Sixth nerve palsy associated with obstruction in Dorello's canal, accompanied by nodular type muscular sarcoidosis

A 52-year-old Japanese woman complaining of horizontal double vision for 10 days was admitted to our hospital. Neurological examination revealed left abducent nerve palsy and muscle swelling in her thighs. Brain MRI showed obstruction in the spinal fluid space of the left Dorello's canal, which transmits a portion of the abducent nerve. In Ga-67-enhanced citrate scintigraphy, wide accumulation was seen in her bilateral thighs, lower legs, and gluteus muscles. Muscular MRI showed a star-shaped central structure on short tau inversion recovery (STIR) images, and the three stripes sign on T2-weighted images. These MRI findings indicated nodular-type muscular sarcoidosis. A muscle biopsy from the quadriceps femoris showed granulomatous epithelioid giant cells and non-necrotizing chronic lymphadenitis, which also indicate sarcoidosis. Her condition was considered to be caused by sarcoid granulomas obstructing Dorello's canal. She was treated with oral prednisolone (1 mg·kg(-1)·day(-1)) and her symptoms and MRI findings improved. This is the first known report of abducent nerve impairment in Dorello's canal, other than fetal hypoplasia. Brain MRI, muscular MRI, and muscle biopsy are useful for the diagnosis of abducent nerve palsy, and it is important to consider Dorello's canal obstruction by sarcoidosis. Complete remission can be achieved with proper treatment.