Chiari Malformation Type I: Symptoms, Mechanisms & Diagnosis

Chiari I malformation: cerebellar tonsils herniate ≥5 mm below foramen magnum. Prevalence ~0.1–0.5%; often asymptomatic.

Symptom Mechanisms

• Brainstem/cranial nerve compression: Headache (occipital, Valsalva-triggered), dysphagia, hoarseness, nystagmus, sleep apnea.
• CSF flow obstruction: Syringomyelia (syrinx in cervical cord) → cape sensory loss, weakness, neuropathic pain.
• Hydrocephalus: Rare in adults; more in pediatric.

Common Symptoms

• Suboccipital headache worsened by cough/strain/Valsalva.
• Neck pain, shoulder radiation.
• Dizziness, vertigo, imbalance.
• Paresthesias, weakness (syrinx).
• Dysphagia, dysarthria.
• Fatigue, cognitive fog.

Diagnosis

• MRI brain + cervical spine (gold standard): tonsillar position, syrinx, CSF flow cine.
• CT myelography if MRI contraindicated.

Management

• Asymptomatic/incidental: observation, serial MRI.
• Symptomatic: posterior fossa decompression ± duraplasty ± tonsillar reduction.
• Syrinx: decompression often resolves syrinx; shunt if persistent.

See a neurosurgeon with Chiari expertise for individualized decision-making.