MRI Findings of Isolated Oculomotor Nerve Palsy after Mild Head Trauma in a Pediatric Patient: Case Report

<b><i>Introduction:</i></b> Traumatic oculomotor nerve injury is usually caused by severe head trauma and is generally associated with other neurological deficits such as basilar skull fracture, orbital injury, or subarachnoid hemorrhage. Isolated traumatic oculomotor nerve injury after minor head trauma and its MRI findings are rarely reported. <b><i>Case Presentation:</i></b> We report a case of a 13-year-old girl with mydriasis, limited inferior and medial movement of the left eyeball, and left ptosis after a mild bump of the left forehead and eye into an electricity pole. The symptoms suggested left oculomotor nerve palsy, but initial facial computed tomography and brain MRI did not reveal any intracranial lesions or fractures in the skull and orbit. Cranial nerve MRI showed segmental hyperintensities and mild thickening of the left oculomotor nerve from the cavernous segment to the proximal orbital segment on T2 short tau inversion recovery and 3D fluid-attenuated inversion recovery volume isotropic turbo spin-echo acquisition sequences. The patient received treatment with oral pyridostigmine for 7 days and was fully recovered at 14 months after injury. <b><i>Discussion:</i></b> As traumatic oculomotor nerve palsy can occur without intracranial hematomas or skull base fractures, routine brain MRI may not always reveal abnormalities; thus, MRI dedicated to imaging of the oculomotor nerve using FS T2WI and high-resolution 3D sequences can be helpful for the diagnosis and management of patients suspected of isolated oculomotor nerve injury.