ICD-10 Code H49.13 – Fourth [trochlear] nerve palsy, bilateral (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code H49.13 – Fourth [trochlear] nerve palsy, bilateral
What it is
Use this code for bilateral trochlear nerve palsy, a cranial nerve disorder that weakens the superior oblique muscles in both eyes. It can cause vertical or torsional misalignment and difficulty with coordinated eye movement.
Clinical signs
Common findings include diplopia, especially on looking down or reading, and a bilateral hypertropia pattern. Clinical features vary; refer to documentation for confirmed neuro-ophthalmic findings.
When to use this code
Use H49.13 when the record specifically documents bilateral fourth nerve palsy or bilateral trochlear nerve dysfunction. You may also use it when an ophthalmology or neurology note confirms the diagnosis after examination or imaging workup. Check documentation if the laterality is unclear.
Do not use for
Do not use this code for unilateral fourth nerve palsy or nonspecific diplopia without a diagnosed cranial nerve palsy. Do not assign it when the chart only mentions suspected palsy; check documentation.
Coding tip
Confirm bilateral laterality in the provider note before coding, because the unilateral and bilateral codes are different.