ICD-10-CM 2027
ICD-10 code for Horner syndrome
From the official ICD-10-CM alphabetic index entry “Horner (-Claude Bernard) syndrome”. Page updated September 29, 2026.
About coding Horner syndrome
The ICD-10-CM code for Horner syndrome is G90.2 (Horner's syndrome).
Within G90 (disorders of autonomic nervous system), G90.2 is specifically for Horner's syndrome. Related codes cover idiopathic peripheral autonomic neuropathy (G90.0), familial dysautonomia [Riley-Day] (G90.1), Multi-system degeneration of the autonomic nervous system (G90.3), autonomic dysreflexia (G90.4), complex regional pain syndrome I (CRPS I) (G90.5), other disorders of autonomic nervous system (G90.8), disorder of the autonomic nervous system, unspecified (G90.9), postural orthostatic tachycardia syndrome [POTS] (G90.A) and 1 more.
It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.
In MS-DRG v44.0, it is part of the grouping logic for DRG 073 (Cranial and Peripheral Nerve Disorders with MCC, relative weight 1.5779) and DRG 074 (Cranial and Peripheral Nerve Disorders without MCC, relative weight 1.0173), in MDC 01 (Diseases and Disorders of the Nervous System), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.
More specific Horner syndrome codes (official index)
- traumatic
Common questions about Horner syndrome ICD-10 codes
What is the ICD-10 code for Horner syndrome?
- G90.2 — Horner's syndrome.
Is G90.2 billable?
- Yes. G90.2 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can G90.2 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict G90.2 as a principal diagnosis.
Is G90.2 a CC or MCC?
- No. G90.2 is neither a CC nor an MCC under MS-DRG v44.0.