[ View Video Collection ]

Video Report

The presenting features of multiple sclerosis

Victoria JM Barrett, James Walker, and John S Elto

Oxford Eye Hospital, Woodstock Road, Oxford, OX2 6HE
Correspondence: Victoria Barrett c/o Mr Elston Secretary Oxford Eye Hospital
Email: vjmb@sjbarrett.freeserve.co.uk

Date of acceptance: 28th March 2005

A 43 year-old woman with episodes of vertical diplopia lsting 10-40 seconds. The video shows a typical episode with development of vertical diplopia (L/R) associated with with left upper lid retraction due to contraction of the left superior rectus and levator muscles and a partial right ptosis.


[View Video]

Note: This video is best viewed in Quicktime


Introduction

Paroxysmal diplopia due to spontaneous ocular muscle contraction is very rare, but has previously been reported in the literature as the presentation of multiple sclerosis.[1] We describe a patient with episodes of transient diplopia and unsteadiness.


Case Report

A 43 year old lady complained of a 6 week history of vertical diplopia occurring approximately 100 times a day, each episode lasting 10-40 seconds. The episodes were associated with a prodrome described as a wave of odd feeling passing over the back of her head into her face. Previous ocular history and medical history were unremarkable. The video demonstrates a typical episode. Vertical diplopia (L/R) develops with left upper lid retraction due to contraction of the left superior rectus and levator muscles and a partial right ptosis is also evident. At the same time she experiences dysarthria with laboured indistinct speech, unsteadiness and uncoordinated movement of the right hand.Examination between episodes showed VA 6/6 bilaterally, normal pupillary reactions, slight right ptosis, a small distance exophoria and full extra ocular movements. Neurological examination revealed generally brisk reflexes with extensor plantars bilaterally and subtle impairment of the fine motor control with rebound bilaterally but no cerebellar signs.Brain MRI revealed extensive periventricular white matter changes as well as multiple lesions throughout the brainstem, including a lesion in the region of the left third nerve fascicle, which is shown (figure 1).

Figure 1 Brain MRI revealing lesions that include the region of the left third nerve fascicle. Arrow indicates lesion.

Cortical visual evoked potentials were normal, as was an EEG, which showed no focal or epileptic abnormalities, despite several typical episodes of diplopia during the investigation. CSF showed oligoclonal bands. A diagnosis of multiple sclerosis (MS) was made, with the symptoms she experienced being attributable to paroxysmal attacks, which may be seen in MS.

Carbamazepine was started and increased to 200mg BD resulting in a resolution of her symptoms of diplopia.

 

Comment

Paroxysmal phenomena in the central nervous system are rare but have been described in patients with MS due to abnormal excitation in demyelinated plaques.[2] Paroxysmal phenomena in MS are more common in the peripheral nerves and include paraesthesia evoked by neck flexion (Lhermitte's sign) and tonic motor spasms evoked by movement.[1]

The differential diagnosis of paroxysmal diplopia includes superior oblique myokymia and ocular neuromyotonia. Cyclic oculomotor pareses although responsible for paroxysmal variable ocular misalignment does not usually cause double vision due to its early onset and therefore poor binocular function.

Superior oblique myokymia is a rare disorder of ocular motility characterized by unilateral paroxysmal oscillopsia and vertical or torsional diplopia due to intermittent contraction/relaxation of the superior oblique muscle.[3,4] The patient may be able to trigger an episode by sustained, voluntary activity of the superior oblique muscle followed by return to the primary position.[1,5,6] Our patient was unable to trigger an episode with any extraocular movement and did not have any torsion. Superior oblique myokymia has been shown with MRI to be likely to result from neurovascular contact at the root exit zone of the trochlear nerve.[4] Pathophysiologically vascular compression syndromes are hypothesised to develop because the junctional area between central and peripheral myelin is particularly vulnerable to continued pulsatile pressure, which may result in focal demyelination and in short circuiting of the impulses (ephaptic transmission).

Ocular neuromyotonia is a rare disorder characterized by transient ocular misalignment with episodic diplopia occurring spontaneously or following sustained eccentric gaze.[8] Ocular neuromyotonia is thought to reflect impaired muscle relaxation due to inappropriate discharges from oculomotor, trochlear, or abducens neurons or axons with unstable cell membranes.[6,8] Most patients have a history of trauma or radiation therapy to the sellar and parasellar region suggesting that compressed, irradiated axons are more prone to discharge spontaneously or in response to transmitted impulses. [1,5,6] Our patient had no significant past medical history. Ephaptic transmission accounts for the co-firing of different muscles by axon to axon cross talk at a site of neural injury.[1,5,6] Carbamazepine is used as a membrane stabilizing agent and usually produces resolution of the symptoms.[8]

The MRI (figure 1) shows there is a demyelination plaque in the region of the third nerve fascicle. It has been reported that isolated superior rectus/levator complex involvement indicates a fascicular rather than a nuclear lesion.[1] In our patient the lesion is in the fascicle and has affected only the superior rectus/levator complex causing vertical diplopia and lid retraction. The symptoms are unilateral as the lesion is only affecting the fascicle and the nucleus is not involved.[9] The contralateral ptosis is likely to be due to the effect of Herrings law. The increased innervation due to the spontaneous firing of the superior rectus/levator complex on the left causes a ptosis on the right due to a relative decrease flow of innervation on the right. We postulate that this plaque caused spontaneous firing due to loss of membrane stability (ephaptic transmission).

Carbamazepine is routinely used in a range of conditions as a membrane stabilizing agent. It acts by raising the membrane potential of the cell by blocking the sodium channels on the cell membrane and by other actions involving the calcium channels. Our hypothesis that ephaptic transmission caused the episodes of diplopia is supported by the resolution of symptoms with carbamazepine due to this membrane stabilizing effect.

Acknowledgement

Thanks to The Oxford Orthoptic Department, Simon DM Chen and Quresh Mohamed for their help with the video.


References

1. Ezra E, Plant GT Paroxysmal superior rectus and levator palpebrae spasm: a unique presentation of multiple sclerosis Br J Ophthalmol 1996;80:187-188

2. Postert T, McMonagle U, Buttner T, Pohlau D, Meves S, Przuntek H Paroxsymal convergence spasm in multiple sclerosis Acta Neurologica Scandinavica 1996;94:35-7 abstract

3. Scharwey K, Krizizok T, Samii M, Rosahl SK, Kaufmann H Remission of superior oblique myokymia after microvascular decompression Ophthalmologica 2000; 214:426-8

4. Yousry I, Dieterich M, Naidich TP, Schmid UD, Yousry TA Superior oblique myokymia magnetic resonance imaging support for the neurovascular compression hypothesis Ann Neurol 2002;51:361-8

5. Miller NR, Lee AG Adult onset acquired oculomotor nerve paresis with cyclic spasms: relationship to ocular neuromyotonia Am J Ophthalmol 2004;137:70-76

6. Shults WT, Hoyt WF, Behrens M, Maclean J, Saul RF, Corbett JJ Ocular neuromyotonia a clinical description of six patients Archives Ophth 1986;104:1028-1034

7. Rappaport ZH, Govan Lippmann R, Devor M An electron microscopic analysis of biopsy samples of the trigemminal root taken during microvascular decompressive surgery Stereotactic functional neurosurgery 1997;68:182-6 abstract

8. Frohman EM, Zee DS Ocular neuromyotonia: clinical features, physiological mechanisms, and response to therapy Ann Neurol 1995;37:620-6

9. Kline LB, Bajandas FJ Neuro-ophthalmology Review manual 4th edition SLACK 1996