INTRODUCTION

Low tension Glaucoma (LTG) is characterized by glaucomatous optic disc cupping and visual field changes in eyes that have normal intraocular pressure. The clinical features of LTG resemble those of primary open angle glaucoma except for absence of increased intraocular pressure¹. Some authors reported significant relationship between migraine and LTG with high prevalence of migraine in LTG patients^2,3.

Migraine is characterized by recurrent, periodic headaches which are commonly unilateral and are usually associated with visual prodromata, nausea, vomiting, and other focal neurological symptoms including, numbness, and tingling of lips, face, and hands, slight confusion of thinking, weakness of an arm or leg, mild aphasia, dizziness and uncertainty of gait or drowsiness^1,4.

Migraine may be classical with three migrainous features, probable with two migrainous features or possible with only one migrainous feature¹. The visual symptoms are probably related to ischemia in occipital cortex^1,5. Ischemia either chronic or intermittent is a possible cause of optic nerve damage in LTG due to migraine related ocular ischemia^1,2.

The aim of this study was to investigate migraine prevalence and the factors that may influence its occurrence in patients with low tension glaucoma.

SUBJECTS AND METHODS

This study was conducted in Mansoura Ophthalmology Centre. Enrolled in the study were 40 control and 39 patients already diagnosed as having LTG (18 males and 21 females) with the range of age between 18 and 35 years. Excluded from the study all eye diseases other than glaucoma, diabetes mellitus, myopia >-8 D, visual acuity below 20/30, opaque optic media and closed anterior chamber angle. LTG was diagnosed by fundus examination and cup-disc ratio (ranging from 0.5 to 0.8), intraocular pressure using applanation tonometer at different time, and perimetry. Brain Magnetic Resonance Imaging (MRI) and Electroencephalography (EEG) were done for all the migraineurs.

All control and patient groups were subjected to fill a standardized headache questionnaire:

1)        Do you have headaches?

2)        If you have headaches

a)        Are they ever on one side of the head or around one eye?

b)        Are they ever associated with nausea and vomiting?

c)        Are they ever preceded by bright light, zigzag lines or partial or complete loss of vision?

For each question the choice answers include (often, occasionally, or no), however for data analysis, we considered both often and occasionally response to be (yes) answers. Patient was considered migraineur if one of the 3 features a, b, or c was answered with (yes).

Statistical Analysis:

               The data were coded and entered into a computer using Statistical Package for Social Sciences (SPSS) version 16.0 (Chicago, IL, USA). Descriptive statistics included number and percent for categorical variables, whereas mean and standard deviation (SD) for normally distributed data were used. Comparison between categorical variables was done by Chi-Square whereas normally distributed continuous variables were compared using t-test. All statistical tests were two-sided, with a p-value of <0.05 taken to indicate statistical significance.

RESULTS

The 39 patients with LTG, included in the study, were 18 (46.2%) males and 21 (53.8%) females (Table 1) with their age ranging from 18-35 years (Table 3). The control and patient groups were matched regarding the sex distribution p=0.1 (Table 2). The mean age in both groups showed no statistically significant difference {28±7 and 27±8 respectively (p=0.3)}.

Patients with LTG had higher prevalence of migraine than the control group [12 out of 39 (30.8%) vs. 4 out of 40 (10%)] (p=0.03). In the migraineurs, the mean age did not differ significantly between patient and control groups [23±5 vs. 22±6 (p=0.2)].

Of the 12 LTG migraineurs, migraine was common in the age group from 20-25 years (15.4%), followed by the group from 25-30 years (10.3%), and 18-20 years (5.1%). As 6 out of 14 (42.9%), 4 out of 12 (33.3%), and 2 out of 8 (25%) patients in the same age groups respectively, suffered migraine at least one time in their lives, whereas no patient with age group ranging from 30-35 experienced migraine (Table 3).

Studying the effect of gender on migraine prevalence in patients with LTG revealed that 20.5% of patients experiencing migraine were females, while only 10.3% were males. Migraine was common in LTG female group patients than male group (38.1% vs. 22.2%) (Table 1).

Of the 12 LTG migraineurs, only 2 (16.7%) had abnormal brain MRI finding in the form of multiple white matter infarcts (Figure 1), and 4 patients (33.3%) had abnormal EEG discharge in the form of sharp wave activity of epileptogenic nature (Figure 2), whereas of the 4 control migraineurs no one had any abnormality in their brain MRI or EEGs.

Table 1. Prevalence of migraine among male and female LTG patients.

Table 2. Sex distribution among control and patient groups.

Table 3. Prevalence of migraine in different LTG patient’s age groups.

Figure 1. MRI of a patient with migraine.

Figure 2. EEG of a patient with migraine.

DISCUSSION

The epidemiology of migraine is difficult to study in part because of lack definitive diagnostic tests. The diagnosis of migraine depends solely on patient’s history and not all investigators agreed on what or how many symptoms are necessary for diagnosis. However, most authorities agreed that the cardinal features of migraine in addition to episodic headaches are unilaterality, nausea or vomiting and visual prodromata and also agreed that not all of these symptoms need to be present in every patient².

In this study migraine was more common in patients with LTG compared to control subjects. Migraine was more prevalent in middle age group, 20 to 30 years of age, than other age groups and more frequent in women than in men that was in agreement with the study conducted by Phelps². On the other hand, large scale non-questionnaire based studies did not show a significant association of open angle glaucoma and migraine^6,7,8 and this could be explained by the fact that diagnosis of migraine depend mainly on history and there is debate on what or how many symptoms are necessary for diagnosis. Migraine was associated with decreased cerebral blood flow and attacks of migraine headache were probably the cause of ischemic infarction of the brain, retinal nerve fiber layer and the optic nerve^2,6. It is well known that migraine is an independent risk factor for subclinical brain lesions^9,10. Other studies^11,12 as the present study supported the hypothesis that cerebral small-vessel ischemia is more common in patients with low-tension glaucoma and migraineurs. Interpretation of EEG can be important for the differential diagnosis of some disorders with headache as a presenting symptom. Interictal EEG (between headache attacks) is not significant in routine evaluation of these patients, but can be useful in patients with unusual symptoms suggesting epilepsy or migraine. It is indicated in patients with an abrupt onset of headache, in patients with migraine followed by neurological signs, in basilar migraine, migraine with extended duration of aura and in cases where epilepsy is suspected¹³. Some studies¹⁴ conclude that EEG revealed in patients with migraine significantly more frequent functional disturbances than in controls.

Conclusion

Migraine is more common in low tension glaucoma patients than controls. It is also more prevalent in low tension glaucoma female gender and those with age ranging from 20 to 25.

[Disclosure: Authors report no conflict of interest]

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