A case of herpes zoster ophthalmicus with isolated trochlear nerve involvement

Herpes zoster ophthalmicus (HZO) can involve the oculomotor nerve; however, isolated trochlear nerve palsy has rarely been reported. An 83-year-old man who suffered from HZO in the right frontal area and scalp subsequently developed vertical diplopia and severe pain. Cerebrospinal fluid examination and brain MRI revealed no abnormalities. Isolated right trochlear nerve palsy was diagnosed based on the findings of neuro-ophthalmological tests. Isolated trochlear nerve involvement associated with HZO is very rare and may be easily overlooked. Physicians should carefully examine oculomotor involvement in HZO.