Clinical and Electrooculographical Finding in Patient with Essential Tremor

Research Article

Austin J Clin Neurol 2021; 8(2): 1150.

Clinical and Electrooculographical Finding in Patient with Essential Tremor

Cenikli U¹, Bir LS², Ardıç FN³ and Degirmenci E²*

¹Department of Neurology, Mugla Sıtkı Kocman University, Turkey

²Department of Otorhinolaryngology, Pamukkale University, Turkey

³Department of Neurology, Pamukkale University, Turkey

*Corresponding author: Eylem Degirmenci, Department of Neurology, Pamukkale University, Medical Faculty, Denizli, Turkey

Received: May 03, 2021; Accepted: May 26, 2021; Published: June 02, 2021


Background: Essential Tremor (ET) is the most common movement disorder, yet the location of the primary disease substrate continues to be a matter of debate. In this study, we aimed to evaluate ocular movement abnormalities with Electrooculography (EOG) in patients with ET to find a possible location of disease pathology.

Methods: Electrooculographic evaluation including saccade, tracking, optokinetic, gaze and positional tests were performed to 36 ET patients and 36 healthy subjects. Patient age on the onset of the tremor, duration of the disease, characteristics and the location of the tremor were also investigated. Fahn- Tolosa-Marin tremor rating scale was used to determine the tremor severity. Differences of abnormal test results between patient and control groups were analysed with Pearson’s and Fisher’s Exact and correlation analyses of EOG tests and clinical data were performed with Spearman’s and Pearson’s correlation tests.

Results: There was not any significant difference in EOG tests between the ET patients and controls. Significant correlation was only found between EOG abnormality and patient age in correlation analyses.

Conclusions: Our results showed that ET patients may not have specific EOG test abnormalities. These tests would be used especially in the different diagnosis of other movement disorders.

Keywords: Essential tremor; Electrooculography; Eye movements; Movement disorders


Essential Tremor (ET) is the most common movement disorder. It is characterized by gradually increasing postural and kinetic tremor without endogenous and exogenous triggers and other neurological symptoms [1]. The pathophysiology of ET is not completely known [2]. In many studies, supporting data have been obtained that essential tremor is caused by abnormalities in the Guillain-Mollaret triangle (rubral nucleus, olivary nucleus and cerebellum). It has been suggested that tremor is caused by intrinsic oscillations that originate from the inferior olivea, spreading with the olivocerebellar network [3]. Various data obtained from clinical, neuroimaging and animal studies show that the cerebellum is involved in the formation and spread of ET [4].

Electrooculography (EOG) is the most technically practical method for recording eye movements [5]. Cornearetinal potentials occur when the cornea carries a positive (+) charge, and the retina carries a negative (-) electrical charge during eye movements [6]. In EOG, it is possible to determine the affected area in the central nervous system after examining the gaze test, saccade test, trekking test, optokinetic test and positional test and collectively examining these all tests [7].

In this study, it was aimed to investigate if there are eye movement abnormalities in patients with ET by using EOG, which is used routinely, and it was aimed to examine possible EOG pathologies that may reveal dysfunction in the cerebellum, brainstem, thalamus, and pathways.



Patients who met the definitive diagnosis of ET according to the Consensus statement of Movement Disorder Society on tremor were included to the study. Detailed disease history such as the age of onset of tremor, its duration, type, and the place of it were questioned. Patients who have abnormal values in their hemograms, biochemistry values, and thyroid function tests were excluded from the study. Fahn Tolosa, Marin clinical tremor rating scale was applied to all patients with ET and values were recorded. The findings were recorded by performing a neurological examination in all patients. As a result, 36 patients with ET who did not have cerebellar pathology examination findings such as vestibular complaint, ataxia, dysmetria and intentional tremor and who did not use any medication that could affect EOG tests and 36 patients with ET who did not use any medication that might affect the EOG tests and 36 healthy control group individuals similar in terms of age and gender were included in the study.

EOG Procedure

After the test records were passed through the 30 Hz Low Pass Filter, they were stored in the computer connected to the system (Chartr ENG, ICS medical, USA) and evaluated in terms of normal distribution and the angular velocity of the slow phase Slow-Phase Velocity (SPV). The wave recorded in the saccadic test was evaluated in terms of validity, latency, and amplitude as well as its morphology. Wave morphology and gain in the trekking test were examined. The numerical values in the saccadic and trekking tests were determined according to the normal group values registered in the computer program.

In the optokinetic test, 40 degrees/second stimulation was used, and it was investigated if there was any asymmetry. If the Slow Phase Velocity (SPV) difference between the two sides is more than 30 degrees/second or the difference is more than 50% of the greater value, it is considered asymmetrical.


After all these procedures, the data obtained from EOG and the clinical information obtained from the patients were uploaded to the Statistical Package for Social Sciences 16 (SPSS 16.0) program for statistical analysis. The Pearson correlation test and Fisher’s Exact Test were used to determine whether there was a difference in the number of patients with disorders in EOG tests and in the saccadic test, trekking test, optokinetic test, positional test and gaze test among the patient and control groups. Spearman Correlation test and Pearson Correlation test were used to investigate whether there was a relationship between EOG tests and the patient’s age, disease duration, and the total value obtained on the Fahn Tolosa, Marin clinical tremor rating scale.


A total of 72 participants, 36 patients with a diagnosis of ET and 36 healthy people, were included in this study. There was no statistically significant difference between the mean age of the patient group 441 ± 19.2 (min=18, max=78) and the mean age of the control group 45.3 ± 18.9 (min=19, max=79) (t=-0.272, p=0.786, Student’s t test). Of the patient group, 24 (66.7%) were male and 12 (33.3%) were female. Of the control group, 22 (61.1%) were male and 14 (38.9%) were female, and there was no significant difference between the two groups (p=0.806).

In patients, the mean age of onset of tremor was 31.6 ± 16.6 (min=13, max=72) years, and the mean duration of the disease was 12.1 ± 7.8 (min=5, max=40) years. When the form of tremor was examined, it was found that only postural tremor in 2 cases (5.6%), postural and kinetic tremor in 27 cases (75%), postural and kinetic tremor in 7 cases (19.4%) were found to be accompanied by resting tremor. It was found that 29 cases (80.6%) had a symmetrical tremor, and 7 cases (19.4%) had a slightly asymmetrical tremor. When the tremor region was examined, only upper extremity tremor in 27 cases (75%), upper and lower extremity tremor in 4 cases (11.1%), upper extremity and head tremor in 2 cases (5.6%), 2 cases (5.6%) upper extremity and voice tremor, 1 case (2.8%) had upper extremity, head and voice tremor were determined. The age of onset of tremor and the duration of the disease are shown in Table 1. The saccadic test was found to be pathological in 8 patients (22.2%) with ET, and an abnormality was found in the validity of the saccadic test in 2 cases (5.6%) and since these cases did not have wave morphology, saccade velocity and latency values, they were excluded from statistical studies and these tests were examined on 34 patients with ET. Disorder was found in 5 control group cases (13.9%), and an abnormality was found in the validity of the saccadic test in 1 case (2.8%) and these cases were excluded from statistical studies because they did not have wave morphology, saccad velocity and latency values, and these tests were examined on 35 participants.