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PubMed1994

The trigger for rectal filling sensation.

In order to evaluate whether rectal volume, weight or pressure is the main trigger for rectal sensation, their respective values were determined at each of the rectal filling sensation thresholds (first, constant, urge, maximum) in 12 adult control subjects. The rectal balloon was filled at 60 ml/min in sitting position using water (twice), air and mercury consecutively. Pressure values were corrected for the elastic properties of the balloon, while the volume of inflated air was recalculated taking into account the prevalent rectal pressure and temperature. The results obtained using water, air and mercury demonstrated a constant relationship between a given rectal sensation level and the pressure recorded in the distending balloon, but not its volume or weight. Pressure values recorded at each sensation level were constant during repeated determinations of rectal sensation, the volume of rectal distension increased, probably because the rectum had already been dilated by previous testing. Balloon distension using air with the patient in the lateral position were found to be most practical for routine evaluation of rectal sensation. It is therefore concluded that any disturbance of rectal sensation will be reflected by changes in pressure and not by changes in the volume needed to produce a given sensation level. The location of the receptors involved has to be elucidated, but it seems that the pelvic floor can be excluded since the weight of the rectal contents was not related to sensation.

Adult↗
PubMed2002

Combined radiologic and manometric study of rectal filling sensation.

PURPOSE: Sensation is an essential aspect of fecal continence. We aimed to correlate manovolumetric and radiologic changes at successive levels of rectal filling sensation. METHODS: Combined anorectal manometry and proctography were performed in nine volunteers. Images, volumes, and pressures were analyzed at the start of the test, at 20 seconds before first sensation, and at first, constant, urge, and maximum tolerable sensation. RESULTS: Consecutive levels of rectal filling sensation were associated with progressive opening and dilation of the upper anal canal (up to 44 mm) and sliding down of the rectal contents (14 mm), which had already started before the first sensation. This coincided initially with a pressure decrease in the proximal anal canal (from 94 to 42 mmHg). With constant sensation and particularly with urge sensation, rectal pressure increase appeared to be responsible for further proximal anal dilation. This was accompanied by a significant increase of proximal anal pressure (up to 133 mmHg) and sharpening of the angle between the anal axis and the horizontal reference line. CONCLUSION: The proximal anal canal or its surrounding structures play an important role in the desire-to-defecate sensation. They can be activated by a progressive buildup of rectal reservoir pressure in the presence of a competent distal anal sphincter barrier.

Adult↗
PubMed2007

Sonographic characteristics of rectal sensations in healthy females.

PURPOSE: This study was designed to characterize rectal sensations by visualizing the internal and external anal sphincter and intra-anal transport of bolus during elicited rectal sensations. METHODS: The anal canal was visualized with real-time transperineal ultrasonography in 13 healthy female volunteers. Rectal sensations were elicited by injecting water into the rectum. The ultrasound images were recorded on a videotape and analyzed offline. RESULTS: The median time between an injection of water and the events studied was calculated in 105 rectal sensations. A relaxation in the internal anal sphincter (4 seconds after the injection of water), an antegrade transport of bolus (4 seconds) into the anal canal, and a contraction in the external anal sphincter (5 seconds) were observed before a sensation (6 seconds) was reported. The antegrade flow continued until the distal internal anal sphincter contracted (18 seconds) and the bolus moved in a retrograde transport direction (17 seconds) thereafter the sensation disappeared (18 seconds) and the external anal sphincter relaxed (22 seconds). A significant correlation in time between the end of the sensation, contraction in the internal anal sphincter, reversed flow of anal contents, and relaxation of the external anal sphincter was found (Pearson, P<0.01). CONCLUSIONS: The results verified that the internal anal sphincter contributes to the perception of rectal sensations by a relaxation allowing intra-anal bolus to increase the pressure on the anoderm during rectal contraction. A new observation is presented on the time relation between contraction in the distal internal anal sphincter, reversed flow in the anal canal, and the end of rectal sensations.

Adult↗
PubMed1982

Paradoxical heat sensations during moderate cooling of the skin.

