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July2007 Vol.44 Issue:      2 Table of Contents
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Vestibular Evoked Myogenic Potentials in Multiple Sclerosis

Obsis Madkour1, Yehia Zakaria1, Nihal El-Shazly2, Iman Maher2

Departments of Neurology1, Clinical Neurophysiology2, Cairo University



ABSTRACT

Background: Vestibular evoked myogenic potential (VEMP) is an otolith-mediated, short-latency reflex recorded from the sternocleidomostoid muscle in response to intense auditory clicks used for evaluation of the vestibulo-spinal pathway. Objective: This study aimed at  shedding light on the sensitivity of VEMPs in detection of occult vestibular pathway lesions in patients suffering from multiple sclerosis (MS). Methods: VEMPs were recorded from 25 MS patients. Clinical data were evaluated for possible brain stem affection, their EDSS scores were recorded. All patients underwent visual evoked potential (VEP), brainstem auditory evoked potential (BAEP), somatosensory evoked potential (SSEP) studies and magnetic resonance imaging (MRI). VEMPs were also recorded in 25 age and sex matched controls as well. Results: VEMPs showed abnormal P13 and N23 waves in 56% of Patients, VEP in 56%, BAEPs in 44%, SSEPs in 28% and MRI in 80%. MRI showed better sensitivity in detecting brain stem plaques yet patients with normal MRI had abnormal VEMPs and  BAEPs and VEMPs had nearly equal sensitivity in detecting brainstem plaques in symptomatizing group; however VEMPs were more sensitive than BAEPs in non symptomatizing group. Also we found no significant correlation between VEMPs and MRI or BAEPs. Conclusion: VEMPs is a simple, non-invasive, safe and quick method, which should be considered as a complementary neurophysiological tool for evaluation of possible brainstem dysfunction.

(Egypt J. Neurol. Psychiat. Neurosurg., 2007, 44(2): 635-646)




INTRODUCTION

 

The human vestibule has preserved an ancestral sound sensitivity and it has been suggested that a reflex could originate from this property inducing cervical muscle microcontractions secondary to strong acoustic stimulations. From this finding, the idea of vestibular evoked myogenic potentials was established.1

Vestibular evoked myogenic potentials (VEMPs) are short-latency electromyograms evoked by high-level acoustic stimuli (as brief clicks) recorded by surface electrodes over the tonically contracted sternocleidomastoid (SCM) muscle. These responses are presumed to originate in the saccule and end at the sternocleidomastoid muscle where myogenic potentials are produced by the flexor neck motor neurons.2,3,4

The biphasic positive-negative potentials (P13-N23), occur in all normal subjects and the response recorded over the muscle on each side, is generated by afferents originating from the ipsilateral ear. Later potentials (N34, P44), present in most but not all subjects, are generated bilaterally after unilateral ear stimulation.5

Patients with multiple sclerosis (MS) frequently report symptoms related to vestibular disorders in the course of their disease.6

At present, the fundamental tests assessing vestibulospinal reflexes are posturography and vestibular evoked myogenic potentials (VEMPs). However posturography cannot be performed if subjects are not able to stand still for a few minutes and this is not always possible for MS patients. VEMPs, on the other hand, do not require any specific motor skill by the subjects and can be recorded in all patients able to sit7 .Vestibular evoked myogenic potentials are thus helpful in either detection of the subclinical lesion affecting the suggested pathway or confirming the patients symptoms.7

The study aims at investigating the role of (VEMPs) in detection of occult vestibular pathway lesions in patients suffering from multiple sclerosis (MS) as well as comparison between VEMPs findings with clinical data, other neurophysiologic tests as well as with radiological investigations.

 

SUBJECTS AND METHODS

 

A Case Control Study was carried out on 25 patients admitted to Kasr El-Aini hospital fulfilling clinical criteria of multiple sclerosis according to MS diagnostic criteria of McDonald et al.8   (their age range was 19- 49 years), as well as twenty five age and sex matched healthy subjects as a control group (their age range was 19-60 years). Patients having clinically definite MS (either relapsing remitting or progressive) were included regardless of the presence of symptoms suggestive of vestibular system lesions (vertigo, diplopia, etc).  Excluded from the study were patients aged less than 18 years, patients suffering from probable or possible MS as well as all patients showing evidence of other neurological disease that may cause symptoms similar to MS e.g. Brainstem neoplasms, vasculitis, etc.

