Lesion of ulnar nerve, left upper limb

This diagnosis code signifies damage or abnormality affecting the ulnar nerve in the patient's left arm. This can manifest as various neurological symptoms such as pain, numbness, tingling, or weakness in the distribution of the ulnar nerve, typically affecting the fourth and fifth fingers and associated intrinsic hand muscles. The lesion can occur at any point along the nerve's path in the left upper limb.

Apply this code when documentation clearly indicates a diagnosed lesion, entrapment, or neuropathy of the ulnar nerve specifically on the left side. Supporting documentation includes physician notes detailing neurological examination findings, nerve conduction studies, electromyography (EMG) results, or imaging reports confirming ulnar nerve pathology in the left upper extremity.

• Ensure laterality is explicitly documented as "left" to support this specific code.
• Distinguish from G56.21 (right) and G56.20 (unspecified) based on physician documentation.
• Consider sequencing with an external cause code if the lesion is due to trauma (e.g., fracture, laceration).