Aetiology and classification
Cerebral arterial malformations are congenital vascular anomalies. They can present with bleeding and compression effects on surrounding tissues [2]. The authors believe that AVMs 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 formed, leading to cerebral blood vessel flow turbulence. In this case, due to the presence of an arteriovenous malformation of the right parietal-occipital lobe, the arterial blood flow passed through local internal atrial veins via the superior petrosal sinus, flowed back to the jugular veins, and then flowed backward to the superior ophthalmic vein, causing the high pressure in 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 changes. Since the drainage vessels on both sides were not connected, the affected eye of the patient was on the same side as the malformed mass, and only one side was affected.
Clinical presentation and differential diagnosis
The main clinical features of a cAVM include intracranial haemorrhage, headache, dizziness and convulsion, as well as neurological dysfunction, brain tissue swelling, etc. Because the patient did not have any history of obvious craniocerebral trauma, the eye disease was not considered to have been caused by intracranial vascular lesions. Hence, relative imaging examinations were not conducted. Therefore, the patient was once mistakenly diagnosed as “1. Dry eye in the right eye; 2. Glaucoma in the right eye”. First, a cAVM and dry eye can be differentiated by corkscrew hyperaemia, and the dry eye would not cause recurrent headache. Second, a cAVM can result in increased intraocular pressure, orbital pain, and headache but without typical keratic precipitates (KP) and iridociliary disorder, which distinguish this condition from secondary glaucoma. Furthermore, the common anti-glaucoma therapy was not effective for this case. Conjunctival congestion, which is usually characterized by dilation of blood vessels away from the limbus of the cornea, also occurs frequently in various types of conjunctivitis, and conjunctivitis is not accompanied by increased intraocular pressure.
After several ineffective treatments, we considered intracranial vascular diseases, such as a carotid-cavernous fistula (CCF). A CCF refers to an aberrant connection between the internal carotid artery (ICA), the external carotid artery (ECA) or any of their branches within the cavernous sinus [3]. The symptoms and signs of a CCF always include eyelid swelling, proptosis, chemosis, and corkscrew hyperaemia, which is similar to this case. At present, the diagnosis of a cAVM and CCF mainly depends on digital subtraction angiography (DSA), which is considered to be the gold standard for the diagnosis of a cerebral artery malformation and can be used to identify a CCF and an AVM. However, since it is an invasive and costly examination, it is not appropriate as a requirement for the purpose of early diagnosis. CTA + CTV can clearly show the 3D structure of the malformed mass, as well as locate the position of the lesions precisely. In addition, the conditions of cranial arteries and veins, as well as the direction of flow 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.
Many patients only present clinically with neurological symptoms. Therefore, when ophthalmic symptoms occur, ophthalmologists would not consider intracranial disease. In clinical practice, when corkscrew hyperaemia accompanied by neurological symptoms is found, cerebral vascular diseases might be considered. In this case, the ophthalmologist’s diagnosis should combine disease history and imaging examination.
In conclusion, it is difficult for an ophthalmologist to diagnose a cAVM without any imaging examination; careful examination of the medical history is a necessary part of diagnosing this disease. According to the medical history, the ophthalmologist should conduct a radiographic examination to decide between conservative treatment or embolization surgery to delay disease development of a cAVM and prevent severe complications, such as intracranial haemorrhage. Additionally, a cAVM can result in ocular symptoms, which is a very unusual situation but to which it is necessary for the ophthalmologist to pay attention.
Treatment
At present, the treatment methods for arteriovenous malformation mainly include excision by microsurgery, endovascular embolism, and 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 its lower invasiveness with less damage to the brain, the interventional embolization via vessels used in this case has become the main treatment method for arteriovenous malformation [6].
