodispersion of the tibial F-wave only). The ETT is useful in confirmation of NC and walking capacity verification, but restriction of walking capacity should be carefully analysed.

Assessment of trunk function in single and multi-level spinal stenosis: a prospective clinical trial

OBJECTIVE

To clarify the biomechanical indicators of single- and multi-level stenosis and to determine the biomechanical outcome of selective conservative decompression.

DESIGN

This study is a prospective clinical trial examining trunk function in spinal stenosis patients operated using a conservative procedure in an orthopaedic clinic.

BACKGROUND

Although several clinical studies have examined the instability and motion characteristics of operated lumbar spinal canal stenosis, few if any studies have prospectively examined the biomechanical outcome of lumbar spinal canal stenosis surgery.

METHODS

Comprehensive pre- and post-operative trunk dynamometer strength and motion analysis tests were performed on 36 patients operated for lumbar canal stenosis. Surgical treatment efficacy was evaluated within a three variable crossed factorial design considering stenosis classification, number of operative levels, and changes in several trunk biomechanical outcomes from pre- to post-operative assessment. Patients were evaluated after a minimum one-year follow-up.

RESULTS

Pre-operatively there were no differential effects associated with stenosis classification or number of operated levels. There was a significant post-operative increase in isometric trunk extension torque and flexion-extension power and a return to a more normal trunk extension-flexion torque ratio. Patients with mixed, single level stenosis demonstrated greater trunk extension power both pre- and post-operatively compared to other patients.

CONCLUSIONS

Conservative surgical treatment of lumbar spinal stenosis produced a marked improvement in the functional mechanical status of the low back.

RELEVANCE

This study assists clinicians and researchers to understand trunk function following conservative surgical treatment of lumbar spinal stenosis.

Paraspinal muscle denervation, paradoxically good lumbar endurance, and an abnormal flexion-extension cycle in lumbar spinal stenosis

STUDY DESIGN

A descriptive study was conducted to investigate the paraspinal muscle function in patients with lumbar spinal stenosis.

OBJECTIVE

To evaluate paraspinal muscle innervation and endurance in lumbar spinal stenosis.

SUMMARY OF BACKGROUND DATA

Abnormal lumbar paraspinal muscle function is associated with chronic low back pain. Abnormal neurophysiologic findings of the lower limbs often are observed in lumbar spinal stenosis, and abnormal lumbar function also can be expected. However, paraspinal muscle function and innervation have not been studied in lumbar spinal stenosis.

METHODS

The study evaluated 25 patients with clinically and radiologically diagnosed lumbar spinal stenosis. Electromyography of the paraspinal muscles was performed from L3 to S1 bilaterally using a concentric needle. At least 20 insertions were analyzed from each muscle. The aim of the examination was to detect abnormal spontaneous activity associated with axonal damage (fibrillation potentials, positive sharp waves, and complex repetitive discharges). Paraspinal muscle activity during trunk flexion-extension movement and muscle endurance during the dynamic isoinertial back endurance test were assessed by surface electromyography. Muscle fatigue was calculated using mean power frequency analysis.

RESULTS

Abnormal findings in needle electromyography of the paraspinal muscles were observed in 18 of the 22 (81.8%) examined patients. Abnormal flexion-extension activation of the paraspinal muscles was observed in all the examined patients. The change in mean power frequency was significantly smaller than in previously evaluated healthy subjects and patients with nonspecific chronic low back pain (P < 0.001) who were not experiencing symptoms of lumbar spinal stenosis. Paraspinal muscle fatigability was not associated with the denervation of the muscles. CONCLUSIONS Denervation and abnormal activation of lumbar paraspinal muscles are frequent findings in patients with lumbar spinal stenosis who have not undergone surgery. The paraspinal muscle endurance of the patients was unexpectedly good.

Spinal stenosis: history and physical examination

The history and physical examination are an essential component in the assessment of patients with lumbar spinal stenosis. The differential diagnosis is broad, and many conditions may be ruled out with a thorough office evaluation. Peripheral neuropathy, arteriovascular disease, and hip arthrosis are common entities with similar symptoms. Imaging studies provide poor specificity. Clinical decision making should be based on a collection of data, including the history and physical findings, functional status, imaging and electrodiagnostic studies, and other adjunctive studies.

