Since the hemorrhoidal vascular cushions contribute 15% of the resting anal tone, surgeries involving these structures may affect continence status. Partial internal sphincterotomy, fistulotomy, anal stretch (Lords operation), hemorrhoidectomy or transanal advancement flaps may all lead to FI post operatively, with soiling being far more common than solid FI. The "keyhole deformity" refers to scarring within the anal canal and is another cause of mucus leakage and minor incontinence. This defect is also described as a groove in the anal canal wall, and may occur after posterior midline fissurectomy or fistulotomy, or with lateral IAS defects. Rare causes of traumatic injury to the anal sphincters include military or traffic accidents complicated by pelvic fractures, spine injuries or perineal lacerations, insertion of foreign bodies in the rectum, and sexual abuse. Nontraumatic conditions causing anal sphincter weakness include scleroderma, damage to the pudendal nerves and IAS degeneration of unknown cause. Radiation induced FI may involve the anal canal as well as the rectum, when proctitis, anal fistula formation and diminished function of internal and external sphincter occur. Irradiation may occur during radiotherapy, e.g. for prostate cancer. Pelvic floor
Many people with FI have a generalized weakness of the pelvic floor, especially puborectalis. A weakened puborectalis leads to widening of the anorectal angle, and impaired barrier to stool in the rectum entering the anal canal, and this is associated with incontinence to solids. Abnormal descent of the pelvic floor can also be a sign of pelvic floor weakness. Abnormal descent manifests as descending perineum syndrome (>4 cm perineal descent).
Prognosis
In keeping with their assignment as WHO grade 1, pilocytic astrocytoma is not usually associated with recurrence after complete resection. The pilomyxoid astrocytoma variant may behave more aggressively than classic pilocytic astrocytoma, but this might also be associated with the younger age at presentation and their more frequent midline location. In cases of progressive/recurrent disease or when maximal surgical removal has been achieved but some residual tumor remains, chemotherapy and/or radiation therapy may be considered by the medical team. Incidence
Regularly updated statistics about the incidence, epidemiology, and survival outcomes of brain tumors can be found in the annual reports of the Central Brain Tumor Registry of the United States (CBTRUS). These figures suggest that an average of just over 1,000 pilocytic astrocytomas are diagnosed per year in the US, representing about 1% of all CNS tumors. In children, however, the proportion is much higher. Pilocytic astrocytoma is the single most common childhood brain tumor, accounting for almost 20% of brain tumors diagnosed in 0-14 year-olds, with a peak incidence between 5–14 years of age. Additional images
References


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