Search

Saccades and smooth pursuit eye movements (SPEM) are two types of goal-directed eye movements whose kinematics differ profoundly, a fact that may have contributed to the notion that the underlying cerebellar substrates are separated. However, it is suggested that some Purkinje cells (PCs) in the oculomotor vermis (OMV) of monkey cerebellum may be involved in both saccades and SPEM, a puzzling finding in view of the different kinematic demands of the two types of eye movements. Such ‘dual’ OMV PCs might be oddities with little if any functional relevance. On the other hand, they might be representatives of a generic mechanism serving as common ground for saccades and SPEM. In our present study, we found that both saccade- and SPEM-related responses of individual PCs could be predicted well by linear combinations of eye acceleration, velocity and position. The relative weights of the contributions that these three kinematic parameters made depended on the type of eye movement. Whereas in the case of saccades eye position was the most important independent variable, it was velocity in the case of SPEM. This dissociation is in accordance with standard models of saccades and SPEM control which emphasize eye position and velocity respectively as the relevant controlled state variables.

The purpose of blinks is to keep the eyes hydrated and to protect them. Blinks are rarely noticed by the subject as blink-induced alterations of visual input are blanked out without jeopardizing the perception of visual continuity, features blinks share with saccades. Although not perceived, the blink-induced disconnection from the visual environment leads to a loss of information. Therefore there is critical need to minimize it. Here we demonstrate evidence for a new type of eye movement serving a distinct oculomotor demand, namely the resetting of eye torsion, likewise inevitably causing a loss of visual information. By integrating this eye movement into blinks, the inevitable down times of vision associated with each of the two behaviors are synchronized and the overall downtime minimized. DOI: http://dx.doi.org/10.7554/eLife.16290.001, eLife digest Blinking lubricates the surface of the eye and prevents it from becoming too dry. People blink around 20 times per minute, but we rarely notice the gaps in our vision because the brain becomes less sensitive to visual input during each blink. Eye movements can also hinder our vision. For example, our vision could easily become blurred when we redirect our gaze to a new target. However, like during blinking, the brain blocks visual input while these movements – known as saccades – take place. Because saccades and blinking both temporarily disrupt vision, the brain synchronizes the two, which keeps this downtime to a minimum. Involuntary eye movements can also disrupt our vision. We perceive an object most clearly when its image falls on the very center of the back of the eye. If the image drifts away from this central position, our eyes make small involuntary ‘resetting’ movements to counteract the drifting. Given that these movements would compromise our vision much like saccades do, Khazali et al. wondered whether the brain might also synchronize them with blinks as well. Khazali et al. tracked the eye movements of people staring straight ahead at a red dot in an otherwise dark room. This revealed that correcting eye movements did indeed occur at the same time as blinks, but unexpectedly the movements were different from those that had been recorded in previous studies. Further experiments then confirmed that the blinks themselves triggered this new type of corrective movement, rather than the loss of vision that resulted from the blinks. Khazali et al. propose that by synchronizing the resetting movements with blinks, the brain ensures that the eyes are damp wiped and restored to their optimal positions while minimizing visual disturbance. The next challenge is to identify the circuit of neurons in the brain that underlies these eye movements and to clarify how this circuit interacts with the one that controls blinking. DOI: http://dx.doi.org/10.7554/eLife.16290.002

Conservative anal surgery, with maximum preservation of the anal sphincters and continence, is becoming increasingly possible with the emergence of new sphincter-sparing treatments. Many surgeons remain skeptical, however, of the nature and impact of incontinence after anal surgery. We aimed to characterize the patterns of anal sphincter injury in patients with fecal incontinence after anal surgery. We reviewed our fecal incontinence database and studied a subset developing incontinence after anal surgery. Maximum resting and squeeze pressures and the distal high-pressure zone to mid–anal canal resting pressure gradient were evaluated. Anal ultrasounds were evaluated and specific postoperative lesions were characterized. Patterns of sphincter injury in 93 patients with fecal incontinence after manual dilation, internal sphincterotomy, fistulotomy, and hemorrhoidectomy were studied. The internal sphincter was almost universally injured, in a pattern specific to the underlying procedure. One-third of patients had a related surgical external sphincter injury. Two-thirds of women had an unrelated obstetric external sphincter injury. The distal resting pressure was typically reduced, with reversal of the normal resting pressure gradient of the anal canal in 89 percent of patients. Maximum squeeze pressure was normal in 52 percent. Incontinence after anal surgery is characterized by the virtually universal presence of an internal sphincter injury, which is distal in the high-pressure zone, resulting in a reversal of the normal resting pressure gradient in the anal canal. These data support concerns that non–sphincter-sparing anal surgery leads to fecal incontinence and is increasingly difficult to justify given the availability of modern sphincter-sparing approaches.

