SVOA Neurology

Salim MEZIANI¹, Yacine FELISSI^1*, Chafik HANDIS¹, Abdelhalim MORSLI¹

¹Bab El Oued University Hospital, Department of Neurosurgery. Dr Youcef El Khatib University of Health Science – Faculty of Medicine, Algiers, Algeria.

*Corresponding Author: Yacine FELISSI, Mohamed Lamine Debaghine University Hospital, Department of Neurosurgery, Algiers university – Faculty of Medicine, Algiers, Algeria.

https://doi.org/10.58624/SVOANE.2025.06.020

Received: June 14, 2025

Published: July 21, 2025

Citation: MEZIANI S. FELISSI Y. HANDIS C. MORSLI A. Special Features of Chiari Malformation Type 0. SVOA Neurology 2025, 6:4, 101-107. doi.10.58624/ SVOANE.2025.06.020

Abstract

Objective: Chiari malformation type 0 (CM-0) is an uncommon condition characterized by syringomyelia and cerebrospinal fluid (CSF) obstruction at the foramen magnum without cerebellar tonsillar descent. This study aims to delineate its clinical, radiological, and surgical aspects to refine diagnostic and therapeutic protocols.

Methods: In a prospective cohort of 80 patients operated for Chiari malformations at Bab El Oued University Hospital between 2017 and 2022, 10 adult cases of CM-0 were identified. All exhibited suboccipital headaches, sensory symptoms, cervicobrachial neuralgia, and syringomyelia. Imaging demonstrated no tonsillar herniation, reduced posterior cranial fossa (PCF) volume (mean 197.4 cm³ vs. normal 228–244 cm³), pointed tonsils, and CSF flow blockage. Treatment involved osteo-dural decompression, arachnoid web dissection, and autologous duraplasty.

Results: Headaches resolved postoperatively, with motor improvement reflected by JOA score increase (15 → 16.6). Syringomyelia regressed in length (16.4 → 13.4 vertebral levels) and width (Vaquero index: 0.76 → 0.38). CSF dynamics normalized in 9/10 patients; tonsils changed from pointed to rounded. However, residual symptoms included thermoalgesic dissociation (7/10) and muscle atrophy (9/10). Arachnoid adhesions blocking the foramen of Magendie were observed intraoperatively in all cases.

Conclusion: CM-0 is marked by a small PCF, atypical tonsillar morphology, and obstructive arachnoid pathology. Outcomes resemble those of Chiari type 1, but success hinges on thorough intradural inspection and arachnoid release. Tonsillar configuration and arachnoid anomalies may be pivotal in syrinx formation, affirming CM-0 as a separate clinical entity requiring individualized management.

Keywords: Chiari Malformation Type 0; Syringomyelia and Cerebrospinal Fluid Obstruction; Posterior Cranial Fossa Volume