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July2005 Vol.42 Issue:      2 Table of Contents
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Effect of Galvanic Vestibular Stimulation on Recovery from Gaze Palsy

Adel Hassanein1, Magdy Arafa2, Ashraf Ahmed2
Departments of Neurology1, Physical Therapy for Neuromuscular Disorders and its Surgery, Faculty of Physical Therapy2, University

ABSTRACT

The purpose of this study was to evaluate the effect of galvanic vestibular stimulation (GVS) on recovery from gaze palsy. Twenty patients with gaze palsy, (14 males and 6 females) their age ranged from 20–63 years with mean age 47.9±12.5 years. Duration of gaze palsy ranged from 4–24 months with mean of 10.6±5.23. Twelve patients were post stroke and eight patients with definite multiple sclerosis. They received galvanic vestibular stimulation three times/ week for four weeks. They were assessed by using three point scale for gaze deviation, line bisection test and line crossing test. These measures were recorded before the vestibular stimulation (pre treatment) and after four weeks (post treatment). Results of this study showed that, there was  significant decrease in the grades of gaze deviation, significant improvement in line bisection and line crossing. It was concluded that, galvanic vestibular stimulation is a beneficial central non invasive modality to improve recovery from gaze palsy.

(Egypt J. Neurol. Psychiat. Neurosurg., 2005, 42(2): 359-364).

 





INTRODUCTION

 

Conjugate eye deviation (CED) occurs in approximately 20% of patients with cerebrovascular disease1 and in 18%-39% of patients with multiple sclerosis2. The underlying mechanism of CED is thought to be a disturbance of the cortical center or subcortical pathways involved in the control of voluntary eye movements. A sudden imbalance between the left and right tonic frontal inputs on the superior colliculus and/or premotor reticular formations of the brain stem is the possible mechanism of the initial eye deviation observed after an acute frontal lesion1.

Disorders of ocular motility may occur after injury at several levels of the neuraxis. Unilateral supranuclear disorders of gaze tend to be transient; bilateral disorders more enduring. Nuclear disorders of gaze also tend to be enduring and are frequently present in association with long tract signs and cranial nerve palsies on opposite sides of the body3. Eye-movement disorders commonly occur in vertebrobasilar stroke, although they are often unappreciated. Vertebrobasilar strokes can yield varied disturbances of eye movements, by affecting specific centers and pathways contained in the brain stem and cerebellum. Unique disorders combining supranuclear, nuclear, and infranuclear syndromes may occur4,5.

Vestibular system plays an important role in maintenance of human balance, posture, coordination of eye movement with head movement and spatial representation6,7. Vestibular stimulation is used to treat abnormalities of muscle tone, gravitational insecurity, movement intolerance, vertigo, and different forms of spatial neglect7,8,9.

The semi-circular canals and the otolith organs both contribute to gaze stabilization during head movement. The six semicircular canals form three functional pairs that lie in planes roughly orthogonal to each other. In addition, each canal works in a reciprocal arrangement with its paired partner in a push-pull fashion. The brain stem supplies the necessary neural connections to deliver the signals from the canals to the eye muscles to move the eyes appropriately for the vestibulo-ocular  reflex (VOR)10.

Two kinds of pathways ascend from the vestibular nuclei; some are concerned with oculomotor control and some are concerned with spatial orientation. Signals concerned with control of the eye movements ascend the medial longitudinal fasciculus to the nuclei of cranial nerves III, IV, and VI. Both sets of vestibular nuclei send bilateral projections to the cranial nerves some of which are excitatory and some of which are inhibitory11.

The vestibular system can be stimulated by galvanic vestibular stimulation (GVS). Galvanic vestibular stimulation has been used for almost 200 years for exploration of vestibular system. The eye movement pattern induced by application of electric currents to labyrinth is known as the galvanically induced vestibule-ocular reflex12.

 

SUBJECTS AND METHODS

 

Subjects:

Twenty patients with gaze palsy where included in this study, twelve patients with post stroke and eight patients with definite multiple sclerosis (MS). Patients with definite multiple sclerosis (MS) were diagnosed as having clinically definite MS according to poser criteria13, or having MRI supported definite MS according to Paty and Li14. All patients chosen from neurology department at El-Kasr El-Aini Hospital, Cairo University. their age ranged from 20 – 63 years with mean age of 47.9±12.5 years. Duration of gaze palsy was ranged from four to twenty four months with mean of 10.6±5.23 months, they were 14 males (70%), 6 females (30%).

 

Exclusion Criteria:

Patients with vestibular disorders, other ophthalmological problems, perceptual deficits, auditory, speech, and mental disturbances were excluded.

Methods:

 Subjects with definite MS patients were subjected to the following.

