Diminished or absent anal reflexes indicate bilateral pyramidal fasciculus or cauda equina nerve damage. Cauda equina damage is a common clinical condition, mostly due to absolute or relative stenosis of the lumbar spinal canal due to various congenital or acquired causes, resulting in a series of neurological dysfunctions due to compression of the cauda equina. If the cauda equina nerve is damaged, the anal perineum and lower extremities may experience sensation and burning pain, and in severe cases, urinary and fecal disorders may occur. This can cause great inconvenience to the patient. How can we diagnose a weakened or absent anal reflex? In the case of cauda equina nerve root damage, various symptoms of nerve damage below lumbar 2 may be manifested. In the case of total cauda equina damage, the sensory impairment is clearly delineated, with the upper boundary being the groin in front and the level of the upper iliac bone in the back. Below this, sensory impairment occurs in the buttocks, perineum and all lower extremities, accompanied by spontaneous pain (electric shock pain), abnormal sensation in the perineum and radiation to the lower extremities, and often painful sensory latency. The height and degree of cauda equina damage varies. Its upper and lower boundaries may vary. It has been reported that the recovery of motor function is better than the recovery of sphincter function, while the recovery of sensory function is the worst. The recovery of sphincter function is better in patients with urinary retention than in patients with urinary incontinence. The examiner lightly strokes the perineal skin around the patient’s anus with a cotton swab or lightly pricks the patient with a large-headed needle, and when normal, anal contraction is seen immediately. If these responses are delayed or do not occur, the anal reflex is diminished or absent.