Foix-Alajouanine syndrome caused by MRI occult thoracic ventral perimedullary arteriovenous fistula: illustrative case.

[BACKGROUND] Foix-Alajouanine syndrome (FAS) is a subacute, progressive spinal cord disorder that usually shows abnormalities on spinal cord MRI. Here, the authors report a case of FAS that showed no abnormalities on MRI and was treated.

[OBSERVATIONS] A 64-year-old woman presented with progressive spinal cord damage in both lower limbs. Repeated hospitalizations for neurological examinations revealed no obvious abnormalities. MRI showed no obvious abnormalities, but angiography suggested a ventral arteriovenous fistula (AVF) in the thoracic spinal cord. A microcatheter confirmed the diagnosis of perimedullary AVF, and shunt occlusion was performed using a combination of a microscope and an oblique endoscope. After surgery, symptoms were mildly alleviated and progression was halted.

[LESSONS] In patients with progressive FAS, spinal vascular disease should be investigated even if MRI findings are normal. In addition, combined endoscopic surgery is a promising tool for treating perimedullary AVFs in the ventral thoracic spinal cord. https://thejns.org/doi/10.3171/CASE25864.