1-     Full clinical assessment including through history taking to detect the disease duration, the number of relapses, the type of symptoms and the proper stage of the disease. The clinical evaluation included also through clinical examination and assessment of the disability by the expanded disability statutes scale (EDSS).

2-     Neurophysiological assessment by the different evoked potential.

3-     Examination by MRI brain and cervical cord if indicated.

4-     Laboratory tests including:

-     Assay of Oligoclomal IgG.

-       Assay of IgG/Albumin Ratio in Serum and CSF.

-     Assay of CSF Myelin Basic Protein.

Subjects with stroke were subjected to examination by MRI brain.

 

Measurement procedures:

1-            Three point scale of gaze evaluation15.

Gaze will be evaluated by asking the patient to look to the left then to the right, to look at specific objects within the left and right fields and to follow slowly the moving objects leftward and rightward and the patient's behavior is scored on a three-point scale,

2-            Line bisection test16.

The subject marks the midpoint of 18 staggered lines of 20-mm, 40-mm, and 60-mm lengths. In left neglect the patients typically displace their mark to the right of the objective midpoint, neglecting part of the left of the line. The distance between the left edge of each line and the patient's mark showing the subjective midpoint was measured to the closest millimeter.

 3-           Line crossing test17.

         The patient was asked to cross out lines (36 black lines, 25X2 mm) slanted in various directions and spaced randomly on a 9 x 12-inch card. All patients received GVS from sitting position on a chair with a back supported, feet rested on the ground with flexed hips and knees, transmastoid GVS was used through two applied plate electrodes covered with sponges after cleaning of the skin with alcohol. The anode was placed on the mastiod process of the affected side, while the cathode was placed on the contralateral mastoid process.

The measurements were conducted pretreatment and repeated after 4 weeks (post treatment).

 

Therapeutic procedures:

All patients received GVS from sitting position on a chair with a back supported, feet rested on the ground with flexed hips and knees, transmastoid GVS was used through two applied plate electrodes covered with sponges after cleaning of the skin with alcohol. The anode was placed on the mastoid process of the affected side, while the cathode was placed on the contralateral mastoid process. The stimulation period lasted 5 minutes in every sitting with current intensity of about 4 MA and frequency of about 0.5-1 Hz. Expressions and reactions of patients were watched carefully during stimulation period which was preceded by precise explanation of what he would feel during stimulation.

 

Statistical Method:

                Statistical package for the social sciences (SPSS) (version 9) was for data analysis. Mean and standard deviation were estimates of quantitative data.

Paired t-test were used to test the significance of difference between two means within the same group. P value is significant at 0.05.

 

RESULTS

 

1-     Assessment of the grades of gaze deviation:

The mean values of the grades of gaze deviation before vestibular stimulation (pre) and after four weeks (post) are presented in Table (1) and Fig (1).

Table 1. Changes in the mean values of the grades of gaze deviation.

 

 

Pre

Post

Mean

2.4

1.6

SD

0.502

0.753

t

-2.85

P

0.007*

* Significant at P<0.05                                            Pre: before treatment.

Post: after the application of galvanic vestibular stimulation.

 

The paired t test shows a statistical significant decrease of post gaze deviation mean value compared to its pre mean value (P < 0.01).

 

 

Fig. (1): Changes of mean values of

gaze deviation.

 

2-            Assessment of the line bisection test:

The mean values of the score of the line bisection before vestibular stimulation (pre) and after four weeks (post) are presented in Table (2) and Fig (2).

 

Table 2. Changes in the mean values of the line bisection test.

 

 

Pre

Post

Mean

0.456

0.291

SD

0.150

0.164

T

11.68

P

0.001*

* Significant at P<0.05                                            Pre: before treatment.

Post: after the application of galvanic vestibular stimulation.

 

The paired t test shows a statistical significant improvement of post  mean value of line bisection . compared to its pre mean value (P < 0.01).

 

Fig. (2): Changes of mean  values

line bisection test.

 

3-            Assessment of the line crossing:

The mean values of the grades before vestibular stimulation (pre) and after four weeks (post) are presented in Table (3) and Fig (3).

 

Table 3. Changes in the mean values of line crossing test.

 

 

Pre

Post

Mean

26.8

30.3

SD

4.942

5.292

t

-8.809

P

0.001*

*  Significant at P<0.05                                           Pre:   before treatment.

Post: after the application of galvanic vestibular stimulation.

 

The paired t test shows a statistical significant improvement of post  mean value of line crossing . compared to its pre mean value (P<0.01).

 

 

Fig. (3): Changes of mean  values of

line crossing test.

 

DISCUSSION

 

Clinical results after four weeks of treatment indicated that patients who received GVS, showed significant improvement of the ability to gaze into the affected field .