Pathogenesis of lumbar spinal stenosis pain: why does an asymptomatic stenotic patient flare?

This article discusses the pathogenesis of lumbar spinal stenosis pain and presents a theory on why asymptomatic stenotic patients flare.

Dermatomal somatosensory-evoked potentials in the evaluation of lumbosacral spinal stenosis

DSEPs are very useful in determining which patients with degenerative lumbar spine disease have the added component of neurogenic compromise. Based on sound physiologic principles, level-by-level prolongation of DSEP latencies, reduction of amplitude, asymmetry, or a complete absence of response is associated with dysfunction in that particular neurologic pathway. This result does not necessarily correspond to the exact level of stenosis noted on MRI, because the rootlets in the lumbar and sacral regions pass through multiple spinal segments as they course through the spinal canal. Given that LSSS develops typically over time, it is not unlikely that the degree of abnormality will be variable between different levels. The pattern of abnormality will correspond to the physiologic slowing occurring in the multiple rootlets of the cauda equina. These recordings are not easy to perform and interpret; but, when done correctly, they provide the best evidence for the type of neurophysiologic dysfunction in LSSS that responds favorably to surgical decompression.

Electrodiagnostic challenges in the evaluation of lumbar spinal stenosis

Taken together, the most common electromyographic finding in lumbar spinal stenosis is bilateral multilevel radiculopathy. The sensitivity of electrodiagnostic testing for radiculopathy is difficult to quantify because there is no criterion standard. Differentiating peripheral neuropathy and lumbar spinal stenosis on electromyography and routine nerve-conduction studies can be clinically challenging, especially when the two entities may be present simultaneously in older patients.

Functional rehabilitation for degenerative lumbar spinal stenosis

Nonoperative treatment for lumbar spinal stenosis must address anatomic and biomechanical factors. The entire functional kinetic chain and patient specific goals must be considered. In addition to passive modalities, manual therapy, and patient education, an active program consisting of flexion-based lumbar stabilization exercises, hip mobilization, proprioceptive training, and general conditioning should be initiated. More studies are needed to establish the benefit of a comprehensive, multifaceted treatment approach and to prove its clear benefit over the natural history of lumbar spinal stenosis.

Lumbar epidural steroid injections in the patient with lumbar spinal stenosis

Epidural steroid injections seem to be a useful component of a comprehensive and functionally oriented rehabilitation program for the patient with LSS. Review of the literature indicates the injections seem to be effective and are safe when performed with proper technique.

Changes in the microhemodynamics of nerve root retraction in patients with lumbar spinal canal stenosis

STUDY DESIGN

Assessment of qualitative and quantitative changes in the microcirculation of nerve roots, such as the diameter of blood vessels and the low rate of erythrocytes, was observed during lumbar interbody fusion.

OBJECTIVE

To ascertain changes in the microcirculation of nerve roots before and after retraction during lumbar interbody fusion surgery.

SUMMARY OF BACKGROUND DATA

The changes in microhemodynamics caused by nerve root retraction have not yet been elucidated.

METHODS

Subjects were patients with lumbar spinal canal stenosis who underwent lumbar interbody fusion. Changes in the microcirculation of nerve roots were examined in the L5 nerve root in 26 patients and the S1 nerve root in 3 patients. Through the use of video images captured by contact endoscope and stored in a computer, erythrocytes were automatically followed to measure flow rate and the diameter of blood vessels.

RESULTS

Plasma skimming, where blood cells and plasma flow separately, was seen in 3 of the 29 patients (10.3%) before retraction of the nerve root and in 8 of the 29 patients (27.6%) following retraction. Intravascular erythrocyte agglutination, when erythrocytes flow in clumps due to changes in the charge state of erythrocytes, was seen in blood vessels larger than 100 microm in 3 patients (10.3%) after retraction. Following nerve root retraction, the flow rate of erythrocytes through blood vessels decreased an average of 23.9% (P< 0.005).

CONCLUSIONS

A contact endoscope was used to observe the microhemodynamics of nerve roots before and after retraction of the nerve root during lumbar interbody fusion surgery, and a decrease in the flow rate of erythrocytes was observed.

