9.2 Mental, Nervous System, Eye, and Ear

Mental, Nervous System, Eye, and Ear

Quick Answer: For hospital outpatient pain injections, neurostimulator insertion, eye procedures, and ear surgery, first-list the reason for this encounter. Category G89 is first-listed when the visit is pain control or pain management; a site code such as M54.50 or M54.2 is additional when it adds information. If the procedure treats the underlying condition (fusion, kyphoplasty, cataract extraction), first-list that condition and do not add G89. Hemiplegia uses printed dominant / nondominant defaults. Glaucoma (H40) needs type, laterality, and stage. Substance-use documentation collapses use / abuse / dependence to one code.

This independent OpenExamPrep section helps learners study FY 2026 ICD-10-CM Official Guidelines Section I.C.5–8 for facility outpatient and ASC diagnosis coding. It does not reproduce the Tabular List. OpenExamPrep does not claim CMS, NCHS, or AAPC approval, review, or partnership.

Why G89, laterality, and stage are COC traps

Facility outpatient departments run pain clinics, injection suites, and ophthalmology ASCs. The CPT family tells you whether a steroid was injected or a cataract was removed. ICD-10-CM tells the payer whether this was a pain-management visit, a visit to treat spinal stenosis itself, or a visit for glaucoma of a stated eye and stage. First-listed logic from Section IV still sits on top: you do not first-list a chronic depression code when the patient came for a right-ear tympanostomy, and you do not first-list G89 when the surgeon is decompressing the nerve, not managing pain as the stated reason for the encounter.

Chapter 5, 6, 7, and 8 guidelines are short compared with neoplasms or circulatory disease. That brevity is the trap. Coders skip G89 sequencing, invent a time cutoff for “chronic” pain, ignore hemiplegia dominance defaults, or report one bilateral glaucoma code when the eyes have different stages.

Mental and behavioral disorders — pain, substances, dementia

Pain exclusively related to psychological factors is F45.41. Category G89 has an Excludes1 note with F45.41: do not assign both. F45.42, Pain disorders with related psychological factors, is used with a G89 code when the record documents a psychological component in a patient who also has acute or chronic pain classifiable to G89.

Psychoactive substance use, abuse, and dependence (categories F10–F19): if the provider documents more than one pattern for the same substance, assign only one code using this hierarchy:

• Use + abuse → abuse only
• Abuse + dependence → dependence only
• Use + dependence → dependence only
• Use + abuse + dependence → dependence only

In remission codes require the provider’s clinical judgment in the documentation; mild substance-use disorder in remission maps to abuse-in-remission codes, and moderate or severe maps to dependence-in-remission codes, as the guidelines state. Unspecified substance-use codes (the .9- family) are not a dumping ground: assign them when the provider documents use and it is associated with a documented substance-related mental/behavioral disorder or medical condition. Medical conditions caused by substances (the guidelines’ example is alcohol-induced acute pancreatitis with alcohol dependence) are coded as the medical condition plus the appropriate F10–F19 dependence/abuse/use code — not as an “other alcohol-induced disorder” F code that replaces the pancreatitis code.

Dementia (F01, F02, F03) is classified by etiology and by severity. If severity is missing, use unspecified severity. Inpatient progression to a higher severity during a stay uses the highest severity; that inpatient progression note does not invent a second dementia code on a single outpatient visit that documents only one severity.

Nervous system — dominant side and category G89

Dominant / nondominant side. Codes in G81 (hemiplegia and hemiparesis) and subcategories G83.1–G83.3 (monoplegia) identify whether the dominant or nondominant side is affected. If the side is documented but dominance is not, and the classification does not print a different default, use:

Example: unspecified hemiplegia affecting the right side, dominance not stated, not ambidextrous → G81.91, Hemiplegia, unspecified affecting right dominant side. The same default logic is restated in Chapter 9 for I69 sequela hemiplegia codes; do not invent a different default because the deficit is “old stroke” rather than a G81 code.

Category G89, Pain, not elsewhere classified. G89 may be used with codes from other chapters to add that pain is acute, chronic, post-thoracotomy, postprocedural, or neoplasm-related. If the pain is not specified as one of those, do not assign G89.