Paradoxical heat sensations during cooling of the skin were examined in two experiments. In Expt. I the number of occurrences of sensation was studied in 19 naive test subjects (Ss) when cooling from thermal indifference both without and with preceding heating. Without preceding heating 13 Ss reported sensations of paradoxical heat (9.8% of all stimulations). Preheating markedly facilitated the occurrence of the sensations (35% of all stimulations). In Expt. II the effects of cooling velocity (velocities 0.4, 0.7 and 2.0 degrees C/s) and the type of skin area stimulated (hairy or glabrous skin of the hand) on the thresholds of paradoxical sensations were studied in 4 Ss without and with preheating. Cooling velocity, type of skin area and preheating had significant effects on the sensation thresholds, the thresholds being the higher (i.e. the sensation appearing at lower stimulation temperatures) the higher the cooling velocity, if the stimuli were applied to the glabrous skin, or if no preheating was used. The results confirm the existence of paradoxical heat sensations during cooling of the skin and suggest that the sensation is mediated by polymodal units supplied by C-fibers.

Adult↗
PubMed2006

Thermal and nociceptive sensations from menthol and their suppression by dynamic contact.

It was recently found that cooling the skin to temperatures as mild as 25-30 degrees C can induce nociceptive sensations (burning, stinging or pricking) that are strongly suppressed by dynamic contact between the thermode and skin (contact suppression). Here we investigated whether nociceptive sensations produced by menthol can be similarly suppressed. In the first experiment subjects rated the intensity of cold and burning/stinging/pricking sensations before and after application of 10% l-menthol to the forearm. Ratings were compared at resting skin temperature ( approximately 33 degrees C) and at 28, 24, or 20 degrees C during static or dynamic contact cooling via a Peltier thermode. At resting skin temperature, menthol produced cold and nociceptive sensations, both of which were suppressed by dynamic contact. When the skin was cooled during static contact, menthol increased nociceptive sensations but not cold sensations; when the skin was cooled during dynamic contact, cold sensations were again unchanged while nociceptive sensations were suppressed. A second experiment tested whether contact suppression of menthol's cold and nociceptive sensations at resting skin temperature was caused by slight deviations of thermode temperature above skin temperature. The results showed that suppression occurred even when the thermode was slightly cooler (-0.5 degrees C) than the skin. These findings support other evidence that the menthol-sensitive channel, TRPM8, plays a role in cold nociception, and raise new questions about how dynamic tactile stimulation may modify perception of nonpainful cold stimulation.

Adolescent↗
PubMed2005

Does hysterectomy affect genital sensation?

OBJECTIVES: To evaluate vaginal and clitoral sensation before and after hysterectomy and to assess pre- and post-surgery changes in sexual function. STUDY DESIGN: Quantitative sensory thresholds for warm, cold, and vibratory sensations were measured at the vagina and clitoris 1 day prior to and 3 months following surgery. A survey was performed 18 months following operation to evaluate long-term changes in sexual function. PARTICIPANTS: Twenty-seven women, aged 30-57 years, who were admitted for elective hysterectomy. MAIN OUTCOME MEASURES: Genital sensation and reported sexual function. RESULTS: There was significant deterioration in sensation to cold and warm stimuli at the anterior and posterior vaginal wall after surgery. Vaginal vibratory sensation thresholds tended to increase. Clitoral thermal and vibratory sensation thresholds remained unchanged before and after surgery. Of the 22 patients who participated in the follow-up survey, 17 did not report any decline in sexual function, while 4 patients reported deterioration in genital sensation and in sexual function. CONCLUSION: The results demonstrate quantifiable sensory loss in the vagina after hysterectomy, with preservation of clitoral sensation. Only a minority of patients reported a decline in their sexual function. These findings highlight the relative importance of clitoral as compared to vaginal sensation in sexual function.

Adult↗
PubMed2002

Noxious cold evokes multiple sensations with distinct time courses.

