Bruce E. Fredrickson

Chronic pain patients are impaired on an emotional decision-making task

&NA; Chronic pain can result in anxiety, depression and reduced quality of life. However, its effects on cognitive abilities have remained unclear although many studies attempted to psychologically profile chronic pain. We hypothesized that performance on an emotional decision‐making task may be impaired in chronic pain since human brain imaging studies show that brain regions critical for this ability are also involved in chronic pain. Chronic back pain (CBP) patients, chronic complex regional pain syndrome (CRPS) patients, and normal volunteers (matched for age, sex, and education) were studied on the Iowa Gambling Task, a card game developed to study emotional decision‐making. Outcomes on the gambling task were contrasted to performance on other cognitive tasks. The net number of choices made from advantageous decks after subtracting choices made from disadvantageous decks on average was 22.6 in normal subjects (n=26), 13.4 in CBP patients (n=26), and −9.5 in CRPS patients (n=12), indicating poor performance in the patient groups as compared to the normal controls (P<0.004). Only pain intensity assessed during the gambling task was correlated with task outcome and only in CBP patients (r=−0.75, P<0.003). Other cognitive abilities, such as attention, short‐term memory, and general intelligence tested normal in the chronic pain patients. Our evidence indicates that chronic pain is associated with a specific cognitive deficit, which may impact everyday behavior especially in risky, emotionally laden, situations.

Abnormal brain chemistry in chronic back pain: an in vivo proton magnetic resonance spectroscopy study

&NA; The neurobiology of chronic pain, including chronic back pain, is unknown. Structural imaging studies of the spine cannot explain all cases of chronic back pain. Functional brain imaging studies indicate that the brain activation patterns are different between chronic pain patients and normal subjects, and the thalamus, and prefrontal and cingulate cortices are involved in some types of chronic pain. Animal models of chronic pain suggest abnormal spinal cord chemistry. Does chronic pain cause brain chemistry changes? We examined brain chemistry changes in patients with chronic back pain using in vivo single‐ voxel proton magnetic resonance spectroscopy (1H‐MRS). In vivo 1H‐MRS was used to measure relative concentrations of N‐acetyl aspartate, creatine, choline, glutamate, glutamine, &ggr;‐aminobutyric acid, inositol, glucose and lactate in relation to the concentration of creatine. These measurements were performed in six brain regions of nine chronic low back pain patients and 11 normal volunteers. All chronic back pain subjects underwent clinical evaluation and perceptual measures of pain and anxiety. We show that chronic back pain alters the human brain chemistry. Reductions of N‐acetyl aspartate and glucose were demonstrated in the dorsolateral prefrontal cortex. Cingulate, sensorimotor, and other brain regions showed no chemical concentration differences. In chronic back pain, the interrelationship between chemicals within and across brain regions was abnormal, and there was a specific relationship between regional chemicals and perceptual measures of pain and anxiety. These findings provide direct evidence of abnormal brain chemistry in chronic back pain, which may be useful in diagnosis and future development of more effective pharmacological treatments.

A prospective study of psychological predictors of lumbar surgery outcome.

Study Design. Prospective design in which 102 patients were evaluated with a battery of psychological assessment tests 1–2 weeks before surgery, and outcome was assessed 6 months and 1 year after surgery. Objectives. The study examined whether three aspects of psychological distress (depression, anxiety, and hostility) predict several surgical outcomes (employment status, subjective pain change ratings, and changes in functional abilities). Summary of Background Data. Surgery for back pain has been shown to yield poor results in 15–45% of patients. Tools are needed to identify those “at risk” for poor outcome. Aspects of emotional distress, including anxiety, depression, and hostility, have been found to be relevant to various illness outcomes (e.g., cancer, heart disease), but their influence has not been prospectively evaluated for back pain surgical outcome. Methods. Study patients completed measures of distress before surgery, including the Spielberger Trait Anxiety Inventory, Zung Depression Scale, Modified Somatic Perception Questionnaire, and Cook–Medley Hostility Scale. At 1-year follow-up, patients completed pain change ratings, functional abilities measure (Dallas Pain Questionnaire), and questions about employment status. Results. Multivariate regression analyses, controlling for significant demographic variables, found that failure to return to work was predicted by presurgical anxiety (P < 0.001) and depression (P < 0.01); failure to report improvement in pain was predicted by presurgical somatic anxiety (P < 0.01) and depression (P < 0.058); and failure to report improved functional abilities was predicted by presurgical somatic anxiety (P < 0.01) and depression (P < 0.05). Hostility did not predict any outcome. Regression analyses found a strong predictor to be a combination of the Zung Depression Scale and Modified Somatic Perception Questionnaire, known as the Distress and Risk Assessment Method (DRAM). Conclusions. These results indicate that screening for presurgical distress is likely to identify those patients at risk for poor outcome. Studies to evaluate whether presurgical psychological treatment improves outcome are warranted.

