16 Migraines As a Source of Vestibular Disorders: Diagnosis and Management

Migraine and vertigo are two common neurologic complaints in the general population. The prevalence of migraine has been shown to be elevated among patients with dizziness, and in particular among patients with unclassified recurrent vertigo.1,2,3 Conversely, significantly more patients with migraine reported vertigo compared with patients with tension headache, namely 27% versus 8%.^4,5 Vertigo was also more common in migraine patients than in headachefree controls in two case-control studies.^6,7 Migraine and vestibular symptoms co-occur more than three times more often than by chance alone. As migraine has a lifetime prevalence of 14% and vestibular vertigo of 7%, the absolute chance consensus is expected to occur in 1% of the population, but was actually found in 3.2% in a large, population-based study.^8,9

Various terms have been used to describe the recurring vestibular symptoms in migraine when an alternative diagnosis has been ruled out. These include migraine-associated dizziness, migraine-related vestibulopathy, migrainous vertigo, and vestibular migraine. These terms imply a link between migraine and the vestibular symptoms based on epidemiology.^5,6 Migraine associated with vertigo/dizziness, with the principal feature being the symptom of vertigo, is referred to as vestibular migraine (VM). The presentation of VM varies from spontaneous and positional vertigo, head motion vertigo/dizziness, and ataxia of variable duration, ranging from seconds to days. Most episodes have no sequential relationship with the headache, which patients experience as a separate episode. VM is considered to be the second most common cause of vertigo and the most common cause of spontaneous episodic vertigo.¹⁰

Recently, the Bárány Society, which represents the international community of physicians committed to vestibular research, mandated a classification group to develop diagnostic criteria for VM. Their classification, developed in conjunction with the Migraine Classification Committee of the International Headache Society, resulted in a joint document defining VM and probable VM.¹¹ The criteria are included in the third edition of the International Classification of Headache Disorders (ICHD-3), where they appear in the appendix of new disorders that need further research for validation (Table 16.1). In addition, the classification of VM is part of the evolving Classification of Vestibular Disorders of the Bárány Society. The new ICHD-3 includes only VM, while the Bárány classification also contains probable VM (Table 16.2).

Clinical Presentation

Migraine is divided into two major subtypes, migraine without aura and migraine with aura. Migraines without aura are recurrent headaches manifesting as attacks lasting 4 to 72 hours. Typical characteristics of the headache are unilateral location, pulsating quality, moderate or severe intensity, aggravation by routine physical activity, and association with nausea and/or photophobia and phonophobia. Migraine with aura is the occurrence of an aura or a perceptual disturbance before the headache begins. It often manifests as the perception of a strange light, an unpleasant smell, or confusing thoughts or experiences. Auras vary by individual; some people experience smells, lights, or hallucinations.¹² Less well-known ocular symptoms include disturbances where the eyes roll back in the head due to photosensitivity-like symptoms. A sufferer of this type of aura may experience tearfulness of the eyes and uncontrollable sensations of light, followed by reduced symptoms after ~ 20 minutes. The diagnosis of a migraine-related condition is based on a transient sign or symptom in the absence of conventional visual aura or prodrome. The headache may or may not be present.

Table 16.1 Diagnostic criteria for vestibular migraine (ICHD-3)

Table 16.2 Diagnostic criteria for vestibular migraine and probable vestibular migraine

^a Vestibular symptoms, as defined by the Bárány Society’s Classification of Vestibular Symptoms and qualifying for a diagnosis of vestibular migraine, include:

^b Vestibular symptoms are rated “moderate” when they interfere with, but do not prohibit, daily activities, and “severe” if daily activities cannot be continued.

^c Duration of episodes is highly variable: About 30% of patients have episodes lasting minutes, 30% have attacks for hours, and another 30% have attacks lasting several days. The remaining 10% have attacks lasting seconds only, which tend to occur repeatedly during head motion, visual stimulation, or after changes of head position. In these patients, episode duration is defined as the total period during which short attacks recur. At the other end of the spectrum, there are patients who may take 4 weeks to fully recover from an episode. However, the core episode rarely exceeds 72 hours.

^d Migraine categories 1.1 and 1.2 of the ICDH-2.

^e One symptom is sufficient during a single episode. Different symptoms may occur during different episodes. Associated symptoms may occur before, during, or after the vestibular symptoms.

^f Phonophobia is defined as sound-induced discomfort. It is a transient and bilateral phenomenon that must be differentiated from recruitment, which is often unilateral and persistent. Recruitment leads to an enhanced perception and often distortion of loud sounds in an ear with decreased hearing.

^g Visual auras are characterized by bright scintillating lights or zigzag lines, often with a scotoma that interferes with reading. Visual auras typically expand over 5 to 20 minutes and last for less than 60 minutes. They are often, but not always, restricted to one hemifield. Other types of migraine aura, for example, somatosensory or dysphasic auras, are not included as diagnostic criteria because their phenomenology is less specific and most patients also have visual auras.