All patients were subjected to complete history taking and full neurological examination, routine laboratory work up 9 liver functions, renal functions, ESR, blood picture, blood sugar and lipid profile. Patients were given scores according to the expanded disability status scale (EDSS)9.

MRI was performed Each brain examination included acquisition of transverse T1 -weighted spin echo images and T2 -weighted spin echo images, gadolinium injection was used when needed. 

The neurophysiological tests were carried out on a Schwarzer Myos 4 apparatus. VEMPs were recorded while the patients were seated upright comfortably. They were instructed to turn their heads to one side (away from the stimulated ear) to activate unilaterally the sternocleido-mastoid muscle. Patients were instructed to push steadily their chin downwards against resistance. A two-channel recording montage of the vestibular evoked myogenic potential (VEMP) was used. Active electrodes were placed at the midpoint of the SCM muscle on each side of the neck, midway between the mastoid process and the sternoclavicular junction (SCJ), the reference electrodes were placed at the ipsilateral sternoclavicular junctions (SCJ), and the ground electrode was placed on the forehead. The montage was as follows: Ch1 Ipsilateral SCM-SCJ, Ch2 Contralateral SCM-SCJ. Rarefaction clicks were presented to each ear separately using head phones operating at intensity of 100 dB NHL. Two or three trials were obtained from each side to ensure reproducibility. The stimulus duration was 100-200 msec,  gain was set at 2 mV/div,  sweep was set at  5 msec/div,  frequency was 5.1 stim/sec, and the band pass was 20-1500 Hz. The resulting response was averaged 125 times. The evaluated parameters were (1) the presence or absence of the response, l(2) latency of the first positive and negative peaks (P13, N23) (30 peak to baseline amplitudes of the of P13 and N23 (4) right –left latency and amplitude difference,

 Visual evoked potentials were carried out mono-ocularly using 32checks. One channel montage was used (Oz-Fpz). Auditory brainstem evoked potentials were carried out using a two channel montage (Ai-Cz) and (Ac-Cz). Acoustic stimuli consisted of 65 dB rarefaction clicks delivered monoaurally above the subject’s threshold white noise was delivered to the contralateral ear.

Somatosensory evoked potentials were carried out to the median nerve. A Three channel montage was used, (Fz-Erb), (Fz-CII), and (Fz-Cc). The active electrodes are Cc, (2 cm behind the 10-20 system C3 and C4 locations), CII, which is placed below the hairline of the patient at the midline, and Erb’s point, which lies above the midpoint of the clavicle. The reference electrode was placed at Fz.

Statistical tools included Two Tailed T test, McNemar’s Test applied to determine the correlation between different tests and VEMPs10, Linear regression test was carried out to determine the correlation between VEMPs test results and EDSS values10.

 

RESULTS

 

25 patients suffering from MS were included in this study, 12 males (48%) and 13 females (52%), their age ranged from 19 to 49 years, mean age 31.3±9.7 years. 14 patients (56%) had relapsing remitting MS and 11 patients (44%) suffered from progressive MS. 14 patients (56%) had brainstem symptoms (S) and 11 patients (44%) presented no symptoms of brain stem affection (N).  The EDSS scores ranged from 2 to 9.

VEMPs were recorded from 25 healthy volunteers (11 females (44%) and 14 males (56%). Their age ranged from 19 to 60 years with mean age 32.4±11 years. P13-N23 waves were recorded in all subjects (100%) while N34-P44 were recorded in 19 subjects (76%), bilaterally in 12 subjects (48%) and unilaterally in 7 subjects (28%). P13 and N23 latencies and amplitudes for the control group are shown in table (1). No statistically significant inter-side difference was found in VEMP’S latencies or amplitudes P>0.05

Table (2) shows the comparison of VEMPs results between males and females among the control group. No statistically significant difference was found in any parameter as well.