The Natural History of Spondylolysis and Spondylolisthesis: 45-year Follow-up Evaluation

Study Design. A prospective study of spondylolysis and spondylolisthesis was initiated in 1955 with a radiographic and clinical study of 500 first-grade children. Objective. To determine the natural history of spondylolysis and spondylolisthesis. Summary of Background Data. Most studies on the natural history of spondylolysis and spondylolisthesis are based on patient populations presenting with pain. Critical to any natural history investigation is the study of a population of affected individuals, whether symptomatic or not, from onset of the condition through their lives. Methods. By study of a population from the age of 6 years to adulthood, 30 individuals were identified to have pars lesions. Data collection at a 45-year follow-up assessment included magnetic resonance imaging, a back pain questionnaire, and the SF-36 Survey. Results. No subject with a pars defect was lost to follow-up evaluation once a lesion was identified. Subjects with unilateral defects never experienced slippage over the course of the study. Progression of spondylolisthesis slowed with each decade. There was no association of slip progression and low back pain. There was no statistically significant difference between the study population SF-36 scores and those of the general population the same age. Conclusions. This report is the only prospective study to document the natural history of spondylolysis and spondylolisthesis from onset through more than 45 years of life in a population unselected for pain. Subjects with pars defects follow a clinical course similar to that of the general population. There appears to be a marked slowing of slip progression with each decade, and no subject has reached a 40% slip.

Four-year follow-up results of lumbar spine arthrodesis using the Bagby and Kuslich lumbar fusion cage.

Study Design. This was a prospective multicenter clinical trial of a lumbar interbody fusion cage with a minimum of 4 years’ follow-up. Objectives. To determine whether the early positive clinical results in fusions with lumbar cages, such as the Bagby and Kuslich (BAK) cage, are maintained beyond 2 years. Summary of Background Data. Threaded cages have been used increasingly for the treatment of symptomatic degenerative intervertebral disc disease. Concerns about the long-term clinical outcomes of this procedure have been posed, particularly regarding bony fusion viability, revision rates, potential adjacent level disease, and late complications. Methods. The study cohort was a 196-patient subset from a prospective investigational device exemption. In addition to early postoperative examinations, these patients were examined biannually with a minimum of 4 years’ follow-up. Patient outcome was assessed by a 6-point scale that evaluated pain relief, and functional improvement was determined by changes in activities of daily living. Fusion rates and return to work were determined. Complications and secondary operations were reported and categorized as non–device related or device related. Results. The patient cohort with 4-year follow-up represented 25.6% of the original study population eligible at that time. Overall, the largest percentage of pain relief and functional improvements occurred by 3 months, and these improvements were maintained at each follow-up. Overall fusion rate was 91.7% and 95.1% at 2 and 4 years, respectively. In this cohort, 39.5% of patients were working or were able to work within 3 months of surgery. After 4 years, 62.7% of patients were gainfully employed or able to work. The late-occurring complication rate in this cohort was 13.8% (27/196). Complications necessitating a second operation occurred in 8.7% (17/196), whereas reoperations that were deemed device related were performed in 3.1% (6/196). Conclusions. This study indicates that the early positive benefits of interbody fusion cage procedures are maintained through 4 years with acceptably low morbidity.

Predictive signs of discogenic lumbar pain on magnetic resonance imaging with discography correlation.

Study Design. The correlation between discogenic lumbar pain and disc morphology was investigated by using magnetic resonance imaging and discography. Objectives. To assess the various pathologic parameters seen on magnetic resonance imaging in patients with discogenic lumbar pain and to correlate them with observations on discography. Summary of Background Data. Although numerous previous studies on the subject have been performed, the correlations between various pathologic findings on magnetic resonance imaging and pain reproduction by provoked discography have not been explained fully. Methods. One hundred and one lumbar discs in 39 patients were studied with magnetic resonance imaging and pain provocation discography. When pain reproduction under discography was concordant, various pathologic parameters on magnetic resonance imaging were analyzed by three statistical parameters to determine the associated magnetic resonance imaging findings. Results. Radial tears commonly are demonstrated on magnetic resonance imaging in discs with concordant pain on discography. The presence of these tears is not a reliable predictor of a painful disc on discography. Although a high‐intensity zone on T2‐weighted images is a relatively reliable predictor of pain, the statistical values were lower than those in previous studies. Massive degeneration and severe disc height loss were rare in this population. These findings were good predictors of pain on disc injection. Conclusions. Although the lumbar intervertebral discs with posterior combined anular tears are likely to produce pain, the validity of these signs for predicting discogenic lumbar pain is limited.

Functional outcome of low lumbar burst fractures. A multicenter review of operative and nonoperative treatment of L3-L5.