The improvement in gaze deviation could be attributed to inhibition of the tonic phase of contraction of antagonistic muscles which causes the horizontal gaze deviation, or facilitation of the agonistic yoked pairs of muscles, thus increasing their voluntary strength. Vestibular stimulation have a direct effect on enhancing alpha motor neurons which resulted in facilitation of extraocular eye movements. This explanation agree with Marshall & Mynard18.

The improvement of conjugate eye movements could be also attributed to brain activation induced by GVS. A significant activation due to vestibular stimulation was demonstrated in regions behind the primary auditory cortex, the insular and retroinsular regions, the inferior parietal lobe, certain temporal areas, and other regions also take part in the processing of vestibular signals received from the periphery. These areas are situated in both hemispheres, with a contralateral predominance over the stimulated side. Additionally, increased activity has been registered in the postcentral gyrus, claustrum, putamen, precentral gyrus, and gyrus cinguli. This explanation agree with Lobel et al.19, and Emri  et al.20.  

GVS provides a direct repetitive stimulus to the ascending tracts of the brain. Thus GVS could improve the reorganization process in which it strengths the synaptic activity. GVS provides more activation of brain areas resulting in improvement of cerebral blood flow. The increase of blood flow in a particular area of the brain is thought to reflect a greater metabolic activity resulting in increased synaptic activity within that region21.

Trans- mastoidal stimulation with the anode over the right and the cathode over the left mastoid induces an inhibition of the right and an excitation of the left vestibular nerve. Behaviorally, this provokes the following effects: The tonic vestibular tone imbalance results in deviations of eye position (ipsilateral to the anode) and the feeling of being tilted ipsiversively.

Concerning the patients of stroke, studies showed that most recovery after stroke occurred within the first three months following stroke22-26.

Recovery takes place very early as a result of post lesion reparative mechanisms in the brain as resolution of oedema and functional recovery27. The duration of illness is an important factor that shouldn’t be neglected in this study. The duration of illness of stroke patients ranged from six to twenty months, so the improvement attributed to GVS rather than spontaneous recovery. It was also the main cause that may be attributed to it than the non-significant improvement in certain patients.

In the present study, a simple method of vestibular stimulation was used to be more applicable, available and tolerable than previous method as caloric method18. In contrast with caloric vestibular stimulation which mediates its effect mainly via semicircular canals, galvanic vestibular stimulation has been shown to act equally on semicircular canal and otolith afferents, also galvanic stimuli can be controlled precisely12.

 

Conclusion:

                It was concluded that, galvanic vestibular stimulation is a beneficial central non invasive modality to improve recovery from gaze palsy.

 

REFERENCES

 

1.      Hideaki,T Arai M, Hirata k: conjugate eye deviation with head version due to a cortical infarction of  the frontal eye field. Stroke 33: 642, (2002).

2.      Miller RJ, Camon Symptoms and Sings in Chronic M.S, Merritt's Neurology, 10th ed., Lipencott Williams and Wikines, PP. 773-791, (2000).

3.      Pedersen RA and troost Bt: Abnormalities of gaze in cerebrovascular disease. Stroke, 12: 251-254, (1981).

4.      Bogousslavsky J and  Meienberg O: Eye-movement disorders in brain-stem and cerebellar stroke. Arch Neurol.; 44(2): 141-8. (1987).

5.      Moncayo J, and Bogousslavsky J. Vertebro-basilar syndromes causing oculo-motor disorders. Curr Opin Neurol.;16(1): 45-50 (2003).

6.      Rode G, Charle  N, Perenin MT, Vighetto A, Trillet M, Aimard G.: Partial remission of hemiplegia and somatoparaphrenia through vestibular stimulation in a case of unilateral neglect. Cortex; 28: 203-8 (1992).

7.      Bottini G, Karnath HO, Vallar G, Sterzi R, Frith CD, Frackowiak SJ and Paulesu E.: Cerebral representations for egocentric space. Functional-anatomical evidence from caloric vestibular stimulation and neck vibration. Brain, 124: 1182-1196 (2001).

8.      Arafa MA.: Spasticity control via electrical vestibular stimulation in stroke patients. Ph,D, THESIS, (1995).

9.      Bacsi AM, Watson SR, and colebatch JG.: Galvanic and acoustic vestibular stimulation activate different populations of vestibular afferents. Clin- Neurophysiol.; 114 (2): 359-365, (2003).

10.    Bockisch C J , Straumann D, and Haslwanter T: Eye movements during multi-axis whole-body rotations.J Neurophysiol; 89: 355-366, (2003)

11.    Cohen H.: Spatial senses 2: The vestibular system. in: Neuroscience for Rehabilitation. New Yourk, 2nd Edition- Chapter 10: 149-167 (1999).

