A 9-year-old boy is brought to the emergency department following a bicycling accident. The patient was riding downhill when he hit a rock and lost control. He was thrown off his bicycle and hit the handlebars before tumbling onto the pavement. The patient was not wearing a helmet but did not lose consciousness. Blood pressure is 118/80 mm Hg and pulse is 140/min. Examination shows ecchymosis over the right superior orbit with underlying tenderness and a few scalp abrasions. Visual acuity is 20/20 in the left eye. Using the right eye, the patient is unable to read the largest letter on the visual acuity chart and is only able to perceive light. There is a relative afferent pupillary defect in the right eye. Extraocular movements are normal, and the red reflex is symmetric bilaterally. Fluorescein dye testing is unremarkable. Which of the following is the most likely diagnosis in this patient?

Question

A 9-year-old boy is brought to the emergency department following a bicycling accident.  The patient was riding downhill when he hit a rock and lost control.  He was thrown off his bicycle and hit the handlebars before tumbling onto the pavement.  The patient was not wearing a helmet but did not lose consciousness.  Blood pressure is 118/80 mm Hg and pulse is 140/min.  Examination shows ecchymosis over the right superior orbit with underlying tenderness and a few scalp abrasions.  Visual acuity is 20/20 in the left eye.  Using the right eye, the patient is unable to read the largest letter on the visual acuity chart and is only able to perceive light.  There is a relative afferent pupillary defect in the right eye.  Extraocular movements are normal, and the red reflex is symmetric bilaterally.  Fluorescein dye testing is unremarkable.  Which of the following is the most likely diagnosis in this patient?

Quizplus · Accepted Answer

11ec25c8_d16a_d8ab_bc81_31e626f88ed1_MD0003_00 This patient has a relative afferent pupillary defect (RAPD) following head trauma, a finding consistent with optic nerve injury. This injury most commonly occurs indirectly via a high-intensity force to the orbit, as seen in this patient. When a blow to the face occurs, shearing forces are transmitted to the optic canal, causing contusion or possibly avulsion of the nerve within the canal. Injury can also occur via direct trauma to the optic nerve (eg, needle puncture during ophthalmologic surgery). Patients typically have acute vision loss, which can range from mildly decreased visual acuity to inability to perceive light. Color vision may also be impaired. Damage to the optic nerve classically causes RAPD. On examination, when light shines into the unaffected eye, the bilateral pupils constrict equally (consensual light reflex). When light then shines into the injured eye, both pupils dilate. RAPD Emergency CT scan of the orbit confirms the diagnosis. Vision improves with conservative management in approximately half of patients, but surgical decompression may be required. Poor initial visual acuity (eg, loss of light perception) is associated with a worse prognosis. (Choices A and D) Corneal abrasion is an epithelial defect of the cornea that is often caused by a foreign body. In contrast to this patient, a staining defect would be visible with fluorescein testing. (Choice B) Lens dislocation can present with acute vision loss after trauma. However, it is commonly associated with iris tremulousness and does not cause RAPD. (Choice E) Vitreous hemorrhage can occur following head trauma and, with significant bleeding, lead to decreased visual acuity and RAPD. However, an abnormal red reflex would be expected. Educational objective: Optic nerve injuries (eg, contusion, avulsion) may occur indirectly following head trauma due to shearing forces on the optic canal. Patients have an acute decrease in visual acuity and a relative afferent pupillary defect in the injured eye. References: Traumatic optic neuropathy-clinical features and management issues. (http://www.ncbi.nlm.nih.gov/pubmed/26052483)

A 9-Year-Old Boy Is Brought to the Emergency Department Following