Anismus

Anismus (also known as spastic pelvic floor syndrome,^[1] anal sphincter dyssynergia,^[2] pelvic floor dyssynergia,^[3] dyssynergic defecation,^[4] and paradoxal puborectal contraction^[5]) is a malfunction (a focal dystonia) of the external anal sphincter and puborectalis muscle during defecation. Normal defecation involves relaxation of both of these muscles. Malfunction involves their failure to relax or their paradoxical increased contraction.^[6] Anismus is a form of functional obstructed defecation and can cause constipation^[7] and painful defecation. It is more common in women than in men, and sometimes is associated with sexual abuse.^[8]

Paradoxical contraction of the anal sphincter is fairly common and in many people it does not cause anismus.^[9]

Diagnosis

Physical examination can rule out anismus (by identifying another cause) but is not sufficient to diagnose anismus. Anismus needs to be distinguished from rectal inertia, another cause of obstructed defecation and constipation. Techniques proposed to do this include the rectal cooling test.^[10] Other techniques include manometry, balloon expulsion test, evacuation proctography (see defecating proctogram), and MRI defecography.^[3] Diagnostic criteria are: fulfillment of criteria for functional constipation, manometric and/or EMG and/or radiological evidence (2 out of 3), evidence of adequate expulsion force, and evidence of incomplete evacuation.^[3] Recent dynamic imaging studies have shown that in persons diagnosed with anismus the anorectal angle during attempted defecation is abnormal, and this is due to abnormal (paradoxical) movement of the puborectalis muscle.^[11][12][13]

Anismus can be classified by type:^[4]

• Type I: paradoxical anal contraction
• Type II: impaired propulsion
• Type III: impaired anal relaxation with adequate propulsion

Complications

Complications of anismus may include fecal impaction and megarectum,^[14] and encopresis.

Treatment

Treatments for anismus include biofeedback training, botox injections, and surgical resection.

Biofeedback training for treatment of anismus is highly effective.^[15][16][17]

Injections of botulin toxin type-A into the puborectalis muscle are very effective in the short term, and somewhat effective in the long term.^[18] Injections may be helpful when used together with biofeedback training.^[19]

Historically, the standard treatment was surgical resection of the puborectalis muscle. Recently, partial resection (partial division) has been reported to be effective in some cases.^[20]

Comorbidity

Anismus sometimes occurs together with other conditions that limit (see contraindication) the choice of treatments. Thus, thorough evaluation is recommended prior to treatment.^[21]

When anismus occurs in the context of intractable encopresis (as it often does), resolution of anismus may be insufficient to resolve encopresis.^[15] For this reason, and because biofeedback training is invasive, expensive, and labor intensive, biofeedback training is not recommended for treatment of encopresis with anismus.

Anismus may occur with anorectal malformation, rectocele,^[22] rectal prolapse^[23] and rectal ulcer.^[23]

History

Anismus sometimes develops in persons with extrapyramidal motor disturbance due to Parkinson's disease.^[24] This observation led in 1988 to the understanding that anismus is a type of focal dystonia.^[25]

See also

• Defecation postures
• Dystonia

References