A noxious cold stimulus can evoke multiple sensations each occurring with a different time course. We have performed psychophysical studies to identify the time course of five sensations evoked by a noxious cold stimulus applied to the hand. Subjects continuously rated either pain, ache, cold, heat or prickle sensations throughout repeated presentations of a noxious cold stimulus (3 degrees C) from a neutral (32 degrees C) baseline. Separate runs were used to assess each of the five types of sensation. Cold was reported throughout the period of cooling. The time course of pain and ache sensations were similar. However, prickle and heat sensations had time courses that could be distinguished from each other, and from ache and pain. Identification of these temporal profiles could provide clues to their underlying mechanisms. The temporal dissociation of these sensations will also enable neuroimaging studies of the cortical mechanisms associated with these sensations. Thus our results constitute a first step toward identifying the distinct modes of neural activity associated with different types of pain sensation.

Adult↗
PubMed2001

A prospective quantitative comparison of breast sensation after superior and inferior pedicle mammaplasty.

Reduction mammaplasty techniques using the inferior pedicle have been recommended to preserve the nipple and areolar sensation after surgery. The vertical scar mammaplasty with a superior pedicle has often been criticised because of the potential for damage to the sensory supply of the nipple-areola complex. The aim of this study was to assess the breast sensation in two prospective series of patients operated upon using superior pedicle and inferior pedicle mammaplasties. Between November 1996 and February 1997, 20 consecutive patients (39 breasts) underwent breast reduction using the inferior pedicle technique with inverted T scar (Robbin's technique). This series of patients was matched with another series of 18 patients (36 breasts) who had breast reduction using a vertical scar mammaplasty with superior pedicle (Lejour's technique) in another centre. Cutaneous pressure thresholds were recorded using Semmes-Weinstein monofilaments. The values were obtained on the quadrants of the skin of the breast, the areola and the nipple. The sensitivity test was performed preoperatively, then at 3 and 6 months postoperatively. Patients' characteristics (age, weight, breast ptosis, breast mass resected and risk factors) were statistically similar between the two groups. The preoperative values of pressure sensation on the different areas tested were statistically similar between the two groups. The sensitivity decreased on almost all the tested areas of the breast at 3 months postoperatively. No patient had an insensitive area on the breast at 6 months after surgery. Some areas of the breast showed a significant difference in pressure sensitivity after one technique compared to the other: better sensation on the skin of the superior and lateral quadrants after the superior pedicle technique at 3 months (P< 0.001), poorer areolar sensation on the inferior quadrant after the superior pedicle technique at 3 and 6 months (P< 0.05) and on the superior quadrant after the inferior pedicle technique at 3 months only (P< 0.05). However, the mean value of the areolar quadrants was statistically similar after both techniques. The nipple sensation was significantly decreased in both groups at 3 months but remained comparable between the two groups. Breast innervation was damaged by breast reduction using both the inferior and the superior pedicle techniques. The breast skin had better sensation after the superior pedicle technique while the areola had slightly better sensation after the inferior pedicle technique. At 6 months, the mean value of nipple-areola complex pressure sensation was comparable in the two series of patients.

Adult↗
PubMed1999

Sensation recovery on innervated radial forearm flap for hemiglossectomy reconstruction by using different recipient nerves.

