A 44-year-old man developed dizziness and oscillopsia after surgical resection of ependymoma in the fourth ventricle, which had manifested with headache and vomiting (figure, A). Examination disclosed newly developed jerky horizontal nystagmus after the surgery. The nystagmus changed its direction periodically with a brief transition period (figure, B and C, video). Follow-up MRI disclosed discrete lesions in the nodulus and left lateral medulla (figure, D). The periodic alternating nystagmus (PAN) almost resolved with baclofen 20 mg BID.
Figure. (A) MRIs show mixed solid and cystic mass (ependymoma) in the fourth ventricle with gadolinium enhancement. The mass extends into the subarachnoid space of the foramen magnum through the foramen of fourth ventricle (arrows). (B) Magnetic search coil recording of the nystagmus shows a spontaneous left beating nystagmus reversing its direction after a transition period of approximately 8 seconds. (C) Temporal profile of slow-phase velocity of the nystagmus consists of left beating nystagmus, a transition phase, and right beating nystagmus. The left beating nystagmus is longer (duration: 140 vs 70 s) and stronger (maximum slow phase velocity: 17 vs 7 O/second) than the right beating one. (D) Follow-up MRIs after surgical resection of the ependymoma disclose discrete lesions in the nodulus and left lateral medulla (arrows). Video: Recording of the eye movements demonstrates initial left beating nystagmus that reverses its direction after a transition period of several seconds.
PAN has been reported in discrete cerebellar lesions.1 Development of PAN in our patient with a circumscribed nodular lesion supports that nodular dysfunction may induce PAN.2
Footnotes
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Disclosure: The authors report no conflicts of interest.
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