What is the primary reason for incontinence and impaired anorectal sensation in spina bifida?

• A. Abnormal Or Absence Of S4-S5
• B. Injury To L1-L2
• C. Damage To T12-L1
• D. Injury To S1-S2

Answer: (A)

The main issue is the sacral nerve roots that control the anal sphincters and sensation in the anorectal area. Specifically, the S4–S5 roots are crucial for the external anal sphincter’s motor control and for sensing the anal canal. In spina bifida, these sacral roots are often abnormal or absent, so the external anal sphincter can’t contract properly and the sensory signals from the anal canal are reduced. That combination leads to incontinence and impaired anorectal sensation.

Injury higher up in the spine (such as at L1–L2 or T12–L1) would cause different neurologic deficits and wouldn’t directly explain the targeted loss of anorectal sensation and continence. Injury to S1–S2 might affect pelvic floor function, but without disruption of S4–S5, continence and anorectal sensation aren’t as fundamentally compromised.