REVIEW For reprint orders, please contact: [email protected]
Interventional therapy for lumbar stenosis
Practice Points
Anthony Chiodo* Evidence for interventional therapy in lumbar stenosis is limited. MRI is not discriminating in the diagnosis of lumbar spinal stenosis. Electromyography has excellent specificity and may help to localize the affected nerve root. Lateral recess and foraminal stenosis are important in electromyography-confirmed radiculopathy. If response to epidural steroids is seen, multiple interventions would likely be necessary due to their
short time of effectiveness. Although a change in pain scores is seen with epidural steroids, change in function or opiate use is not. Lack of response usually portends to similar results from re-injection and should only be considered
under unusual circumstances. Surgical management for patients who fail conservative management improves pain without significant
changes in physical function.
SUMMARY
The clinical syndrome of lumbar stenosis is one where neurophysiological abnormalities better correlate than anatomical ones. However, strategies to impact the disorder are based on improving the anatomical abnormalities seen on advanced imaging. Interventional therapy is one such treatment. However, the literature has fewer controlled prospective trials than clinical series or reviews that support the use of interventional therapy for lumbar stenosis. This review will look at the literature that defines lumbar stenosis and the attempts to show what value interventional therapy has in the management of these patients. Future literature should capitalize on the technology of comparative effectiveness research to better understand how these and newer therapies should best be used in the care of patients with lumbar stenosis. Lumbar spinal stenosis is considered a clinical diagnosis. The hallmark of the diagnosis is the presence of neurogenic claudication, the increase in leg pain that occurs with walking or standing. It is differentiated from vascular claudication in
that leaning forward mitigates the pain. It is also differentiated in that neurogenic claudication leads to radicular distribution of abnormalities on neurological exam, while patients with vascular claudication have vascular changes with
*University of Michigan Health System, Department of Physical Medicine & Rehabilitation, Spine Program, 325 E. Eisenhower Parkway, Ann Arbor, MI 48108, USA; Tel.: +1 734 936 7379; [email protected]
10.2217/PMT.12.23 © 2012 Future Medicine Ltd
Pain Manage. (2012) 2(4), 383–389
part of
ISSN 1758-1869
383
Review Chiodo neurological findings, if present, only seen distally in the most affected limb. Lumbar stenosis commonly has the classic history of pain being relieved when leaning over a grocery cart. As this is most commonly seen in older persons, there are commonly other medical problems that need to be given consideration when considering treatment options. Some patients may have health problems that make them a serious surgery risk. Patients may seek other options to treatment than surgery, concerned about their morbidity risk or not considering the symptoms serious enough to consider surgery, but wanting further treatment due to symptom impact on function. Consideration for interventional therapy for lumbar stenosis has been given very limited attention in the literature. This includes the evaluation of the use of epidural injections, facet injections, or their combination. Although many case studies or series indicate the benefit of injection or aspiration of the facet joint in patients with stenosis from synovial cysts [1] , there are very limited prospective studies on the management of lumbar spinal stenosis with interventional therapy compared with a control group with a long enough follow-up time to assess the longer term impact of the intervention. Lumbar spinal stenosis: MRI versus electromyography A problem in designing a study is operationa l izing the definition of lumbar stenosis. Although the classical clinical presentation as noted above is recognized, ways of using diagnostic testing to define these patients is elusive. One problem is that lumbar spinal stenosis implies narrowing in the spinal canal, with the MRI typically used to define the anatomy. However, the Michigan Lumbar Stenosis Study demonstrated that in predicting the clinical syndrome of lumbar stenosis, MRI findings were not discriminating, but electrodiagnostic findings of limb fibrillation potentials and abnormal paraspinal mapping score were [2] . This was a study of 150 subjects over the age of 50 years in three groups: asymptomatic controls; patients with back pain; and patients with clinical lumbar stenosis. In this study, subjects were evaluated with a codified physical examination by a physiatrist that included a 15-min walk test and 7-day home pedometer reading, a codified electromyography (EMG) of the lower limbs and paraspinal mapping by a board-certified physician blinded from
384
Pain Manage. (2012) 2(4)