The influence of vibrations on the quality of the processed surface is an important problem applying an industrial robot for machining prototypes. The intrinsic frequency of individual pieces of the robot may cause resonance due to vibration that appear in the machining process. The conducted experiment has investigated the activity of vibration along the process of milling wood, polypropylene and extruded polystyrene in the three-axe system. According to the influence of induced vibrations in the cutting process and considering surface roughness, feed rates for cutting taking into account every material have been chosen. Santrauka Atliekant prototipų mechaninį apdirbimą pramoniniu robotu, svarbi problema yra vibracijos poveikis apdirbamo paviršiaus kokybei. Dėl atskirų sujungto roboto dalių savojo dažnio rezonansas gali atsirasti dėl apdirbimo proceso vibracijų. Atliktas eksperimentas, kurio metu ištirtas roboto vibracinis aktyvumas frezuojant medieną, polipropileną ir ekstruzinį polistireną trijų ašių sistemoje. Kiekvienai medžiagai parinktos pjovimo pastūmos, atsižvelgiant į pjovimo proceso sukeliamų vibracijų įtaką paviršiaus šiurkštumui. Raktiniai žodžiai: prototipų mechaninis apdirbimas, pramoninis robotas, apdirbimo optimizavimas, vibracinio aktyvumo tyrimai

Background. Surgery for anorectal malformations (ARMs) attempts to position the neo-anus anatomically within the anal sphincter complex. Currently, MRI is the imaging modality of choice in determining the position of the neo-anus after reconstructive surgery. Objective. The aim of this study was to compare the accuracy of anal endosonography (AES) with conventional MRI in demonstrating the anatomy of the neo-anus following repair of ARMs. Materials and methods. Fourteen children (ten girls, four boys), born with ARMs (four low, ten high) underwent both AES and pelvic MRI following anorectoplasty. The results of both investigations were compared with muscle stimulation and were reported blindly by a clinician and a radiologist. Results. AES findings were comparable with MRI in 9 of the 14 cases. In four cases, MRI and AES findings differed, with nerve stimulation supporting AES but not MRI. Conclusions. AES is an accurate alternative to MRI in the assessment of anorectoplasty. It provides more detailed information and can be performed under anaesthesia in combination with a surgical procedure.

A consecutive series of 23 patients with colonic J pouch-anal anastomosis for low rectal cancer (17 men; mean age 64.4 (range 44–76) years) was studied prospectively. The mean distance from the pouch-anal anastomosis to the anal verge was 3.5 (range 2.0–4.5) cm. During follow-up one patient died from an unrelated cause and four developed metastases, two local and two hepatic. In 19 surviving patients a mean of 7 months after ileostomy closure mean bowel frequency was 2.1 (range 1–4) per day, five patients had urgency and four had mild faecal seepage up to three times per week, and seven patients had some degree of incomplete evacuation. In 13 patients there were no manometric differences before and after surgery with respect to maximum tolerated volume or maximum resting pressure, but maximum squeeze pressure was significantly lower after surgery (mean 189 versus 132 cmH2O before and after surgery respectively, P < 0.05). Colonic pouch reconstruction should be considered as an alternative to straight coloanal anastomosis in patients undergoing very low anterior resection.

PURPOSE: Fibrin glue is a novel treatment for anal fistulas and possesses many advantages in the treatment of difficult high fistulas. Fibrin glue treatment is simple and repeatable; failure does not compromise further treatment options; and sphincter function is preserved. We aimed to compare the outcomes of patients with low and high anal fistulas randomly assigned to either fibrin glue or conventional treatment. METHODS: Patients with simple fistulas (low fistulas) and complex fistulas (high, Crohn’s, and low fistulas with compromised sphincters) were randomly assigned to either fibrin glue or conventional treatment (fistulotomy or loose seton insertion with or without subsequent advancement flap). Patients with rectovaginal fistulas and anal fistulas associated with chronic cavities, acute sepsis, and side branches were excluded. The primary end point was fistula healing. Secondary end points were complications, changes in preoperative continence score, changes in maximum resting and squeeze pressure, satisfaction scores, and pain scores and time off work (simple fistulas only). RESULTS: Patients in the fibrin glue and conventional treatment arms were well matched for gender, median age, duration of fistula symptoms, and follow-up. Fibrin glue healed three (50 percent) of six and fistulotomy seven (100 percent) of seven simple fistulas (difference, 50 percent; confidence interval, 10 to 90 percent; P = 0.06, Fisher’s exact probability test). There was no change in baseline incontinence score, maximum resting pressures, or squeeze pressures between the study arms. Return to work was quicker in the glue arm, but pain scores were similar and satisfaction scores higher in the fistulotomy group. Fibrin glue healed 9 (69 percent) of 13 and conventional treatment 2 (13 percent) of 16 complex fistulas (difference, 56 percent; 95 percent confidence interval, 25.9 to 86.1 percent; P = 0.003, Fisher’s exact probability test). There was no change in baseline incontinence score, maximum resting pressures, or squeeze pressures in either study arm. Satisfaction scores were higher in the fibrin glue group. CONCLUSIONS: No advantage was found for fibrin glue over fistulotomy for simple fistulas, but fibrin glue healed more complex fistulas than conventional treatment and with higher patient satisfaction.