The objectives of this study were (1) to determine the extent of sensory recovery on hemitongues reconstructed with innervated radial forearm flaps and (2) to assess the influence of various clinical and surgical factors over the return of sensation, including the use of different recipient nerves for neurorrhaphy. Twenty-eight patients with tongue cancer who underwent hemiglossectomy and primary reconstruction with innervated radial forearm flaps over a 3-year period were studied. Mean postoperative follow-up was 18.2 months (range 6 to 32 months). Sensory recovery was assessed in a blind manner by two examiners that used (1) static two-point discrimination, (2) light touch sensation, (3) pain perception, and (4) hot and cold temperature perception. Different surfaces were assessed with each method on the reconstructed hemitongue and on the intact contralateral hemitongue (used as control). The following factors and their relationship with flap sensory recovery were analyzed: age, smoking history, size of the reconstructed defect, administration of postoperative radiation therapy, recipient nerve, and neurorrhaphy technique. Comparative statistical analysis (p < 0.05) between both hemitongues was performed using paired t test followed by Bonferroni correction for static two-point discrimination and light touch sensation. Fisher exact test analysis was used for pinprick and hot and cold temperature perception. The control side was ignored in analyzing the effects of the risk factors. The tip, dorsal aspect, ventral surface, and floor of mouth on the reconstructed hemitongue had comparable static two-point discrimination when compared with the intact hemitongue. Light touch sensation was also similar in the tip and dorsal aspect of both hemitongues; however, a statistically significant difference (p < 0.05) was observed on the ventral surface and floor of mouth of the reconstructed hemitongues. Likewise, pain perception was significantly decreased in the floor of the mouth, compared with other surfaces. No clearly dependent association was established between return of flap sensation and age, tobacco use, and size of the reconstructed defect. Light touch sensation, pain, and temperature perception were significantly decreased when the patients had received postoperative radiation therapy. In addition, all four sensory tests were significantly diminished (p < 0.05) when the recipient nerve used for neurorrhaphy was a nerve other than the lingual or the inferior alveolar nerve, and also when an end-to-side nerve repair was used. Sensation recovery of the innervated radial forearm flap after hemitongue reconstruction approaches normal compared with the contralateral intact hemitongue. Lower return of sensation may be anticipated in patients who receive postoperative radiotherapy. Good recovery of sensation is predictable when either the lingual or inferior alveolar nerve is used for neurorrhaphy, in contrast to using other recipient nerves.

Adult↗
PubMed2001

Changes in respiratory sensations induced by lobeline after human bilateral lung transplantation.

1. The sensations evoked by the injection of lobeline into the right antecubital vein were studied in 8 subjects after bilateral lung transplantation and 10 control subjects. In control subjects, two distinct sensations were experienced. There was an early noxious sensation (onset approximately 10 s) followed by a late sensation of breathlessness (onset approximately 26 s) associated with involuntary hyperventilation. The early sensation was accompanied by respiratory and cardiovascular changes. 2. In contrast to control subjects, the early respiratory events and the noxious sensations evoked by injections of lobeline (18-60 microg kg(-1)) did not occur in subjects with recent bilateral lung transplantation. This suggests that the early respiratory sensations are mediated by the discharge of receptors in the lungs. 3. The late hyperventilation and the accompanying sensation of breathlessness occurred in both transplant and control subjects and are therefore likely to be mediated by receptors elsewhere in the body, presumably systemic arterial chemoreceptors stimulated by lobeline. 4. In control subjects, but not transplant subjects, there was a consistent decrease in mean arterial pressure associated with the lobeline injection. This suggests that pulmonary afferents mediate the hypotension. 5. For transplant subjects studied more than a year after transplantation, there was some evidence that the noxious respiratory sensations evoked by lobeline had returned. This suggests that some functional reinnervation of pulmonary afferents may occur.

Adult↗
PubMed1990

Relation between rectal sensation and anal function in normal subjects and patients with faecal incontinence.

The relation between sensory perception of rapid balloon distension of the rectum and the motor responses of the rectum and external and internal anal sphincters in 27 normal subjects and 16 patients with faecal incontinence who had impaired rectal sensation but normal sphincter pressures was studied. In both patients and normal subjects, the onset and duration of rectal sensation correlated closely with the external anal sphincter electrical activity (r = 0.8, p less than 0.0001) and with rectal contraction (r = 0.51, p less than 0.001), but not with internal sphincter relaxation. All normal subjects perceived a rectal sensation within one second of rapid inflation of a rectal balloon with volumes of 20 ml or less air. Six patients did not perceive any rectal sensation until 60 ml had been introduced, while in the remaining nine patients the sensation was delayed by at least two seconds. Internal sphincter relaxation occurred before the sensation was perceived in three of 27 normal subjects and 11 of 16 patients (p less than 0.001), and could be associated with anal leakage, which stopped as soon as sensation was perceived. The lowest rectal volumes required to induce anal relaxation, to cause sustained relaxation, or to elicit sensations of a desire to defecate or pain were similar in patients and normal subjects. In conclusion, these results show the close association between rectal sensation and external anal sphincter contraction, and show that faecal incontinence may occur as a result of delayed or absent external anal sphincter contraction when the internal anal sphincter is relaxed.

