DESCENDENT ATROPHY OF OPTIC NERVE AND SECONDARY BILATERAL GLAUCOMA AS COMPLICATIONS OF CAROTID-CAVERNOUS FISTULA AND ANEURISM: CASE REPORT

Endocranial aneurysm of the internal carotid artery (ICA) is a fusiform or saccular enlargement of the lumen of the blood vessel for at least 50 % of the anatomy diameter. Health problem occurs due to compression, rupture, thrombosis, or embolus. Carotid- cavernous fistula (CCF) is an abnormal communication between the carotid arterial system and cavernous sinus (arteriovenous fistula). According to communication, Barrow (1985) classifies four types of CCF: A, B, C, and D. Classification: direct-indirect, traumatic-spontaneous, high-low pressure. Clinical presentation: conjunctival congestion, orbital „brui“, pulsating exophthalmos, ophthalmoplegia externa, secondary glaucoma. The descendent atrophy of the optic nerve is due to a lesion of the third neuron of the visual pathway. Secondary glaucoma is exogenous due to elevated venous pressure (episcleral, v.vortikosae and ophthalmicae). Treatment: embolization of the fistula and medica- mentous. Herein we present a case of a 59-year-old patient, operated due to the left carotid cavernous fistula and right aneurysm, blindness of the left eye one year after surgery due to descending optic nerve atrophy and concentric constriction of the visual field in the right eye as a result of untimely diagnosed secondary glaucoma after surgery. Presentation considers diagnostic and therapeutic approach to the patient in order to preserve vision in the functionally remaining eye. Acta Medica Medianae 2016;55(3):57- 65.


Introduction
Aneurysm is permanent, fusiform or saccular pathological enlargement of the arterial vessel lumen, at least 50% of the anatomy diameter. Aneurysms of the internal carotid artery (ICA, ACI) are very rare (0.27 -5% of the total number of operations on the carotid arteries) (1). Internal carotid artery is a terminal branch of the common carotid artery (a.carotis communis). It is formed between C3 and C5 cervical vertebra via bifurcation of the common carotid artery to the internal (ICA) and external (ECA) carotid artery (2). Terminologia Anatomica (1998) subdivided ACI into four segments:cervical, petrous, cavernous, and cerebral (3).
There are several classifications, abd according to the basic anatomic localization, aneurysms of ACI are divided into extracranial and endocranial. A more detailed classification system with clinical implications by neuroradiologists, neurosurgeons and neurologists, recommended from Bouthillier et al. (1996), based on angiographic findings, identifies seven anatomical segments presented in the corresponding alphanumeric nomenclature (4) (Figure 1) C1:Cervical segement C2: Petrous (horizontal) segment C3: Lacerum segment C4: Cavernous segment C5: Clinoid segment C6: Ophthalmic (supraclinoidal) segment C7: Terminal segment Aneurysms of the carotid artery due to etiology could be true (a.vera) and false (pseudoaneurysm, a.spuria). True aneurysms are the most common consequences of atherosclerosis, arteritis, fibromuscular dysplasia, or infective etiology (mycotic). False aneurysms could be: post-trauma tic, dissecting, and iatrogenic. They represent a serious medical problem due to compression of adjawww.medfak.ni.ac.rs/amm cent structures, rupture, thrombosis, or distal embolization. Mortality in unoperated population is about 70 %, and mycotic aneurysms rupture more often (1).
Therapy: -Medicamentous (artificial tears, antiglaucoma medications) -Ophthalmosurgical (Tarsorrhaphy) -Neurosurgical, including: I) transcranial exploration of cavernous sinus with a ligature of the ICA proximal and distal to the fistula (rarely) and, II) endovascular treatment via transarterial (direct) or transvenous access (indirect) by applying a thin platinum coil fiber embolizationcoiling, balloon embolization or stent for aneurysm with wide neck. The diameter of the neck to perform coiling introduced in 1991, (by the author Guido Guglielmi) is 4 mm and the lumen less than 25 mm (10).
Clamping of an aneurysm in its neck is also possible (6,9,11).
The most common ophthalmic complications are: choroidal ablation, OVCR, descending atrophy of the optic nerve, and secondary glaucoma. The descending optic nerve atrophy occurs as a consequence of the lesion of the third neuron in visual pathway (12). Secondary glaucoma can be caused by different pathomechanisms, the most common being open-angle.
-Closed angle glaucoma in rare cases, due to increased orbital venous pressure, and the following congestion of the iris and choroid, pushing the iridolental diaphragm forward (pushing mechanism), blocking the anterior chamber angle by iris root.