This study was performed to determine the endosonographic features of the anal canal in normal children and to compare these findings with the endosonographic features in children with congenital anorectal malformations.Two groups of children were examined by anal endosonography (AES): group 1 ( n=30) were controls, and group 2 ( n=15) were children born with anorectal malformations.In the normal group, the sphincter elements were clearly visualised. The intersphincteric plane produced a double image, which differs from the adult appearance. Of 15 patients who had anorectoplasty, AES identified accurate placement of the neoanus within the sphincters in 13 and slight malposition in two patients.This study details the endosonographic appearances of the anal canal in healthy children aged from 1 month to 14 years. AES provided useful anatomical detail in patients following anorectoplasty.

Background Intractable idiopathic constipation in women is often associated with psychosocial problems. Aims To determine the past and current psychological factors associated with slow and normal transit constipation. Patients Twenty-eight consecutive patients referred for biofeedback treatment were interviewed before the procedure. All were women. Transit studies revealed that 12 had slow transit constipation (STC) and 16 had normal transit constipation (NTC). Methods Patients were assessed for evidence of previous and current psychiatric diagnoses using a standardized diagnostic interview schedule. A full family and social history was noted. Self-rating scales were used to measure psychological distress, abnormal attitudes to eating and current psychosocial functioning. Results The mean age of the 28 patients was 38.2 years (SD = 10.8) with a mean duration of symptoms of 17.5 years (SD = 16.9). Seventeen (61%) had a current psychiatric disorder and 18 (64%) a previous episode of psychiatric illness. The mean age of the 16 NTC patients was 38.4 years (SD = 10.1) with a mean duration of symptoms of 12.4 years (SD = 15.9). By contrast, the 12 STC patients had a much longer mean duration of constipation (24.3 years; SD = 16.4), a mean age of 37.9 years (SD = 12.1), with half having an onset in childhood. The STC patients reported more psychosocial distress on the rating scales than those with NTC, and only one did not experience some form of adverse life event or gynaecological procedure in the 6 months before the onset of constipation. Eleven (39%) of the 28 women had had a hysterectomy at a mean age of 36 years, but only four (14%) reported a history of sexual abuse. Of the nine (32%) patients who reported markedly distorted attitudes to food, six had NTC and three had STC. Conclusions Of consecutive patients undergoing psychological assessment for intractable constipation, three fifths had evidence of current, and two thirds a previous, affective disorder. One third reported distorted attitudes to food. Although STC is a chronic disorder accompanied by high rates of psychological distress, it does not appear to be associated with gross functional impairment. We suggest that patients who present to surgical departments with chronic intractable constipation should routinely have a psychological assessment.

Background Topical preparations have been used in the treatment of anal fissure. However, they are not universally successful and there is confusion over the site and dose of application. This study assessed the effectiveness of oral nifedipine in reducing resting anal pressure and on fissure healing. Methods Anal manometry was performed on eight healthy volunteers and 15 patients with chronic anal fissure before and after oral administration of nifedipine 20 mg. Nifedipine was taken twice daily. Fissure healing was assessed over an 8-week period and pain scores were monitored. Results Oral nifedipine produced an initial reduction in maximum resting anal pressure (MRP) of 35 per cent (P < 0·001) and of 28 per cent after 5 days (P < 0·001) in healthy volunteers. A reduction in MRP of 36 per cent (P < 0·001) was observed in patients with fissure. Pain scores were significantly reduced during the treatment period. Healing was complete in nine patients after 8 weeks and a further three were asymptomatic. Ten patients experience flushing and four had mild headaches. There were no episodes of postural hypotension or incontinence. Conclusion Oral nifedipine reduces resting anal pressure. It is well tolerated and offers an alternative treatment for chronic anal fissure.