Adult↗
PubMedDate not supplied

[Sensation seeking and mood dimensions in depressive states].

This study presents the investigation of the relations between dimensions of depressive mood and sensations seeking in 55 hospitalized depressed subjects. The concept of sensation seeking, identified by M. Zuckerman as a personality dimension, has been defined as the need for the subject to reach his optimal level of activation. The four subscores of sensation seeking, relatively independent, are identified in the sensation seeking scale; they stand at different levels on the dimensions of activation and pleasure which are emotional dimensions. These emotional dimensions are investigated in the exploration of the emotional components of depressive mood; the different symptomatic regroupings, such as blunted affect or impulsivity, do not have the same relations with these dimensions. The sensation seeking concept appears fruitful to investigate the different troubles of affective dynamic, which stand on the expressive and behavioral level, and on the subjective level. As in several studies with normal populations, we find again the same inverse relation between age and sensation seeking, and men obtain higher scores on the Thrill and Adventure seeking factor and on the Desinhibition factor. Globally, depressed subjects have lower scores of sensation seeking than normal subjects (paired by age and sex); but the weakness of sensation seeking is not proportional to the intensity of depression (Hamilton Depressive Scale) and to the the intensity of anxiety (Covi Brief Anxiety Scale). Interesting relations appear with the depressive mood factors, which agree with previous studies of sensation seeking in psychology and psychopathology.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Corneal sensation following excimer laser photorefractive keratectomy in humans.

BACKGROUND: For the correction of myopia, small amounts of corneal tissue--including corneal nerves--are removed, resulting in flattening of the central cornea. METHODS: We studied the changes in corneal sensation in five regions of the cornea following photorefractive keratectomy at varying depths. We examined and compared the recovery of sensation in 17 sighted myopic eyes, with preoperative refractive ranges from -1.00 to -7.25 D. Eyes were divided into shallow (0 to 30 microns) or deep (31 to 70 microns) ablation groups depending on the attempted laser correction. Corneal sensation was measured in the central ablated area and the temporal, inferior, nasal, and superior unablated regions preoperatively and at 1, 3, and 6 months postoperatively. RESULTS: Central and inferior sensation were significantly reduced in the deep ablations at 1 month and continued in the central cornea 6 months postoperatively. There were no overall differences in the sensations in the unablated nasal, temporal, and superior regions between either group or over time. There was a significant second order trend (p = .034) in these three regions, indicating a sharper increase in sensation from baseline in the deeper group at 1 month than the gradual upward trend of the shallow group. CONCLUSIONS: Corneal sensation of both the central ablated area and the unablated peripheral cornea is decreased after deep anterior stromal excimer laser ablations and does not recover within 1 month. Although the deeper group showed isolated areas in the periphery of significant second order trends in sensation, the overall trends were not large, indicating no significant anesthetic effect. Fluctuations in sensation can be detected in the five regions even 6 months after excimer laser keratectomy. The clinical importance of these data remain to be defined.

Adult↗
PubMed1981

Masseter inhibitory periods and sensations evoked by electrical tooth pulp stimulation.

