[Isolated abducens nerve palsy caused by pontine infarction].

An 82-year-old hypertensive man suddenly developed diplopia during right lateral gaze. Neurological examination revealed right isolated abducens nerve palsy without any other findings. By cranial CT scan, a low density area over the posterior limb of right internal capsule and tortuosity of basilar artery were noted. 3 months later, his symptom disappeared and then he was well in next 2 years til he felt diplopia during left lateral gaze. On this time he showed left isolated abducens nerve palsy. Though cranial CT scan failed to find out new abnormality, T2-weighted cranial MRI disclosed high intensity spot over left pontine base located between medial lemniscus and pyramidal tract, which was supposed to coincide to fascicle of left abducens nerve Three months later, he recovered in the same manner as 2 years before. Hemilateral isolated abducens nerve palsy may be caused by many origins, but pontine infarct was not detected so much in pre-MRI era. Being the long-term prognosis of the lacunar infarction not satisfactory, it is important for the cases of isolated abducens palsy to ascertain whether there is pontine small infarction or not. So in these cases, precise examination including MRI should be needed.