Traumatic Optic Neuropathy Treatment & Management

Updated: Sep 13, 2018
  • Author: Ryan S Jackson, MD; Chief Editor: Arlen D Meyers, MD, MBA  more...
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Treatment

Medical Therapy

The main treatment options for traumatic optic neuropathy (TON) include systemic corticosteroids and surgical optic nerve decompression, either alone or in combination. Review and analysis of the literature are complicated by the variety of therapeutic approaches and a lack of randomized, controlled studies on the use of these modalities for TON. [4]

The current knowledge base on the use of steroids for TON is based on small retrospective studies, anecdotal reports, and extrapolation from national traumatic brain and spinal cord injury studies. Steroid therapy for TON can be categorized as follows: moderate dose (60-100mg of oral prednisolone), high dose (1 gram of intravenous methylprednisolone/day), or mega dose (30 mg/kg loading dose of intravenous methylprednisone, followed by 5.4 mg/kg/h for 24 hours).

Steroids have been used in TON since the early 1980s because of their perceived benefits in various animal models of central nervous system injury. Steroids were thought to provide neuroprotection in traumatic central nervous system injury through their antioxidant properties and inhibition of free radical-induced lipid peroxidation.

In 1990, Bracken and colleagues published their findings on the use of mega dose corticosteroid therapy in the National Acute Spinal Cord Injury Study 2 (NASCIS 2). [5] The NASCIS 2 was a multicenter clinical trial that evaluated patients with acute spinal cord injury treated with placebo, methylprednisolone, or naloxone. The study showed that methylprednisolone (30 mg/kg loading dose, followed by 5.4 mg/kg/h for 24 hours) started within 8 hours of injury was associated with a significant improvement in both motor and sensory function compared with patients treated with a placebo.

The findings of the NASCIS trials significantly influenced clinical practice and led to an increased use of steroids in treating TON. However, the clinical improvement was modest in these studies, and concern existed that the clinical benefit demonstrated for those patients treated in the first eight hours with mega dose steroids was the result of a statistical bias, since the analysis was performed post hoc rather than prospectively.

In 2005, the results of the Corticosteroid Randomization After Significant Head Injury (CRASH) trial raised concerns regarding the use of mega dose steroids (same dose as given in the NASCIS 2 study) in traumatic brain injury. [6] This study was the largest randomized study that evaluated steroids in patients with traumatic brain injury and was stopped early due to the significantly increased risk of death in patients that received mega dose steroids at their 6-month follow-up when compared with the placebo group (25.7% vs 22.3%; RR 1.15 CI 1.07 to 1.24; p=0.0001). Although the etiology of the increased risk of death was not determined, the findings of this study should be taken into consideration when managing cases of TON with concurrent traumatic brain injury.

Furthermore, concerns have been raised regarding the extrapolation of data from spinal cord injury studies to TON. There are important histologic distinctions between the spinal cord and optic nerve; for example, the optic nerve is a pure white matter tract and the spinal cord is a mixed gray and white matter tract. As a result, significant biologic differences may exist between the repair mechanisms of the optic nerve axons and insults to the spinal cord.

The International Optic Nerve Trauma Study (IONTS) was a nonrandomized intervention trial that compared visual outcomes for patients with TON treated with observation, systemic steroids, or optic canal decompression. [7] Published in 1999, the study included 133 patients who were evaluated and treated within 7 days of the traumatic event, with most of the patients being treated with either corticosteroids (n=85) or surgical decompression of the optic canal (n=33). Follow-up results showed that visual acuity increased by more than 3 lines in 32% of the surgery group, 52% of the corticosteroid group, and 57% of the observation group. However, the study was nonrandomized and uncontrolled, and the small numbers of patients in the observation group (n=9) limited the strength of the study’s statistical power.

Recent animal studies have also found variable results with steroid therapy. These animal models involve a direct, crush injury mechanism for inducing TON in rats, and any extrapolation of the data to humans with indirect insults to the optic nerve must be made with caution. However, no study has demonstrated a beneficial effect for steroid therapy in animals with TON, and one study, in particular, found that steroids exacerbated axonal loss as evidenced by a dose-dependent decline in axonal counts with increasing doses of steroids. [8] Such findings may suggest that steroids can exert a negative effect on ganglion cell survival, especially at higher, mega dose levels, due to their suppression of endogenous neuroprotective pathways.