The masseter inhibitory period and sensations evoked by electrical tooth pulp stimulation were assessed in 30 human subjects. Five intensities of electrical stimuli, producing sensations varying from below sensory detection threshold to suprathreshold pain, were applied to upper central incisors. At each stimulus intensity a train of 30, 1-msec, cathodal pulses with an interpulse interval of 2 sec was applied. The averaged masseter activity evoked by the 30 pulses at a fixed stimulus intensity was compared to the quality of the sensation elicited. The threshold for the masseter inhibitory period coincided approximately with an individual's detection threshold for the tooth pulp stimulation. Three configurations of masseter inhibitory periods (single, double and merged) were produced by different stimulus intensities. However, no particular configuration was associated unequivocally with pain sensation. Increases in stimulus intensity evoked changes both in the configuration of the masseter inhibitory period and in the quality of the sensation produced. Chi square analyses showed significant, but progressively weaker, associations between: (1) masseter inhibitory period configuration and stimulus intensity; (2) quality of sensation and stimulus intensity; and (3) quality of sensation and masseter inhibitory period configuration. The weakness of the association between the quality of sensation and masseter inhibitory period configuration also was demonstrated in a double-blind study of the effects of a narcotic analgesic, fentanyl. Although the strengths of non-pain and pain sensations were reduced significantly after fentanyl, there were no changes in the masseter inhibitory periods.

Adolescent↗
PubMed1998

Oral irritant effects of nicotine. Psychophysical evidence for decreased sensation following repeated application of and lack of cross-desensitization to capsaicin.

When delivered to the oral mucosa, a variety of naturally occurring chemicals such as capsaicin from red chili peppers, piperine from black pepper, and nicotine from tobacco, cause a diffuse burning sensation often referred to as irritation. The burning sensation evoked by capsaicin increases when delivered repeatedly at 1 min intervals (sensitization), but then decreases markedly following a 10 min rest period (self-desensitization). It is also interesting that following desensitization by capsaicin, irritant sensations evoked by other chemicals are also reduced (cross-desensitization), suggesting that oral irritation from some agents may be mediated by a population of capsaicin-sensitive trigeminal polymodal nociceptors. Although nicotine is a major component in tobacco smoke, little is known about its sensory properties. Accordingly, a study of the oral irritant effects of nicotine as compared with capsaicin was initiated. Whereas capsaicin (0.5 or 3 ppm; repeated at 1 min intervals over 10 min) evoked significantly stronger sensations (sensitization), there was a significant decrement in sensations to repeated application of nicotine (0.1%). After the subjects had received either repeated capsaicin or nicotine on one side of the tongue, a rest period ensued followed by a bilateral application of either capsaicin or nicotine. Subjects were, then, asked to choose which side yielded a stronger sensation (two-alternative forced choice). Following capsaicin pretreatment, all subjects reported that capsaicin evoked a stronger sensation on the previously untreated side (capsaicin self-desensitization). Similar self-desensitization was observed with nicotine. Furthermore, nicotine was reported to evoke a significantly weaker sensation on the side of the tongue pretreated with capsaicin (cross-desensitization). In contrast, equal numbers of subjects reported capsaicin to evoke a stronger sensation on either the nicotine-pretreated side or the untreated side, indicating an absence of cross-desensitization. These results are discussed in terms of physiological mechanisms that might underlie the contrasting sensory effects of nicotine versus capsaicin.

Capsaicin↗
PubMed2004

Eighteen sensations after breast cancer surgery: a two-year comparison of sentinel lymph node biopsy and axillary lymph node dissection.

PURPOSE/OBJECTIVES: To evaluate the prevalence, severity, and level of distress of 18 sensations at baseline (3-15 days) and 24 months after breast cancer surgery and to compare sensations after sentinel lymph node biopsy (SLNB) with those after SLNB plus immediate or delayed axillary lymph node dissection (ALND). DESIGN: Prospective, descriptive. SETTING: Evelyn H. Lauder Ambulatory Breast Center at Memorial Sloan-Kettering Cancer Center in New York, NY. SAMPLE: 294 women with breast cancer; 214 had undergone breast conserving therapy, and 80 had undergone total mastectomy; 197 had had SLNB, and 97 had had SLNB and ALND. METHODS: Patients completed the Breast Sensation Assessment Scale (BSAS) at baseline and 3, 6, 12, and 24 months after surgery. MAIN RESEARCH VARIABLES: Prevalence, severity, and level of distress of sensations in patients who had undergone breast cancer surgery. FINDINGS: Sensations were less prevalent, severe, and distressing in patients undergoing SLNB than those undergoing ALND. This difference appeared to be limited to those undergoing breast conserving therapy. Most sensations after SLNB and ALND, even if prevalent, were not very severe or distressing. Some sensations persisted as long as two years. These included tenderness after SLNB and numbness after ALND. Patients often reported phantom sensations after total mastectomy. CONCLUSIONS: Overall, prevalence, severity, and level of distress were lower after SLNB compared to ALND, but some morbidity existed after SLNB. Certain sensations remained prevalent in both groups for as long as 24 months. IMPLICATIONS FOR NURSING: Nurses can use information from this study to provide more accurate education and support to patients.

