InterNuclear Ophthalmoplegia

This paper describes an unusual Clinically Isolated Syndrome of Inflammatory DeMyelination that was characterized by a right VI Nerve Palsy and right InterNuclear Ophthalmoparesis (INO), along with an unusual form of dissociated Nystagmus.

Magnetic Resonance Imaging (MRI) revealed an isolated lesion within the right DorsoMedioLateral Pontine Tegmentum.

Four years later, the subject developed a partial Sensory Transverse Myelitis, confirming Clinically Definite Multiple Sclerosis (MS).

This paper extends the range of Isolated Syndromes associated with MS.

Background
There is a poor correlation between Multiple Sclerosis disease activity, as measured by Magnetic Resonance Imaging, and clinical disability.

Objective
To establish OculoGraphic criteria for the diagnosis and severity of InterNuclear Ophthalmoparesis (INO), so that future studies can link the severity of Ocular Dysconjugacy with NeuroRadiological abnormalities within the DorsoMedial BrainStem Tegmentum.

Methods
The study involved 58 patients with Multiple Sclerosis and chronic INO and 40 normal subjects.

Two dimensional infrared Oculography was used to derive the Versional Dysconjugacy Index (VDI)-the ratio of abducting to adducting eye movements for peak velocity and acceleration.

Diagnostic criteria for the diagnosis and severity of INO were derived using a Z score and Histogram analysis, which allowed comparisons of the VDI from Multiple Sclerosis patients and from a control population.

Results
For a given Saccade, the VDI was typically higher for acceleration v velocity.

Whereas the Z scores for velocity measures were always higher than values derived from comparable acceleration VDI measures; this was related to the greater variability of acceleration measures.

Thus velocity was a more reliable measure from which to determine Z scores and thereby the criteria for INO and its level of severity. The mean (SD) value of the VDI velocity derived from 40 control subjects was 0.922 (0.072).

The highest VDI for velocity from a normal control subject was 1.09, which was 2.33 SD above the normal control mean VDI.

We therefore chose 2 SD beyond this value (that is, a Z score of 4.33) as the minimum criterion for the OculoGraphic confirmation of INO.

Of patients thought to have UniLateral INO on clinical grounds, 70% (16/23) were found to have BiLateral INO on OculoGraphic assessment.

Conclusions
INO can be confirmed and characterised by level of severity using Z score analysis of quantitative OculoGraphy.

Such assessments may be useful for linking the level of severity of a specific clinical disability with NeuroRadiological measures of Brain tissue pathology in Multiple Sclerosis.

Background
The existence of a PreNuclear Abduction Paresis is still debated.

Methods
In a retrospective design, we identified 22 patients with isolated UniLateral (n = 20) or BiLateral (n = 2) Abduction Paresis and ElectroPhysiologic abnormalities indicating rostral Pontine and/or Mesencephalic lesions.

Another 11 patients had Unilateral Abduction Paresis with additional Ocular Motor abnormalities indicating MidBrain Dysfunction. Eight of these 11 patients also had ElectroPhysiological abnormalities supporting this location.

ElectroPhysiological examinations in all patients included Masseter and Blink Reflexes (MassR, BlinkR), BrainStem Auditory Evoked Potentials (BAEP), and direct current Elctro-OculoGraphy (EOG).

Results
UniLateral MassR abnormalities in patients with UniLateral Abduction Paresis were seen in 17 patients and were almost always (in 16 of 17 patients) on the side of the Abduction Paresis.

Another 11 patients had BiLateral MassR abnormalities. BlinkR was always normal.

EOG disclosed slowed Abduction Saccades in the non-paretic eye in 6 patients and slowed Saccades to the side opposite to the Abduction Paresis in another 5 patients.

Re-examinations were done in 27 patients showing normalization or improvement of Masseter Reflex abnormalities in 18 of 20 patients and in all patients with EOG abnormalities. This was always associated with clinical improvement.

Conclusions
ElectroPhysiologically documented or clinically evident rostral Pontine and/or Mesencephalic lesions in our patients exclude an Infranuclear IntraPontine 6th Nerve lesion and indicate the existence of an Abduction Paresis of PreNuclear origin.

An increased tone of the antagonistic Medial Rectus muscle during Lateral Gaze either by abnormal Convergence or impaired Medial Rectus inhibition seems most likely.

Deep Hemispheric or BrainStem small Infarcts can lead to atypical Lacunar Syndromes. Unilateral InterNuclear Ophthalmoplegia (INO) and Cerebellar Ataxia has not been reported previously.

A 57-year-old hypertensive female presented with BiLateral Appendicular and left truncal Cerebellar Ataxia and right INO.

Cranial MRI showed a right ParaMedian Infarct of lacunar size located in the Tegmentum of caudal Mesencephalon.

