Use of cluster analysis to validate IHS diagnostic criteria for migraine and tension-type headache.

Cluster analysis was used to validate headache diagnostic criteria of the International Headache Society (IHS). Structured diagnostic interviews were conducted on 443 headache sufferers from a community sample, which was randomly split to allow replication. Hierarchical cluster analysis of symptoms in both subsamples revealed two distinct (P<.001) clusters: (1) unilateral pulsating pain, pain aggravated by activity, and photophobia and phonophobia, and (2) bilateral pressing/tightening pain, mild to moderate intensity, and absence of nausea/vomiting. These clusters were consistent with IHS migraine and tension-type classifications, respectively. Replication using a non-hierarchical clustering technique, k-means cluster analysis, revealed a migrainelike patient cluster, reflecting more frequent pulsating, unilateral pain; more severe pain; and pain aggravated by activity; nausea, vomiting, photophobia, and phonophobia. A tensionlike patient cluster was also identified, reflecting more frequent pressing/tightening pain, mild to moderate pain, bilateral location, and absence of nausea/vomiting. These patient clusters were consistent across subsamples. International Headache Society diagnoses corresponded with classification based upon statistically derived clusters (P<.001). These results indicate that headache symptoms cluster empirically in a manner consistent with IHS criteria for migraine and tension-type headaches. Criterion overlap problems regarding pain intensity and duration were identified. Overall, these data support migraine and tension-type headache as distinct entities, and provide support for the IHS diagnostic criteria with minor modifications.

Neuropsychological functioning in migraine headache, nonheadache chronic pain, and mild traumatic brain injury patients.

There are conflicting reports in the literature concerning the neuropsychological functioning of migraine headache patients. The finding in some studies that migraineurs performed more poorly than healthy controls led to the hypothesis that chronic migraine may result in subtle but persistent cerebral dysfunction. Reports describing acute and between-headache neurophysiological disturbances in migraineurs lent support to this hypothesis. To elucidate the cognitive status of these patients, we administered a brief neuropsychological battery to 60 individuals with migraine headache (HA), nonheadache chronic pain (PAIN), or mild traumatic brain injury (MTBI). The PAIN group was included to test the hypothesis that cognitive difficulty in migraineurs might result from the discomfort, depression, medications, etc. often associated with chronic pain, rather than from brain dysfunction. The MTBI patients were considered a useful comparison for the migraineurs because their level of impairment was also expected to be mild, at worst. A MANOVA, with three cognitive index scores as the dependent variables, revealed that the three groups differed significantly. Follow-up contrasts demonstrated that the MTBI group was significantly more impaired on the memory index compared to the HA and PAIN groups, which did not differ from each other. The use of two different normative-based cutoffs to identify individuals who were impaired on the test battery revealed that the frequency of impairment within the two groups of pain patients, but not the MTBI patients, was within normal limits. Thus, the results did not support a link between migraine headache and cognitive impairment.

An examination of the validity of the IHS classification system for migraine and tension-type headache in the college student population.

The validity of the International Headache Society (IHS) classification system for college-aged students with headache was examined using cluster analysis. Undergraduate college student volunteers (N = 369) underwent a structured diagnostic interview for headaches, and the sample was divided into two subsamples for purposes of replication. A hierarchical cluster analysis (Ward's method) of the headache characteristics reported by the first subsample suggested a statistically distinct three-cluster solution, and the solution was replicated using the second subsample. It appeared that one cluster was tensionlike, while the other two were migrainelike. Nonhierarchical cluster analyses (K-means) of the cases from each subsample revealed a similar pattern of a tensionlike and two migrainelike clusters. Identical three-cluster solutions were found for the second subsample both by using cluster centers from the first subsample and by clustering the cases independently, suggesting that the cluster solution was not a random finding. The IHS classification system appears to lack adequate specificity and sensitivity for college-aged students with headache who report migrainelike symptoms. Thus, the generalizability of research results using college-aged students with headache to the adult population may be questionable.

