|Year : 2022 | Volume
| Issue : 2 | Page : 186-190
Supranuclear and internuclear ophthalmoplegia - Gaze palsy
Cyril Mathew George, Padmaja Krishnan, Ashwati Sankar
Department of Ophthalmology, MES Medical College Hospital, Malappuram, Kerala, India
|Date of Submission||20-Jun-2022|
|Date of Decision||03-Jul-2022|
|Date of Acceptance||19-Jul-2022|
|Date of Web Publication||30-Aug-2022|
Dr. Cyril Mathew George
Department of Ophthalmology, MES Medical College, Perinthalmanna, Malappuram, Kerala
Source of Support: None, Conflict of Interest: None
Gaze palsy is the loss of binocular control because of lesions of the pathways above the level of the nucleus. To localize the lesion, an understanding of the supranuclear and internuclear pathways is necessary.
Keywords: Diplopia, gaze palsy, ophthalmoplegia
|How to cite this article:|
George CM, Krishnan P, Sankar A. Supranuclear and internuclear ophthalmoplegia - Gaze palsy. Kerala J Ophthalmol 2022;34:186-90
| Introduction|| |
Gaze is described as binocular, synchronous, and symmetrical eye movements in the same or opposite direction, such that the image of the object of interest falls on the fovea of each eye.
There are six systems of ocular movements, namely, the saccades, smooth pursuit, vestibular reflex, optokinetic, fixation, and vergences.
In this portion, we will discuss the horizontal and vertical saccadic eye movements [Table 1] and smooth pursuit movements [Table 2] along with some common lesions in the pathways.
Saccades are fast eye movements to fixate on an object of interest in the field of view when its image is not on the fovea. The impulse for saccades arises in the frontal eye fields.
Pursuits are slow tracking movements to maintain fixation on a moving object, and the impulse arises from the parieto-occipito-temporal cortex, cerebellum, and the superior colliculus.
Vestibular and tonic neck reflex eye movements maintain the alignment of the retinal image with respect to head position or neck position with the help of vestibular part of the ear and proprioceptors of the neck [Table 3].
Horizontal gaze centre
The horizontal gaze centre, situated in the pons, is formed by the parapontine reticular formation (PPRF) and abducens nucleus. The sixth nerve nucleus contains two types of neurons. About 60% of the motor neurons project directly to the ipsilateral lateral rectus muscle as the abducens nerve, whereas the remaining 40% are interneurons that project via the medial longitudinal fasciculus (MLF) to the medial rectus subnucleus of the contralateral third nerve innervating the medial rectus of the opposite side. The PPRF and sixth nerve nucleus are situated very close to each other such that lesions here can only be differentiated by dissociation of saccadic and pursuit eye movements.
Horizontal gaze pathway
The pathway for horizontal gaze is slightly different for saccadic and pursuit eye movements as impulse to the nucleus arises from different parts of the brain. But both these have a common final pathway beyond the abducens nucleus.
The final common pathway from abducens nucleus consists of the following:
- Motor neurons to ipsilateral lateral rectus via abducens nerve that causes abduction of the ipsilateral eye.
- Internuclear neurons via contralateral MLF to medial rectus subnucleus in third nerve nucleus of opposite side that causes adduction of the contralateral eye.
Therefore, both the eyes move towards the side of stimulated abducens nucleus.
[Table 1]: Saccadic movements
Cortex of one side of the brain controls saccadic eye movements to the opposite side [Figure 1]a.
|Figure 1: Horizontal gaze pathway (a) Saccadic movement - eye movements to one side controlled by contralateral hemisphere. (b) Smooth pursuit movement - eye movement to one side controlled by ipsilateral hemisphere|
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[Table 2]: Smooth pursuit movements
Cortex of one side of the brain controls pursuit eye movements to same side. Pathway for pursuit eye movement does not relay in PPRF as pursuit eye movements do not need excitatory burst neurons in PPRF that is required to make high velocity saccades [Figure 1]b.
[Table 3]: Vestibulo Ocular system
Stimulation of horizontal semicircular canal results in horizontal ocular rotations away from the side of the canal. This is the basis of vestibular nystagmus in labyrinthine dysfunction.
Horizontal gaze paresis
Features of horizontal gaze paresis depend on the location of the lesion. Lesions in the pons are the most common cause of horizontal gaze paresis. Common etiologies for any gaze paresis (horizontal and vertical) include the following:
- Multiple sclerosis
- Central pontinemyelinolysis
- Wernicke's encephalopathy.
Progressive supranuclear palsy (vertical saccades are affected mainly, later all eye movements are affected as the disease progresses).
Lesion of the PPRF
Loss of all ipsilateral horizontal saccadic eye movements.