At this level the involvement of Medial Longitudinal Fascicle (MLF) led to right INO and the lesion of Brachium Conjunctivum caused the BiLateral Cerebellar Ataxia.

Ipsilateral involvement of both Cerebellofugal Fibers, before and after decussation, was responsible for bilateral Cerebellar Ataxia.

Copyright 2001 S. Karger AG, Basel

Vascular Disorders of the BrainStem manifest characteristic Neurologic symptoms according to their localization.

The Medial Longitudinal Fasciculus (MLF) lies in the ParaMedian portion of the upper BrainStem Tegmentum, and the lesion in this fasciculus shows specific abnormality of the Eye Movement Pattern which is known as the MLF Syndrome.

Although the MLF Syndrome was reported frequently to be accompanied by varieties of other Neurologic deficits according to the lesion extending into the adjacent structures in the BrainStem.

The combination of MLF syndrome and Cerebellar Ataxia has attracted less attention of Neurologists. Recently we experienced three cases of Cerebellar Ataxia arisen simultaneously with MLF Syndrome.

Magnetic Resonance Imaging (MRI) tomography or X-ray computed tomography visualized lacunar lesion(s) in the upper BrainStem Tegmentum in all of three cases. It was obvious that the lesion included the MLF and caused the MLF Syndrome in these cases.

It was speculated that Ventro-Caudal extension of the lesion involved the Decussation of the Superior Cerebellar Peduncle, and was responsible for the association of Cerebellar Ataxia with MLF Syndrome.

According to the recent discussion about the feeding arteries in the BrainStem, we decided that the damage of the ParaMedian branches diverging from the Basilar Tip resulted in the lacunar lesion(s).

The development of diagnostic procedures especially MRI enables the diagnosis of the Vascular Disorders in the BrainStem with considerable accuracy.

InterNuclear Ophthalmoplegia (INO) is a Gaze Disorder characteristic of lesions involving the Medial Longitudinal Fasciculus (MLF).

Two patients aged 62 and 74 years presented with acute Neurologic deficits characteristic of INO. Computed axial Tomography (CT) did not detect abnormalities in the region of the MLF.

Magnetic Resonance Imaging (MRI) however, demonstrated BrainStem hypersignals with long T₂ characteristics in the region of the MLF which correlated with the clinical symptoms.

These cases illustrate the value of the MRI in evaluation of patients with INO and suggest that MRI is superior to CT in evaluating Gaze Disorders attributable to Brain Dysfunction.

The site of lesions responsible for Horizontal Gaze Palsy and various types of InterNuclear Ophthalmoplegia (INO) was established by identifying the common areas where the abnormal MRI signals from patients with a given Ocular-Motor Disorder overlapped.

Patients with UniLateral Gaze Palsy had lesions in the ParaMedian area of the Pons, including the Abducens Nucleus, the Lateral part of the Nucleus Reticularis Pontis Caudalis and the Nucleus Reticularis Pontis Oralis.

Patients with Abducens Nucleus lesions showed additional clinical signs of Lateral Rectus weakness. Lesions responsible for BiLateral Gaze Palsy involved the Pontine Tegmental Raphe.

Since this region contains the Saccadic Omnipause Neurons, this finding suggests that damage to Omnipause Cells produces slowing of Saccades rather than OpsoClonus, as previously proposed.

All INOs, regardless of the presence of impaired Abduction or Convergence, had similar MRI appearances.

Frequently the lesions in patients with INO, were not confined to the Medial Longitudinal Fasciculus (MLF) but also involved neighboring structures at the Pontine and MidBrain levels.

There was a statistically significant association between the clinical severity of the INO and the presence of abnormal Abduction or Convergence.

The findings suggest that the lesions outside the MLF, which may affect Abducens, Gaze or Convergence Pathways, are responsible for the presence of features additional to INO, depending on the magnitude of functional disruption they produce.

Background And Purpose
Patients with Multiple Sclerosis (MS), due to the diverse nature of the disease, have many types of eye movement disorders, particularly InterNuclear Ophthalmoplegia (INO).

The aim of the study was to evaluate the usefulness of a quantitative statistical saccade test analysis for identification of INO in MS patients.

Methods
Sixty MS patients and 50 volunteers underwent clinical bedside ocularmotor examination and Electrooculographic Evaluation in a tertiary referral university hospital.

Simultaneous Electro-Oculography recordings of each eye separately were made.

In the Saccade test, the versional dysconjugacy index (VDI) for saccades velocity and the Z score analysis were applied.

Results
Clinical eye movements disorders were found in 32 % of patients. In the MS patients saccades velocity was significantly lower compared with the control group.

Based on the results of the control group, we established the cut off values for VDI (1.04) and corresponded Z score (4.46) as the criterion indicated the presence of INO signs in MS patients.

