Revealing an Uncommon Presentation of Chiari I Malformation With Diverse Craniovertebral Anomalies in the Absence of Syringomyelia and Atlanto-Occipital Subluxation: A Case Report.

A Chiari I malformation is a frequently encountered anomaly of the posterior fossa, occurring in a notable percentage of the population. It often coexists with various other craniovertebral junction abnormalities, albeit less frequently with Klippel-Feil syndrome. Interestingly, the majority of individuals with Chiari I malformation do not exhibit any symptoms. We present a rare case of a 25-year-old male with chronic neck and occipital pain, along with progressive weakness and sensory disturbances in all four limbs, urinary urgency, and elevated left shoulder. Examination unveiled spasticity, weakness, and brisk reflexes. On extensive radiological evaluation (X-ray, CT, and MRI), findings revealed various anomalies in the craniovertebral junction, including complete atlanto-occipital assimilation, basilar invagination, and platybasia. Furthermore, cervical segmentation abnormalities indicative of Klippel-Feil syndrome were observed, along with Sprengel's deformity. MRI confirmed Chiari I malformation with tonsillar herniation and myelomalacia, as well as compression at the cervico-medullary junction. This patient underwent a surgical procedure that included transoral odontoidectomy combined with occipito-cervical fixation, after which a good clinical response was observed. It emphasizes the necessity of radiological imaging for the diagnosis of Chiari and other associated abnormalities in the craniovertebral junction.