2026 ICD-10-CM Diagnosis Code G11.9Hereditary ataxia, unspecified

ICD-10-CM Codes›G00–G99›G10-G14›G11

ICD-10-CM G11.9
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

G11.9 is a billable ICD-10-CM diagnosis code for hereditary ataxia, unspecified. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026). In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other nervous system disorders (often hereditary or degenerative).

Code Identity

ICD-10-CM Code
G11.9
Billable Status
Yes — Valid for Submission
Code Describes
Hereditary ataxia, unspecified
Short Description
Hereditary ataxia, unspecified
Same as the full description in the CMS dataset.
Parent Code
G11
Hereditary ataxia

Code Classification

ChapterG00–G99Diseases of the nervous system
SectionG10-G14Systemic atrophies primarily affecting the central nervous system
CategoryG11Hereditary ataxia
This CodeG11.9Hereditary ataxia, unspecified

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Ataxia due to mitochondrial mutations
  • Ataxia with deafness and intellectual disability syndrome
  • Ataxia with tapetoretinal degeneration syndrome
  • Autosomal dominant cerebellar ataxia, deafness and narcolepsy syndrome
  • Autosomal recessive ataxia due to ubiquinone deficiency
  • Autosomal recessive cerebellar ataxia due to STUB1 deficiency
  • Autosomal recessive cerebellar ataxia with oculomotor apraxia type 1
  • Autosomal recessive cerebellar ataxia with oculomotor apraxia type 2
  • Autosomal recessive cerebellar ataxia, epilepsy, intellectual disability syndrome due to RUBCN deficiency
  • Autosomal recessive cerebellar ataxia, epilepsy, intellectual disability syndrome due to TUD deficiency
  • Boucher Neuhäuser syndrome
  • Cerebellar ataxia
  • Cerebellar ataxia and ectodermal dysplasia
  • Cerebellar ataxia associated with another disorder
  • Cerebellar ataxia with oculomotor apraxia type 4
  • Cerebellar ataxia, areflexia, pes cavus, optic atrophy, sensorineural hearing loss syndrome
  • Cerebral ataxia
  • Chorea due to hereditary ataxia
  • Choreoathetosis
  • Chronic deafness
  • Congenital cataract with ataxia and deafness syndrome
  • Cutaneous syndrome with ichthyosis
  • Early-onset progressive neurodegeneration, blindness, ataxia, spasticity syndrome
  • Episodic ataxia
  • Episodic ataxia type 7
  • Fragile X associated tremor ataxia syndrome
  • Gemignani syndrome
  • Hereditary ataxia
  • Hereditary cerebellar atrophy
  • Hereditary cerebellar degeneration
  • Hereditary choroidal dystrophy
  • Ichthyosis, cerebellar degeneration and hepatosplenomegaly
  • Infantile cerebellar and retinal degeneration
  • Myoclonus, cerebellar ataxia, deafness syndrome
  • Narcolepsy
  • Neurodevelopmental delay, hypotonia, cerebellar ataxia, cardiac conduction defects syndrome
  • Non-progressive cerebellar ataxia
  • Optic atrophy, ataxia, peripheral neuropathy, global developmental delay syndrome
  • Paroxysmal choreoathetosis
  • Paroxysmal dystonia
  • Paroxysmal dystonic choreoathetosis with episodic ataxia and spasticity
  • Posthemiplegic ataxia
  • Primary cerebellar degeneration
  • Primary hypersomnia
  • Primary progressive cerebellar degeneration
  • Progressive cerebellar ataxia
  • PUM1-associated developmental disability, ataxia, seizure syndrome
  • Retinal pigment epithelial dystrophy
  • Retinitis pigmentosa-deafness syndrome
  • Retinitis pigmentosa-deafness-ataxia syndrome
  • Saldino-Mainzer dysplasia
  • Seizure, sensorineural deafness, ataxia, intellectual disability, electrolyte imbalance syndrome
  • Spinocerebellar disease
  • X-linked progressive cerebellar ataxia