STUDY DESIGN A retrospective review of 42 patients treated at three major medical centers for burst fractures of L3, L4, and L5. This is the largest low lumbar (L3-L5) burst fracture study in the literature to date. The study was designed to assess both radiographic and clinical outcomes in a cohort of patients treated during a 16-year period. OBJECTIVES The objective of this study was to determine whether conservatively treated patients with low lumbar burst fractures had satisfactory outcomes compared with those in a surgically treated cohort of patients. The study included patients with and without neurologic deficits. SUMMARY OF BACKGROUND DATA Burst fractures of the low lumbar spine (L3-L5) represent a small percentage of all spine fractures. The iliolumbar ligaments and location below the pelvic brim are two stabilizing factors that are unique to these fractures when compared with burst fractures at the thoracolumbar junction. METHODS Forty-two (n = 42) patients with low lumbar burst fractures were identified from 1980 through 1996. Medical records, radiographs, and follow-up Dallas Pain Questionnaires were obtained. Loss of anterior vertebral height, kyphotic angulation, and amount of retropulsion were recorded at several phases of treatment. Mean follow-up time was 45.2 months (range, 5-132 months). Twenty patients were treated without surgery (18 were neurologically intact, and 2 had isolated nerve root injury), and 22 underwent surgery (14 had neurologic injury, 8 were intact). RESULTS No patient showed neurologic deterioration, regardless of treatment. Fracture of the third lumbar segment showed the greatest tendency toward kyphotic collapse and loss of height in the nonoperative group, although this was not reflected in the final functional outcome of both groups. The ability to return to work and achieve a good-to-excellent long-term result was not significantly different among fracture levels or between surgical and nonsurgical treatments. CONCLUSIONS The results of nonoperative treatment of low lumbar burst fractures were comparable with those of operative treatment. The rate of repeat surgery (41%) and absence of a clearly definable long-term functional or radiographic benefit in patients without neurologic compromise may make surgery less appealing.

Rehabilitation of the patient with chronic back pain: a search for outcome predictors

This prospective study was initiated 3 years ago to evaluate the outcome and to identify predictors of success or failure in patients admitted to a rehabilitation program for chronic low-back pain. Multiple parameters were evaluated, including psychologic data (MMPI, personal interview, pain drawing, etc.), physical measurements (flexibility, strength and endurance), and demographic data concerning the patients home and working environment. Information was available on each patient admitted to the program prior to his admission, at completion of the program, 6 weeks following completion of the program and 3 months following completion of the program. A telephone interview was carried out 2½ years following the patients discharge from the program. Linear regression analysis was used to identify the important independent variables with regard to the dependent variables of relief of back pain, return to work and increased activities at home. Demographic data were of no value as a predictor with the exception of age and returning to work. The patients over the age of 50 returned to work with much less frequency than those less than 50. Psychologic information from the MMPI and similar tests were of no value. The personal preadmission interview of a trained psychologist, however, was a good predictor of an individuals eventual return to work and overall improvement. Workers Compensation and other litigation was a negative factor in a patients prognosis. The treatment teams prognosis at the time of discharge from the program was the best overall predictor of a patients chance of success or failure in the longterm.

Imaging the pain of low back pain: functional magnetic resonance imaging in combination with monitoring subjective pain perception allows the study of clinical pain states

Most brain imaging studies of pain are done using a two-state subtraction design (state-related design). More recently event-related functional magnetic reasonance imaging (fMRI) has also been used for studying pain. Both designs severely limit the application of the technology to clinical pain states. Recently we demonstrated that monitoring time fluctuations of perceived pain could be used with fMRI to identify brain regions involved in conscious, subjective perception of pain. Here we extend the methodology to demonstrate that the same approach can be used to study clinical pain states. Subjects are equipped with a finger-spanning device to continuously rate and log their perceived pain during fMRI data collection. These ratings are convolved with a canonical hemodynamic response function to generate predictor waveforms with which related brain activity can be identified. Chronic low back pain patients and a normal volunteer were used. In one series of fMRI scans the patient simply lies in the scanner and indicates spontaneous fluctuations of the subjective pain. In other fMRI scans, a straight-leg raising procedure is performed to exacerbate the back pain. In the normal volunteer, fMRI scans were done during painful and non-painful straight-leg raisings. The results indicate the feasibility of differentiating between different pain states. We argue that the approach can be generalized to identify brain circuitry underlying diverse clinical pain conditions.

Variability of somatosensory cortical evoked potential monitoring during spinal surgery

The Intraoperatlve variability of somatosensory cortical evoked potentials (SCEPs) has been measured for 320 consecutive spinal surgeries and found to be a function of patient diagnosis, neuromuscular status, age, and procedural factors. In many cases, It is likely that this variability severely limits the reliability and usefulness of spinal cord monitoring in detecting early cord compromise. Patients with Idlopathlc scollosis, spondylolisthesls, and pseudarthrosis have the smallest spontaneous variability and strongest amplitudes, while those with congenital, paralytic scollosis, stenosis, or tumor have very variable, weak SCEPs. Patients with neurologic disorders, particularly cerebral palsy, myelomeningocele, Frledrelchs ataxia, and peripheral deficits, also have high variability and weak amplitudes. A monitoring quality scoring system is proposed that may be useful during surgery In judging how well the SCEPs can discern surgically related changes In cord function from background variations.