Pontine Paramedian Reticular Formation, vertical gaze, and supranuclear ophthalmoplegia.

[Xalatan]

How is the PPRF wired for vertical gaze, and how does this apply in Supranuclear Ophthalmoplegia?

 

Can't find a good clear explanation for this piece of neuroanatomy, would really appreciate if someone can describe. Thank you!

[DrmDoc]

How is the PPRF wired for vertical gaze, and how does this apply in Supranuclear Ophthalmoplegia?

 

Can't find a good clear explanation for this piece of neuroanatomy, would really appreciate if someone can describe. Thank you!

 

Perhaps this link to Darmouth.edu will help. From the link:

 

Voluntary horizontal gaze and vertical gaze utilize different neuronal circuitry. Voluntary conjugate horizontal gaze is initiated by neurons in the frontal eye fields of the cerebral cortex (figure 28). Activation of the right frontal eye field will cause the eyes to look to the left and activation of the left frontal eye field will cause the eyes to look to the right. Projections from the frontal eye field go directly and indirectly (via the superior colliculus) to the contralateral paramedian pontine reticular formation (the PPRF). The PPRF, the region of reticular formation immediately ventral to the abducens nucleus, contains neurons that are critical for generating horizontal saccades. Damage to the left PPRF, for example, will completely prevent the movement of either eye to the left. Projections from the PPRF go to the ipsilateral abducens nucleus and, through the medial longitudinal fasciculus, to the contralateral oculomotor nucleus. This results in conjugate eye movement away from the frontal eye field that started the process and towards the side of the PPRF that was involved in the movement. The medial longitudinal fasciculus (MLF) is the link that yokes the medial movement of one eye to lateral movement of the other eye during lateral gaze. Damage to the MLF permits the abducting eye to move, while preventing the adducting eye from following (internuclear ophthalmoplegia).

 

Voluntary vertical gaze follows a different pathway (figure 29). First of all, there is no single cortical center responsible for vertical gaze. Instead, diffuse areas of the cortex project to the rostral interstitial nucleus of the MLF (Cajal; located in the rostral midbrain). This nucleus projects bilaterally to the oculomotor and trochlear nuclei, with many of these fibers passing through the posterior commissure. Damage to the rostral interstitial nucleus or the posterior commissure can impair voluntary vertical gaze while still permitting reflex vertical movement. This can be seen with pathology of the rostral, dorsal midbrain.

Edited May 1, 2016 by DrmDoc