I see double! Searching for the abnormal cranial nerve in diplopia

Diplopia or double vision is a common symptom that can be caused by various neurological or ophthalmologic pathologies. Diplopia can be monocular or binocular. In monocular diplopia, the patient sees double with only one eye open. In binocular diplopia, the patient sees double with both eyes open with subsequent resolution of the symptom when one of the eyes is closed. Binocular diplopia is the main manifestation caused by involvement of cranial nerves III, IV and VI. Infections, inflammatory, vascular, degenerative, traumatic, iatrogenic and malignant pathologies can cause diplopia. The combination of medical history, physical examination and imaging is crucial for an accurate diagnosis. Magnetic resonance imaging (MRI) of the brain and orbits with contrast is the modality of choice for the evaluation of patients with diplopia. Computed tomography (CT) of the head without contrast is useful to rule out lesions of the bones and skull base. Imaging of the brain and orbits allows assessment of the normal anatomy of cranial nerves III, IV and VI, and is useful to identify and characterize the various pathologies causing diplopia.