Case report
The patient, aged 59 years, underwent surgery at the Clinic of Neurosurgery (August 2006) for left-sided arterio-venous fistula (caroticoophthalmicae), followed by sudden and intense headache, right hemiplegia, crisis of consciousness. In May 2007, previously diagnosed infraclinoid fusiform aneurysm of the internal carotid artery (ICA) in the right cavernous sinus was operated. Two to three years postoperatively, the patient was treated with antiepileptic drugs (Tbl.Phenobarbiton), and within antiedematous therapy Tbl. Acetazolamide 2x1 were administered. After the operation, the patient manifested transient bilateral external ophthalmoplegia that lasted several months, with spontaneous recovery of ophthalmoplegia and complete loss of vision in the left eye, after which in November 2007 for the first time computerized visual field examination was done. She visited to the reffered ophthalmologist who due to elevated values of intraocular pressure (IOP) prescribed Sol Timolol 0.5 %. Patient was irregularly controlled further. The next visual field testing was done in 2008, but the therapy was interrupted by herself. First visit to the ophthalmologist at Clinic of Ophthalmology Niš, was in June 2011, due to repeated headaches and visual acuity control. At clinical examination residual discreet ptosis of the right eye was evident. Ophthalmologic examination found normal visual acuity of the right eye (VOD = 0.9-1.0), while in the left eye therre was an apparent decline in visual acuity, reduced to light perception with accurate projection (VOS = L+P+). Intraocular tension measured by the Goldman applanation tonometer in both eyes was TOU = 22 mmHg. At slit-lamp (biomicroscopy), left pupil was mydriatic with sluggish reaction to light-relative afferent pupillary defect (SLOS: RAPD). Ophtalmoscopy revealed excavation of the optic nerve head, cup/disc ratio of the right eye C/ D = 0.6-0.7/II, and on the left C/D = 0.9-1.0/III. (Figure 6  cranium in T2 sequence, in transverse and coronary projection, and magnetic resonance angio- nary projection and magnetic resonance angiography of carotid and cerebral blood vessels were performed in a patient one year later. A fusiform infraclinoid aneurysm of ICA (internal carotid artery) in the cavernous sinus is presented on the right. Computed tomography (CT) of the cranium. Condition after craniotomy temporally on both sides. Brain tissue infra-and supratentorialy without densitometry alterations. Discontinuity in the temporal bones because of surgical intervention. (Figure 12, 13a, 13b) Testing during hospitalization: 1-SAP Humphrey FA(30-2) Threshold Test 3-Doppler sonography of neck blood vessels: normal finding.
Follow-up and testing were continued in glaucoma department: -SAP Humphrey FA (30-2) threshold test (2012)OD: Residual central visual field island of 10-15 degrees (MD=26.22dB CPSD 9.93dB)( Figure  15). a Figure 13. a Magnet Resonance Imaging (MRI) of endocranium in T2 sequence, the transverse and coronary projection and magnetic resonance angiography of carotid and cerebral blood vessels, a fusiform infraclinoid aneurysm of ICA (internal carotid artery) in cavernous sinus is presented on the right. As findings showed the progression of the disease, the therapy in drops was corrected: Sol Timolol, Sol Dorzolamid and Sol Brimonidine 0.2 %. Due to allergic reactions to locally applied antiglaucoma drugs, the patient underwent allergy testing, which did not confirm any allergic reaction, and the patient went to a competent neurologist, who diagnosed trigeminal neuralgia.
Ophthalmologist prescribed therapy Sol. Dexa-methasone-Neomycin for two weeks which improved the local findings. Within neuralgia, intermittent worsening of ptosis was apparent. Due to the measured values of intraocular pressure TOU=20 mmHg, antiglaucoma therapy was corrected: Sol Timolol, Dorzolamide, Bri-monidine and Lata-noprost 0.005 %, which has reduced the IOP to TOD=13 mmHg/TOS=12 mmHg.

Discussion
The prevalence of asymptomatic cerebral aneurysms varies from 0.2 % to 8.9 % in the general population, and 30 % of these patients have multiple aneurysms. Carotid-cavernous fistula (CCF) is represented with 12 % among all arteriovenous fistulas. Approximately, 70-90 % of all CCF are direct fistulas, spontaneous, or traumatic remaining up to two years after injury (7,14,15). The patient with acute symptoms of CCF was taken care of as an emergency at the Clinic of Neurosurgery. Transient postoperative ophthalmoplegia was originated as a consequence of brain lesions in the lateral wall of the cavernous sinus (n. oculomotorius, trochlearis, V1 and V2 branches of n. trigeminus) and in sinus lumen (n. Abducens) (16). Loss of vision in the left eye was a consequence of cerebral pathological processes and neuronal lesions of visual pathway (12).
Administered postoperative edematous therapy (Tbl Acetazolamide) had the effect of intraocular pressure lowering as the drug belongs to the group of carbonic anhydrase inhibitors. This enzyme is present in high concentration in the epithelium of the ciliary body, and therefore participates in the creation of aqueous humor. Its inhibition reduces the production of aqueous humor, and therefore the pressure in the eye. It can be concluded that the clinical manifestation of glaucoma was masked as an increase in IOP was noticed after discontinuation of the drug, and the patient was refered to an ophthalmologist for the headaches (17,18). The neuroprotective effect of the drug also showed transient reduction of the visual field loss in the interval 2007 to 2008. OCT finding and RNFL values indicates thinning on both sides, and although the electrophysiological study was pathological, functional tests were repeated. Computerized perimetry finding was a residual central island of vision, with indexes MD = 26.22 dB and CPSD = 9.93 dB.
Due to the loss of RGC, patients with glaucoma have abnormal PERG and PVEP, even with normal visual acuity. Extension of the P100 wave latency in patients with glaucoma indicates the importance of the function evaluation of the optic nerve in glaucoma, whether with or without a decreased visual acuity (17,19). The clinical examination confirmed a suspicion of glaucoma, and local therapy was started as well as a systemic administration of neuroprotective drug (vinpocetine). Vinpocetine selectively inhibits Na+channels and reduces extracellular Ca++ concentration, which reduces excitotoxicity, as well as damage induced by ischemia/reperfusion (20). Correction of topical therapy was necessary in the presented case in order to control IOP and preserve visual function in the remaining eye. Despite the difficulty of movement in the darkness, ptosis operation was not indicated due to neurogenic etiology.

Conclusion
The paper presents a patient with severe, life-threatening vascular disease, which firther caused the damage of n. opticus: compressive optic neuropathy on the left, with the descending consequent atrophy and glaucoma optic neuropathy of the right eye of exogenous origin. The resulting irreversible damage to the optic nerve affects the quality of patient life. This condition requires regular monitoring, while secondary glaucoma and glaucomatous optic neuropathy deserve special attention, timely diagnosis and treatment.

Note
We wish to thank Vladimir Radenković for technical assistance and processing contributions.