Postoperative outcome of lumbar spinal canal stenosis after fenestration: correlation with changes in intradural and extradural tube on magnetic resonance imaging

PURPOSE

To evaluate the serial changes in clinical results and the intradural and extradural spaces on magnetic resonance imaging (MRI) after bilateral fenestration in 48 patients with lumbar spinal canal stenosis (LSCS).

METHODS

A prospective interventional study was performed to study the clinical results, magnetic resonance imaging scans among patients who were followed up for more than 3 years.

RESULTS

All patients showed improvement in clinical symptoms after operation, but clinical results deteriorated in 9 (19%) patients. Postoperative MRI scans showed that poor dural tube expansion, grouping of the cauda equina, and decrease in the cross-sectional area of the dural tube were factors associated with poor outcomes. The cross-sectional area of the dural tube and images of the cauda equina observed by MRI, before and after fenestration and during follow-up, reflected changes in clinical symptoms involving decompressed segments.

CONCLUSION

Serial changes in the cross-sectional area of the dural tube and images of the cauda equina observed preoperatively, postoperatively, and on follow-up by MRI may be useful when evaluating patients' condition before and after operation. It is also useful for predicting outcomes.

Gait analysis of patients with neurogenic intermittent claudication

STUDY DESIGN

The gait of patients with neurogenic intermittent claudication was analyzed before and after surgery using a ground reaction force plate.

OBJECTIVES

To analyze the gait characteristics of patients with neurogenic intermittent claudication, to evaluate quantitatively their gait improvement after surgical treatment, and to examine the differences in gait characteristics and postoperative improvement among different types of neuropathy.

SUMMARY OF BACKGROUND DATA

A number of reports have been published on the pathophysiology or treatment of neurogenic intermittent claudication. However, almost no detailed reports exist on the gait abnormalities associated with this condition.

METHODS

The subjects were 60 lumbar canal stenosis patients with intermittent claudication who underwent surgery at the authors' hospital. A ground reaction force plate was used for the analysis, and factors related to time and distance (speed, stride, interval, and pitch) were analyzed, as well as factors related to the style of walking (symmetry, reappearance, smoothness, sway, rhythm, and impact).

RESULTS

Before surgery, there were abnormalities of various factors related to the style of walking soon after the patients began to walk. Gait analysis also showed that the pattern of gait abnormality and its improvement after surgery varied depending on the type of neuropathy.

CONCLUSIONS

Gait analysis permits objective and quantitative evaluation of the gait characteristics of patients with lumbar canal stenosis and is useful for evaluating responses to surgical treatment in these patients.

Reversible prolongation of motor conduction time after transcranial magnetic brain stimulation after neurogenic claudication in spinal stenosis

STUDY DESIGN

A consecutive and controlled cohort study.

OBJECTIVES

To assess the value of motor conduction time (MCT) between cortex and symptomatic leg muscles after transcranial magnetic brain stimulation as an indicator of reversible root ischemia in patients with neurogenic claudication in spinal stenosis.

SUMMARY OF BACKGROUND DATA

Neurogenic claudication in spinal stenosis is thought to result from transient ischemia of active nerve root fibers. Subgroups of these patients have slowing of sensory or motor nerve root conduction during spinal claudication.

MATERIAL AND METHODS

Forty-two patients with spinal claudication and radiologically confirmed signs of spinal stenosis were consecutively recruited. Motor conduction time was measured before and repetitively after challenge of walking on a treadmill (four stimuli per minute) until disappearance of the symptoms. Data of 30 patients (65 +/- 10 years) with a defined onset of motor-evoked potentials were compared with those of 12 control subjects (62 +/- 12 years).

RESULTS

One minute after treadmill challenge, MCT increased in all 13 patients with signs of an exercise-dependent neurologic deficit by at least 1 msec (mean increase, 1.6 +/- 0.6 msec; < 0.001). Test-retest comparisons in six of these patients revealed good reproducibility of the MCT increase (coefficient of repeatability, 1.24 msec). In contrast, MCTs were unchanged or decreased in all 17 patients without exercise-dependent neurologic deficit ( < 0.01) and in the control subjects ( < 0.05).

CONCLUSIONS

Measurements of MCT before and after treadmill challenge can demonstrate reversible root ischemia in patients with spinal claudication and exercise-dependent deficit of thickly myelinated nerve root fibers.