the clinical assessment, lumbar MRI scan with neuroradiologist reading and surgical evaluation by a neurosurgeon blinded from the clinical assessment but with knowledge of the MRI and EMG findings. Minimum antero-posterior canal or number of patients with values one or two standard deviations below the mean of the asymptomatic group failed to differentiate the groups. MRI can distinguish patients with clinical lumbar stenosis from patients with back pain, but could not from asymptomatic people, but only if mean values for measurements of canal size on MRI were used. However, trying to use a cut-off score to distinguish these groups, as one would use in a clinical setting, was not possible [2] . Similarly, minimal AP canal size was shown to not be associated with symptoms or functional measures of walking. BMI was the only factor related to walking distance [3] . In the Michigan Lumbar Stenosis Study, 32 asymptomatic controls were as likely to be diagnosed by a blinded neuroradiologist as having stenosis on lumbar MRI scan as patients with symptomatic lumbar spinal stenosis [4] . Similarly, many patients with symptomatic lumbar stenosis were not considered by a blinded neuroradiologist to have lumbar spinal stenosis on MRI. Whether the MRI is not helpful or has limited value if not seen within clinical context is not clear. The value of EMG is clear from the standpoint of specificity, although it lacks the sensitivity desired in clinical practice. The addition of a paraspinal mapping evaluation improves sensitivity [4] . EMG does predict lumbar MRI measurements in patients with lumbar spinal stenosis, primarily by prolongation or disappearance of the fibular F-wave or the soleus H-reflex. The MRI changes that best correlated to these neurological abnormalities were lateral recess stenosis at L4–5 and L5–S1 respectively, foraminal stenosis at L5–S1 for the fibular F-wave, and central stenosis at L4–5. It would certainly make sense to pursue interventions to impact these changes as possible treatment strategies to impact the symptoms of lumbar spinal stenosis [5] . A study by Campbell attempted to look at the critical canal dimension in a retrospective series of patients with lumbar spinal stenosis to predict response to epidural steroids [6] . Using CT scans, transverse canal diameter, transverse osseous canal diameter and mid-sagittal antero-posterior diameter were measured. These are measures of lateral recess and central stenosis. Of the
future science group
Interventional therapy for lumbar stenosis 84 patients seen, 34 improved and 50 required surgical intervention for their symptoms. There were no significant differences in the two groups regarding demographic factors or the presence or absence of back pain, leg pain or impaired walking. These canal measurements did not predict responders from those that required surgery. Some weaknesses of the study included that epidural steroids were done weekly for 3 weeks with an interlaminar approach without fluoroscopic confirmation, and the location of injection was not modified for the location of patient symptoms [6] . There is concern that the lack of fluoroscopic confirmation leaves some doubt as to the accuracy of the data. The concerns are that epidural injection was not successful, or dye flow was not in the location that is consistent with the patient’s symptoms. Fluoroscopic confirmation would have been able to document these findings. In the Michigan Lumbar Stenosis Study, 83 of 126 subjects were retested at 18 months, where it was shown that patients with lumbar spinal stenosis don’t necessarily have a course of continuous progression in symptoms. Among persons with clinically diagnosed stenosis, every measure trended for improvement, including significant changes in pain, ambulation and EMG. Of 32 patients with low back pain, only 16 stayed in that group with 11 clinically rated with stenosis and five rated as asymptomatic. Of the 33 with stenosis, three were asymptomatic, 11 were rated as having mechanical back pain and 18 with stenosis. The subgroup of patients with lumbar stenosis had an improvement in visual analog scale (VAS) score (4.1 to 2.7), Pain Disability Index scores, and in 15‑min ambulation velocity over the 18 month test period. This finding will have a dramatic impact on any study that uses a stenosis group as a control group in a study if the assumption is that a lumbar stenosis control group will either stay the same or get worse. It is clear from the findings of this longitudinal study that this group is changing, and sometimes those changes are improvements [7] . Epidural steroids in lumbar spinal stenosis The evidence of epidural injections as a treatment for radicular pain for lumbar stenosis is minimal, with limited prospective trials of merit and with retrospective studies of significant methodological weakness. It continues to be recommended and considered a treatment option, primarily achieved because of the relative
future science group
Review
safety of the procedure, although the impact of carrying out ineffective procedures on healthcare costs is a relevant concern. A randomized trial comparing physical therapy, fluoroscopicguided inter-laminar epidural injections and no treatment was completed in 33 patients with lumbar spinal stenosis [8] . This was clearly a small sample. No power analysis was offered. Diagnosis was by history, physical examination and MRI (AP diameter
Interventional therapy for lumbar stenosis
Practice Points
Anthony Chiodo* Evidence for interventional therapy in lumbar stenosis is limited. MRI is not discriminating in the diagnosis of lumbar spinal stenosis. Electromyography has excellent specificity and may help to localize the affected nerve root. Lateral recess and foraminal stenosis are important in electromyography-confirmed radiculopathy. If response to epidural steroids is seen, multiple interventions would likely be necessary due to their
short time of effectiveness. Although a change in pain scores is seen with epidural steroids, change in function or opiate use is not. Lack of response usually portends to similar results from re-injection and should only be considered
under unusual circumstances. Surgical management for patients who fail conservative management improves pain without significant
changes in physical function.
