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I ANATOMY                

 

II PHYSIOLOGY                               

III EXAMINATION: EYE MOVEMENTS & NYSTAGMUS 

IV FIXATION INSTABILITY   

VI VESTIBULAR SYSTEM  

 VII CEREBELLAR EYE   MOVEMENTS 

VIII CN PALSIES, VISUAL FIELDS, PUPIL & THE EYES

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Lesions affecting the cortical connections to the nuclei of cranial nerves 3, 4 and 6, are termed SUPRANUCLEAR

Lesions affecting the connections between nuclei are INTERNUCLEAR

Lesions affecting the nerves, neuromuscular junction, or muscles are INFRANUCLEAR1.

Video 1. Supranuclear Gaze. Professor A Moodley, NASA Neurology Registrar Weekend, 2019

 

(vv)SNGaze.mp4(tt)

 

Supranuclear deficits arise from involvement of:
-Oculomotor control pathways above the level of the abducens nucleus for horizontal eye movements
-Oculomotor control pathways above the level of the structures (cranial nerves III and IV, and the interstitial nucleus of Cajal (INC) in the dorsal midbrain) for vertical eye movements

Supranuclear ocular motor disturbances usually impair the movement of both eyes, for example, affecting the following:

The abducens nucleus, located in the pontine tegmentum, contains motor neurons that innervate the ipsilateral lateral rectus, as well as interneurons which decussate in the MLF, and innervate the contralateral medial rectus subnucleus.  Abducens nucleus involvement can be distinguished from abducens nerve injury in that a nuclear lesion produces a gaze palsy to the side of the lesion, whereas nerve injury produces only a lateral rectus palsy. 

Lesions of the nucleus make the vestibular ocular reflexes (VOR) dysfunctional, and the gaze palsy arising from a nuclear lesion therefore cannot be overcome by oculocephalic testing or caloric stimulation, as opposed to supranuclear lesions, or lesions of the PPRF.  This indicates that the abducens nucleus is a central integrating final common pathway for horizontal eye movements, as is the INC for vertical eye movements 2.  

 

 

References

 

  1. Glisson CC. Approach to Diplopia [published correction appears in Continuum (Minneap Minn). 2020 Feb;26(1):240]. Continuum (Minneap Minn). 2019;25(5):1362-1375. doi:10.1212/CON.0000000000000786
  2. Strupp M, Kremmyda O, Adamczyk C, et al. Central ocular motor disorders, including gaze palsy and nystagmus. J Neurol. 2014;261 Suppl 2:S542-58