Giant Cell Arteritis

DIFFERENTIATION OF ARTERITIC FROM NON-ARTERITIC AION

AION is by far the most common cause of visual loss due to GCA and was seen in our study in 76.4% of eyes with visual symptoms associated with GCA.² For some unknown reason the most common ocular artery to be involved by GCA is the posterior ciliary artery.^2,7,11-14 In fact, in our studies, all patients with visual loss due to GCA showed evidence of posterior ciliary artery occlusion on fluorescein fundus angiography. That has also been demonstrated by histopathologic studies of eyes gone blind due to GCA.^7,13 Posterior ciliary arteries are the main source of blood supply to the optic nerve head^13,14. Therefore, posterior ciliary artery occlusion in GCA results in ischemia of the optic nerve head and development of AION. Quite often the visual loss and/or progression in visual loss is discovered on waking up from sleep in the morning or from a nap, because the fall of blood pressure during sleep acts as the final insult to produce ischemia of the optic nerve head.

The most important fact in this context is that AION is a common disease in the middle-aged and elderly population and etiologically is of two types: (i) arteritic AION is due to GCA, and (ii) non-arteritic AION due to other causes. Non-arteritic AION is the more common of the two and is one of the most prevalent, visually crippling diseases in the middle-aged and elderly. Although the two types of AION have a similar clinical picture and presentation, their management is entirely different. Arteritic AION is an OCULAR EMERGENCY because of imminent danger of bilateral total blindness, which is usually PREVENTABLE; with early and adequate treatment these patients usually should not lose any further vision. In sharp contrast to that, so far there is no proven therapy available for non-arteritic AION.¹⁴

Therefore, once patients aged over 55 years are diagnosed as having AION, the first, crucial step is to identify immediately whether it is arteritic or non-arteritic. I have seen more than a thousand patients with AION since 1970. From that experience, I have developed a number of criteria that can help us to make this differentiation. I have discussed this in detail elsewhere.^7,11,14 The criteria are:

DIFFERENTIATING CRITERIA

1. Systemic symptoms of GCA: Typically, in GCA, there are aches and pains all over the body, malaise, anorexia, flu-like symptoms, weight loss, fever of unknown origin, headaches, jaw claudication, neck pain, anemia and other vague systemic symptoms; the patient feels that there is something wrong but cannot really pinpoint what is wrong with him/her. I have described above the prevalence of various systemic symptoms and signs seen in our study.¹ But it is extremely important to remember that 21% of our patients with GCA related visual loss had no systemic symptoms and signs of GCA, i.e. occult GCA.³
2. Visual symptoms: I have described above the visual symptoms seen in our study.² In this regard, the most important visual symptom is amaurosis fugax which was seen by us in 26% of the eyes or 31% of the patients, and almost invariably preceded the visual loss. Thus, if a patient with AION has had amaurosis fugax, that is strongly suggestive of arteritic AION. Similarly, if a patient with GCA develops amaurosis fugax, that is an ominous sign of impending arteritic AION and requires immediate treatment.
3. ESR, CRP, platelet count and other hematologic tests: I have discussed above their role in the diagnosis of GCA (see above).
4. Early, massive visual loss: Our studies have shown that arteritic AION patients usually present with much worse visual loss than those with non-arteritic AION. This is evident from the following table, based on our data of visual acuity in arteritic and non-arteritic AION.

5. Chalky white optic disc swelling:^2,11-14 During the acute phase, this was seen in 69% of eyes with arteritic AION² (see figure 2-b) but is very rare in eyes with typical non-arteritic AION. Thus, chalky white swelling of the optic disc is extremely suggestive of arteritic AION.

Figure 2b: Fundus photograph of right eye during the early stages of AION, shows typical chalky white optic disc edema.

6. Optic disc swelling associated with cilioretinal artery occlusion: If this combination is seen during the early stages of AION, that is very strongly suggestive of arteritic AION.^11-14 It is practically non-existent in non-arteritic AION.
7. Posterior ciliary artery occlusion on fluorescein fundus angiography: If fluorescein angiography is performed during the very early stages, in arteritic AION there is always evidence of posterior ciliary artery occlusion with massive filling defect of the choroid^2,11-14 (see figure 1-b). This is extremely rare in non-arteritic AION. Therefore, angiography provides extremely useful information in diagnosis of GCA and arteritic AION and must always be performed in all AION cases to rule out arteritic AION.

Figure 1b: Fluorescein fundus angiogram. Left eye with arteritic AION, showing choroidal filling defects (dark areas) during the early stages of AION. (Reproduced from Hayreh¹¹)

8. Temporal artery biopsy: Finally, temporal artery biopsy must be performed in every patient, even if one is absolutely confident about the diagnosis based on other clinical parameters. This is because patients with GCA require years of treatment with systemic corticosteroids, and are at great risk of developing serious systemic side-effects of steroid therapy. If a patient develops some serious complication(s) and blames the physician for that, the physician may have no scientific defense for the diagnosis, and the prolonged steroid therapy and consequent complications unless he/she has morphological confirmation of the diagnosis from a temporal artery biopsy. Various aspects of temporal artery biopsy are discussed above.¹

Thus, I have found that, although almost none of these parameters is seen in 100% of the cases with GCA, the cumulative information supplied by all of them can almost always differentiate arteritic from non-arteritic AION.

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