Spontaneous dural arteriovenous fistula (DAVF) is a relatively rare pathological condition, representing 10-15% of all intracranial arteriovenous malformations, including ~6% of supratentorial and 35% of infratentorial vascular malformations (1). The reported annual incidence is ~0.15 per 100,000 individuals, and DAVFs are most frequently diagnosed in patients aged 40-60 years (2). DAVF is primarily characterized by arterial blood flow that drains directly into the cavernous sinus (CS) via an abnormal arteriovenous fistula. This abnormal drainage may lead to increased intracranial pressure and various cerebral complications (3). This condition exhibits a predilection for middle-aged men and is often associated with hypertension, trauma or other vascular pathologies. Epidemiological data on DAVF indicate a low incidence rate, and its clinical symptoms are complex and varied, which increases the difficulty of diagnosis (2). Typical clinical manifestations include ocular symptoms, such as exophthalmos and conjunctival congestion, as well as neurological symptoms. In the early stages, these symptoms may be atypical and are easily misdiagnosed as common ocular diseases, such as conjunctivitis (4). The current study reports a case of spontaneous CS-DAVF complicated by remote cerebellar hemorrhage. The study highlights the potential complications and diagnostic challenges associated with this condition, offering valuable insights for similar cases.

A 52-year-old man presented to The Second People's Hospital of Liao Cheng (Linqing, China) in December 2023 with nausea, vomiting and decreased appetite. A total of 10 days prior to this, the patient had developed redness of the left conjunctiva accompanied by a foreign body sensation in the left eye and was initially diagnosed with conjunctivitis. Oral antibiotic therapy with amoxicillin was administered and yielded poor results, with persisting symptoms; the exact dose and duration are not available. The patient had a history of hypertension and denied any trauma. On admission, a physical examination revealed the following: Temperature, 36.5˚C (normal range, 36.0-37.3˚C); pulse, 64 beats/min (normal range, 60-100 beats/min); respiratory rate, 16 breaths/minute (normal range, 12-20 breaths/min); and blood pressure, 154/104 mmHg (normal range, <140/90 mmHg for an adult male). No facial weakness, sensory disturbance, dysarthria, ataxia or gait instability was observed. Bilateral pupillary light reflexes were intact, and no visual acuity deterioration, proptosis or tinnitus was noted. The patient was conscious and oriented, with left conjunctival congestion and mild limitation of the abduction of the left eye. An abdominal examination revealed a soft abdomen without tenderness or rebound pain. No hepatic or renal percussion tenderness was elicited. Bowel sounds were normal, and the lower extremities were free of edema. Routine laboratory investigations, including coagulation function, were unremarkable. Further workup with a non-contrast computed tomography scan of the whole abdomen demonstrated hepatic calcifications (Fig. 1). Despite symptomatic supportive treatment, including antiemetics and hydration, which yielded mild improvement in the vomiting, the left conjunctival congestion persisted severely. Further head magnetic resonance imaging demonstrated a subacute intracerebral hemorrhage in the left cerebellar hemisphere (Fig. 2A-C), and magnetic resonance angiography revealed a left CS fistula (Fig. 2D). Therefore, the patient was transferred to the Department of Neurosurgery for further management.

After the exclusion of surgical contraindications, the patient underwent a diagnostic angiography in January 2024, for a comprehensive assessment of the vascular pathology. Selective angiography of the left external carotid artery revealed a vascular network arising from the distal branches of the ascending pharyngeal artery and supplying the CS. Drainage was observed into the ophthalmic vein, inferior petrosal sinus and superior petrosal sinus, confirming the presence of a CS-DAVF (Fig. 3).

The patient underwent an interventional embolization for the DAVF on day 6 post-presentation. During the procedure, a 5F single-curve angiographic catheter was selectively advanced into the left internal jugular vein over a Glidewire^® (Terumo Medical Corporation), with the tip positioned at the junction of the inferior petrosal sinus and jugular vein. The patency of the inferior petrosal sinus was confirmed by Glidewire exploration, which successfully accessed the CS. A pre-shaped Echelon-10 (Medtronic plc) microcatheter was then navigated over a microwire into the anterior CS, adjacent to the origin of the ophthalmic vein. Microcatheter angiography confirmed the intracavernous position. Multiple coils were deployed in a basket configuration, embolizing the ophthalmic vein origin and anterior CS. After preparing the microcatheter with a dimethyl sulfoxide flush, Onyx-18 (Medtronic plc) was slowly injected through the microcatheter, permeating the ophthalmic vein origin, CS compartments and fistula sites.

