From the Research
Thalamopeduncular Lesions and Downbeat Nystagmus
- Thalamopeduncular lesions can cause downbeat nystagmus due to the involvement of cerebellar-modulated crossed oculovestibular fibers of the superior cerebellar peduncle 1
- The paramedian thalamopeduncular region is supplied by the superior cerebellar artery, and infarction in this area can lead to downbeat nystagmus 1
- Downbeat nystagmus is typically associated with lesions in the cerebellar flocculus or the brainstem, and can be caused by a variety of factors, including vascular disorders, tumors, and demyelinating diseases 2, 3
Mechanism of Downbeat Nystagmus
- Downbeat nystagmus is characterized by a slow downward drift of the eyes, followed by a fast upward corrective saccade 2, 3
- The pathomechanism of downbeat nystagmus is thought to involve damage to the inhibitory vertical gaze-velocity sensitive Purkinje cells in the cerebellar flocculus, leading to disinhibition of brainstem target neurons and spontaneous upward drift 4
- The cerebellar flocculus is involved in the generation and control of smooth pursuit and gaze holding, and damage to this area can lead to a range of ocular motor deficits, including downbeat nystagmus 4
Clinical Presentation
- Downbeat nystagmus can present with a range of symptoms, including blurred vision, oscillopsia, and vertigo 2, 3
- The diagnosis of downbeat nystagmus is based on a systematic clinical examination of eye movements, including spontaneous nystagmus, smooth pursuit, and gaze-holding function 3
- Treatment options for downbeat nystagmus include pharmacotherapy, such as 4-aminopyridine, and rehabilitation techniques to improve gaze stability and reduce symptoms 2, 3