A plexiform neurofibroma of the eyelid is a benign tumor that develops from the cells covering and protecting nerves. While not cancerous, its location can lead to issues with both appearance and function. The tumor forms within the complex network of nerves in the eyelid, leading to a diffuse thickening of the tissue. This growth is often slow and may be present at birth, becoming more noticeable as a child ages.
The appearance of this tumor is more than a localized issue, as it often serves as a prominent indicator of a systemic genetic disorder.
The Link to Neurofibromatosis Type 1
Plexiform neurofibromas are strongly associated with a genetic condition called Neurofibromatosis Type 1 (NF1). NF1 is an autosomal dominant disorder, meaning it can be inherited from one parent, though about half of cases result from a spontaneous gene mutation. The condition is caused by a mutation in the NF1 gene on chromosome 17, which is responsible for producing a protein called neurofibromin that helps regulate cell growth.
When this protein’s function is lost, cells can grow uncontrollably, leading to the formation of tumors along nerves. The discovery of a plexiform neurofibroma on the eyelid is often the first major sign that leads to an NF1 diagnosis in a child.
The presence of a single plexiform neurofibroma is one of the main diagnostic criteria for the condition, which affects approximately 30-50% of all individuals with NF1.
Eyelid Symptoms and Vision Complications
A plexiform neurofibroma infiltrates the eyelid’s soft tissues, giving it a thickened, swollen appearance. The area may have a texture described as a “bag of worms” due to the underlying mass of enlarged nerve bundles. This infiltration commonly causes the upper eyelid to droop, a condition known as ptosis, which is the most frequent sign. The tumor’s weight can also distort the eyelid’s natural curve, creating a characteristic “S-shaped” deformity of the eyelid margin.
Severe ptosis can physically obstruct the visual axis. If this obstruction occurs during the periods of visual development in childhood, it can lead to amblyopia, or “lazy eye.” This condition occurs when the brain begins to favor the unobstructed eye, causing permanent vision reduction in the affected eye.
The tumor’s growth can also expand into the orbit (the bony socket of the eye), causing the eye to bulge forward (proptosis). In some cases, it can interfere with the eye’s drainage system, leading to increased intraocular pressure and glaucoma, or cause astigmatism, which results in blurred vision.
Diagnostic Evaluation
Diagnosis begins with a physical examination by a specialist, such as a pediatric ophthalmologist. The doctor will assess the eyelid’s appearance, feel for the characteristic tumor texture, and evaluate for signs like ptosis and the S-shaped curve. A comprehensive eye exam is performed to measure vision, check for amblyopia, assess eye pressure for glaucoma, and look for other ocular signs of NF1, such as Lisch nodules (harmless bumps on the iris).
To understand the full extent of the tumor, imaging studies are necessary. Magnetic Resonance Imaging (MRI) is the preferred method because it provides detailed images of soft tissues, showing the tumor’s precise size, location, and infiltration into surrounding structures. This information is important for planning treatment and monitoring growth.
A biopsy is often avoided in children if the diagnosis of NF1 is already established or highly likely, as the clinical and imaging findings are sufficient for a diagnosis. The evaluation will also involve a multidisciplinary team, including neurologists and geneticists, to manage the broader aspects of NF1.
Treatment and Management Strategies
Management of an eyelid plexiform neurofibroma is tailored to the individual, focusing on preserving vision and improving function and appearance. For small, stable tumors that do not cause symptoms, regular monitoring may be all that is needed. When treatment is required, it can involve surgical intervention, medical therapy, or a combination of both.
Surgery has historically been a primary treatment, but its goal is often debulking—removing as much of the tumor as can be done safely. Because these neurofibromas infiltrate healthy nerve and vascular tissues, total removal is often impossible without causing significant functional loss. Multiple surgeries may be required over time to manage regrowth or address ptosis to clear the visual axis.
A primary medical therapy involves MEK inhibitors, such as selumetinib (Koselugo). These oral medications work by blocking a specific signaling pathway that is overactive in NF1 and drives tumor growth. Selumetinib is approved for children with inoperable, symptomatic plexiform neurofibromas and has been shown to shrink the tumors in many patients, reducing pain and improving quality of life. This therapy offers a non-surgical option that can reduce tumor volume and potentially delay the need for high-risk surgeries.
Managing complications is another focus of the treatment plan. Children with amblyopia may require vision therapy, such as patching the stronger eye, to encourage visual development. Due to the chronic nature of the condition, long-term follow-up with a multidisciplinary team is necessary to monitor for tumor growth and address any new complications.