Retinal Migraine Headache

Etiology

Based on theories and pathophysiology of retinal migraine, precipitating factors for a retinal migraine are the same for migraine, with and without aura. Factors include, but are not limited to, emotional stress, high blood pressure, and hormonal contraceptive pills, as well as exercise, being at a higher altitude, dehydration, smoking, low blood sugar, and hyperthermia. Comorbidity with lupus, atherosclerosis, and sickle cell disease increases the risk of having a retinal migraine [1][2].

Epidemiology

A retinal migraine is a rare disorder, but the prevalence is not known. Data specific to retinal migraines do not exist, but migraines, in general, have a prevalence of 18.2% in females and 6.5% in male patients, with a higher prevalence in whites followed by blacks followed by Asians.  Retinal migraine can start as early as 7 years of age, but most cases start in the second decade and peak in the fourth decade of life. Based on a study by Pradhan et al., it was found that 50% of retinal migraine patients said the vision loss was complete in one eye, up to 20% said it was just blurring, 12% reported an incomplete loss, 7% dimming, and 13% scotoma. More than 75% of patients had a headache on the same side as the vision disturbance within an hour. [3][2]

Twenty-nine percent of retinal migraine patients have a history of migraine headache, and 50% have a family history of migraine headache. [2]

Pathophysiology

The pathophysiology of migraine remains controversial. One theory of ocular migraine is that it is due to vasospasm within the retinal or ciliary vasculature while others think it is a spreading depression of the neuron in the retina that is similar to the spreading depression of the cerebral cortex. The spreading depression of the cerebral cortex is usually seen in the visual aura of a classic migraine; it has been observed in patients having an episode of retinal migraine, vasoconstriction of both veins, and arteries that could be diffuse or segmental. It also can be noticed by ocular hypoperfusion on fundoscopy. Fluorescein angiography can confirm the diagnosis. The fluorescein angiogram shows delayed filling or occlusion of the central retinal artery and its branches with either a normal ciliary circulation or patchy choroidal defects and capillary dropout. [4][1][2] 

Retinal migraine attacks are precipitated by similar factors as a migraine with aurae such as stress, smoking, hypertension, hormonal contraceptive pills, exercise, bending over, high altitude, dehydration, hypoglycemia, or excessive heat. Strong family history in these patients suggests that a retinal migraine has a genetic predisposition but no clear pattern of inheritance has been described. The vasospasm theory is controversial due to the complexity of the retinal vascular supply. Retina has dual circulation, central retinal artery supplies, inner retinal layers, lacks adrenergic innervation, maintains sensory nerves, and is auto-regulated. The choroidal circulation supplies the posterior retina including the photoreceptors it carries adrenergic fibers without autoregulation. [1][2] 

History and Physical

The patient will present with a wide range of symptoms. Many patients describe positive symptoms such as flashing lights and scintillating scotomas. The negative symptoms are black, shaded, white areas of different sizes of scotomata. Attacks happen a few times per day and can last from 5 to 20 minutes. A retinal migraine shares many properties with migraine with an aura and acephalgic migraine. Many times, these are difficult to differentiate. However, it is less common to have monocular vision disturbance in an acephalgic migraine or a migraine with aura classic migraine. The visual symptoms during a retinal migraine usually do not last as long as with a visual aura of migraine. Physical examination will show monocular visual acuity loss and/or loss of the visual field, all other cranial nerves and the rest of the neurological examination will be normal. [5][2] 

Evaluation

The attacks must fulfill the criteria for migraine with aura. The aura must be fully reversible and monocular, that is, positive or negative phenomena confirmed during an attack by visual field examination or patient’s drawing of a field defect and at least 2 of the following [2] 

• Spreading gradually over 5 minutes or longer
• Symptoms last 5 to 60 minutes
• A headache within an hour of visual symptoms

Treatment / Management

If the attacks are infrequent, such as one per month, then treatment is not necessary. When attacks are more frequent, first-line therapy starts with lifestyle changes that include avoiding dietary triggers such as alcohol and caffeine, controlling stressors like high blood pressure, and ceasing to smoke. If that does not help, then the patient must start a diary to help evaluate the success of the therapy and initiate prophylaxis therapy. It is usually recommended to avoid ergot and beta-blockers in retinal migraines due to the increased incidence of irreversible vision loss. Calcium channel blockers such as nifedipine and verapamil (most effective) are the mainstay of treatment here. Contraindications to calcium blockers include congestive heart failure, hypotension, sick sinus syndrome, cardiac conductive defects, concomitant, and renal or hepatic failure. Other medications such as coumadin and heparin have been used in isolated cases of patients with antiphospholipid antibody syndrome and retinal migraine. Aspirin and antiepileptic drugs have all been shown to reduce the severity of attacks. Abortive therapy is not used in this condition due to the brief duration of episodes; the main focus of treatment would be to reduce the recurrence of attacks. Medications such as Triptans, ergots, and beta-blockers should be avoided in migraines with transient vision loss since there is a concern for exacerbation of vasoconstriction and increasing the risk of potential irreversible visual loss. [1][2] 

Differential Diagnosis

The most important initial step in evaluating a patient with suspected retinal migraine is to determine if the visual symptoms are monocular or binocular. Once it is confirmed that it is a monocular visual loss, then the healthcare professional has to rule out all other causes of monocular vision loss because a retinal migraine is a diagnosis of exclusion. The other diagnoses that need to be considered are amaurosis fugax as in embolic phenomena of carotid or cardiac source, increase intracranial pressure, orbital apex mass, optic neuritis, giant cell arteritis, migraine with visual aura, or anterior ischemic optic neuropathy. [5][2] 

Prognosis

Although a retinal migraine is considered a benign condition, permanent symptoms can persist after the acute attacks. [1][2]

Complications

Complications of a retinal migraine include central retinal artery occlusion (CRAO), retinal infarction, central retinal venous occlusion, branch retinal artery occlusion (BRAO), retinal hemorrhages that can lead to edema of the retina and disc, ischemia of choroid or optic nerve, and vitreous hemorrhage. Many of those could lead to irreversible vision loss in the patient. It is important to avoid the use of triptans, ergots, and beta-blockers in migraines with transient vision loss secondary to the risk of potentiating vasoconstriction and increasing the risk of irreversible visual loss. [1][2]