1. A 33 year old woman with chronic dizziness
Teaching NeuroImages
Neurology
Resident and Fellow Section
© 2017 American Academy of Neurology

2. Vignette 33-year-old woman Chronic dizziness for two years
On exam is gaze-evoked nystagmus and hypermetric saccades
Choi SY et al.
© 2017 American Academy of Neurology

3. Video
Video : The patient shows horizontal gaze-evoked nystagmus and macrosaccadic oscillations following gaze shift and horizontal head impulses.
Choi SY et al.
© 2017 American Academy of Neurology

4. Imaging
Figure: Brain magnetic resonance images (MRIs). T2-weighted sagittal (A) and axial (B) brain MRIs show a huge epidermoid cyst at the fourth ventricle that compresses the brainstem and cerebellum.
Choi SY et al.
© 2017 American Academy of Neurology

5. Macrosaccadic Oscillations Induced by Horizontal Head Impulses
Macrosaccadic oscillation (MSO) are hypermetric saccades around the fixation point with intersaccadic intervals that are usually induced by gaze shift, attempted fixation, or in darkness.
MSO occurs with pontine or cerebellar lesions that compromise either the omnipause neurons or fastigial nucleus input, to premotor burst neurons1,2.
Retinal slip following horizontal head impulses can also trigger MSO.
1. Selhorst JB, Stark L, Ochs AL, Hoyt WF. Disorders in cerebellar ocular motor control. II. Macrosaccadic oscillation. An oculographic, control system and clinicoanatomical analysis. Brain 1976;99:
2. Leigh RJ, Zee DS. The neurology of eye movements, Fifth edition. ed. New York: Oxford University Press, 2015.
Chung and Edlow
© 2017 American Academy of Neurology