Foix-Alajouanine syndrome is a rare disorder characterized by the formation of an arteriovenous fistula in the spine and subsequent venous congestion leading to myelopathy. Initial signs and symptoms are nonspecific, which is why the diagnosis is often delayed for months. Imaging studies, such as magnetic resonance imaging and computed tomography, are necessary to visualize the fistula.
Formation of a spinal dural arteriovenous fistula (SDAVF) is the clinical hallmark of Foix-Alajouanine syndrome  . Two types are recognized - ventral, in which shunting between the anterior spinal artery and a draining vein occurs; and dorsal, described when arteriovenous communication is established at the level of a dural root sleeve . Over time, venous congestion of the spinal cord and thrombosis (but without hemorrhage) ensues, resulting in myelopathy and the appearance of non-specific symptoms - gait disturbances, ranging from mild to severe enough to impair walking, paresthesias and sensory deficits (mostly involving distal lower extremities in an asymmetrical fashion), leg weakness, and micturition problems (urinary hesitancy and retention)    . Additionally, anal sphincter disturbance, cramping, erectile dysfunction and severe leg pain, are encountered in the majority patients in whom the diagnosis is delayed, and a mean delay of 15 months was observed in some reports   . The absence of symptoms related to the upper limbs is one of the main distinguishing features of Foix-Alajouanine syndrome since fistulas very rarely develop in the cervical spine. In fact, the mid-thoracic and lumbar spine are most frequent sites where SDAVFs are diagnosed  . A slowly progressive clinical course over months or years is typical for Foix-Alajouanine syndrome , but acute episodes of deterioration were encountered after prolonged standing or exercise .
The diagnosis of Foix-Alajouanine syndrome and SDAVF may be difficult to attain, especially in early stages of the disease. For this reason, workup must start with a detailed patient history that will identify the onset of symptoms and their features, followed by a rigorous physical examination. Physicians must conduct a meticulous neurological exam that will identify all deficits, as initial diagnosis of disorders involving the spinal cord can be made if the exam is done properly. Imaging studies, however, are necessary to confirm the presence of a fistula. Magnetic resonance imaging (MRI) of the spine can reveal T2 enhancement in the lower part of the spinal cord (conus medullaris), the presence of serpentine vessels involving the spinal roots and end-on vessels on the sagittal images, grossly abnormal perimedullary vascular flow and spinal cord edema   . Because the procedure often provides sufficient clues that support the initial diagnosis, it should be performed first, followed by more specialized techniques - digital subtraction angiography (DSA), spinal computed tomography angiography (CTA) and spinal magnetic resonance angiography (MRA) . DSA is considered to be the gold standard, as it provides the most detailed view of the arterial and venous vessels . But because a very high radiation dose is required, CTA and MRA are more frequently performed .