An examination of the psychometric structure of the Multidimensional Pain Inventory.

Factor analyses to create the Multidimensional Pain Inventory (MPI) warrant further examination due to small sample size, the use of separate factor analyses for each MPI section, and lack of evidence for the replicability of the factor model. The present study randomly assigned 972 respondents to one of three samples. Study 1 used data from Sample 1 (n = 452) to examine the replicability of the MPI factor structure reported by Kerns, Turk, and Rudy (1985), and to measure the internal consistencies of MPI scales. In Study 2, confirmatory factor analyses using Sample 2 data (n = 267) verified a revised MPI factor structure that was generated in Study 1; cross-validation was achieved using data from Sample 3 (n = 253). The revised MPI model differed from the original model in its number of scales and pattern of scale loadings. Recommendations for the refinement of the MPI are proposed.

Assessment of lumbar EMG during static and dynamic activity in pain-free normals: implications for muscle scanning protocols.

The purpose of this study was to provide a thorough description of lumbar surface integrated electromyography (EMG) in pain-free normals during a standardized assessment protocol of static isometric and unresisted dynamic tasks. It has been proposed that in pain-free normals, symmetrical tasks that bend the trunk forward or extend the trunk backward produce symmetrical paraspinal EMG activity, and asymmetrical tasks that rotate or laterally bend the trunk produce asymmetrical paraspinal EMG activity. In addition, it has been observed that lumbar EMG assessment during static tasks has been more consistent than tasks involving dynamic activities. Twenty-eight pain-free normals were assessed during symmetrical and asymmetrical tasks in both static and dynamic activities in a counterbalanced manner. The assessment of paraspinal EMG patterns was conducted while subjects were secured in a triaxial dynamometer, which provided standardization of body position and concurrent measurement of torque, range of motion, and velocity. The results provided experimental evidence for the above-stated propositions. An implication derived from this research is that clinicians may be better served utilizing local norms when using EMG for classification purposes.

Assessment of sexual beliefs and information in aging couples with sexual dysfunction.

The incidence and prevalence of sexual dysfunction indicate that a large portion of the U.S. population will experience a sexual dysfunction, with older individuals being particularly at risk. Cognitive factors (e.g., attitudes, misinformation, beliefs) may contribute to the development of sexual dysfunction or influence response to treatments. The purpose of the current study was to evaluate the psychometric properties of a brief instrument designed to assess information and beliefs regarding sexual functioning in an aging population. Results indicate that the Sexual Beliefs and Information Questionnaire (SBIQ) had adequate test-retest reliability and is an internally consistent measure of sexual knowledge and beliefs. MOst individuals had adequate knowledge regarding sexual functioning as indicated by correct responses to most items; however, there were several items missed more often than expected. Exploratory factor analysis suggests an underlying five-factor structure of the SBIQ. Scores were not correlated with years of education, mood, or marital satisfaction. Scores on the SBIQ improved after a brief standardized educational intervention. The SBIQ is a simple and psychometrically sound measure of sexual knowledge and myths that can assist clinicians to identify and possibly rectify knowledge deficits.

The incremental validity of lumbar surface EMG, behavioral observation, and a symptom checklist in the assessment of patients with chronic low-back pain.

This study evaluated the comparative ability of lumbar surface EMG, behavioral observation, and a symptom checklist to correctly classify three groups of participants, (1) 18 patients with chronic low-back pain (CLBP), demonstrating excessive and/or anatomically inconsistent motor, sensory, and tenderness responses during a neurological examination, (2) 33 patients with CLBP exhibiting few or no inconsistent responses, and (3) 30 healthy matched controls. Discriminant analyses were used to develop predictive models. Correct classification rates for the individual assessments and all combinations of assessments were contrasted. Each modality predicted group membership significantly better than weighted chance (23%), with the symptom checklist approach having the highest individual correct classification rate (64%). The best combination of modalities was the symptom checklist and lumbar surface EMG (70% correct classification rate). The sensitivity and specificity of the individual assessments and all combinations of assessments are also presented.