 Now, here's another psychotic abnormality called obsoclonus. This is characterized by rapid, brief, random, conjugate saccads. They're chaotic. In this patient's example, it's caused by brainstem and cephalitis. It can also be seen as a perineoplastic effect and can be seen due to drug toxicity. These are not voluntary saccads. Look at these random, chaotic, conjugate saccads. There's no control over these movements. Sometimes they're brought out very easily by rapid refixation movements. This is a poorly characterized disorder but is thought to be related to dysfunction of the pause cells. Now, whether that's in the brainstem or the cerebellum has not been worked out well. Sometimes ocular flutter, which is a rapid, two-and-fro movement of the eyes, can be superimposed on obsoclonus. Sometimes hard to tell the difference. Here again, I think you can easily see these random, conjugate, somewhat chaotic, saccadic movements. And that's the characterization of obsoclonus. Again, in the differential, think infection, toxicity, tumor. What you can see here is when asking the patient to shift gaze, it seems to bring out this flurry of obsoclonic movements. In children, for example, one of the perineoplastic effects is neuroblastoma, the so-called dancing eyes, dancing feet syndrome. You can see that this patient has some cerebellar trouble as well, mainly truncal ataxia, titubation, very unsteady. This was all the result of presumed viral encephalitis, particularly affecting the brainstem and posterior fossa structures. Now we're going to demonstrate that the lateral cerebellar hemispheric function is not really too bad. Fingered outstretched finger testing is slightly unsteady, but certainly not as impaired as midline cerebellar function. She does that fairly quickly.