The natural history of lumbar degenerative spinal stenosis

The purpose of this review is to present current information on the natural course of lumbar spinal stenosis. As the population becomes older this condition is encountered more frequently. The diagnosis accuracy has improved and the number of cases detected is increasing intemationally. Because of the relative unpredictability of surgical treatment, good knowledge of natural evolution and of the predictive factors influencing the course of the disease is crucial. Unfortunately, and in contrast with numerous surgical series few studies have dealt with natural evolution. In addition to anecdotal reports, a few non randomized studies will be reviewed. Only one randomized study has compared shortand long term results of medical versus surgical treatment. Most of these studies are retrospective, with methodological flaws and are difficult to compare. At the present time no scientifically based recommandations can be made to LSS. patients at diagnosis. Similarly predictors of success of medical and surgical treatment still need to be identified. However results of the studies analyzed in this review suggest that a substantial proportion of patients do not automatically deteriorate and will remain unchanged or even improved by medical means. They also suggest that patients with severe baseline symptoms, block stenosis and degenerative spondylolisthesis tend to require surgical decompression. Randomized studies with the necessary ethical precautions are needed to obtain clear-cut conclusions.

Functional outcome study of patients after surgical decompression for lumbar spinal stenosis: effects of concomitant pathology

The aim of this study is to identify factors associated with poor outcome in the medium (2-5 years) postoperative period following lumbar stenosis surgery. Fifty-six consecutive patients who underwent decompression for lumbar spinal stenosis were retrospectively analyzed using chart and radiologic review, questionnaire using American Association of Orthopaedic Surgeon's MODEM questionnaire containing disability, symptoms, and illness rating, as well as Short Form-36 questionnaires. Postoperatively, there was 98% partial or total relief in leg pain, 85% had partial or total relief in back pain, and 69% had partial or total recovery of neurologic deficit. Functional outcome according to the Short Form-36 was comparable with the age-adjusted population when other comorbidities were taken into account. We found a direct relationship between poor outcome and coexisting medical conditions (p <0.001). Accompanying comorbid conditions have a significant impact on outcome after surgical decompression for lumbar spinal stenosis.

Spinal stenosis vs traumatic spinal cord injury: a rehabilitation outcome comparison

OBJECTIVE

Nontraumatic spinal cord injury (NT/SCI), which can occur secondary to spinal stenosis, has been shown to represent a significant proportion of individuals admitted for SCI rehabilitation. The objective of this study was to compare demographics and outcomes of patients with spinal stenosis-induced SCI (SS/SCI) with those with traumatic spinal cord injury (T/SCI) following inpatient rehabilitation.

DESIGN

This 7-year prospective review compared 81 patients with SS/SCI and 102 patients with T/SCI admitted to an SCI rehabilitation unit with similar levels and completeness of injury. Main outcome measures included rehabilitation hospital length of stay (LOS), Functional Independence Measure (FIM) scores, FIM change, FIM efficiency, rehabilitation charges, and discharge rates to home.

RESULTS

Results indicate that, when compared with the T/SCI, patients with SS/SCI had a significantly (P < .05) higher mean age (64.1 years vs 44.4 years), were more often female (39% vs 20%), and tended to present with paraplegia vs tetraplegia (69% vs 46%) and with motor incomplete SCI vs incomplete SCI (100% vs 49%). When comparing etiologies of SCI within tetraplegic and paraplegic groups, results showed that individuals with tetraplegic SS/SCI had a significantly (P < .05) shorter rehabilitation LOS (25.7 vs 35.9 days), and lower FIM change (24.5 vs 32.5) and FIM efficiency (1.0 vs 1.3); however, no statistical differences were noted for discharge FIM scores and discharge to home rates. Individuals with paraplegic SS/SCI also had significantly lower FIM change (20.2 vs 28.7); however no significant differences were noted for rehabilitation LOS, charges, FIM efficiency, or discharge-to-home rates.