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

  • Hereditary cerebellar ataxia NOS
  • Hereditary cerebellar degeneration
  • Hereditary cerebellar disease
  • Hereditary cerebellar syndrome

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Ataxia, ataxy, ataxic
      • brain (hereditary)
    • Ataxia, ataxy, ataxic
      • cerebellar (hereditary)
    • Ataxia, ataxy, ataxic
      • cerebral (hereditary)
    • Ataxia, ataxy, ataxic
      • hereditary
    • Degeneration, degenerative
      • cerebellar NOS
        • primary (hereditary) (sporadic)
    • Disease, diseased
      • spinocerebellar (hereditary)
    • Paralysis, paralytic(complete) (incomplete)
      • ataxic (hereditary)
    • Sclerosis, sclerotic
      • hereditary
        • cerebellar
    • Syndrome
      • cerebellar
        • hereditary

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR NVS006
Other nervous system disorders (often hereditary or degenerative)
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Narcolepsy

    a condition characterized by recurrent episodes of daytime somnolence and lapses in consciousness (microsomnias) that may be associated with automatic behaviors and amnesia. cataplexy; sleep paralysis, and hypnagogic hallucinations frequently accompany narcolepsy. the pathophysiology of this disorder includes sleep-onset rapid eye movement (rem) sleep, which normally follows stage iii or iv sleep. (from neurology 1998 feb;50(2 suppl 1):s2-s7)

  • Cerebellar Ataxia

    incoordination of voluntary movements that occur as a manifestation of cerebellar diseases. characteristic features include a tendency for limb movements to overshoot or undershoot a target (dysmetria), a tremor that occurs during attempted movements (intention tremor), impaired force and rhythm of diadochokinesis (rapidly alternating movements), and gait ataxia. (from adams et al., principles of neurology, 6th ed, p90)

  • Myoclonic Cerebellar Dyssynergia

    a condition marked by progressive cerebellar ataxia combined with myoclonus usually presenting in the third decade of life or later. additional clinical features may include generalized and focal seizures, spasticity, and dyskinesias. autosomal recessive and autosomal dominant patterns of inheritance have been reported. pathologically, the dentate nucleus and brachium conjunctivum of the cerebellum are atrophic, with variable involvement of the spinal cord, cerebellar cortex, and basal ganglia. (from joynt, clinical neurology, 1991, ch37, pp60-1)

  • Spinocerebellar Degenerations

    a heterogenous group of degenerative syndromes marked by progressive cerebellar dysfunction either in isolation or combined with other neurologic manifestations. sporadic and inherited subtypes occur. inheritance patterns include autosomal dominant, autosomal recessive, and x-linked.

  • Narcolepsy

    a sleep disorder characterized by a tendency for excessive sleepiness during the day which occurs even after adequate sleep in the nighttime. the persons who suffer from this condition experience fatigue and may fall asleep at inappropriate times during the day.

  • Narcolepsy in Conditions Classified Elsewhere with Cataplexy|Narcolepsy in conditions classified elsewhere with cataplexy

    evidence of narcolepsy in conditions classified elsewhere with cataplexy.

  • Narcolepsy in Conditions Classified Elsewhere without Cataplexy|Narcolepsy in conditions classified elsewhere without cataplexy

    evidence of narcolepsy in conditions classified elsewhere without cataplexy.

  • Narcolepsy with Cataplexy|Narcolepsy with cataplexy

    evidence of narcolepsy with cataplexy.

  • Narcolepsy without Cataplexy|Narcolepsy without cataplexy

    evidence of narcolepsy without cataplexy.

Patient EducationClinical

Cerebellar Disorders

When you play the piano or hit a tennis ball you are activating the cerebellum. The cerebellum is the area of the brain that controls coordination and balance. Problems with the cerebellum include:

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert G11.9 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
334.9 Spinocerebellar dis NOS
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About G11.9Overview

Is G11.9 (Hereditary ataxia) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report hereditary ataxia, unspecified on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What is the ICD-9 equivalent of G11.9?

Under the General Equivalence Mappings, hereditary ataxia, unspecified converts to ICD-9-CM 334.9 (spinocerebellar dis NOS). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.