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12 Articles in Volume 12, Issue #5
A-Delta Pain Fiber Nerve Conduction Study Benefits Patients With Spinal Pain
Chronic Pain Management of the Noncompliant Patient
Clinical Applications of Radiofrequency Lesioning for Back and Neck Pain
Current Understanding and Management Of Medication-overuse Headache
Fibromyalgia: An Overview of Etiology and Non-pharmaceutical Treatment Options
June 2012 Pain Research Updates
Junk The Term Narcotics—Call Them Opioids
Managing Adverse Drug Effects in Pain: Focus on Muscle Relaxants
Music Therapy for Pain Management
Perioperative Pain Management in the Opioid-tolerant Elderly Patient: Case Challenge
Practical Tips in the Treatment Of Osteoarthritis of the Knee
Sudden, Unexpected Death in Chronic Pain Patients

A-Delta Pain Fiber Nerve Conduction Study Benefits Patients With Spinal Pain

Of 151 pain fiber nerve conduction studies administered to patients with cervical and lumbar spinal pain, 56% changed treatment plans for the patient and 35% confirmed the planned treatment. Additionally, in 8% of patients, the studies changed the side of the patient receiving treatment.
Practical Pain Management is interested in publishing and promoting diagnostic tools to improve pain management. This includes laboratory, written questionnaires, x-rays, electrodiagnostics, and nerve conduction stimulus tests to help determine spinal nerve-root pathology. Results reported here validate the age-old principle of how finding a proper diagnosis before treatment is initiated benefits outcome.

Because spinal pain has many causes, any test that can accurately diagnose the source of pain serves as an invaluable tool for making sure the patient receives the correct treatment. A 2002 study by Cork et al studied the nerve conduction of pain fibers with a device that had 94.6% sensitivity in detecting lumbar nerve-root function pathology as confirmed by epidurograms.1 The basis for this type of testing is the pain fiber nerve conduction study (pfNCS). The pfNCS uses electrical voltage applied at predetermined points that correspond to areas innervated by a specific nerve root2 to determine whether that nerve root has a normal response to the current. A hyperresponse indicates increased sensitivity to the current, while a hyporesponse indicates impaired sensitivity of that nerve root.

Despite the sensitivity of the pfNCS, no prospective clinical studies have been able to demonstrate that the pfNCS improves the management and clinical outcomes of patients with spinal pain any better than other methods. Indeed, the Center for Medicare and Medicaid Services in 2004 concluded that prototype devices (like that used by Cork), which relied on the patient’s psychophysiological assessment (perception of a sensation), were unacceptable for Medicare coverage because, “there continues to be insufficient scientific and clinical evidence to consider the pfNCS test and device used in performing this test as reasonable and necessary.”3

More recently, however, the use of a potentiometer, in conjunction with pfNCS, precisely recorded an objective increase of 20 millivolts or more a second or two before the patient felt a sensation generated by the pfNCS.Thus, theoretically, the pfNCS gives more than just a “psychophysiologic assessment” as to whether a given patient perceives pain.

This study was undertaken to determine the effectiveness of the pfNCS in improving outcomes of patients suffering from cervical and lumbar pain. The pfNCS (performed with a Neural-Scan, PainDX, Inc., Laguna Beach, California) employs a voltage-regulated stimulus in conjunction with a potentiometer, an objective measurement of the amplitude of the action potential.

Evaluating the sensitivity of the test in determining which nerve generates a given patient’s pain, as well as the specificity of that test in reducing the patient’s pain while improving the patient’s function, will demonstrate whether the use of the pfNCS is “reasonable and necessary.”

From August 1, 2008, through July 31, 2009, 151 individual pfNCS electrodiagnostic examinations were performed on 124 patients, who were then followed for at least 1 month after receiving treatment. The patients’ ages, sexes, clinical diagnoses as determined by history, physical findings, x-rays/magnetic resonance imaging/computed tomography scans, and results of the pfNCS were recorded. The pfNCS results demonstrated that a given nerve root had one of six responses: a normal, mild, moderate, marked, severe, or very severe reaction (see box). All patients had their visual analog scale (VAS) and Oswestry Disability Index (ODI) measured and recorded before and after they received treatment. Patient treatment was dependent upon what the pfNCS showed to be causing the patient’s pain.

If the results were normal, the patient underwent conservative treatments including physical therapy, medication, and counseling where indicated. If the results showed mild, moderate, or marked nerve root abnormalities, then diagnostic medial branch facet joint blocks (MBB) were performed at the appropriate level according to International Spine Intervention Society Guidelines,5,6 and medial branch facet rhizotomies were performed when indicated.7,8 If the results showed severe or very severe nerve root abnormalities, then transforaminal lumbar epidural steroid injections (TF/LESI), LESI, or cervical epidural steroid injections (CESI) were performed at the appropriate level. Some patients received other interventional techniques such as sacroiliac (S/I) joint injections, piriformis injections, percutaneous disc decompression (Disc Dekompressors, Stryker, Kalamazoo, Michigan), or vertebroplasties.