CONCLUSIONS

The findings indicate that patients with SS/SCI present with less severe clinical impairments (motor incomplete and paraplegia) in comparison with patients with T/SCI. Clinically similar SS/SCI groups were noted to achieve rates of functional gain and community discharge comparable with T/SCI patients. Although patients with T/SCI achieved greater overall functional improvement, patients with SS/SCI had shorter rehabilitation LOS and lower rehabilitation charges. These findings have important implications for the interdisciplinary rehabilitation process in the overall management and outcome of individuals with NT/SCI.

Unilateral calf hypertrophy seen in lumbosacral stenosis: case report and review of the literature

STUDY DESIGN

A case report of a patient with neurogenic unilateral calf hypertrophy and review of the literature are reported.

OBJECTIVES

To provide further evidence that S1 radiculopathy is predisposed to develop neurogenic muscle hypertrophy.

SUMMARY OF BACKGROUND DATA

Calf hypertrophy, specifically hypertrophy of the gastrocnemius muscle, is a rare but recognized presentation of S1 and less commonly L5 radiculopathies. The pathophysiology of this is incompletely understood.

METHODS

We present a 59-year-old patient with painless progressive distal right leg weakness and calf enlargement. Electrodiagnostic studies and MAGNETIC RESONANCE IMAGING scanning were performed to evaluate the extent and cause of radicular damage as the etiology for unilateral calf hypertrophy.

RESULTS

Examination and electrodiagnostic studies revealed right L5, right S1, and left L5 radiculopathies. Imaging studies demonstrated lumbar stenosis at L3-L4, L4-L5, and L5-S1 vertebral levels as well as L4-L5 and L5-S1 foraminal stenosis. After decompressive surgery the progressive nature of the patient's symptomatology halted, and he had partial resolution of his deficits.

CONCLUSION

Although the patient had bilateral L5 radiculopathies, he only had hypertrophy in the distribution of his right S1 radiculopathy. This supports the hypothesis that dysfunction of the S1 nerve root or its distribution is a predisposing factor to develop neurogenic muscle hypertrophy. Furthermore, patients presenting with unilateral calf hypertrophy need a careful diagnostic evaluation for S1 radiculopathy as well as to exclude asymmetric presentation of systemic neuromuscular conditions.

The relation among spinal geometry on MRI, paraspinal electromyographic abnormalities, and age in persons referred for electrodiagnostic testing of low back symptoms

STUDY DESIGN

A retrospective EMG study with blinded radiologic measurement was conducted.

OBJECTIVE

To determine the relation among spinal measurements on MRI, paraspinal denervation, and age in patients referred for electrodiagnostic and radiologic evaluation of low back pain.

SUMMARY OF BACKGROUND DATA

Spinal pathology, including disc herniation and spinal stenosis, can cause denervation of the paraspinal muscles. Various mechanisms including direct compression, inflammation, vascular compromise, and mechanical stretch of the posterior primary ramus may play a role in denervation. The relation between the amount of denervation and the size of the spinal canal can assist in understanding the pathophysiology of back pain. Since paraspinal denervation may increase with age in asymptomatic persons, age is an important covariable.

METHODS

At a university hospital, 44 patients referred to undergo both electrodiagnostic evaluation and MRI for low back pain were studied. The study investigated the relation among the following: 1) axial MRI spinal measurements (canal transverse diameter, anteroposterior diameter, and area; thecal sac anteroposterior diameter and area; and the radiologist's overall impression at each level) and denervation measurements in terms of scores on the MiniPM, a quantified needle electromyographic measure of paraspinal denervation; 2) various models of multilevel spinal compression (smallest, smallest two, and average spinal levels for each measurement) and MiniPM scores; and 3) MRI spinal canal measurements and age.

RESULTS

Although individual MRI measurements and combinations of measurements did not relate to MiniPM scores, the radiologist's impression was significantly related. The "smallest two" levels measurement had the strongest relation (r = 0.400; P < 0.007). Age related to the MiniPM scores (P = 0.004) and radiologic impression (P = 0.031). A regression suggested that MiniPM was an independent predictor of age.

CONCLUSIONS

The radiologist's overall impression is more accurate than axial image measurements in predicting paraspinal denervation. A combination score of the smallest two levels is the most accurate, perhaps relating to the vascular pathophysiology of stenosis. There is more denervation with increasing age in this symptomatic population.