12.    Lobel E, Kleine JF, Bihan DL, Leroy-Willig A, and Alain B: Functional MRI of galvanic vestibular stimulation. J Neurophysiology; 80 (5): 2699-2709 (1998).

13.    Poster CM, Paty DW and Scheinberg L.: New diagnostic criteria for multiple sclerosis: guidelines for research protocols. Ann. Neurol.; 13: 227-231, (1983).

14.    Paty, Dand Li, D,: Diagnosis of multiple sclerosis 1998: Do we need new diagnostic criteria? In Siva A, Kesselring J, Thampson A, ed. Frontiers in multiple sclerosis. Martin Dunitz; 2: 47-50, (1999).

15.    De Renzi E, Colombo A, Faglioni P and Gibertoni M: Conjugate gaze paresis in stroke patients with unilateral damage. Arch Neurol; (39): 482-486, (1982).

16.    Schenkenberg, T., Bradford, D C, and Ajax E T.: Line bisection and unilateral visual neglect in patients with neurologic impairment. Neurology; 30: 509-517, (1980).

17.    Rubens AB: Caloric stimulation and unilateral visual neglect Neurology. 35(7): 1019-24. (1985).

18.    Marshall CR and Maynard FM: Vestibular stimulation for supranunclear gaze palsy: Case report. Arch phys Med Rehabil. 64: 134-136, (1983)

19.    Lobel E, kleine JF, Leroy- willig A: Cortical areas activated by bilateral galvanic vestibular stimulation- (Abstract), Anna's of the new york academy of sciences, 871: 313-323, (1999).

20.    Emri M, Kisely M,  Lengyel Z, Balkay L, Márián T, Mikó L and Berényi E: Cortical Projection of Peripheral Vestibular Signaling J Neurophysiol (1), ( 2003).

21.    Turton A.: Mechanisms for recovery of hand and arm function after stroke: a review of evidence from studies using non-invasive investigative techniques. British Journal of Occupational Therapy; 61 (8): 359-363, (1998).

22.    Kinsella G and Ford B.: Acute recovery patterns in stroke patients, Medical Journal of Australia, 2, 663-666 (1980).

23.    Skillbeck C, Wade D, Langton Hewer R and Wood V.: Recovery after stroke, Journal of Neurology, Neurosurgery and Psychiatry, 45, 5-8 (1983)

24.    Wade D, Langton Hewer R, Skilbeck C and David R.: Stroke: A critical approach to diagnosis, treatment and management, Chapman and Hall, London (1985).

25.    Lindmark B.: The improvement of different motor functions after stroke, Clinical Rehabilitation, 2, 275-283 (1988).

26.    Ashburn A.: Physical Recovery following Stroke. Physiotherapy; 83: 480-490 (1997).

27.    Duncan PW: Synthesis of intervention trial to improve motor recovery following stroke. Topics in Stroke Rehabilitation. 3 (4): 1-20 (1997).


  

الملخص العربي

 

تأثير التنبيه الكهربي لدهليز الأذن على الشفاء من الشلل التحديقي

 

يعتبر الشلل التحديقي الذي ينتج عن بعض الأمراض من الأشياء التي تؤثر على الوظائف اليومية. وقد أختير عشرون مريضاً يعانون من الشلل الحدقي أربعة عشر من الذكور وستة من الإناث) نتيجة (السكتة الدماغية –التصلب المتناثر) وترواحت أعمارهم بين 20-63 بمتوسط عمري 47.9 ± 5.23 وقد تم علاج هؤلاء المرضى باستخدام التنبيه الكهربائي لدهليز الأذن بمعدل ثلاث مرات أسبوعياً ولمدة أربعة أسابيع وقد تم تقييم حالة المرضى عند بداية العلاج وفي نهاية الأربع أسابيع واشتمل التقييم على الآتي:

[1]                  تقييم حركة العين باستخدام مقياس ثلاثي النقاط.

[2]                  تقييم التجاهل البصري باستخدام اختبار تنصيف الخط.

[3]                  تقييم التجاهل البصري باستخدام اختبار قطع الخطوط.

وقد أوضحت المعالجة الإحصائية للنتائج:

-                     وجود تحسن ملحوظ في مقدار انحراف حركة العين وهذا التحسن ذو دلالة إحصائية.

-                     وجود تحسن ذو دلالة إحصائية في اختيار تنصيف الخط.

-                     وجود تحسن ملحوظ ذو دلالة إحصائية في اختبار قطع الخطوط.

مما سبق يتضح أن استخدام التنبيه الكهربائي لدهليز الأذن يفيد كثيراً في علاج مرضى الشلل التحدقي.



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