Overview
Arnold-Chiari malformation type I (also known as Chiari malformation type I, or CM-I) is a structural condition in which the lower part of the cerebellum, specifically the cerebellar tonsils, extends downward through the foramen magnum (the opening at the base of the skull) into the upper spinal canal. This displacement can compress the brainstem and spinal cord and disrupt the normal flow of cerebrospinal fluid (CSF), potentially leading to a fluid-filled cavity within the spinal cord called a syringomyelia (syrinx). The condition primarily affects the nervous system. Key symptoms include headaches (classically occipital headaches worsened by coughing, straining, or Valsalva maneuvers), neck pain, balance difficulties, dizziness, numbness or tingling in the hands and feet, difficulty swallowing (dysphagia), and sleep-related breathing disorders. Some patients may also experience tinnitus, visual disturbances, and weakness in the extremities. The severity of symptoms varies widely; some individuals remain asymptomatic and are diagnosed incidentally on brain imaging, while others experience significant neurological impairment. Chiari malformation type I is typically diagnosed in adolescence or adulthood, often through magnetic resonance imaging (MRI) of the brain and spine. Treatment depends on symptom severity. Asymptomatic patients may be monitored with periodic imaging and clinical assessments. For symptomatic patients, the primary treatment is posterior fossa decompression surgery, which aims to create more space for the cerebellum and restore normal CSF flow. Additional surgical procedures may be needed if a syrinx is present. Pain management, physical therapy, and occupational therapy may also be part of a comprehensive care plan. While surgery can improve or stabilize symptoms in many patients, outcomes vary and long-term follow-up is important.
Clinical phenotype terms— hover any for plain English:
Multifactorial
Caused by a mix of several genes and environmental factors
Variable
Can begin at different ages, from infancy through adulthood
FDA & Trial Timeline
3 eventsCentre Hospitalier Universitaire, Amiens — NA
Fondazione I.R.C.C.S. Istituto Neurologico Carlo Besta
Hacettepe University — NA
Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.
Treatments
No FDA-approved treatments are currently listed for Arnold-Chiari malformation type I.
2 clinical trialsare actively recruiting — trials can provide access to cutting-edge therapies.
View clinical trials →Treatment Centers
8 centersBaylor College of Medicine Rare Disease Center ↗
Baylor College of Medicine
📍 Houston, TX
🏥 NORDStanford Medicine Rare Disease Center ↗
Stanford Medicine
📍 Stanford, CA
🔬 UDNNIH Clinical Center Undiagnosed Diseases Program ↗
National Institutes of Health
📍 Bethesda, MD
🔬 UDNUCLA UDN Clinical Site ↗
UCLA Health
📍 Los Angeles, CA
🔬 UDNBaylor College of Medicine UDN Clinical Site ↗
Baylor College of Medicine
📍 Houston, TX
🔬 UDNHarvard/MGH UDN Clinical Site ↗
Massachusetts General Hospital
📍 Boston, MA
🏥 NORDMayo Clinic Center for Individualized Medicine ↗
Mayo Clinic
📍 Rochester, MN
👤 Mayo Clinic Center for Individualized Medicine
🏥 NORDUCLA Rare Disease Day Program ↗
UCLA Health
📍 Los Angeles, CA
Travel Grants
No travel grants are currently matched to Arnold-Chiari malformation type I.
Community
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Start the conversation →Latest news about Arnold-Chiari malformation type I
Disease timeline:
New recruiting trial: Neurosurgical Outcome Network
A new clinical trial is recruiting patients for Arnold-Chiari malformation type I
New recruiting trial: Investigation of the Effects of Exercise Program in Patients With Chiari Type 1 Malformation
A new clinical trial is recruiting patients for Arnold-Chiari malformation type I
Caregiver Resources
NORD Caregiver Resources
Support, advocacy, and financial assistance for caregivers of rare disease patients.
Mental Health Support
Rare disease caregiving can be isolating. Connect with counseling and peer support.
Family & Caregiver Grants
Financial assistance programs specifically for caregivers of rare disease patients.
Social Security Disability
Learn how rare disease patients may qualify for SSDI/SSI benefits.
Common questions about Arnold-Chiari malformation type I
What is Arnold-Chiari malformation type I?
Arnold-Chiari malformation type I (also known as Chiari malformation type I, or CM-I) is a structural condition in which the lower part of the cerebellum, specifically the cerebellar tonsils, extends downward through the foramen magnum (the opening at the base of the skull) into the upper spinal canal. This displacement can compress the brainstem and spinal cord and disrupt the normal flow of cerebrospinal fluid (CSF), potentially leading to a fluid-filled cavity within the spinal cord called a syringomyelia (syrinx). The condition primarily affects the nervous system. Key symptoms include he
How is Arnold-Chiari malformation type I inherited?
Arnold-Chiari malformation type I follows a multifactorial inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
Are there clinical trials for Arnold-Chiari malformation type I?
Yes — 2 recruiting clinical trials are currently listed for Arnold-Chiari malformation type I on UniteRare. See the clinical trials section on this page for phase, sponsor, and site details sourced from ClinicalTrials.gov.
Which specialists treat Arnold-Chiari malformation type I?
22 specialists and care centers treating Arnold-Chiari malformation type I are listed on UniteRare, sourced from ClinicalTrials.gov principal investigators, published research, and the NPPES NPI registry.