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Biomedical subjects

Susan R Mercer

Publications and source records attributed to Susan R Mercer.

8 recordsLinked to original sources
PubMed2005

The lumbar multifidus muscle and patterns of pain.

This paper describes the patterns of pain induced by injecting hypertonic saline into the lumbar multifidus muscle opposite the L5 spinous process in 15 healthy adult volunteers. All subjects experienced local pain while referred pain was reported by 13 subjects in one of two regions of the thigh; anterior (n=5) or posterior (n=8). These results confirm that the multifidus muscle may be a source of local and referred pain. Comparison of these maps with pain maps following stimulation of the L4 medial dorsal rami and L4-5 interspinous ligaments shows that pain arising from the band of multifidus innervated by the L4 dorsal ramus has a segmental distribution. In addition patterns of pain arising from multifidus clearly overlap those reported for other lumbar structures. These findings highlight the difficulty of using pain distribution to accurately identify specific lumbar structures as the source of pain.

Adult↗
PubMed2005

Hamstring muscles: architecture and innervation.

Knowledge of the anatomical organization of the hamstring muscles is necessary to understand their functions, and to assist in the development of accurate clinical and biomechanical models. The hamstring muscles were examined by dissection in six embalmed human lower limbs with the purpose of clarifying their gross morphology. In addition to obtaining evidence for or against anatomical partitioning (as based on muscle architecture and pattern of innervation), data pertaining to architectural parameters such as fascicular length, volume, physiological cross-sectional area, and tendon length were collected. For each muscle, relatively consistent patterns of innervation were identified between specimens, and each was unique with respect to anatomical organization. On the basis of muscle architecture, three regions were identified within semimembranosus. However, this was not completely congruent with the pattern of innervation, as a primary nerve branch supplied only two regions, with the third region receiving a secondary branch. Semitendinosus comprised two distinct partitions arranged in series that were divided by a tendinous inscription. A singular muscle nerve or a primary nerve branch innervated each partition. In the biceps femoris long head the two regions were supplied via a primary nerve branch which divided into two primary branches or split into a series of branches. Being the only muscle to cross a single joint, biceps femoris short head consisted of two distinct regions demarcated by fiber direction, with each innervated by a separate muscle nerve. Architecturally, each muscle differed with respect to parameters such as physiological cross-sectional area, fascicular length and volume, but generally all partitions within an individual muscle were similar in fascicular length. The long proximal and distal tendons of these muscles extended into the muscle bellies thereby forming elongated musculotendinous junctions.

Aged↗
PubMed2004

Effects of exposure on perception of pain expression.

The present study evaluated the effects of exposure to facial expression of pain, on observers' perceptions of pain expression. Thirty-one male and 49 female observers judged 1-s video excerpts in a signal detection paradigm. The excerpts showed facial expressions of shoulder-pain patients displaying no pain or moderate pain. Participants were randomly allocated to one of four groups, which varied in the number of prior exposures of a 1 s display of strong pain. On each test trial, participants indicated whether the test stimulus showed no pain or pain. Data were analyzed using signal detection theory methods. There was a linear relationship between the density of exposure to strong pain and observers' response criteria: greater exposure was associated with more conservative decisions. On average, participants showed very high levels of sensitivity to pain expression, with women significantly outperforming men. Results are discussed in terms of their implications for pain judgments of health care professionals, adaptation-level theory, and the psychophysical method of selective adaptation.

Adaptation, Physiological↗
PubMed2004

Development of sensitivity to facial expression of pain.

The ability to perceive pain in others is an important human capacity. Its development has not been studied. The present study examined the development of sensitivity to evidence of pain from childhood to early adulthood. One hundred and thirty-four males and females from four age groups (5-6, 8-9, 11-12 years and young adult) took part. They judged the amount of pain displayed on videotaped excerpts of the facial expressions of pain patients. Excerpts were selected to display no pain, some pain and strong pain, based on facial measurements, and were displayed to participants in a signal-detection paradigm. All participant groups were more sensitive to evidence of strong than some pain. The ability to detect pain expressions increased across the young, middle and older groups of children, but older children did not differ from adults. Increasing age was generally associated with increasing sensitivity to more subtle facial signs of pain. The results indicate that the ability to perceive pain in others is already significantly developed by the ages of five to six, but refinements in the ability continue through to early adulthood. These findings represent the first description of the development of the ability to perceive pain in others. Important areas for future research into the neurobiological, personal and social determinants of this ability are highlighted.

Adolescent↗
PubMed2003

Clinical anatomy of ligamentum nuchae.

In view of the disparities in the anatomical, clinical, and biomechanical literature this study was undertaken to reappraise the gross anatomy of ligamentum nuchae with the objective of providing an accurate anatomical basis for biomechanical studies and for clinical theories and practices. Ligamentum nuchae was studied by gross dissection in ten embalmed human adult cadavers and was found to be comprised of two structures: a dorsal raphe and a midline fascial septum. The dorsal raphe was formed by the interweaving of the right and left upper trapezius, splenius capitis, and rhomboid minor. It spanned the cervical spine and was firmly attached to the external occipital protuberance and to the spinous process of C7. The fascial septum consisted of dense connective tissue and ran ventrally from the midline raphe to be confluent with the interspinous ligaments and atlanto-axial and atlanto-occipital membranes. These findings agree with those anatomical descriptions that portray ligamentum nuchae as a two-part structure but not with those studies in which it is characterized as a strong ligament attaching to all cervical spinous processes. Importantly, the findings of this study emphasize the need for clinical and biomechanical literature to portray the gross anatomy of ligamentum nuchae accurately.

Adult↗
PubMed1994

Encoding and decoding of pain expressions: a judgement study.

The communication of pain requires a sufferer to encode and transmit the experience and an observer to decode and interpret it. Rosenthal's (1982) model of communication was applied to an analysis of the role of facial expression in the transmission of pain information. Videotapes of patients with shoulder pain undergoing a series of movements of the shoulder were shown to a group of 5 judges. Observers and patients provided ratings of the patients' pain on the same verbal descriptor scales. Analyses addressed relationships among patients' pain reports, observers' judgements of patients' pain and measures of patients' facial expressions based on the Facial Action Coding System. The results indicated that although observers can make coarse distinctions among patients' pain states, they (1) are not especially sensitive, and (2) are likely to systematically downgrade the intensity of patients' suffering. Moreover, observers appear to make insufficient use of information that is available in patients' facial expression. Implications of the findings for pain patients and for training of health-care workers are discussed as are directions for future research.

Adult↗
PubMed1989

Pain expression in patients with shoulder pathology: validity, properties and relationship to sickness impact.

This study dealt with the validity and correlates of facial expressions of pain. Twenty-four patients seeking treatment for gleno-humeral joint pain and 12 controls underwent a standardized physiotherapy assessment protocol involving active and passive arm movements, and experimental pain induced by pressure. Subjects rated pain intensity on each trial using categorical, sensory and affective scales. Independent of testing, they completed a questionnaire measure of sickness impact. Facial behavior was measured by an abbreviated version of the Facial Action Coding System. Facial actions that related to pain indices included eyebrow lowering, narrowing and closing of the eyes, lip pulling, nose wrinkling and mouth opening. Facial actions during clinical tests showed consistent relationships with sensory and affective pain scales. Greater physical disability was associated with more intense pain actions on active, but not passive, tests. The results support the validity and generality of facial measures of pain, show that they yield graded sensitive information and suggest that they encode information about the psychosocial context of pain problems. Theoretical implications of these findings are discussed.

Adult↗