Do not assign G89 when the underlying definitive diagnosis is known unless the reason for the encounter is pain control/management rather than management of the underlying condition. When the encounter is a procedure aimed at treating the underlying condition (the guidelines name spinal fusion and kyphoplasty), first-list the underlying condition. No G89.

G89 is acceptable as first-listed:

• When pain control or pain management is the reason (example: displaced disc with nerve impingement and severe back pain presenting for spinal steroid injection). Report the underlying cause additional if known.
• When the patient is admitted/seen for neurostimulator insertion for pain control. If a procedure treating the underlying condition and a neurostimulator for pain control occur in the same encounter, the underlying condition is first-listed and G89 is additional.

G89 with site-specific pain codes. Assign both when G89 adds acute versus chronic (or another G89 detail) that the site code does not carry. Sequencing:

Postoperative pain: use the provider’s documentation. The default for post-thoracotomy and other postoperative pain not specified as acute or chronic is the acute form (G89.18 Other acute postprocedural pain is the usual “other” postoperative bucket). Routine or expected postoperative pain immediately after surgery is not coded. Postoperative pain tied to a specific complication (painful wire sutures is the printed pattern) lives in Chapter 19, with G89.18 or G89.28 additional if acute or chronic pain is identified.

Chronic pain is G89.2-. There is no official time cutoff that turns acute into chronic; the provider’s documentation controls. G89.3 is neoplasm-related pain whether acute or chronic. G89.3 may be first-listed when the stated reason is pain control; the neoplasm is additional. When the encounter is management of the neoplasm and neoplasm pain is also documented, G89.3 may be additional; a separate site-of-pain code is not required with G89.3. Central pain syndrome (G89.0) and chronic pain syndrome (G89.4) are not synonyms for “chronic pain”; assign them only when specifically documented.

Eye — glaucoma laterality and stage

Assign as many H40 codes as needed to identify the type, the affected eye, and the stage. Seventh characters for stage include unspecified (0), mild (1), moderate (2), severe (3), and indeterminate (4). Indeterminate means the stage cannot be clinically determined. Unspecified (0) means the record has no stage documentation. Do not mix those two ideas.

Example: primary open-angle glaucoma, right eye mild, left eye severe → two codes (right mild and left severe), not a single bilateral code with the worse-eye stage. Cataract surgery laterality still needs a matching eye diagnosis when glaucoma is only a comorbidity; first-list the cataract if that is why the patient is in the ASC.

Blindness / low vision: if both eyes are documented as blind or low vision without a visual-impairment category, H54.3. One eye without category: H54.6-. No information on whether one or both eyes: H54.7.

Ear and mastoid — laterality without a long guideline

Chapter 8 is reserved for future guideline expansion. That does not mean unspecified-ear codes are preferred. Otitis media, impacted cerumen, and hearing loss still take right, left, or bilateral when the classification provides laterality (H66.91 otitis media unspecified, right ear; H90.3 sensorineural hearing loss, bilateral). First-list the ear condition that occasioned tympanostomy, myringotomy, or mastoid procedure. A stable depression or chronic-pain history is additional only when it meets reporting rules for that visit, not because it appears on an old problem list.

Facility scenario

Hospital outpatient pain clinic: lumbar epidural steroid injection. The operative/procedure note states the reason for the encounter is pain management for documented chronic low back pain; no fusion is performed. First-list a G89 chronic pain code such as G89.29, then the site (M54.50 when unspecified low back pain is what the record supports). If the same patient instead comes to the ASC for lumbar fusion to treat stenosis, first-list the stenosis (or other documented underlying condition). Do not add G89 for expected postoperative ache. If a neurology clinic note says “hemiplegia, right-sided” with no dominance word, do not park the code on unspecified side: default right dominant. If ophthalmology documents primary open-angle glaucoma mild in the right eye and severe in the left, report two H40 codes.

Source

FY 2026 ICD-10-CM Official Guidelines for Coding and Reporting (CMS PDF) — Section I.C.5–8 and Section IV.