 

VEMPs results in the patient group :

VEMPs were found to be abnormal in 14 patients (56%). 5 patients (20%) showed no symptoms of brainstem affection (N) and 9 patients (36%) were symptomatizing (S).They showed the following types of abnormalities:

·       6 patients (24%) had unilateral delay in the latency of the P13 and /or N23.

·       4 patients (16%) had bilateral delay in the latency of the P13 and /or N23.

·       2 patients (8%) had severe unilateral amplitude reduction (over 85% reductions).

·       2 patients (8%) had unilateral absent responses.

 

Case-Control Comparison

a)      Symptomatizing (S) and Non-Symptomatizing (N) vs. Control group: 

P13 and N23 latencies showed a statistically significant difference in Groups N and S compared to the control group however it was obvious that unilateral abnormalities were detected in Group N and bilateral abnormalities were encountered in group S. no statistically significant difference was encountered between group S and M (Table 3).

b)      Normal and Abnormal VEMPs vs. Control group: 

Taking a cutoff for normal VEMPs latencies as mean + 2SD of the control group, patients group was classified into group with normal VEMPs (group I) and  group with abnormal VEMPs (group II).   Figure (4) shows the mean values of both groups and the control group while table (4) shows their means, standard deviations, and p-values, calculated using the two-tailed distribution T-test.

Group I showed no statistically significant difference compared to the control group. However, on comparing control and group II there was statistically significant difference regarding: Rt P13 L (p<0.02), Lt P13L (p<0.0003), Rt N23 L (p<0.005), and Lt N23 L (p<0.0002) and the P13 and N23 inter-side latency differences (p<0.02, p<0.0002 respectively). Comparing group I and group II revealed a statistically significant difference regarding: Lt P13L (p<0.009), Rt N23 L (p<0.04), and Lt N23 L (p<0.009) and the N23 inter-side latency difference (p<0.03).

The absolute values of the amplitude of the P13 and N23 waves were found to be not statistically significant in any comparison.

c)      Pathological side and normal side in cases with unilateral abnormal VEMPs vs control group:

Considering abnormal VEMPs results to be those exceeding the mean + 2SD of the control group, normal and abnormal sides were compared.

There was a statistically significant difference regarding N23 latencies (p<0.05) on comparing the two sides. Regarding P13 latency there was an obvious difference but did not reach statistical significance (p= 0.074). However, on comparing control and normal side groups there was a non significant difference. Comparing control group and abnormal side group revealed that the most statistically significant difference was found between: N23 L (p<0.0002) followed by P13 L (p<0.002).

The absolute values of the amplitude of the P13 and N23 waves were found to be not statistically significant in any comparison (Table 5).

d)      Other neurophysiological tests and MRI (Fig. 5):

VEPs were found to be abnormal in 14 patients (56%), 7 patients (28%) showed no symptoms of brain stem affection (N) and 7 patients (28%) were symptomatizing from the brainstem (S). BAEPs were found to be abnormal in 11 patients (44%), 2 patients (8%) showed no symptoms of brain stem affection (N) and 9 patients (36%) had symptom(S). SSEPs were found to be abnormal in 7 patients (28%), 2 patients (8%) showed no symptoms of brain stem affection (N) and 5 patients (20%) had brainstem symptoms (S).

MRI results were abnormal in 20 patients (80%), 9 patients (36%) showed no symptoms of brainstem affection (N) while 11 patients (44%) had   symptoms (S).

There were brain stem plaques in only 7 (28%) patients who all were clinically symptomatizing (S). No brain stem plaques were found in any patient showing no symptoms of brain stem affection.

e)             Correlation with brainstem symptoms:

No correlation could be found between having brainstem symptoms and abnormalities of VEMPs.  Out of 14 patients with brainstem symptoms, VEMPs were abnormal in 9 (64%) and out of 11 non-symptomatizing patients, VEMPs were abnormal in 5 (45%) patients. c2 =0.1, P-value=0.75.

 

Correlation with EDSS (Fig. 6):

No significant correlation was found between EDSS score values and the VEMPs results (r=0.00004, P-value=0. 9).