Table:  A-Delta Pain Fiber Nerve Conduction Classifcation

The test results were then divided into three categories (Table 1). The treatment selected for a given patient was considered to have “helped” if the patient’s VAS was reduced by at least 2 points or 25% and/or the ODI was less than 40 and improved by at least 25%.9 Overall average changes in the VAS and ODI were evaluated using several different parameters. In addition, the patients were divided into those who had pfNCS of either the lumbar or cervical spinal regions and evaluated according to the treatment given to them and their response to treatment.

Data from 151 pfNCS were analyzed. The average patient age was 56.9 years, with a range of 14 to 94 years; 59 men and 92 women were tested. Of the patients tested, the average decrease in VAS score was 49% and an average functional improvement in the ODI was 44%. When analyzed by category, results of the pfNCS had one of three influences on the treatment patients received: change in the treatment given (56%, n=84); confirmation of what clinical findings recommended as appropriate treatment (35%, n=53); no influence on treatment (9%, n=14).

Of those 84 patients where the pfNCS helped change treatment, 72 tests (86%) helped patients decrease their VAS scores by 75%, on average, and demonstrated approximately 42% improvement in functioning. Of special note are the 12 patients where the pfNCS changed the side that received treatment (8%). None of these 12 patients would have had the correct side of their pain generator treated without the use of the pfNCS. On average, these 12 patients demonstrated an 88% decrease in their VAS and a 54% improvement in function.

As noted, the pfNCS also confirmed what the patient history, physical findings, and diagnostic tests such as plain x-ray films, CT scans, and MRIs suggested should be the appropriate treatment. Of these 53 patients, improvement was seen in 40 patients (75%), while 13 patients (25%) were not helped. The average patient in this group decreased their VAS by 55% and improved their ODI by 55%.

Fourteen of the pfNCS did not influence the treatment a given patient received; 6 patients (43%) were helped anyway and 8 patients (57%) were not helped. On average, those treated in this group had a 42% decrease in VAS and a 27% improvement in ODI.

Table 1: Test Categories for fNCS

Treatment Procedures
The pfNCS resulted in 151 procedures or therapies being evaluated; 40% of all the pfNCS (60) suggested that diagnostic MBBs should be done. These 60 MBBs resulted in 44 medial branch rhizotomies (MBR) being performed while results from 16 of the MBBs did not recommend that an MBR be performed (Table 2). Of the MBBs administered, 12 gave such long-term relief with just the use of local anesthetic that no MBR was needed; 4 of the MBBs failed to indicate that the patient would benefit from an MBR. Patients were helped by 50 (83%) of the diagnostic block procedures while 10 procedures (17%) did not help. The average patient in this group had a 63% decrease in VAS and a 32% improvement in ODI. TF/LESI was suggested by 34% of all pfNCSs (51), which helped 49 patients (78%), but did not help 11 patients (22%). The average patient in this group had a 46% decrease in VAS and a 34% improvement in ODI.

Data from 19 pfNCS (13%) suggested that patients should receive medical therapy. These conservative therapies helped 10 patients (53%) who received them but did not help 9 patients (47%). The average patient in this group had a 38% decrease in VAS and a 26% improvement in ODI.

Table 2: Procedures for pfNCS

Only 9% of all pfNCS (14) resulted in other treatments being given. These procedures included S/I joint injections, piriformis injections, percutaneous Disc Dekompressors, or vertebroplasties. Of these procedures, nine (64%) helped, but five (36%) did not. The average patient in this group had a 65% decrease in VAS and a 34% improvement in ODI. Interlaminar epidural steroid injections were done in 4% of all pfNCS (6), three in the cervical spine and three in the lumbar spine. Three of these procedures (50%) helped and three (50%) did not. The average patient in this group had a 65% decrease in VAS and a 14% improvement in ODI.

Anatomic Location
Of the 151 pfNCS performed, 40 were done for problems in the cervical spine (36%) and 111 for problems in the lumbar spine (64%) (Table 3). In 16 patients who received lumbar pfNCS, various forms of medical therapy were recommended including oral steroids and physical therapy, which helped 10 patients (63%). Other forms of interventional treatments including S/I joint injections, piriformis injections, percutaneous Disc Dekompressor procedures, and vertebroplasties, were administered for 11 patients; seven of these procedures helped (64%).

Table 3 Cervical vs Lumbar pfNCS Tests

The use of pfNCS in this series showed that more than half (56%) of the tests performed changed the treatment planned for the patient, approximately one third (35%) confirmed the planned treatment, and less than one tenth (9%) did not influence the treatment. The pfNCS changed the planned therapy due to several factors. The test demonstrated which level generated the patient’s pain when the MRI showed “multilevel degenerative disc and facet changes,” and also changed the diagnosis of the pain generator from the disc to the facet or vice versa.

Additionally, the pfNCS determined the best therapy for the patient, and confirmed in 12 patients that the generator of a patient’s pain was located on the opposite side of the patient’s body. This last finding was very significant.

The data in this study offer clear and convincing “scientific and clinical evidence to consider the pfNCS electrodiagnostic examinations” as both a “reasonable and necessary” aid in helping all who wish to practice scientific and effective pain medicine.

If other studies confirm these findings, then an important diagnostic tool will be available to greatly improve the surgical, interventional, and medical treatment of spinal pain.

Last updated on: September 25, 2012
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