Pathophysiology of inflammatory, degenerative, and compressive radiculopathies

In answering the patient's question regarding how treatments are likely to "help [her] herniated disc," the mechanical and chemical components of radiculopathy should be addressed. Focal disc abnormalities often can be observed in those without pain, and symptomatic discs can become asymptomatic. Disc lesions can resolve radiologically with time, and patients' symptoms can improve before their radiographs. The literature reviewed in this article suggests that the best opportunity to offer therapies that address the chemical component of injury might be in those patients with acute disc pathology. In the case of degenerative stenosis, gradually evolving mechanical stressors may comprise the primary component of injury. In other instances, patients with radiographic evidence of neural foraminal or lumbar central stenosis may become symptomatic secondary to a superimposed mechanochemical injury. Such stressors can include a focal disc protrusion, leaking nuclear material from an annular tear, or synovial fluid from an adjacent arthrotic zygapophyseal joint. In these patients, the successful treatment of the acute injury process might allow the affected neural elements to return to their state of accommodation in an environment of gradually evolving mechanical compromise. A growing body of literature has helped clinicians to better understand the mechanisms behind radicular disorders. As spine clinicians, we should strive to educate our patients so that they may become more knowledgeable consumers of spine care. As the components of radicular pathology are elucidated further, new biochemical therapies will likely evolve. Similarly, there will probably always be a subset of patients who will require mechanical decompression, and some of these individuals should be offered such treatment without delay. There may a time in the radicular injury process at which a window of opportunity for treatment begins to close. After this point, any therapy offered will not be as likely to result in a more complete symptomatic response. Patients with chronic radicular pain may have neural structural insults and an increased sensitivity of the somatosensory system. Clinicians should strive to avoid this end stage of neural injury, which is less reversible from a chemical or mechanical standpoint and may respond only to chronic pain management modalities.

Lumbar spinal stenosis, cauda equina syndrome, and multiple lumbosacral radiculopathies

Narrowing of the vertebral canal, the lateral recess, or the neural foramina causes lumbar spinal stenosis. Stenosis results from degenerative changes that usually are superimposed on a congenitally narrowed spinal canal and can result in significant pain and disability, especially in the elderly. Signs and symptoms are related to the compression of neural and vascular elements from the limited canal space. The article reviews the anatomy and pathophysiology, clinical syndrome, diagnostic workup, and natural history of lumbar spinal stenosis to aid in proper diagnosis and treatment.

The effects of OP-1206 alpha-CD on walking dysfunction in the rat neuropathic intermittent claudication model

IV prostaglandin E1 improves clinical symptoms in patients with spinal canal stenosis. In the present study, we assessed the effects of OP-1206 alpha-CD, an orally active prostaglandin E1 analog, on walking dysfunction in the rat neuropathic intermittent claudication model. To induce spinal stenosis, two pieces of silicon rubber were placed in the lumbar (L4-6) epidural space in rats. Postsurgical walking function was measured using a treadmill apparatus. Spinal cord blood flow (SCBF) and skin blood flow (SKBF) were measured using a laser-Doppler flowmeter. OP-1206 alpha-CD was administered orally bid for 11 days from postoperative Day 3. In Control nontreated rats, a significant walking dysfunction was observed from Day 1 after the induction of spinal stenosis and persisted for 14 days when compared with the Sham-Operated group. On postoperative Day 15, SCBF revealed a significant reduction in the territory of spinal stenosis, although SKBF was not affected. OP-1206 alpha-CD significantly improved walking dysfunction on postoperative Days 5 (300 microg/kg), 7 (150 and 300 microg/kg), and 14 (150 and 300 microg/kg) when compared with the Vehicle-Treated group. On postoperative Day 15, the decrease in SCBF was significantly (150 and 300 microg/kg) improved by OP-1206 alpha-CD treatment, albeit SKBF remained unaffected. These data show that oral treatment with OP-1206 alpha-CD is effective in improving walking dysfunction induced by spinal canal stenosis, and this therapeutic effect is likely mediated by improved SCBF at the territory of spinal stenosis.

IMPLICATIONS

Intermittent motor dysfunction is a clinical symptom associated with partial spinal compression. The present study provides evidence that oral treatment with the prostaglandin E1 analog (OP-1206 alpha-CD) is effective in improving motor dysfunction and spinal cord blood flow in rats with spinal compression.