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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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The Interstitial Nucleus of Cajal (INC) is essential for vertical eye movement. This holds true for saccades, the vestibulo-ocular reflex, smooth pursuit and optokinetic nystagmus. 
INC stimulation produces a combined torsional-vertical eye movement, which is maintained until the next eye movement occurs, indicating that the velocity commands from the gaze control system producing the eye movement has been integrated to an eye position signal which maintains the eye displacement.This position signal also influences head posture.

The INC has a major role in torsional-vertical eye movement control, acting as a velocity-to-position integrator and could, if damaged, produce torsional-vertical nystagmus.

The INC has two populations of neurons that are responsible for:
-Neural integration (ie, gaze holding) during vertical and torsional movements
-Eye–head coordination in the roll plane1.
 

The INC has extensive rostral and caudal connections, particularly with the vestibular nuclei, and is the most prominent group of cells within the medial longitudinal fasciculus2.

It receives inputs from:

The INC itself sends outputs to the:

 

Lesions of the INC

Unilateral INC inactivation produces:
An ipsilesional torsional nystagmus (i.e., beats in opposite direction to that caused by a riMLF lesion), with or without a downbeat component.
Slight to moderate degree of contralesional torsional deviation.
Ocular tilt reaction:skew deviation (contralesional hypotropia), excyclotorsion of the contralesional eye (and incyclotorsion of the ipsilesional eye), and contralesional head tilt.

Bilateral INC lesions produce:
Severe deficit of vertical gaze-holding and of the VOR.
Upbeat nystagmus

 

 

Figure 1. Axial section through the midbrain, showing the relationship of the INC to the nucleus of CN 3.

Redrawn from: Hathout, G., 2009. Clinical Neuroradiology. Cambridge, UK: Cambridge University Press.

 

References

 

  1. Wong, A. M. (2008). Eye movement disorders. Oxford: Oxford University Press.
  2. Yu M, Wang SM. Neuroanatomy, Interstitial Nucleus of Cajal. In: StatPearls. Treasure Island (FL): StatPearls Publishing; 2020.