 

Correlation with BAEPs results:

VEMPs and BAEPs were found to be not correlated. Combined BAEPs and VEMPs abnormalities were found in 7 patients (28%), 4 patients (16%) had abnormal BAEPs and normal VEMPs, 7 patients (28%) had normal BAEPs and abnormal VEMPs results, 7 patients out of the 25 patients (28%) had normal BAEPs and VEMPs   (c2 0.36, P value=0.54)

 

Correlation with MRI results:

No correlation could be found between MRI and VEMP, (c2 =1.5625, P value=0.213) abnormalities. 5 patients (20%), {3(12%) having brainstem symptoms (S) and 2 (8%) with no symptoms (N),} had normal or non conclusive MRI results and abnormal VEMPs results. 11 patients (44%) had normal VEMPs results and their MRI showed multiple plaques, only 4 patients (16%) out of them had brain stem plaques. 9 patients (36%) had abnormal VEMPs results and abnormal MRI as well.

Out of 18 patients with no brain stem plaques in the MRI, 11 had abnormal VEMPs.  Out of 7 patients with brain stem plaques, only 3 had abnormal VEMPs (Table 6).

 

 

Sensitivity and Specificity of different tests:

Sensitivity of the VEMPs test in detecting symptomatizing patients was 65% while the specificity was 54%. In detecting non symptomatizing patients the sensitivity was 45% and the specificity was 35%. Sensitivity of the BAEPs test in detecting symptomatizing patients was 64% while the specificity was 72%. In detecting non symptomatizing patients the sensitivity was 18% and the specificity was 35%. Sensitivity of the MRI in detecting symptomatizing patients was 78% while the specificity was 18%. In detecting non symptomatizing patients the sensitivity was 82% and the specificity was 21%. Sensitivity of the MRI regarding brain stem plaques in detecting symptomatizing patients was 50% while the specificity was 100%. In detecting non symptomatizing patients the sensitivity was 0% and the specificity was 50%.


 

Table 1. Mean, standard deviation and range of P13 and N23 latencies and amplitudes in control group.

 

Parameter

Mean±SD

Range

Rt P13 L (msec)

10.76±1.23

8.75 - 13.52

Lt P13 L (msec)

10.77±1.53

8.67 - 14.39

Inter side difference

1.17±0.82

0.08 - 3.13

Rt P13 A (mV)

8.30±5.99

0.94 - 24.14

Lt P13 A (mV)

8.64±6.07

1.16 - 19.18

Inter side difference

2.71±2.93

0.02 - 8.51

Rt N23 L (msec)

16.66±1.99

13.28 - 21.95

Lt N23 L (msec)

16.19±1.81

12.58 - 20.94

Inter side difference

1.35±0.88

0 - 3.05

Rt N23 A (mV)

15.59±14.03

2.22 - 57.14

Lt N23 A (mV)

13.86±10.00

0.53 - 36.1

Inter side difference

7.13±6.77

0.2 - 25.34

Rt = Right, Lt = Left, L= Latency, *amplitude difference never exceeded 70 %. A= Amplitude

 

Table 2. Male-Female comparison in control group.

 

Parameter

Male

Mean±SD

Female

Mean±SD

P-value

Rt P13 L (msec)

10.99±1.22

10.47±1.23

0.30

Lt P13 L (msec)

11.06±1.59

10.39±1.43

0.28

Inter side difference

1.18±0.62

1.16±1.05

0.95

Rt N23 L (msec)

17.15±2.08

16.04±1.77

0.20

Lt N23 L (msec)

16.36±1.95

15.98±1.67

0.61

Inter side difference

1.29±0.78

1.43±1.02

0.69

Rt P13 A (mV)

7.78±5.49

8.96±6.80

0.64

Lt P13 A (mV)

7.96±5.59

9.5±6.79

0.54

Inter side difference

2.46±2.89

3.03±3.09

0.64

Rt N23 A (mV)

14.34±12.49

17.18±16.26

0.63

Lt N23 A (mV)

12.92±9.81

15.05±10.59

0.60

Inter side difference

5.83±6.49

8.78±7.05

0.29

Rt = Right, Lt = Left, L= Latency, A= Amplitude, Significant at  p<0.05

Fig. (1): Example of an abnormal VEMP, (RT P13L=13.28, RT N23L=20.47, LT P13L=17.50, LT N23L=26.95) showing increased latency of both P13 and N23 on the left side..

