Neurofibromatosis type 1 (NF1) is a genetic disorder characterized by the growth of tumors along nerves in the body. However, clinicians in Denmark were faced with an unusual case when a 38-year-old woman with NF1 developed choroidal Yasunari nodules in both eyes. Choroidal Yasunari nodules are typically challenging to detect on a routine ophthalmic examination but can be visualized using near-infrared photography. In this article, we will delve into the complexities of this unique manifestation and the possible underlying factors that contributed to its development.
The patient under examination had no previous history of systemic vasculopathy but did present with peripheral retinal capillary nonperfusion in her left eye. She had previously undergone panretinal photocoagulation treatment to manage this condition. Despite these ocular issues, her visual acuity was 20/20 in both eyes, and no gliomas were detected in recent MRI scans.
Upon comparing the current findings with those of a previous assessment, the clinicians noticed thinning of the central retinal artery and branching arcades. Furthermore, they observed the formation of a chorioretinal anastomosis in the superotemporal macula, which had developed at the site of a previous photocoagulation scar. The anastomosis consisted of a spiral-shaped choroidal vessel interconnected with both arterial and venous vessels, effectively perfusing the arterial supply of the central retina.
The Role of Retrograde Arterial Supply: A Closer Look
Fluorescein angiography confirmed the presence of retrograde arterial supply through the anastomosis. Rapid initial filling of the temporal macular vasculature was observed, followed by anterograde filling of the central retinal artery branches, providing perfusion to the nasal retina. The authors of the study theorized that the development of the anastomosis could be attributed to a combination of hydrostatic pressure gradient and vascular endothelial growth factor production associated with retinal capillary nonperfusion.
Retinal Vascular Abnormalities in NF1: Shedding Light on Prevalence
Larger cohorts have demonstrated that retinal vascular abnormalities affect approximately 17% to 37% of individuals with NF1. These abnormalities can range from peripheral or central retinal vascular occlusion to neovascular glaucoma. While severe retinal vascular abnormalities are rare in NF1, they have been documented in at least 13 patients. The majority of these cases involve impaired arterial inflow and worsening nonperfusion of the retinal capillary.
Treatment Techniques and their Implications
High-energy photocoagulation, such as the one employed in the patient’s previous treatment, can lead to defects in the Bruch membrane and stimulate the growth of new blood vessels from the choroid. Under certain conditions, these vessels can develop into a laser-induced chorioretinal anastomosis (LICRA). The creation of a LICRA serves as a treatment approach for nonischemic central retinal vein occlusion (CRVO). This procedure aims to normalize retinal venous pressure and establish an auxiliary flow between high-pressure retinal venous circulation and low-pressure choroidal venous circulation.
In a study involving patients with nonischemic CRVO, those who underwent LICRA procedure alongside intravitreal ranibizumab injections showed superior visual acuity and required fewer anti-vascular endothelial growth factor injections. However, it is essential to note that LICRA creation is successful in only two out of three attempts, and complications requiring secondary surgery occur in every third patient.
Most attempts to create LICRA in eyes with ischemic CRVO have been unsuccessful, likely due to significant damage sustained by endothelial cells resulting from the detrimental effects of ischemia and venous thrombosis on retinal circulation. In this particular case study, the incidental LICRA resulting from the previous treatment may have played a role in preserving the retina and maintaining the patient’s 20/20 visual acuity despite the severe retinal artery occlusion.
The case study presented here provides new insights into the diverse manifestations of neurofibromatosis type 1. The development of choroidal Yasunari nodules in this patient with NF1 highlights the complexities of the disorder and the potential effects of previous treatments on ocular structures. Further research is necessary to better understand the mechanisms underlying these phenomena and explore possible treatment avenues. By studying unique cases like this one, clinicians can continually expand their understanding of NF1 and improve patient care.