Acute esotropia, convergence-retraction nystagmus and contraversive ocular tilt reaction from a paramedian thalamomesencephalic infarct

Convergence‐Retraction Nystagmus Associated with Dorsal Midbrain Lesions in Three Dogs

“…Convergence‐retraction nystagmus is an irregular, jerky nystagmus in which both eyeballs rhythmically converge and retract into the orbit, particularly on attempting an upward gaze . In humans it is seen as part of Parinaud's syndrome, also known as dorsal midbrain syndrome, in which a lesion of dorsally located midbrain structures (the ventral pretectum, the periaqueductal area, and the medial longitudinal fasciculus in the dorsal tegmentum) prevents upward or downward movement of the eyes . It has been hypothesized that convergence‐retraction nystagmus is caused by damage (ischemia, neoplasia, compression, or demyelination) to supranuclear fibers that have an inhibitory effect on the convergence neurons or divergence neurons in the midbrain, resulting in a sustained discharge of medial rectus and other extraocular muscle neurons .…”

“…It results from simultaneous contraction of all of the extraocular muscles in response to efforts to change the direction of gaze. This rhythmic contraction is thought to result from a sustained discharge of axons in the medial longitudinal fasciculus . The RINMLF of the midbrain (Fig ), located dorsal to the oculomotor nuclei, contain the final relays producing all vertical eye movements and hence compromise of the neuronal cell bodies, their afferent and efferent pathways or both are thought to generate convergence and retraction of the eyeballs .…”

“…[2][3][4] It has been hypothesized that convergence-retraction nystagmus is caused by damage (ischemia, neoplasia, compression, or demyelination) to supranuclear fibers that have an inhibitory effect on the convergence neurons or divergence neurons in the midbrain, resulting in a sustained discharge of medial rectus and other extraocular muscle neurons. 2,3 The rostral interstitial nuclei of the medial longitudinal fasciculus (RINMLF) of the midbrain, located dorsal to the oculomotor nuclei, contain the final relays producing all vertical saccades, and hence it has been suggested that Parinaud's syndrome may result from damage to their neuronal cell bodies, as well as their afferent and efferent pathways. 2,4 Convergence-retraction nystagmus is a highly localizing clinical sign that to the best of our knowledge has not yet been described in the dog.…”

See-saw nystagmus, convergence-retraction nystagmus and contraversive ocular tilt reaction from a paramedian thalamomesencephalic infarct

“…It involves the central otolithic connections, especially in the interstitial nucleus of Cajal (INC) 1. Convergence-retraction nystagmus in patients with thalamomesencephalic lesion is rare 2. This may be related to the damage of supranuclear fibres having an inhibitory effect on the convergence neurons or ischaemia of the divergence neurons in midbrain, which could result in a sustained discharge of medial rectus neurons 2.…”

“…Convergence-retraction nystagmus in patients with thalamomesencephalic lesion is rare 2. This may be related to the damage of supranuclear fibres having an inhibitory effect on the convergence neurons or ischaemia of the divergence neurons in midbrain, which could result in a sustained discharge of medial rectus neurons 2. The contraversive OTR is likely due to ischaemia of the INC 3…”