Based on the current evidence, a therapeutic role for corticosteroids in the management of TON is unsubstantiated. If steroids are considered for TON, they should not be used in cases with concomitant traumatic brain injury or in patients that present 8 hours or more after initial injury. Whether clinicians should use mega dose rather than lower doses of steroids for selected cases of TON is also not clearly defined by the literature. The NASCIS studies used mega dose steroids in their protocol to demonstrate a beneficial effect in a subset of their patients, but the CRASH study identified several serious complications associated with their use in the trauma setting. Additionally, animal studies have demonstrated an association between increasing doses of steroids and retinal ganglion cell death. [9, 10]

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Surgical Therapy

The rationale for surgical therapy in indirect traumatic optic neuropathy (TON) is to decompress the optic nerve at the site of injury, which is often the intracanalicular segment. Surgical decompression is thought to help reduce optic nerve compression and subsequent vascular compromise that may occur as a result of the indirect injury. Additionally, surgery has been postulated to remove bone fragments that may be impinging on the optic nerve within the optic canal.

However, no randomized, controlled studies have been performed to evaluate the role of surgery in TON. As mentioned previously, one of the largest series is from the IONTS, which did not provide any convincing evidence that surgical decompression of the optic canal in TON is superior to observation or corticosteroid therapy. Additionally, in cases in which bony fragments are impinging on the optic nerve within the canal, the prognosis of visual recovery is extremely poor because the bony fragments are more likely to have anatomically disrupted the optic nerve axons, leading to irreversible visual loss.

Interpreting the efficacy of surgical decompression when reviewing the published studies is difficult because they consist of small, retrospective series that have variable methodologies and inclusion criteria (ie, degree of vision loss, timing of surgery, whether concomitant steroids were used). In addition, the probability of selection bias for TON patients who elect to have surgical decompression cannot be ignored because patients with the worse visual function at presentation or those who have failed steroid therapy tend to be included in these surgical series. The timing of surgery and the preferred surgical approach is also controversial.

The variety of surgical approaches used in optic nerve decompression include intracranial, extracranial, orbital, transethmoidal, endonasal, and sublabial approaches, and the selection of the technique tends to be based on the surgeon’s training, background, and experience. Patients with profound vision loss and a visualized bone fragment impinging on a segment of the intracanalicular optic nerve on neuroimaging have been considered to be the best candidates for surgical intervention. Although anecdotal reports of impressive visual recovery exist for such patients, most cases with direct injuries to the optic nerve do not improve, and the risk of possible surgical complications such as cerebrospinal fluid leak or postoperative bleeding cannot be ignored.

A study by Yu et al reported that in children with indirect TON, endoscopic trans-ethmosphenoid optic canal decompression (ETOCD) produced better results in patients with residual vision prior to surgery than in those who had no light perception, with the investigators finding improvement rates of 69.7% and 37.9%, respectively. [11]

At this time, conclusive evidence that surgical decompression has a beneficial role for most patients with TON does not exist. Because a significant rate of spontaneous recovery is found in cases of TON, a randomized controlled trial comparing observation with optic canal decompression is the only reliable way to evaluate the therapeutic benefit for surgical intervention. The decision to perform surgical decompression of the optic canal should be made on a case-by-case basis, with the patient being informed that, to date, surgery has not been shown to improve the prognosis over observation alone.

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Outcome and Prognosis

Most studies show a significant association between initial and final visual acuities. Patients with no light perception (NLP) likely have little to no recovery in vision. However, studies show that up to 50% of patients with traumatic optic neuropathy (TON) can have some improvement in vision, with or without treatment, although most of the time improvement is minimal. No well-designed study has shown whether surgical decompression or steroids has any better outcome than observation alone. In fact, the rate of minimal but spontaneous visual improvement in indirect TON is relatively high, ranging from 20-57% in published series.

Studies have shown that TON with concomitant orbital fractures tends to have more severe visual loss. [12, 13] Up to 85% of the patients with an orbital fracture (29 out of 34) presented with NLP in one particular study. [13] The presence of an orbital fracture implies a greater transmission of force to the optic canal, and hence, a greater injury to the optic nerve.

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Future and Controversies

Traumatic optic neuropathy (TON) can lead to profound visual loss from either indirect or direct mechanisms. The diagnosis can be made with accurate history taking and clinical examination, based on the presence of visual loss (with accompanying loss of color vision and possible visual field defects) and an accompanying relative afferent pupillary defect (APD).

The optimal treatment for TON, however, remains debated among physicians. A review of the available literature, especially the IONTS and CRASH studies, provides insufficient evidence to conclude that corticosteroid therapy and/or optic canal surgery provides a therapeutic benefit over observation alone in patients with TON. Patients with TON treated with systemic steroids appear to have similar rates of visual recovery as untreated patients, and both animal and human studies suggest that under certain conditions, systemic steroids may actually be harmful, particularly at higher doses.

Therefore, corticosteroids should not be used in cases with concomitant traumatic brain injury or in patients who present 8 hours or more after initial injury. Based on the available evidence, surgical decompression of the optic canal in cases is not routinely recommended in TON. If treatment with either steroids or surgical intervention is considered, appropriate counseling should be given to the patient and their family about their potential benefits and risks in order to help them make an informed decision.

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