Characterisation of MRI Appearance of the Spinal Cord Syrinx in the Whole Spectrum of Chiari Malformation

Chiari malformations constitute a spectrum of hindbrain anomalies characterized by downward herniation of posterior fossa structures through the foramen magnum and are frequently associated with spinal cord syrinx, a fluid-filled intramedullary cavity that can result in progressive neurological deficits. With the advent of MRI, accurate, non-invasive characterization of Chiari malformations and associated syrinx has become possible, particularly in pediatric populations where early detection is crucial. This hospital-based cross-sectional study was conducted between February 2020 and July 2021 at the Institute of Post-Graduate Medical Education and Research and Seth Sukhlal Karnani Memorial Hospital, Kolkata, and included 31 (100%) pediatric patients (<12 years) with suspected or confirmed Chiari malformations. MRI of the brain and spine was performed using a 3.0 Tesla system to evaluate syrinx presence, level, length, morphology, and continuity, while clinical features of upper motor neuron (UMN) and lower motor neuron (LMN) involvement were documented. Results revealed that most patients were female, 65% (N=21), with earlier presentation in Chiari Type II and III cases (<18 months) compared to Type I and 0 (>24 months). Syrinx was present in 43% (N=13) of cases, but its occurrence showed no statistically significant independent association with specific Chiari subtypes (p = 0.4395). The syrinx most frequently involved the cervico-dorsal region (31.4% (N=9)), followed by the cervical (30.4% (N=8)) and dorsolumbar (21.7% (N=7)) segments, and extended beyond 3 cm in length in 55.6% (N=17) of cases. All syrinxes were centrally located and continuous, with no eccentric or skip-pattern cavities observed. Clinically, LMN features were more common (55%, N=17) than UMN signs (45%, N=14). The study concludes that MRI is indispensable for the detailed characterization of Chiari malformations and syrinx, with the cervico-dorsal segment being most commonly affected, syrinx morphology typically central and continuous, and its association with Chiari malformations appearing random rather than subtype-specific. These findings underscore the importance of MRI in early diagnosis, clinical correlation, and surgical planning while also highlighting the need for larger, multicentric studies to clarify pathogenetic relationships and optimize patient management strategies.