Objective To assess the etiology, treatment, and utility of anal ultrasound in men with fecal incontinence and to review the outcomes of conservative (nonoperative) treatment. Background Data The etiology of fecal incontinence in women is almost exclusively from obstetric or iatrogenic surgical injuries resulting in damage to the anal sphincters and/or pudendal nerves. Corresponding data on men with fecal incontinence are sparse. Methods Between January 1995 and January 1998, 37 men with fecal incontinence were evaluated in the John Radcliffe Hospital anorectal ultrasound unit. Their clinical histories, anal ultrasound results, anorectal physiology studies, and responses to conservative therapy were reviewed. Results Median age was 57 years. Major incontinence was present in 27% of the patients. Anal ultrasound localized anal sphincter damage in nine patients, and the characteristics of these nine patients with sphincter damage were then compared with the remaining 28 without sphincter damage. Prior anal surgery was more common in patients with sphincter damage. Hemorrhoids were more common in patients without sphincter damage. Anorectal physiology studies revealed significantly lower mean maximum resting and squeeze pressures in patients with sphincter damage, confirming poor sphincter function. With 92% follow-up, patients without sphincter damage were more likely to improve with nonoperative therapy. Conclusions Anal ultrasound is extremely useful in the evaluation of fecal incontinence in men. Unlike women, the majority of men do not have a sphincter defect by anal ultrasound, and conservative management is usually successful in these patients. In contrast, in men with anal sphincter damage, almost all of these defects resulted from previous anal surgery. Conservative management rarely is successful in these cases, and surgical repair of the anal sphincter may be indicated. Therefore, because the presence or absence of sphincter damage on anal ultrasound usually predicts the response to nonoperative treatment, anal ultrasound should be used to guide the initial management of men with fecal incontinence.

Anorectal function after anterior resection may be impaired as a result of reduced luminal capacity in the pelvis. The aim of this study was to evaluate the colonic J pouch neorectum by means of ambulatory manometry. Twelve patients with a colonic pouch following anterior resection and seven healthy controls were studied for a median of 6 (range 6–24) h using a probe with two pouch-rectal and two anal canal transducers. Records were interpreted by visual inspection. Pressure values and wave frequencies were determined by software analysis. Pouches had been functioning for a median of 32 (range 11–55) months. All patients with a pouch had an acceptable stool frequency. Seven of 12 patients complained of incomplete evacuation. Resting anal canal pressure (73 versus 100 cmH2O), pouch-rectal pressure (29 versus 15cmH2O) and anal canal pouch-rectal pressure gradients (60 versus 85 cmH2O) were similar in patients and controls. The frequency of slow-wave activity in patients with a pouch was significantly lower than that in controls (7 versus 16 cycles per min, P =0.001). Coordination between the colonic J pouch and the anal canal, in the form of sampling episodes, was observed in more than half of the patients with a functioning pouch. Large isolated contractions (pressure greater than 30cmH2O and lasting longer than 20 s) and rhythmic contractions were the most frequent pattern of pouch motility.

PURPOSE: The aim of this study was to determine whether a colonic J-pouch has similar properties to that of a normal rectum, including recovery of rectoanal coordination. METHODS: Ten patients with colonic J-pouch-anal anastomosis (anastomotic distance from anal verge, 3–5 (range, 2.0–4.5) cm for low rectal cancer (7 men; mean age, 64.7 (range, 44–76) years) were studied clinically and in the anorectal physiology laboratory at least one year after operation. Results were compared with a series of ten matched patients who underwent high anterior resection for upper rectal carcinoma (anastomotic height, 12.7 (range, 9.5–16) cm). RESULTS: Although results seemed to be slightly better in the group with the rectum preserved, no statistical differences could be found either in functional outcome or anorectal physiology. One-half of the patients with colonic J-pouch (neorectum) had a positive rectoanal inhibitory reflex. CONCLUSION: Addition of a colon pouch neorectum would appear to improve function to the level of those patients with a high anastomosis and “normal” rectum.

One principal aim in follow-up after curative surgery for colorectal cancer is to identify recurrent disease at an early and possibly treatable stage. The major problem for patients with rectal carcinoma is local recurrence, which occurs in 3–30 per cent of cases and carries a 5-year survival rate of less than 5 per cent. Since 1989, in addition to digital and sigmoidoscopic examination, endorectal ultrasonography has routinely been used in the follow-up of patients with rectal cancer. Sixty-six patients (40 men) who had undergone attempted radical surgery for mid- and lower-third rectal cancer were included in the study. The mean age was 68 (range 43–87) years. A total of 190 scans were performed, with a mean of 3 (range 1–9) for each patient. Thirteen (20 per cent) of the 66 patients developed local recurrence; in all cases this was suggested by rectal ultrasonography. Digital examination and rigid sigmoidoscopy failed to detect recurrence in three patients. Four detected recurrences were treated radically; the remaining patients received radiotherapy, palliative transanal resection or laser management because of advanced age or refusal to undergo surgery. Six patients were alive a mean of 21 (range 4–50) months after recurrence. Of these six patients, four were free from disease (three had undergone salvage surgery and one radiotherapy). Postoperative rectal ultrasonography can detect some local recurrences at an early treatable stage. The method is more accurate than digital examination and sigmoidoscopy, and should be used as part of a regular follow-up programme.