We confirmed clinical evidence of different degrees of INO in 15 % of patients, and found subclinical INO signs in 20 % of patients.

Conclusion
The EOG registration is a sensitive ElectroPhysiological method for detecting subtle deficits of Ocular motility.

Saccade test analysis with calculation of the VDI and the Z-test score is a valuable method for identifying subclinical INO signs in MS patients.

Objective
The goal of this investigation was to demonstrate that InterNuclear Ophthalmoparesis (INO) can be utilized to model the effects of body temperature-induced changes on the fidelity of Axonal Conduction in Multiple Sclerosis (Uhthoff's phenomenon).

Methods
Ocular motor function was measured using infrared Oculography at 10-minute intervals in patients with Multiple Sclerosis (MS) with INO (MS-INO; n = 8), patients with MS without INO (MS-CON; n = 8), and matched healthy controls (CON; n = 8) at normothermic baseline.

During, whole-body heating (increase in core temperature 0.8 degrees C as measured by an ingestible temperature probe and transabdominal telemetry), and after whole-body cooling.

The Versional Disconjugacy Index (velocity-VDI), the ratio of abducting/adducting eye movements for velocity, was calculated to assess changes in interocular disconjugacy.

The First Pass Amplitude (FPA), the position of the adducting eye when the abducting eye achieves a centrifugal fixation target, was also computed.

Results
Velocity-VDI and FPA in MS-INO patients was elevated (p < 0.001) following whole body heating with respect to baseline measures, confirming a compromise in Axonal electrical impulse transmission properties.

Velocity-VDI and FPA in MS-INO patients was then restored to baseline values following whole-body cooling, confirming the reversible and stereotyped nature of this characteristic feature of DeMyelination.

Conclusions
We have developed a NeuroPhysiologic model for objectively understanding temperature-related reversible changes in Axonal Conduction in Multiple Sclerosis.

Our observations corroborate the hypothesis that changes in core body temperature (heating and cooling) are associated with stereotypic decay and restoration in Axonal Conduction mechanisms.

The objective was to describe in Multiple Sclerosis, a Cerebellar Eye Movement Syndrome that resulted from an acute episode of Inflammatory DeMyelination.

Contrapulsion is an Ocular Motor Disturbance characterised by a triad of:
1. Hypermetric Saccadic eye movements in a direction opposite from a precisely localized lesion within a specific White Matter Pathway, the Uncinate Fasciculus:
   • At the level of the Superior Cerebellar Peduncle (SCP)
2. Hypometric Saccades towards the side of the lesion
3. Oblique Saccades directed away from the side of the lesion on attempted Vertical Saccades

Infrared OculoGraphy was used to demonstrate the characteristic features of Contrapulsion in two patients with Multiple Sclerosis. Brain MRI showed lesions within the region of the Uncinate Fasciculus and Superior Cerebellar Peduncle in both patients.

Eye movement recordings showed Saccadic Hypermetria away from the side of the lesion and Saccadic Hypometria towards the side of the lesion.

The Hypometria decomposed into a series of stepwise movements as the Eye approached the target. Oblique Saccades directed away from the side of the lesion were seen on attempted Vertical Saccades.

In conclusion, Ocular Contrapulsion can be seen in patients with Multiple Sclerosis and results from a lesion in the region of the SCP, involving the Uncinate Fasciculus.

Two women presented with BiLateral InterNuclear Ophthalmoplegia evolving in a few days to complete BiLateral Horizontal Gaze Paralysis. Convergence and Vertical Eye Movements were normal.

Cerebral MRI showed a few Small White matter lesions in the Lateral Ventricle regions, and, at the BrainStem level, a single, small, BiLateral lesion affecting the posterior part of the Medial Pontine Tegmentum and responsible for the clinical syndrome.

The condition gradually improved in both patients, following a similar progression as at the onset.

Improvement first involved the Adduction movements in both eyes, whereas BiLateral Abduction Paresis still persisted for a few weeks, before complete recovery of eye movements.

BiLateral damage to the Medial Longitudinal Fasciculus and subsequent lateral extent of damage to the region of the two Abducens emerging Fibers may explain the clinical findings. In both cases, the cause was probably Multiple Sclerosis.

A prerequisite for a qualified analysis of Nystagmus is the recognition of uncommon forms of this condition. In InterNuclear Ophthalmoplegia (INO), a Dissociated Nystagmus in Side Gaze is typical.

This is accompanied by limited medial excursion of the Adducted Eye together with a Dissociated Nystagmus, which is stronger in the Abducting Fellow Eye.

This motility disturbance stems from a lesion in the Medial Longitudinal Fasciculus running in the BrainStem between the Sixth and the Third Nerve Nuclei.

The lesion is often due to Multiple Sclerosis, but can also be Ischemic, Traumatic, Neoplastic or Inflammatory (e.g. HIV infection).