A Rare Course of Chiari Malformation With Large Syringomyelia Presenting at 54 Years Old.

Chiari malformation type 1 (CM1) is considered a congenital condition. The symptoms include severe headache, hypalgesia, and loss of temperature sensation. It constitutes a significant burden among children and young adults. The onset of symptoms of CM1 is more commonly observed in relatively young children and is very rare in those over 50 years old. This study aims to present a rare surgical case of CM1 associated with a large syringomyelia in a 54-year-old man. A 54-year-old man with low back pain was introduced to our department. He had slight hyperreflexia of the extremities, slight muscle weakness in both legs, and numbness in the right leg (3/10). He also had urinary and bowel incontinence and spastic gait. Cervical magnetic resonance imaging (MRI) showed CM1 with large syringomyelia extending from C1 to T11. The cervical canal was widened because of a long history of spinal cord expansion. The patient was successfully treated surgically by foramen magnum decompression and syringosubarachnoid shunting under the guidance of O-arm navigation. The muscle weakness and sensory function recovered almost entirely on the one-year follow-up. The patient's cervical Japanese Orthopedic Association (JOA) score had improved from 11/17 to 16/17. Gradually enlarging syringomyelia with slight CM1 is rare, but surgeons should consider this condition's possibility. Foramen magnum decompression achieves good results even in cases with a long history of syringomyelia. This new navigation technique provides an excellent result for a large syringomyelia with CM1.