SUMMARY
The clinical syndrome of lumbar stenosis is one where neurophysiological abnormalities better correlate than anatomical ones. However, strategies to impact the disorder are based on improving the anatomical abnormalities seen on advanced imaging. Interventional therapy is one such treatment. However, the literature has fewer controlled prospective trials than clinical series or reviews that support the use of interventional therapy for lumbar stenosis. This review will look at the literature that defines lumbar stenosis and the attempts to show what value interventional therapy has in the management of these patients. Future literature should capitalize on the technology of comparative effectiveness research to better understand how these and newer therapies should best be used in the care of patients with lumbar stenosis. Lumbar spinal stenosis is considered a clinical diagnosis. The hallmark of the diagnosis is the presence of neurogenic claudication, the increase in leg pain that occurs with walking or standing. It is differentiated from vascular claudication in
that leaning forward mitigates the pain. It is also differentiated in that neurogenic claudication leads to radicular distribution of abnormalities on neurological exam, while patients with vascular claudication have vascular changes with
*University of Michigan Health System, Department of Physical Medicine & Rehabilitation, Spine Program, 325 E. Eisenhower Parkway, Ann Arbor, MI 48108, USA; Tel.: +1 734 936 7379; [email protected]
10.2217/PMT.12.23 © 2012 Future Medicine Ltd
Pain Manage. (2012) 2(4), 383–389
part of
ISSN 1758-1869
383
Review Chiodo neurological findings, if present, only seen distally in the most affected limb. Lumbar stenosis commonly has the classic history of pain being relieved when leaning over a grocery cart. As this is most commonly seen in older persons, there are commonly other medical problems that need to be given consideration when considering treatment options. Some patients may have health problems that make them a serious surgery risk. Patients may seek other options to treatment than surgery, concerned about their morbidity risk or not considering the symptoms serious enough to consider surgery, but wanting further treatment due to symptom impact on function. Consideration for interventional therapy for lumbar stenosis has been given very limited attention in the literature. This includes the evaluation of the use of epidural injections, facet injections, or their combination. Although many case studies or series indicate the benefit of injection or aspiration of the facet joint in patients with stenosis from synovial cysts [1] , there are very limited prospective studies on the management of lumbar spinal stenosis with interventional therapy compared with a control group with a long enough follow-up time to assess the longer term impact of the intervention. Lumbar spinal stenosis: MRI versus electromyography A problem in designing a study is operationa l izing the definition of lumbar stenosis. Although the classical clinical presentation as noted above is recognized, ways of using diagnostic testing to define these patients is elusive. One problem is that lumbar spinal stenosis implies narrowing in the spinal canal, with the MRI typically used to define the anatomy. However, the Michigan Lumbar Stenosis Study demonstrated that in predicting the clinical syndrome of lumbar stenosis, MRI findings were not discriminating, but electrodiagnostic findings of limb fibrillation potentials and abnormal paraspinal mapping score were [2] . This was a study of 150 subjects over the age of 50 years in three groups: asymptomatic controls; patients with back pain; and patients with clinical lumbar stenosis. In this study, subjects were evaluated with a codified physical examination by a physiatrist that included a 15-min walk test and 7-day home pedometer reading, a codified electromyography (EMG) of the lower limbs and paraspinal mapping by a board-certified physician blinded from
384
Pain Manage. (2012) 2(4)
