Biomedical subjects
Publications and source records attributed to Paul Enck.
Neurophysiology of the pelvic floor is not completely understood yet. The importance of its symmetry and asymmetry of innervation has been pointed out lately. These facts have the clinical relevance in case of pelvic floor trauma or incontinence surgery. New techniques of EMG are necessary to confirm correlations between symptoms development and asymmetry of sphincter innervation.
Fecal incontinence affects men and women of all ages, leading to personal disability and high financial costs. The evaluation of the patient should clarify the pathophysiology of the symptoms and provide guidance in choosing the appropriate treatment. A comprehensive history and physical examination including endoscopic assessment is able to identify the cause of most cases of fecal incontinence. If necessary, functional methods can be used to confirm the diagnosis. Patient selection for suitable treatment is most important and should be based on clinical and physiologic findings. Conservative dietary or medical treatment is often effective, when the symptoms are mild. Biofeedback therapy is effective in most patients. It has no side effects and is well tolerated. Structural damage to the anus may be repaired by surgery, like sphincter repair, the best treatment of selective sphincter defects. Neoanal sphincters and artificial sphincters are the last possibility after failed surgery and before colostomy. They are less attractive because of technical difficulties and low success rate. A multidisciplinary approach to treatment has the potential to improve the outcome for patients with fecal incontinence.
Anorectal manometry includes a number of specific tests that are helpful in the diagnostic assessment of patients with fecal incontinence and constipation; their purpose is to delineate the pathophysiological mechanism for these symptoms. Some of these tests may also provide helpful information in the assessment of patients with rectal pain or diarrhea, but their sensitivity and specificity are less well established for these symptoms. Tests for which there is consensus regarding their clinical utility include 1) resting anal canal pressure, 2) anal canal squeeze pressure (peak pressure and duration), 3) the rectoanal inhibitory reflex elicited by balloon distension of the rectum, 4) anal canal pressure in response to a cough, 5) anal canal pressure in response to defecatory maneuvers, 6) simulated defecation by means of balloon or radiopaque contrast, 7) compliance of the rectum in response to balloon distension, and 8) sensory thresholds in response to balloon distension. Anal endosonography and pelvic floor electromyography from intra-anal plate electrodes are nonmanometric tests that are also specifically useful in the evaluation of constipation and fecal incontinence. The clinical utility of all anorectal manometric tests is limited by the relative absence of 1) standardization of test protocols and 2) normative data from a large number of healthy individuals. The interpretation of these diagnostic tests is also complicated by the fact that patients are able to compensate for deficits in specific physiological mechanisms maintaining continence and defecation by utilizing other biological and behavioral mechanisms.
The placebo response in medicine and psychology is incompletely understood, and is usually either mystified or down-played; a rational approach to the understanding of the placebo response, however, can be deduced from the scientific literature. We present 3 theories that may explain most of the placebo response in medical and psychological interventions: a) Regression to the mean (RTM): This refers to "errors" in measuring the outcome of therapies, that are due to small samples sizes, global assessment variables, spontaneous variability of symptoms, and other methodological reasons. b) Pavlovian Conditioning (PC): here the placebo response occurs as the consequence of successful association of diagnostic and therapeutic procedures in the past (illness history) of the individuum that resulted in symptom improvement. Neutral stimuli in the context of a treatment can thus gain therapeutic potency (become conditioned stimuli), e. g. the procedure of an injection or the colour of a drug. c) Signal detection theory (SDT): manipulation of expectencies and cognitions of the patient by suggestions and verbal instructions of the health care system will change the willingness of the patient to perceive symptoms as improved/worsened, specifically if this happens under "noisy" circumstances, e. g. with high spontaneous variability of symptoms. All three models are illustrated with examples from medical and psychological treatments or experiments, including recent findings of cortical correlates of the placebo response in functional brain imaging investigations. Potential biological mechanisms for the placebo response are discussed, including the possibility of genetic predisposition to be a placebo responder.
OBJECTIVES: Pre-exposure to an environment in which a nausea-inducing body rotation will subsequently be given constitutes a latent inhibition procedure that might act to reduce anticipatory and postrotation nausea. METHODS: This was tested in 24 healthy subjects randomly assigned to receive no pre-exposure (group 0), a single pre-exposure (group 1), or three pre-exposures (group 3). Rotation was standardized as 5 x 1 minute rotation, but the subjects could terminate it on request. Nausea was determined on a 7-item symptom rating scale before, during, and after rotation on days 3 and 4, whereas anticipatory nausea was measured before presumed rotation on day 5. Saliva cortisol and tumor necrosis factor alpha (TNF-alpha) levels were determined at baseline before, directly, and 15 and 30 minutes after rotation every day, and before presumed rotation on day 5. RESULTS: Pre-exposure significantly reduced the degree of anticipatory nausea on day 5. Cortisol levels increased with rotation and were higher at baseline on days 4 and 5, but subjects habituated from day 3 to day 4; levels were lower in women than in men. In contrast, TNF-alpha decreased with rotation but showed no habituation. For both cortisol and TNF-alpha, no effects on postrotational nausea were found. CONCLUSION: It is concluded that repetitive pre-exposure (latent inhibition) reduces anticipatory but not postrotation nausea; behavioral measures (rotation time) and measures of acute stress (cortisol, TNF-alpha) do not respond to latent inhibition. Thus, Pavlovian conditioning rules are effective in healthy humans with anticipatory nausea but not with postrotation nausea. Hormonal responses--TNF-alpha decrease with stress, compensatory cortisol increase--and gender-related effects on learning and habituation are discussed with regard to psychophysiological and psychoimmunological processes.