Figure 2.

Schematic of five neurological examinations used to diagnose distal symmetric polyneuropathy (A) Ankle reflexes: The examiner should gently tap the Achilles tendon on one side of the subject’s foot using a percussion hammer. The ankle reflex is considered absent if the foot cannot be plantarflexed, weakened if the plantar flexion is not significant, and positive if the bilateral ankle reflexes are weakened or absent. (B) Vibration sensing: After striking a 128 Hz tuning fork, it is placed on the dorsal side of the big toe of both feet to observe whether the participants can feel the tuning fork’s vibration. Vibrational sensation is positive if the sense of vibration on either side disappears or decreases. (C) Temperature sensing: One end of the temperature tester (metal or polyester) is s placed on the skin of the dorsum of the foot (avoiding calluses, ulcers, scars, and necrotic tissue). The result is positive if the participant cannot correctly distinguish the temperature at either end. (D) Pressure sensing: A 10 g Semmes–Weinstein monofilament is placed on the dorsal side of the hallux with gradually increasing pressure, repeated four times on each side, eight times in total on both feet, and 1 point is recorded if no pressure is sensed once. The result is considered positive if the total score is ≥ 5 points. (E) Pinprick pain sensing: Gently prick the skin of the dorsum of the foot with the tip of a pin without causing skin damage. Participants who cannot feel pain or are hyperresponsive to pain are considered positive.