the clinical assessment, lumbar MRI scan with neuroradiologist reading and surgical evaluation by a neurosurgeon blinded from the clinical assessment but with knowledge of the MRI and EMG findings. Minimum antero-posterior canal or number of patients with values one or two standard deviations below the mean of the asymptomatic group failed to differentiate the groups. MRI can distinguish patients with clinical lumbar stenosis from patients with back pain, but could not from asymptomatic people, but only if mean values for measurements of canal size on MRI were used. However, trying to use a cut-off score to distinguish these groups, as one would use in a clinical setting, was not possible [2] . Similarly, minimal AP canal size was shown to not be associated with symptoms or functional measures of walking. BMI was the only factor related to walking distance [3] . In the Michigan Lumbar Stenosis Study, 32 asymptomatic controls were as likely to be diagnosed by a blinded neuroradiologist as having stenosis on lumbar MRI scan as patients with symptomatic lumbar spinal stenosis [4] . Similarly, many patients with symptomatic lumbar stenosis were not considered by a blinded neuroradiologist to have lumbar spinal stenosis on MRI. Whether the MRI is not helpful or has limited value if not seen within clinical context is not clear. The value of EMG is clear from the standpoint of specificity, although it lacks the sensitivity desired in clinical practice. The addition of a paraspinal mapping evaluation improves sensitivity [4] . EMG does predict lumbar MRI measurements in patients with lumbar spinal stenosis, primarily by prolongation or disappearance of the fibular F-wave or the soleus H-reflex. The MRI changes that best correlated to these neurological abnormalities were lateral recess stenosis at L4–5 and L5–S1 respectively, foraminal stenosis at L5–S1 for the fibular F-wave, and central stenosis at L4–5. It would certainly make sense to pursue interventions to impact these changes as possible treatment strategies to impact the symptoms of lumbar spinal stenosis [5] . A study by Campbell attempted to look at the critical canal dimension in a retrospective series of patients with lumbar spinal stenosis to predict response to epidural steroids [6] . Using CT scans, transverse canal diameter, transverse osseous canal diameter and mid-sagittal antero-posterior diameter were measured. These are measures of lateral recess and central stenosis. Of the
future science group
Interventional therapy for lumbar stenosis 84 patients seen, 34 improved and 50 required surgical intervention for their symptoms. There were no significant differences in the two groups regarding demographic factors or the presence or absence of back pain, leg pain or impaired walking. These canal measurements did not predict responders from those that required surgery. Some weaknesses of the study included that epidural steroids were done weekly for 3 weeks with an interlaminar approach without fluoroscopic confirmation, and the location of injection was not modified for the location of patient symptoms [6] . There is concern that the lack of fluoroscopic confirmation leaves some doubt as to the accuracy of the data. The concerns are that epidural injection was not successful, or dye flow was not in the location that is consistent with the patient’s symptoms. Fluoroscopic confirmation would have been able to document these findings. In the Michigan Lumbar Stenosis Study, 83 of 126 subjects were retested at 18 months, where it was shown that patients with lumbar spinal stenosis don’t necessarily have a course of continuous progression in symptoms. Among persons with clinically diagnosed stenosis, every measure trended for improvement, including significant changes in pain, ambulation and EMG. Of 32 patients with low back pain, only 16 stayed in that group with 11 clinically rated with stenosis and five rated as asymptomatic. Of the 33 with stenosis, three were asymptomatic, 11 were rated as having mechanical back pain and 18 with stenosis. The subgroup of patients with lumbar stenosis had an improvement in visual analog scale (VAS) score (4.1 to 2.7), Pain Disability Index scores, and in 15‑min ambulation velocity over the 18 month test period. This finding will have a dramatic impact on any study that uses a stenosis group as a control group in a study if the assumption is that a lumbar stenosis control group will either stay the same or get worse. It is clear from the findings of this longitudinal study that this group is changing, and sometimes those changes are improvements [7] . Epidural steroids in lumbar spinal stenosis The evidence of epidural injections as a treatment for radicular pain for lumbar stenosis is minimal, with limited prospective trials of merit and with retrospective studies of significant methodological weakness. It continues to be recommended and considered a treatment option, primarily achieved because of the relative
future science group
Review
safety of the procedure, although the impact of carrying out ineffective procedures on healthcare costs is a relevant concern. A randomized trial comparing physical therapy, fluoroscopicguided inter-laminar epidural injections and no treatment was completed in 33 patients with lumbar spinal stenosis [8] . This was clearly a small sample. No power analysis was offered. Diagnosis was by history, physical examination and MRI (AP diameter
