The description of a strange sensation when wiping with toilet paper is a common phrasing indicating numbness in the S3/4/5 region. S2 and S1 dermatomes are located on the medial thigh and L5 on the lateral thigh.

The cauda equina consists of nerve roots spanning L3-S5.

With preserved deep tendon reflexes and strength the proximal cauda equina is unlikely affected, as L3 and L4 are used in the patellar reflex and S1 and sometimes S2 in the ankle.

A distal cauda equina lesion such as at S3/4/5, however, would explain isolated saddle anesthesia without hyper/hyporeflexia or weakness.

Bladder continence is controlled by Onuf’s nucleus, located between S2/3/4, and thus would also be impacted. Although cauda equina can often be unilateral, it is difficult to discern unilaterality with distal sacral nerve roots as the dermatomes converge midline.