Aetiology and classification
Cerebral arterial malformations are congenital vascular anomalies. These can present with bleeding and compression effects on surrounding tissues.[2] The authors believe that AVM will gradually cause different degrees of symptoms with age and deterioration of vascular conditions. Due to the absence of capillaries between cerebral veins and cerebral arteries in the area of cerebrovascular diseases, arteriovenous communication and vascular regulation mechanism barriers are caused, leading to cerebral blood vessel flow turbulence. In this case, due to the presence of arteriovenous malformation of right parietal-occipital lobe, the blood flow in arteries passed through local internal atrial veins via superior petrosal sinus then back to jugular veins, then flow backward to the superior ophthalmic vein, causing the high pressure of the superior ophthalmic vein. In this case, early CTA+CTV examination revealed that the right superior ophthalmic veins were enlarged and tortuous, which was in accordance with such change. Since the drainage vessel on both sides were not connected, the affected eye of the patient was on the same side as the malformation mass and only one side was affected.
Clinical presentation and differential diagnosis
The main clinical features of cAVM including intracranial hemorrhage, headache, dizzy and convulsion, as well as neurological dysfunction, brain tissue swelling, etc.. Because the patient didn’t have any history of obvious craniocerebral trauma, it was not considered that the eye disease was caused by intracranial vascular lesions, hence relative imaging examinations were not conducted. Therefore, the patient was once mistakenly diagnosed as "1. Dry Eye in right eyes; 2. Glaucoma in the right eye". Firstly, cAVM and dry eye can be differentiated by corkscrew hyperemia, and the dry eye would not cause recurrent headache. Secondly, cAVM can result in increased intraocular pressure, orbital pain, headache, but without typical keratic precipitates (K.P) and iridociliary disorder, which distinguish this condition from secondary glaucoma. Furthermore, the common anti-glaucoma therapy was not effective for this case. Conjunctival congestion also occurs frequently in various types of conjunctivitis. which is usually characterized by dilation of blood vessels away from the limbus of the cornea. And conjunctivitis are not accompanied by increased intraocular pressure.
After the several ineffective treatment, we considered about intracranial vascular disease such as Carotid-cavernous fistula (CCF). CCF refers to an aberrant connection between the internal carotid artery (ICA), the external carotid artery (ECA) or any of their branches with the cavernous sinus [3]. The symptoms and signs of CCF always include eyelid swelling, proptosis, chemosis, and corkscrew hyperemia, which is similar to this case. At present, the diagnosis of cAVM and CCF mainly depends on digital subtraction angiography(DSA), which is considered to be the golden standard for the diagnosis of cerebral artery malformation and can be used to identify CCF and AVM. But since it’s an invasive examination and costly, it is not appropriate for the requirement of early diagnosis purpose. CTA+CTV can clearly show the 3D structure of the malformation mass, as well as locating the position of the lesions precisely, meanwhile the conditions of cranial arteries and veins as well as the flowing direction of draining veins can be shown clearly[4]. The mature application of combined techniques including CTA, CTV and MRI have provided visualized 3D images of the relation between lesions and their surrounding structures for clinicians, which is more suitable for early diagnosis.
Treatment
At present, the treatment methods of arteriovenous malformation mainly include excision by microsurgery, endovascular embolism, stereotactic radiotherapy. Endovascular embolization has been playing an increasingly important role in AVM therapy due to its convenience and minimally invasive features[5]. Due to it’s less invasive and causes less damage to the brain, the interventional embolization via vessels used in this case has become the main treatment method for arteriovenous malformation[6].