Post-embolization bilateral common carotid angiography revealed complete occlusion of the left CS, with visible coil mesh and Onyx cast. No opacification was identified in the ophthalmic vein and superior petrosal sinus, while the delayed venous phase showed minimal faint opacification in the posterosuperior CS draining into the inferior petrosal sinus (Fig. 4). The procedure was successfully completed with adequate anesthesia. Postoperatively, the patient received nutritional support, dexamethasone (5 mg, intravenous, stat), glycerol fructose (250 ml, intravenous drip, every 12 h) to reduce intracranial pressure, and vitamin B6 (0.2 g, intravenous drip, once daily) for neurotrophic support. At the 1-week follow-up, the left conjunctival edema had improved compared with the preprocedural status, with mild restriction of left ocular movement and preserved limb mobility, muscle strength and muscle tone. No postoperative hemorrhagic, ischemic or infectious complications were observed during hospitalization. At the 1-month follow-up, the patient showed marked improvement in conjunctival congestion and ocular motility, without evidence of recurrent hemorrhage or neurological deficits. The patient is scheduled for regular clinical and imaging follow-up every 3 months to monitor for recurrence. The prognosis of the patient is considered favorable based on the complete occlusion of the fistula and the progressive resolution of symptoms.

Spontaneous DAVF in the CS region is an uncommon vascular malformation, typically characterized by ophthalmic and neurological symptoms, such as ocular motility disorders, elevated intraocular pressure and headaches (4). Current literature indicates that patients are frequently misdiagnosed with mild ocular conditions, such as conjunctivitis, at the initial presentation, leading to a delay in appropriate treatment (3,5). In the current case, the patient presented with remote cerebellar hemorrhage, an atypical manifestation that may be attributed to hemodynamic changes in the CS, especially in cases of obstructed venous drainage of the orbit (6,7). This unusual manifestation underscores the complexity of DAVF and the severity of its associated symptoms.

Clinically, the diagnosis of DAVF often faces challenges, as early symptoms can easily be confused with other diseases. Patients may seek medical attention due to ocular symptoms such as conjunctival congestion, and the preliminary diagnosis is often misidentified as conjunctivitis (4). Therefore, in radiological evaluation, it is crucial to pay close attention to the abnormal signals on cranial MR and the manifestations of cerebral hemorrhage, particularly in patients presenting with concomitant ocular and neurological signs. Therapeutically, interventional embolization has demonstrated favorable outcomes in managing DAVF, effectively alleviating symptoms and improving quality of life (8,9). The treatment plan for the present case was determined through a multidisciplinary consultation, considering the patient's high-risk factors, particularly hypertension, emphasizing the necessity of early recognition and intervention (10). Future research should further explore the optimal management strategies and epidemiological characteristics of different DAVF subtypes, thereby optimizing clinical outcomes and mitigating complications (11,12).

From the pathological perspective, the development of CS arteriovenous fistula is closely associated with hypertension, particularly in non-traumatic cases. The etiology of DAVF is likely multifactorial, involving hypertension, chronic venous obstruction and other vascular lesions. Arteriovenous fistulas in non-traumatic patients usually occur in the setting of elevated venous pressure. Long-term venous hypertension may lead to vascular wall fragility and pathological remodeling, thereby promoting the formation of fistulas, resulting in the direct shunting of arterial blood into the venous system (13,14). This abnormal blood flow pattern may lead to venous hypertension, especially in cases where venous drainage from the eye is obstructed. When the pressure within the CS increases, it may induce hemodynamic alterations at distant sites. Common causes of distant cerebellar hemorrhage include arterial embolism and ischemia, lesions of the venous system, traumatic factors, tumors, cerebral infections or inflammation (15). At presentation, the current patient lacked common precipitating factors, such as arterial embolism, ischemia or trauma. Therefore, the condition was attributed to the DAVF-induced abnormal hemodynamics.

The clinical significance of the present case lies in the accompanying remote cerebellar hemorrhage, underscoring the intricate pathological mechanisms associated with DAVF. Through detailed analysis, the case reminds clinicians to maintain a high level of vigilance for similar symptoms to prevent a misdiagnosis and delays in treatment. Imaging studies play a key role in the diagnosis of DAVF, especially when the patient presents with ocular and neurological symptoms (4).

There are certain limitations to the present study. Firstly, this is a single-case report describing a rare presentation of CS-DAVF associated with remote cerebellar hemorrhage. Therefore, the findings may not be generalizable to all patients with DAVF. Secondly, the retrospective nature of this report may have introduced incomplete clinical information and potential publication bias related to the rarity of the condition. Thirdly, the follow-up period was relatively short, limiting comprehensive evaluation of the long-term prognosis and recurrence risk after endovascular treatment. In addition, the diagnostic evaluation and treatment strategy were based on single-center clinical experience, which may differ across institutions. Further multicenter studies with larger sample sizes are needed to better clarify the clinical characteristics, pathophysiological mechanisms and optimal management strategies of DAVF. Despite the inherent limitations of this study, it offers valuable insights for clinical practice and emphasizes the importance of early recognition and intervention for DAVF. This report paves the way for further investigations, aiming to improve the understanding of DAVF and subsequently enhance the overall prognosis for patients.