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Start free with EleplanArnold-Chiari malformation type I
ORPHA:268882Morphological anomaly
Also called Chiari malformation type 1 · Chiari malformation type I · Arnold-Chiari malformation type 1
What it is
A central nervous system malformation characterized by caudal displacement of the cerebellar tonsils exceeding 5mm below the foramen magnum with or without syringomyelia. Symptoms vary in onset and severity and include suboccipital headache, neck pain, vertigo, tinnitus, ocular symptoms (diplopia, blurred vision, photofobia, nystagmus), lower cranial nerve signs, cerebellar ataxia, and spasticity. Some affected individuals can be asymptomatic.
Key facts
- Age of onset
- Infancy, Neonatal
- Inheritance
- Unknown
- Classified as
- Morphological anomaly
Signs and symptoms
Common30–79%
27- Abnormality of the clivus
- Abnormality of the eleventh cranial nerve
- Abnormality of the twelfth cranial nerve
- Abnormality of the vestibulocochlear nerve
- Anteriorly placed odontoid process
- Areflexia of upper limbs
- Cervical C2/C3 vertebral fusion
- Cranial nerve compression
- Cranial nerve paralysis
- Distal peripheral sensory neuropathy
- Dysesthesia
- Dysphagia
- Functional abnormality of the inner ear
- Fused cervical vertebrae
- Gait ataxia
- Increased intracranial pressure
- Lower limb hyperreflexia
- Myelopathy
- Nystagmus
- Progressive cerebellar ataxia
- Scoliosis
- Somatic sensory dysfunction
- Stiff neck
- Syringomyelia
- Tinnitus
- Vertigo
- Vocal cord paralysis
These ranges are how often a sign appears across everyone diagnosed, not a prediction for one person — most people have some of these and not others. Orphanet also records findings that are specifically absent in this disease; those are in the data but not listed here.
Gene
ICD-10 codes
Related health topics
Reached through the ICD-10 categories this disease is filed under, so these describe the broader group rather than this disease specifically.
Cross-references
Orphadata Science: Free access data from Orphanet. © INSERM 1999. Data version 2026-06-23. Available under CC BY 4.0. This is a reference, not medical advice.
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