 

 

Fig. (2): Example of an abnormal VEMP showing absent response on the left side.

 

Fig. (3): Example of an abnormal VEMP, (RT P13L=20.39, RT N23L =23.91, LT P13L=20.08, LT N23L=27.58), showing bilateral increase in P23 and N23 latencies.

Table 3. Comparison of VEMPs results in non-symptomatizing (group N) and symptomatizing (group S) vs. control group.

 

Parameter

Symptom

Mean±SD

P-value w.r.t.

Control group

P-value

(N vs. S)

Rt P13 L (msec)

Group N

10.93±1.52

0.761

0.125

Group S

13.28±4.421

0.012*

Control

10.76±1.23

 

Lt P13 L (msec)

Group N

12.17± 2.21

0.046*

0.448

Group S

13.28±4.08

0.011*

Control

10.77±1.53

 

Inter-side difference

Group N

1.32±1.18

0.44

0.228

Group S

3.07±4.31

0.201

Control

1.17±0.82

 

Rt N23 L (msec)

Group N

16.74±2.27

0.938

0.060

Group S

20.26±5.22

0.005*

Control

16.66±1.99

 

Lt N23 L (msec)

Group N

18.55±3.51

0.016*

0.67

Group S

19.34±4.89

0.008**

Control

16.19±1.81

 

Inter-side difference

Group N

2.49±2.70

0.978

0.164

Group S

4.61±3.97

0.034*

Control

1.35±0.88

 

Rt. = Right, Lt = Left, L= Latency * significant p<0.05 , ** highly significant at  p<0.01 *

 

Table 4. Comparison of VEMPs results in group I (Normal VEMPs) and group II (abnormal VEMPs) vs. control group.

 

Parameter

VEMPs

Mean±SD

P-value w.r.t

Control group

P-value

(I vs. II)

Rt P13 L (msec)

Group I

10.95±1.16

0.751

0.096

Group II

13.46±4.64

0.014

Control

10.76±1.23

 

Lt P13 L (msec)

Group I

10.96±1.12

0.813

0.0087

Group II

14.48±3.89

0.0003

Control

10.77±1.53

 

Inter-side difference

Group I

0.94±0.67

0.348

0.061

Group II

3.57±4.36

0.016

Control

1.17±0.82

 

Rt N23 L (msec)

Group I

16.73±1.55

0.996

0.036

Group II

20.56±5.51

0.005

Control

16.66±1.99

 

Lt N23 L (msec)

Group I

16.67±1.41

0.549

0.009

Group II

21.12±4.94

0.00017

Control

16.19±1.81

 

Inter-side difference

Group I

1.98±1.19

0.103

0.0246

Group II

5.25±4.32

0.00019

Control

1.35±0.88

 

Rt = Right, Lt = Left, L= Latency, Significant at p<0.05

 

Fig. (4): Comparison between the mean values of the control and groups I and II.

 

Table 5. Comparison of abnormal VEMPs results in: Normal side and Abnormal side vs. control group.

 

Parameter

VEMPs

Mean±SD

P-value w.r.t

Control group

P-value

(Normal vs. Abnormal)

P13 L (msec)

Normal

10.78±1.62

0.972

0.074

Abnormal

14.65±5.42

0.0016**

P13 A (mV)

Normal

7.69±6.07

0.745

0.641

Abnormal

9.86±11.34

0.645

N23 L (msec)

Normal

16.62±2.72

0.812

0.039*

Abnormal

21.87±5.93

0.0002**

N23 A (mV)

Normal

13.65±8.50

0.806

0.385

Abnormal

9.95±8.024

0.273

Rt = Right, Lt = Left, L= Latency *significant at p < 0.05 highly significant p<0.01

 

 

Fig. (5): Comparison between different tests.

 

Fig. (6): Comparison between VEMPs results and EDSS. Normal VEMPs corresponded to 1

while abnormal VEMPs corresponded to 2 and EDSS varies between 2 to 9.

 

Table 6. Correlation between MRI and VEMP.

