H49.1 ICD-10-CA code: Fourth [trochlear] nerve palsy
H49.1 is the ICD-10-CA code for “Fourth [trochlear] nerve palsy” in CIHI’s FY 2026–2027 release, in effect from Apr 1, 2026.
Official description
H49.1Fourth [trochlear] nerve palsy
ICD-10-CA · Canada · Also written H491
Index terms
Entries in CIHI’s alphabetical index that lead to H49.1. Searching the index by the condition the note names is how coders reach this code.
- Neuritis, trochlear (nerve)
- Atrophy, atrophic, nerve, trochlear
- Disorder (of), nerve, trochlear NEC
- Disorder (of), nerve, cranial, fourth NEC
- Neuritis, cranial nerve, fourth or trochlear
- Atrophy, atrophic, nerve, cranial, fourth (trochlear)
- Paralysis, paralytic (complete) (incomplete), trochlear (nerve)
- Inflammation, inflamed, inflammatory (with exudation), trochlear (nerve)
- Paralysis, paralytic (complete) (incomplete), nerve, fourth or trochlear
- Paralysis, paralytic (complete) (incomplete), muscle, muscular NEC, eye (extrinsic), oblique
Notes for H49.1
As CIHI prints them, with any note H49.1 takes from the headings above it.
Excludes
Conditions classified elsewhere.
- Ophthalmoplegia:• internal (H52.5)• internuclear (H51.2)• progressive supranuclear (G23.1)From H49 Paralytic strabismus
- Nystagmus and other irregular eye movements (H55)From H49-H52 Disorders of ocular muscles, binocular movement, accommodation and refraction
- Certain:• conditions originating in the perinatal period (P00-P96)• infectious and parasitic diseases (A00-B99)complications of pregnancy, childbirth and the puerperium (O00-O99)congenital malformations, deformations and chromosomal abnormalities (Q00-Q99)endocrine, nutritional and metabolic diseases (E00-E90)injury, poisoning and certain other consequences of external causes (S00-T98)neoplasms (C00-D48)symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R99)From Chapter 7: Diseases of the eye and adnexa (H00-H59)
Where H49.1 sits
- 1ChapterChapter 7: Diseases of the eye and adnexa (H00-H59)
- 2Block H49-H52Disorders of ocular muscles, binocular movement, accommodation and refraction
- 3Category H49Paralytic strabismus
- 4Valid code H49.1Fourth [trochlear] nerve palsy
Source and release
- Data release
- ICD-10-CA · FY 2026–2027
- Effective date
- Apr 1, 2026
- Publisher
- CIHI
This page is built from the ICD-10-CA catalog that Vero Codes reads when it suggests codes: Canadian Institute for Health Information’s FY 2026–2027 release, imported from the publisher’s file and checked against it. The description, notes and structured data come from the same record.
Frequently asked questions
What does ICD-10-CA code H49.1 mean?
H49.1 is the ICD-10-CA code for “Fourth [trochlear] nerve palsy” in CIHI’s ICD-10-CA FY 2026–2027 release.
Where is H49.1 in ICD-10-CA?
H49.1 sits under H49 Paralytic strabismus, within H49-H52 Disorders of ocular muscles, binocular movement, accommodation and refraction, within Chapter 7: Diseases of the eye and adnexa (H00-H59).
What coding notes apply to H49.1?
ICD-10-CA lists Excludes notes for H49.1, including those from the headings it sits under. They are listed on this page with where each one comes from.
Which ICD-10-CA release does this page use?
It uses CIHI’s FY 2026–2027 release, in effect from Apr 1, 2026 to Mar 31, 2027. It is a reference: confirm the code against the current list and the payer’s rules before you submit it.