Extraocular muscle entrapment (EOME) occurs when a muscle controlling eye movement becomes trapped by a fracture within the bony socket of the eye, known as the orbit. This physically restricts the eye’s ability to move. While EOME can affect adults, the mechanism and presentation are often distinctly different in children, making prompt identification challenging. This unique pediatric injury represents an urgent medical situation.
The Pediatric Terminology: Trapdoor Fractures
The specific type of extraocular muscle entrapment seen in children is commonly known as a “trapdoor fracture” or a “white-eyed blowout fracture.” This mechanism is unique to the pediatric orbit. When a child’s orbit sustains blunt trauma, the thin floor of the eye socket fractures in a linear pattern. Instead of shattering outward like an adult fracture, the bone acts like a hinge, briefly opening and then snapping back into its original position.
This mechanism creates a narrow gap that tightly ensnares the extraocular muscle, most often the inferior rectus muscle, or the surrounding fat and connective tissue. The entrapment is dangerous because the fracture fragment returns to its anatomical place, leaving little or no bone displacement. Since the orbital tissue is trapped under high pressure, blood flow to the muscle is compromised (ischemia). This lack of blood flow is the primary concern, as it can quickly lead to tissue damage and permanent loss of muscle function if not relieved.
The term “white-eyed blowout fracture” refers to the fact that external signs of injury—such as bruising, swelling, or subconjunctival hemorrhage—are often minimal or absent. This lack of visible trauma can misleadingly suggest a minor injury, despite the severe internal muscle entrapment. The combination of a subtle external appearance and mechanical entrapment makes the trapdoor fracture a high-risk injury for delayed diagnosis.
Recognizing the Urgent Symptoms
The most noticeable symptom of muscle entrapment is restricted eye movement, specifically the inability to look up or down, depending on the trapped muscle. This restriction causes double vision (diplopia), as the eyes cannot align. The child may tilt their head in an unusual position to compensate for the double vision.
Pain is often reported, especially when the child attempts to move the affected eye. A particularly concerning sign in children is the presence of systemic symptoms like nausea, vomiting, or a slow heart rate (bradycardia). These symptoms are caused by the oculocardiac reflex, where pressure on the entrapped muscle stimulates a nerve pathway connecting the eye to the heart and stomach.
The presence of nausea and vomiting indicates muscle entrapment, even in the absence of obvious external signs. The oculocardiac reflex, which can occasionally lead to syncope, signals severe tension on the muscle and warrants immediate medical attention. Since young children may be unable to clearly describe their symptoms, these systemic signs and restricted gaze are important indicators of the underlying injury.
Diagnostic Procedures and Critical Timing
Diagnosis begins with a physical examination, focusing on eye movement and the presence of diplopia. Ophthalmologists perform a forced duction test, which involves gently moving the eyeball to confirm whether the restriction is due to mechanical entrapment rather than muscle weakness. This clinical assessment is often the most reliable way to identify extraocular muscle entrapment.
A computed tomography (CT) scan of the orbit is the standard imaging procedure used to confirm the diagnosis. The scan provides detailed images of the bone and soft tissues, allowing the radiologist to look for evidence of incarcerated muscle or connective tissue. In trapdoor fractures, the bony defect may be subtle or even appear normal because the fracture fragments have sprung back into place.
The timing of intervention following diagnosis is critical in pediatric cases. To prevent irreversible damage to the entrapped muscle from ischemia and subsequent scarring, surgical repair is recommended within 24 to 48 hours of the injury. Delays beyond this time frame significantly increase the risk of persistent diplopia and other long-term complications. The presence of the oculocardiac reflex also indicates a need for immediate surgical management.
Surgical Management and Recovery
The goal of surgical management is to release the trapped orbital contents and restore the function of the extraocular muscle. The surgeon accesses the fracture site, typically through a small incision in the eyelid or the conjunctiva, to maneuver the incarcerated muscle and tissue out. Once the tissue is free, the bony defect in the orbital floor is reconstructed, often using an absorbable implant or a thin plate to cover the area and prevent re-entrapment.
Following the procedure, the child is monitored for resolution of symptoms, particularly double vision and any signs of the oculocardiac reflex. Post-operative care includes a course of antibiotics to prevent infection and potentially corticosteroids to reduce swelling within the orbit. The recovery of the muscle, which may be temporarily stunned or weakened by the entrapment, can take time.
While many children achieve a full recovery of eye movement, persistent double vision is the most common complication. The incidence of this complication is directly related to the elapsed time between the injury and surgical release. Continued follow-up with an ophthalmologist is necessary to monitor eye alignment and movement, sometimes for several months, to ensure optimal long-term visual function.