 

 

VEMPs

 

Normal

Abnormal

Total

MRI

 

 

 

No-brain stem plaques

7

11

18

Brain stem plaques

4

3

7

Total

11

14

25

c2 =2.4,  P-value=0.12

 

 


DISCUSSION

 

Several studies aimed at investigating the role of VEMPs in clinically definite MS patients. Abnormalities of VEMP were reported in a range of 31%-70% of the patients7,11,12,13. In this study VEMPs abnormalities were detected in 56% of clinically definite Ms  patients.  This wide range of results may be due to the variability in the frequency of brainstem pathology in the selected samples, one sample may have included a lot of patients with clinically or radiologically evident brainstem affection7, while another sample may not13 for (Alpini et al, (2004), in which 60% of patients had brainstem affection while for  Bandini et al.13, in which 45% of patients had brainstem lesions)

Various types of abnormalities were detected in previous studies. Unilateral or bilateral latency delay was found to be the commonest abnormality, on the other hand amplitude reduction was less commonly found. In our study 40% of patients had prolonged latencies whether unilateral or bilateral while 8% had severe unilateral amplitude reduction and in another 8% there was unilateral absent response, which was close to the results of Bandini et al.13, who found 39% of patients had prolonged latencies whether unilateral or bilateral, and 14% had amplitude abnormalities and different from Versino et al.11, who found more amplitude (19.2%) abnormalities than the others.  Being a demyelinating disease as well as the dependence on the EMG level of SCM muscle contraction,   it is obvious that the latency of the P13-N23 wave is a more important parameter in assessing VEMPs in MS patients than amplitude. In patients where VEMPs were absent, we assume that it is due to severe damage of the myelin sheaths “possibly’ but not necessarily with axonal damage.

Bandini et al.13 found significant correlation between P13 latency and EDSS score values (r=0.29 p<0.01) and a weaker but also significant correlation between N23 latency and EDSS score values (r=0.3, p<0.05) and they found no correlation between amplitudes and the EDSS and they suggested that VEMPs by describing the impact of demyelination or secondary axonal loss on the function of the vestibule-spinal pathway, can probably provide useful information about the severity of the disease. Such a relation could not be verified in this study, no significant correlation was found between VEMPs results and EDSS score (r=0.0004, p=0.9) which may be explained by the possible early involvement of the vestibular pathways in MS patients without any accompanying functional disability affecting other systems.

Correlating VEMPs results with clinical symptoms or signs of brainstem affection was non significant, (p= 0.75).  VEMPs were abnormal in 64% of symptomatizing patients and 45 % of non-symptomatizing patients, compared to 69% of symptomatizing patients  in the study by Bandini et al.13  and 42.5% of patients in the study by Alpini et al.7. The most significant parameters were P13 latency, N23 latency and the interside latency difference

VEMP’s and VEPs were found to be equally sensitive in detection of brain lesions in MS (56 % sensitivity). However, Bandini et al.13 found that VEPs were superior to VEMPs (83% versus 53% sensitivity respectively). Versino et al.11 and Itoh et al.14 compared between VEMPs and BAEPs in patients with clinically definite MS. They found that VEMPs were abnormal in 31% while BAEPs were abnormal in 38%. In our study, VEMPs were abnormal in 56% while BAEPs were abnormal in 44%, also we found that VEMPs and BAEPs have nearly equal sensitivity for detecting BS lesion in symptomatizing group while VEMPs have higher sensitivity than BAEPs in non-symptomatizing group (65% and 45% respectively in VEMPs and 64% and 18% respectively in BAEPs). Versino et al.11 found that BAEPs abnormalities correlated with the clinical symptoms, especially dizziness, while VEMPs did not show such a relation, also no relation could be verified between BAEPs and VEMPs results, probably since BAEPs investigate brain stem rostral to the vestibular nuclei while VEMPs investigate BS more caudally. On these grounds, VEMPs should be considered a complementary neurophysiological tool for possible brainstem dysfunction evaluation.