Adult↗
PubMed2003

Correlation of corneal sensation, but not of basal or reflex tear secretion, with the stage of diabetic retinopathy.

PURPOSE: To examine the possible relation between corneal sensation or tear secretion and the stage of diabetic retinopathy in diabetic patients. METHODS: Total reflex or basal tear secretion and corneal sensation were determined in 95 patients with type II diabetes mellitus and 58 nondiabetic control subjects. Tear secretion was measured by the Schirmer test and corneal sensation with a Cochet-Bonnet esthesiometer. RESULTS: Corneal sensation and total or reflex tear secretion were significantly reduced in diabetic patients compared with nondiabetic controls. The loss of corneal sensation, but not that of tear secretion, was significantly correlated with stage of diabetic retinopathy in diabetic patients who were diagnosed with no diabetic retinopathy, simple diabetic retinopathy, preproliferative retinopathy, or proliferative retinopathy. CONCLUSION: Both corneal sensation and total or reflex tear secretion are reduced in individuals with diabetes. The decrease in corneal sensation, but not that in each tear secretion, was correlated with the stage of diabetic retinopathy. Given that loss of corneal sensation is a manifestation of diabetic polyneuropathy, these results are consistent with the notion that both diabetic retinopathy and polyneuropathy result from a basement membrane abnormality.

Adult↗
PubMed2002

Innocuous cooling can produce nociceptive sensations that are inhibited during dynamic mechanical contact.

In a previous study of the heat grill illusion, sensations of burning and stinging were sometimes reported when the skin was cooled by as little as 2 degrees C. Informal tests subsequently indicated that these nociceptive sensations were experienced if cooling occurred when the stimulating thermode rested on the skin, but not when the thermode was cooled and then touched to the skin. In experiment 1 subjects judged the intensity of thermal (cold/warm) and nociceptive (burning/stinging) sensations when the volar surface of the forearm was cooled to 25 degrees C (1) via a static thermode (Static condition), or (2) via a cold thermode touched to the skin (Dynamic condition). The total area of stimulation was varied from 2.6 to 10.4 cm(2) to determine if the occurrence of nociceptive sensations depended upon stimulus size. Burning/stinging was rated 10.3 times stronger in the Static condition than in the Dynamic condition, and this difference did not vary significantly with stimulus size. In experiment 2, thermal and nociceptive sensations were measured during cooling to just 31 degrees, 29 degrees or 27 degrees C, and data were obtained on the frequency at which different sensation qualities were experienced. Stinging was the most frequently reported nociceptive quality in the Static condition, and stinging and burning were both markedly reduced in the Dynamic condition. In experiment 3 we tested the possibility that dynamic contact might have inhibited burning and stinging not because of mechanical contact per se, but rather because dynamic contact caused higher rates of cooling. However, varying cooling rate over a tenfold range (-0.5 degrees to -5.0 degrees /s) had no appreciable effect on the frequency of stinging and burning. Overall, the data show that mild cooling can produce nociceptive sensations that are suppressed under conditions of dynamic mechanical contact. The latter observation suggests that cold is perceived differently during active contact with objects than during passive heat loss to the environment. Hypotheses about the physiological basis of the nociceptive sensations at mild temperatures and their possible role in the phenomena of paradoxical heat and synthetic heat are discussed.

Adult↗