Traumatic carotid-cavernous fistula (TCCF) is an acquired pathological arteriovenous shunt between the internal carotid artery (ICA) and the cavernous sinus (CS) secondary to traumatic brain injury (1). It accounts for ~2.5-3% of all intracranial vascular malformations (2). The diagnosis of TCCF is based on clinical manifestations and is confirmed by radiological modalities. Typical TCCFs drain into the ophthalmic veins, which causes the progressive congestion of venous sinuses and subsequent pathognomonic ocular symptoms. However, the perimedullary venous drainage pathway and the presentation of delayed myelopathy in TCCF are rare, and only three cases to date have been reported (3-5), at least to the best of our knowledge. In addition, low-flow direct CCFs are also rarely reported. Due to its rarity, there is limited information available regarding the clinical characteristics and the underlying mechanisms of delayed myelopathy induced by TCCF. The present study describes the case of a patient with a history of traumatic brain injury who presented with delayed myelopathy consequent to spinal venous hypertension induced by TCCF.

CCFs are abnormal communications between the ICA and the CS and can be divided into two groups as follows: Direct CCFs (type A, where the pathological shunt involves the cavernous segment of the ICA and the CS directly) and indirect CCFs (types B-D, where the pathological shunt involves the meningeal branches of the ICA or the ECA and the CS) (7). TCCFs are direct lesions often acquired consequent to brain injury, which account for up to 75% of all cases (8). The drainage pathways of CCFs flow anteriorly via the ophthalmic veins, inferiorly via the inferior petrosal sinus, posteriorly via the deep venous system, SPS and cerebellar veins; and superiorly via the superficial middle cerebral vein (9). The clinical signs and symptoms are related to the drainage pattern of the fistula and the rapidity of progression.

Inferior and anterior drainages are the most common routes in all CCFs. Superior and posterior drainages are noted only in long-standing direct and high-flow fistulas. The majority of TCCFs drain into the ophthalmic veins, which causes the progressive congestion of venous sinuses and leads to the sudden onset of pathognomonic ocular symptoms. The clinical presentation of progressive myelopathy induced by CCFs is relatively rare. A similar case presented with myelopathy was prevously reported due to a dural arteriovenous fistula, which drains into the cervical perimedullary veins via the petrosal sinus system (10). The patient in the present study had the rare clinical presentation of myelopathy, and his cerebral DSA revealed a TCCF with posterior drainage into the perimedullary veins. To the best of our knowledge, only three cases of CCFs with progressive myelopathy have been reported to date, among which, two were spontaneous CCFs (3,4) and one was a TCCF (5).

Posterior drainage may be noted in high-flow and long-standing direct fistulas. Direct fistulas are usually considered as high-flow shunts with an acute onset of symptoms (11). Although TCCFs manifest symptoms at an early stage following brain injury, the longest duration acknowledged in a previous study released was 8 weeks (12). One proper interpretation for the delayed clinical presentation of TCCFs is that cavernous sinuses are composed of several small venous compartments (lateral, medial, antero-inferior and postero-superior compartments), and these compartments are joined by several anastomoses. Thus, the development of a low-flow direct CCF without steal phenomena is highly probable when the fistula orifice is inside the lateral venous space of the CS (a narrow space with small connections with the rest of CS) (13). In the case presented herein, the patient suffered from a direct TCCF and presented with delayed myelopathy at ~2 years after suffering brain injury without any steal phenomena. Thus, the assumption was that the fistula orifice may be located in the lateral venous compartment, which is separated from the remaining sections of the CS, and led to a relatively low shunt flow rate. Thus, this type of vascular malformation may be referred to as a low-flow direct CCF from the perspective of flow rate, based on the interval between the initial brain injury and the onset of symptoms.

Patients with progressive myelopathy usually undergo an MRI to confirm the presence of CCFs. In these cases, a spinal MRI examination reveals swelling and a pathologically altered spinal cord signal with contrast enhancement. However, an MRI has a sensitivity of only 50% (14). Thus, DSA is the gold standard in the diagnosis and treatment planning of CCFs. DSA provides a thorough understanding of fistula location, the pathological angioarchitecture and venous drainage pattern. Endovascular embolization using embolic agents is the preferred treatment (15). The goal of treatment is to occlude the fistula and proximal venous drainage, reduce venous congestion and prevent the recruitment of collateral vessels (16). Adjacent vessels can be recruited and CCFs may recur if residues remain in the fistula and drainage veins. The diverse manifestations of CCFs may mimic certain spinal cord pathologies; thus, it is suggested that CCFs as a possible cause of cervical myelopathy need to be taken into consideration.