Cortical representation of the anal canal

Stottrop, K.; Schnitzler, A.; Witte, OW; Freund, H.‐J.; Enck, Paul

doi:10.1016/s0016-5085(98)83435-5

Cited by 8 publications

(6 citation statements)

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“…The S1 activation of the somatosensory cortex inbetween the hand and the foot representation as previously described by Stottrop et al (1998) seems to be specific for anal somatosensory stimuli. Aziz et al (2000b) concluded that visceral and somatosensory representation differentiates in the S1 activation since only somatosensory stimulation elicits activation in S1.…”

Section: Discussionsupporting

confidence: 60%

“…Except for one magnetoencephalographic study (Stottrop et al, 1998) and one fMRI study (Binkofski et al, 2000), cortical activation following anal stimulation has not been described, and only the latter one compared rectal and anal stimulation. These studies have shown that information from the anal canal projects into the primary sensory cortex (S1) halfway between the hand and the foot representation and directly into the secondary somatosensory cortex (S2)-they are in agreement with brain imaging studies of the esophagus representation (for a summary see Aziz et al, 2000a).…”

Section: Introductionmentioning

confidence: 99%

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Cerebral Activation during Anal and Rectal Stimulation

et al. 2001

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While the rectum is innervated by visceral afferents, the anal canal is innervated by the somatosensory pudendal nerve. The representation of these two central domains of intestinal sensations in the human brain is largely unknown. Nonpainful pneumatic stimulation of the anal canal and the distal rectum using event-related functional magnetic resonance imaging (fMRI) was performed in eight healthy subjects. Subjective scaling of sensations revealed no differences in unpleasantness and pain during both stimuli. Both types of stimuli revealed fMRI activation in secondary somatosensory, insula, cingular gyrus, left inferior parietal, and right orbitofrontal cortex. Anal stimulation resulted in additional activation of primary sensory and motor cortex, supplementary motor area, and left cerebellum. We concluded that viscerorectal and somatosensory anal stimulation predominantly differ in their primary sensory activation and additional activation in motor areas. This motor response following aversive somatosensory stimuli may be caused by a reflexive avoidance reaction which is not observed after the more diffuse experienced visceral stimulation.

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Section: Discussionsupporting

confidence: 60%

Section: Introductionmentioning

confidence: 99%

Cerebral Activation during Anal and Rectal Stimulation

et al. 2001

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“…While these discrepancies call for further evaluation and explanation, the data leave no doubt about the feasibility of cerebral activity source localization after visceral stimulation – at least from the oesophagus – but first data are now also available from the lower end of the gastrointestinal system 28 …”

Section: Discussionmentioning

confidence: 77%

Cortical activation during oesophageal stimulation: a neuromagnetic study

Loose

Schnitzler

Sarkar

et al. 1999

Neurogastroenterology Motil

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We investigated the neuromagnetic responses to mechanical stimulation of the oesophagus. In six healthy right-handed volunteers (mean age 31.6 years) the proximal and distal oesophagus were stimulated by electronically controlled pump-inflation of a silicone balloon once every 4.5-5.5 sec (dwell time 145 msec). The balloon volume was adjusted to induce different sensation levels (i) just above threshold of perception, (ii) strong sensation and (iii) painful sensation. Evoked magnetic brain responses were recorded time-locked to stimulus onset with a Neuromag-122TM whole-head neuromagnetometer and modelled as equivalent current diploe (ECD) sources. ECDs were superimposed on individual magnetic resonance imaging (MRI) scans. Magnetic brain responses following distal oesophageal stimulation were adequately explained by a time-varying 2-4 dipole model with unilateral or bilateral sources in second somatosensory cortex and later sources in the frontal cortex. With increasing stimulus intensities, latencies of the sources decreased and amplitudes increased. Proximal oesophageal stimulation led to activation of source areas spatially similar to those of distal oesophageal stimulation but with shorter response latencies. Both painful and nonpainful mechanical stimulation of the oesophagus activate the second somatosensory cortex (SII). Evidence for topographic organization of oesophageal afferents in SII is poor.

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“…A similar study by another group [Witscher et al, 1998] showed comparable results. When the sensory representation of the pelvic £oor over the cortex was investigated by means of functional MRI and other techniques, it was found that at least in a subgroup of volunteers this representation was furthermore asymmetrical [Stottrop et al, 1998]. Hamdy et al [1999] found that right or left pudendal nerve stimulation evoked anal responses of similar latencies, but asymmetric amplitudes in a subgroup of subjects.…”

Section: Discussionmentioning

confidence: 99%

Asymmetric sphincter innervation is associated with fecal incontinence after anal sphincter trauma during childbirth

Wietek

Hinninghofen

Jehle

et al. 2006

Neurourology and Urodynamics

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Aims: Functional asymmetry of pelvic £oor innervation has been shown to exist in healthy subjects, and has been proposed to be a predictor of increased risk for fecal incontinence in case of trauma. However, this remains to be shown for di¡erent clinical conditions such as traumatic childbirth. Methods: A conventional surface EMG system was used to assess the innervation of the external anal sphincter. A symmetry index was used to de¢ne the relative EMG amplitude asymmetry of the external anal sphincter between 0 (symmetric) and 1 (asymmetric). Three cohorts were studied: 40 nulliparous women in the third trimester (Study 1), 15 primiparous women within 6 months following vaginal delivery without clinically apparent anal sphincter trauma (Study 2), and 50 women after childbirth-related third or fourth degree perineal tear 6^12 months postpartum (Study 3). Furthermore, all women underwent conventional anorectal manometry. Results: Sixteen or forty nulliparous women reported signs of fecal incontinence; however, relative asymmetry was not correlated to symptom severity (P ¼ 0.345), and not to manometric measures (Study 1). In Study 2, Women who had su¡ered clinically apparent anal sphincter trauma (P ¼ 0.07) tended to have a stronger association between incontinence and asymmetry. In Study 3, 19/50 women reported moderate to severe incontinence. Asymmetry and symptom severity were signi¢cantly correlated (P < 0.001). Patients with incontinence had a signi¢cantly higher asymmetry score than their continent counterparts. Conclusion: Functional asymmetry of anal sphincter innervation is signi¢cantly associated with incontinence symptoms, but only after childbirth-related sphincter injuries and therefore, should be regarded as an additional risk factor. Neurourol. Urodynam. 26: 134^139, 2007. ß 2006

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Cortical representation of the anal canal

Cited by 8 publications

References 0 publications

Cerebral Activation during Anal and Rectal Stimulation

Cerebral Activation during Anal and Rectal Stimulation

Cortical activation during oesophageal stimulation: a neuromagnetic study

Asymmetric sphincter innervation is associated with fecal incontinence after anal sphincter trauma during childbirth

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