Comparison between MRI results and VEMPs abnormalities was carried in several studies. There was a non significant correlation between MRI results and VEMPs abnormalities (p=0.21) with respect to MRI plaques in general and with respect to brainstem plaques specifically (p=0.12). Versino et al.11 found also no correlation between MRI results and VEMPs abnormalities, which agreed with Bandini et al.13, as well (p=0.82). VEMPs are able to detect brainstem dysfunction in MS patients who have a normal MRI. This finding is consistent with most of the previous studies11,13 and supports the view that the two techniques provide independent and complementary information, which is not directly comparable: the presence of a hyperintense signal along a nervous pathway does not necessarily imply a significant change in nerve conduction; conversely, small demyelinating areas can cause a slowing of conduction without being revealed by MRI. Hence we may conclude that VEMPs is a simple, quick and easy tool, which needs minimal cooperation by the patient and does not cause much discomfort as other tests used to assess otolith function and vestibulospinal reflex, such as caloric test, electronystagmography and rotating chair tests. VEMPs can also help in diagnosis of MS in early stages of the disease.

 

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14.    Itoh A., Kim Y., Yoshioka K., Kanaya M., Enomoto H., Hiraiwa F., Mizuno M. (2001): Clinical study of vestibular-evoked myogenic potentials and auditory brainstem responses in patients with brainstem lesions. Acta Otolaryngologica; Suppl. 545: 116-225.


 الملخـص العربى

 

الجهد المثار بالعصب الدهليزى و دوره فى تشخيص حالات التصلب المنتثر فى الجهاز العصبى

 

زاد الاهتمام حديثا باختبار الجهد المثار لعصب الاتزان و بدأت أهميته تزداد لدراسة بعض الأمراض العصبية و على الرغم من ذلك لم يتم تقنينه على الوجه الأكمل فى المستشفيات المصرية.

تم إجراء هذا الاختبار على ٢٥ شخصا سليما ليكونوا المجموعة الضابطة. كما تم إجراء هذا الاختبار على ٢٥ مريضا (١٢ ذكر- ١٣ أنثى) بمرض التصلب المنتثر بالجهاز العصبي وقد قسم المرضى إلي مجموعتين: الأولى تحتوي على ١٤ مريضا يعانون من أعراض المرض في جذع المخ و الثانية تحتوي على ١١ مريضا لا يعانون من أي أعراض تدل على تأثر جذع المخ. و لقد خضع كل المرضى للفحص الإكلينيكي الدقيق مع تقييم اى دى اس اس وللاختبارات الآتية: الجهد المثار البصري، الجهد المثار السمعي، الجهد المثار الحسي و الرنين المغناطيسي.

من خلال دراسة مقدار جهد و كمون الموجه لكل من ب١٣، ن٢٣ في المجموعة الضابطة و كذلك في مرضى التصلب المنتثر بالجهاز العصبي وجد أن مقدار جهد كلا الموجتين شديد التغير بين الأفراد و انه يتأثر بعوامل عديدة و لهذا فانه لا يمكن الاعتماد عليه في تشخيص الأمراض. أما بالنسبة الي كمون الموجه لكل من ب١٣، ن٢٣ فلقد وجد أن زمن كلا الموجتين يتغير بشكل طفيف و له مدى محدد و لهذا فانه يعتبر العامل الأساسي في تشخيص الأمراض.

ولقد جاءت نتائج الاختبارات كالتالى:

-    الجهد المثار لعصب الاتزان كان ايجابيا فى ٥٦% من المرضى. الجهد المثار البصري كان ايجابيا فى ٥٦% من المرضى. الجهد المثار السمعي كان ايجابيا فى ٤٤% من المرضى. الجهد المثار الحسي كان ايجابيا فى ٢٨% من المرضى. أما الرنين المغناطيسي فلقد كان ايجابيا فى ٨۰% من المرضى.

-    كما لم يوجد أي ارتباط بين نتائج هذا الاختبار ونتائج الاختبارات الأخرى أو الحالة الاكلينيكيه للمريض.

-    ومما قد سبق ذكره فإننا نجد أن الجهد المثار لعصب للاتزان هو اختبار بسيط، امن وسريع و نوصى بأن يعتد به كاختبار من الاختبارات المكملة لتقييم إصابات جذع المخ.

 



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