Indirect traumatic optic neuropathy following head injury: report of five patients and review of the literature

Resting-state functional MRI of the visual system for characterization of optic neuropathy

Optic neuropathy refers to disease of the optic nerve and can result in loss of visual acuity and/or visual field defects. Combining findings from multiple fMRI modalities can offer valuable information for characterizing and managing optic neuropathies. In this article, we review a subset of resting-state functional magnetic resonance imaging (RS-fMRI) studies of optic neuropathies. We consider glaucoma, acute optic neuritis (ON), discuss traumatic optic neuropathy (TON), and explore consistency between findings from RS and visually driven fMRI studies. Consistent with visually driven studies, glaucoma studies at rest also indicated reduced activation in the visual cortex and dorsal visual stream. RS-fMRI further reported varying levels of functional connectivity in the ventral stream depending on disease severity. ON patients show alterations within the visual cortex in both fMRI techniques. Particularly, higher-than-normal RS activity is observed in the acute phase and decreases as the disease progresses. A similar pattern is observed in the visual cortex of TON-like, open globe injury (OGI), patients. Additionally, visually driven and RS-fMRI studies of ON patients show recovery of brain activity in the visual cortex. RS-fMRI suggests recovery of signals in higher-tier visual areas MT and LOC as well. Finally, RS-fMRI has not yet been applied to TON, although reviewing OGI studies suggests that it is feasible. Future RS-fMRI studies of optic neuropathies could prioritize studying the fine scale RS activity of brain areas that visually driven studies have identified. We suggest that a more systematic longitudinal comparison of optic neuropathies with advanced fMRI would provide improved diagnostic and prognostic information.

Visually driven functional MRI techniques for characterization of optic neuropathy

Optic neuropathies are conditions that cause disease to the optic nerve, and can result in loss of visual acuity and/or visual field defects. An improved understanding of how these conditions affect the entire visual system is warranted, to better predict and/or restore the visual loss. In this article, we review visually-driven functional magnetic resonance imaging (fMRI) studies of optic neuropathies, including glaucoma and optic neuritis (ON); we also discuss traumatic optic neuropathy (TON). Optic neuropathy-related vision loss results in fMRI deficit within the visual cortex, and is often strongly correlated with clinical severity measures. Using predominantly flickering checkerboard stimuli, glaucoma studies indicated retinotopic-specific cortical alteration with more prominent deficits in advanced than in early glaucoma. Some glaucoma studies indicate a reorganized visual cortex. ON studies have indicated that the impacted cortical areas are briefly hyperactive. For ON, brain deficits are greater in the acute stages of the disease, followed by (near) normalization of responses of the LGN, visual cortex, and the dorsal visual stream, but not the ventral extrastriate cortex. Visually-driven fMRI is sensitive, at least in ON, in discriminating patients from controls, as well as the affected eye from the fellow eye within patients. The use of a greater variety of stimuli beyond checkerboards (e.g., visual motion and object recognition) in recent ON studies is encouraging, and needs to continue to disentangle the results in terms of change over time. Finally, visually-driven fMRI has not yet been applied in TON, although preliminary efforts suggest it may be feasible. Future fMRI studies of optic neuropathies should consider using more complex visual stimuli, and inter-regional analysis methods including functional connectivity. We suggest that a more systematic longitudinal comparison of optic neuropathies with advanced fMRI would provide improved diagnostic and prognostic information.

Microsphere antioxidant and sustained erythropoietin-R76E release functions cooperate to reduce traumatic optic neuropathy

Wild-type erythropoietin (EPO) is promising for neuroprotection, but its therapeutic use is limited because it causes a systemic rise in hematocrit. We have developed an EPO-R76E derivative that maintains neuroprotective function without effects on hematocrit, but this protein has a short half-life in vivo. Here, we compare the efficacy and carrier-induced inflammatory response of two polymeric microparticle (MP) EPO-R76E sustained release formulations based on conventional hydrolytically degradable poly(lactic-co-glycolic acid) (PLGA) and reactive oxygen species (ROS)-degradable poly(propylene sulfide) (PPS). Both MP types effectively loaded EPO-R76E and achieved sustained release, providing detectable levels of EPO-R76E at the injection site in the eye in vivo for at least 28 days. Testing in an in vitro oxidative stress assay and a mouse model of blast-induced indirect traumatic optic neuropathy (bITON) showed that PPS and PLGA MP-mediated delivery of EPO-R76E provided therapeutic protection. While unloaded PLGA MPs inherently increase levels of pro-inflammatory cytokines in the bITON model, drug-free PPS MPs have innate antioxidant properties that provide therapeutic benefit both in vitro and in vivo. Both PLGA and PPS MPs enabled sustained release of EPO-R76E, providing therapeutic benefits including reduction in inflammation and axon degeneration, and preservation of visual function as measured by electroretinogram. The PPS-based MP platform is especially promising for further development, as the delivery system provides inherent antioxidant benefits that can be harnessed to work in complement with EPO-R76E or other drugs for neuroprotection in the setting of traumatic eye injury.

