Chiari I Deformity: Beyond 5 mm below the Foramen Magnum.

Area of Science:

• Neurology
• Radiology
• Developmental Biology

Background:

• Chiari syndrome encompasses a spectrum of developmental deformities, with heterogeneity complicating diagnosis and management.
• Current understanding of pathophysiologic characteristics leads to inconsistent radiologic reporting and challenges in tailoring treatment strategies.

Purpose of the Study:

• To provide clarity on Chiari 1 and related deformities (0, 0.5, 1.5) for improved radiologic assessment and patient outcomes.
• To guide radiologists in differentiating Chiari deformities from other causes of cerebellar tonsillar herniation.
• To detail imaging assessment, surgical techniques, and postoperative evaluation for Chiari deformities.

Main Methods:

• Review of recent literature on the pathophysiology of Chiari 1 and related deformities.
• Detailed description of ideal morphologic and physiologic imaging assessments.
• Discussion of surgical techniques and recognition of postoperative complications.

Main Results:

• Chiari syndrome is categorized into types 0-1.5 (postnatal development) and types 2-5 (congenital neural tube defects).
• Radiologists play a crucial role in defining disease state, surgical candidacy, and approach selection.
• Accurate interpretation of imaging is vital to avoid inappropriate surgery and assess treatment efficacy.

Conclusions:

• A comprehensive understanding of Chiari deformities and related conditions is essential for optimizing patient management.
• Radiologists must go beyond simple cerebellar tonsillar herniation criteria for accurate diagnosis.
• This review aims to enhance diagnostic accuracy and surgical decision-making for Chiari 1 and related deformities.