Congenital horizontal gaze palsy is a rare disorder that is considered
to be due to either the absence of or a lesion in the abducens nucleu
s. Magnetic resonance (MR) imaging of two cases with isolated congenit
al bilateral horizontal gaze palsy showed a lack of the normal protrus
ion of both abducens nuclei on the anterior wall of the fourth ventric
le, These MR findings, with the support of the clinical picture of the
cases, are consistent with the absence of bilateral abducens nuclei,
To the best of our knowledge, this is the first report of MR evidence
of the absence of abducens nuclei in horizontal gaze palsy.