Steroid Treatment of Optic Neuropathies

The etiologies of optic neuropathy include inflammation, ischemia, toxic and metabolic injury, genetic disease, and trauma. There is little controversy over the practice of using steroids in the treatment of optic neuritis--it is well established that intravenous steroid treatment can speed visual recovery but does not alter final visual function. However, there is controversy surrounding the acceptable routes of administration, dosage, and course of treatment. Additionally, the typical patient with optic neuritis is young and otherwise healthy, and thus is likely to tolerate steroids well. In ischemic and traumatic causes of optic neuropathies, the initial injury is not inflammatory, but damage may be compounded by secondary injury due to resultant inflammation and swelling in the confined space of the optic canal. Steroids have been considered as a means of minimizing inflammation and swelling, and thus minimizing the secondary injury that results. However, the use of steroids in traumatic and ischemic optic neuropathies is highly controversial-the evidence for the efficacy of treatment with steroids is insufficient to show that there is significant benefit. Additionally, patients with these conditions are more likely to have comorbidities that make them vulnerable to significant adverse events with the use of steroids. In this article, we attempt to analyze the current state of the literature regarding the use of steroids in the treatment of optic neuropathies, specifically optic neuritis, nonarteritic anterior ischemic optic neuropathy, and traumatic optic neuropathy.

Treatment Outcomes following Traumatic Optic Neuropathy

BACKGROUND

Traumatic optic neuropathy is characterized by sudden loss of vision following facial trauma leading to variable visual deficits. The purpose of this study was to evaluate recent institutional trends in the treatment of traumatic optic neuropathy, evaluate the outcomes of different treatment strategies, and identify factors associated with improved vision.

METHODS

Institutional review board approval was obtained to retrospectively review patients diagnosed with traumatic optic neuropathy at a high-volume trauma center from 2004 to 2012. Pretreatment and posttreatment visual acuity was compared using quantitative analysis of standard ophthalmologic conversion.

RESULTS

A total of 109 patients met inclusion criteria (74.3 percent male patients), with a mean age of 38.0 ± 17.5 years (range, 8 to 82 years). Management of traumatic optic neuropathy involved intravenous corticosteroids alone in 8.3 percent of patients (n = 9), 56.9 percent (n = 62) underwent observation, 28.4 percent (n = 31) had surgical intervention, and 6.4 percent (n = 7) underwent surgery and corticosteroid administration. Only 19.3 percent of patients returned for follow-up. Vision improved in 47.6 percent of patients, with a mean follow-up of 12.9 weeks. Patients younger than 50 years had a trend toward higher rates of visual improvement, 60 percent versus 16.7 percent (p = 0.15).

CONCLUSIONS

The majority of traumatic optic neuropathy patients are unlikely to return for a follow-up examination. Optic nerve decompression has fallen out of favor in the authors' institution, and observation is the most common management strategy. Outcomes following corticosteroid administration and observation are comparable.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

Increased Th17 cells and IL‑17 in rats with traumatic optic neuropathy

T helper 17 (Th17) cells are strong inducers of numerous autoimmune diseases and inflammation. However, the role of Th17 cells and interleukin (IL)‑17 in traumatic optic neuropathy (TON) are yet to be elucidated. In the present study, a rat model of TON was established using a fluid percussion brain injury device. Th17 cells were found to be upregulated in the spleens of rats in the TON group. In addition, the level of IL‑17 in the retina of rats in the TON group was observed to increase with the upregulation of the Th17 cells. Furthermore, the expression of IL‑17 in the optic nerve was found to be upregulated between one and seven days following injury in the rats in the TON group. These findings strongly suggest that the ratio of Th17 cells and the expression of IL‑17 are upregulated in rats with TON. These findings also provide a rationale for developing therapeutic agents to treat TON.