Oculopalatal myoclonus: eye movement studies, MRI findings and the difficulty of treatment

Two cases of oculopalatal myoclonus with bilateral horizontal gaze palsies are presented. The abnormal vertical eye movements developed several months after brain stem haemorrhage. Eye movement measurements showed rhythmical vertical eye movements at similar rates (2.3 Hz and 2.4 Hz), unaffected by attempts to fixate, converge or gaze in any direction. T2-weighted MRI scans showed bilateral enlargement of the inferior olivary nuclei in both cases, which confirms the expected pathology previously demonstrated on autopsy. Both patients had severe oscillopsia and an attempt was made to improve this by bilateral disinsertion of the vertical rectus muscles. The pendular eye movements continued but were greatly reduced, in one case enough to relieve the oscillopsia. However, after 6 months retrobulbar botulinum toxin was required to continue to provide relief from the oscillopsia. Other treatment options, including pharmacological agents, are discussed.