Nystagmus

Nystagmus

In this section, the speaker introduces nystagmus and explains that there are localizing and non-localizing forms of nystagmus. The speaker also mentions that they will only be discussing the localizing forms.

Localizing Forms of Nystagmus

• Non-localizing forms of nystagmus are more common, such as gaze-evoked nystagmus in primary position.

• Localizing forms of nystagmus depend on the waveform or morphology seen in the nystagmus. Downbeat and upbeat nystagmus are localized to specific areas.

• Downbeat nystagmus is characterized by a fast phase towards down and is worse when looking down. It localizes to the cervical medullary junction.

• Upbeat nystagmus is characterized by a fast phase going up and usually localizes to the vermis of cerebellum.

• Convergence retraction nystagmus is not really a true form of nystagmus but an aesthetic movement that results from co-firing of all three medial rectus muscles. It localizes to the dorsal midbrain.

• C-seesaw nystagmus looks like a seesaw with one eye going up while the other goes down. It localizes to the third ventricular area or parasellar regions.

• Other cerebellar forms of localized nystagmus include rebound and periodic alternating nystagmus, which localize to different areas.

Bruns Cushing Nystagmus

• The Bruns Cushing nystagmus is a combination of gaze-evoked and gaze-paretic nystagmus. It has a larger amplitude and slower frequency on gaze to the right and a smaller amplitude on gaze to the left. It localizes to the cerebellopontine angle.

Non-Localizing Forms of Nystagmus

• All other forms of nystagmus are non-localizing and may be caused by drugs or toxins. MRI post ear should be considered in these cases.