Vestibulo ocular reflex and pursuit eye movements are spared as their fibers innervate the abducens nucleus without relay in PPRF [Figure 2]a.
|Figure 2: (a) Lesion of the PPRF or 6th nerve nucleus affects horizontal gaze to the ipsilateral side. Lesion of the abducens nucleus affects the vestibulo ocular system also. (b) Unilateral MLF lesion (purple) affects only ipsilateral adduction whereas bilateral MLF lesion (red) affects adduction bilaterally|
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Lesion of abducens nucleus/6th nerve nucleus
Loss of all ipsilateral voluntary (saccadic and pursuit) and reflex (vestibulo ocular) conjugate eye movements. Infarction of the anterior cerebellar artery can lead to lesion in the PPRF and/or the abducens nucleus [Figure 2]a.
Internuclear ophthalmoplegia (INO)
INO occurs when lesion is in the MLF that connects the abducens nucleus to contralateral third nerve nucleus (hence, the term internuclear). It can be unilateral or bilateral INO.
- Ipsilateral adduction deficit
- Contralateral dissociated horizontal abduction nystagmus [Figure 2]b.
INO is considered to be only half gaze palsy. Localization of the lesion in MLF (rostral or caudal) can be made by checking for the involvement of convergence. Stimulus from the near reflex system synapses directly to the third nerve nucleus in the rostral midbrain region. Therefore, if
- Convergence normal – caudal MLF lesion;
- Convergence impaired – rostral midbrain lesion.
Usually, there is no strabismus in primary gaze, but in rostral lesion, patient may have exotropia in primary gaze called as wall-eyed monocular INO.
Bilateral adduction deficit with simultaneous abduction nystagmus;
- Convergence normal or impaired, based on the location of lesion;
- When there is exotropia of both eyes in primary gaze, it is called as wall-eyed bilateral INO [Figure 2]b.
One and a half syndrome
- Lesion of PPRF or sixth nerve nucleus and MLF on same side
- Ipsilateral horizontal gaze palsy (one) and ipsilateral INO (half)
- Convergence will be spared as the lesion in MLF is essentially close to the PPRF [Figure 3]a.
|Figure 3: (a) Lesion seen in one and half syndrome. (b) Lesion seen in half and half syndrome|
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Eight and half syndrome
One and a half syndrome with facial nerve palsy because of ipsilateral involvement of facial fascicular nerve as it wraps around the abducens nucleus in dorsal pons.
Causes – vascular or demyelinating lesions in the dorsal tegmentum of caudal pons.
Half and half syndrome
Lesion of MLF of one side with ipsilateral sixth nerve fascicular involvement (not sixth nerve nucleus).
Therefore, HALF–HALF horizontal gaze palsy because of INO and other HALF because of sixth nerve palsy [Figure 3]b.
Reverse INO/Lutz posterior INO/INO of abduction
Here, there is abduction restriction on attempted gaze to the same side with contralateral adduction nystagmus that is the reverse of INO.
- Reflex pathways are intact
- Described with ipsilateral rostral pontine or mesencephalic lesions
- Can be unilateral or bilateral.
Vertical gaze centre
The vertical gaze centre is situated in the midbrain (thalamomesencephalic junction), rostral to superior and inferior colliculus, and is formed by
- Rostral interstitial nucleus of the MLF (riMLF)
- Interstitial nucleus of Cajal
- Nucleus of posterior commissure
- Posterior commissure.
Vertical gaze pathway [Table 4]
|Table 4: Initiation in frontal cortex, pretectum, and supplementary eye fields (bilateral event)|
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Vertical gaze also has saccadic as well as pursuit movements with similar cortical control except the fact that initiation occurs in bilateral cortex for vertical gaze of the eye. The pathways from the higher centers project to the riMLF.
Upgaze pathway [Figure 4]a.
|Figure 4: Vertical gaze pathway (a) Upgaze pathways.(b) Downgaze pathway|
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Dorsal midbrain syndrome/Parinaud syndrome
- Lesions of the posterior commissure/nucleus of posterior commissure.
- Pineal region tumors are a common cause.
Other specific causes include infarction of paramedian/top of basilar artery infarction and obstructive hydrocephalus (Sylvian aqueduct syndrome).
- Lid retraction (Collier's sign) – damage to inhibitory neurons to eyelid muscles,
- Light near dissociation (when pretectal involvement is present).
- Convergence retraction – nystagmoid movement with altered upgaze because of asynchronous convergent saccades.
- Skew deviation often with higher eye on the side of the lesion.
Downgaze pathway [Figure 4]b and [Table 5].
|Table 5: Initiation in frontal cortex, pretectum, and supplementary eye fields (bilateral event)|
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Unilateral riMLF lesion
Downward saccade is more affected than upward saccade (as third nerve nuclei receive bilateral innervation from riMLF for upgaze, but not for downgaze).
Bilateral riMLF lesion
More common compared to unilateral riMLF lesion as it occurs because of infarction of paramedian arteries at the top of basilar artery (one medial artery supplies both riMLF).
More severe than unilateral lesions.
Downward saccades are affected more than upward saccades, but a complete vertical gaze paralysis also occurs.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]