^h History and physical examinations do not suggest another vestibular disorder or such a disorder is considered, but ruled out by appropriate investigations, or such disorder is present as a comorbid or independent condition, but episodes can be clearly differentiated. Migraine attacks may be induced by vestibular stimulation. Therefore, the differential diagnosis should include other vestibular disorders complicated by superimposed migraine attacks.

Patients with VM typically report spontaneous or positional vertigo. Some experience a sequence of spontaneous vertigo that transforms into positional vertigo after several hours or days.13 This positional vertigo is distinct from benign paroxysmal positional vertigo (BPPV) with regard to duration of individual attacks (often as long as the head position is maintained in VM versus seconds only in BPPV), duration of symptomatic episodes (minutes to days in VM versus weeks in BPPV), and nystagmus findings. Altogether, 40 to 70% of patients experience positional vertigo in the course of the disease, but not necessarily with every attack.¹⁴ A frequent additional symptom is head motion intolerance, i.e., imbalance, illusory motion, and nausea aggravated or provoked by head movements.^9,15 Visually induced vertigo, that is vertigo provoked by moving visual scenes, such as traffic or movies, can be another prominent feature of VM.¹⁶ Nausea and imbalance are frequent, but nonspecific, accompaniments of acute VM.

Benign paroxysmal vertigo of childhood is an early manifestation of VM that is recognized by the ICHD-3. It is characterized by brief attacks of vertigo or disequilibrium, anxiety, and often nystagmus or vomiting, recurring for months or years in otherwise healthy young children.¹⁷ Many of these children later develop migraines, often years after vertigo attacks have ceased. A family history of migraine in first-degree relatives is increased twofold in these children compared with controls. In a population-based study, the prevalence of recurrent vertigo probably related to migraine was estimated at 2.8% in children between 6 and 12 years old.¹⁸

VM often misses not only the duration criterion for an aura as defined by the ICHD-3, but also the temporal relationship to migraine headaches: vertigo can lead to headache (as would be typical for an aura), may begin with headache, or may appear late in the headache phase. Many patients experience attacks both with and without headache,¹⁹ or attenuated headache with their vertigo as compared with their usual migraine.¹⁵ In some patients, vertigo and headache never occur together.^19,20 Along with the vertigo, patients may experience photophobia, phonophobia, osmophobia, and visual or other auras. These phenomena are of diagnostic importance because they may represent the only apparent connection of vertigo and migraine. Patients need to be asked specifically about these migraine symptoms because they often do not volunteer them. A dizziness diary can be useful for prospective recording of associated features.

Pathophysiology

The pathogenesis of isolated vertigo in migraine likely shares a mechanism similar to other transient events observed in migraine, such as tinnitus, hyperacusis, hemiplegia, visual aura, torticollis, and headache. Current theories focus on disturbances in serotonergic and noradrenergic neurons of the brainstem due to an inherited voltage-gated calcium channelopathy. A primary neuronal initiation begins a cascade of neurochemical processes, culminating in a spreading wave of cortical neuronal depolarization and regional oligemia.²¹ The transient vestibular events of migraine could be explained by the same focal brain dysfunction that also causes migraine-associated hemiplegia, visual aura, torticollis, and headache. However, other than discovery that a regional hyperpolarization of neurons exists in the cortical areas of the regions responsible for visual aura, the precise physiology of neurologic events in migraine remains obscure.²² The current pathophysiologic model of VM is based on the overlap in CNS pathways responsible for pain, equilibrium, and a sense of well-being, and modulators mediated largely by norepinephrine and serotonin.²³

The development of diagnostic criteria for migrainous vertigo was an important step in bringing together diagnostic standards for a condition like VM, which lacks any biomarkers. The term vestibular migraine has been convincingly advocated as a condition that stresses particular vestibular manifestations of migraine and therefore best avoids confusion with nonvestibular dizziness associated with migraine.²⁴

Clinical Evaluation

Traditionally, patients with recurrent vertigo associated with migraine are seen in consultation by neurologists. Otolaryngologists and internists are now becoming more familiar with this condition. In patients with vertigo and migraine, clinicians must determine whether they have vertigo that is caused by migraine or rather dizziness/vertigo of an unrelated cause, which may occur by chance in a migraine patient. Of note, VM accounted for only a third of migraine patients with a history of vertigo, which indicates the need for a thorough neurotologic work-up for exclusion of other diagnoses.²⁵ The clinical evaluation of migraine as a source of vestibulopathy is often a time-consuming task, because the associated vestibular symptoms are so often varied. Histories taken without careful consideration of associated symptoms often focus on the intensity of vertigo and the accompanying emotional and systemic symptoms, ignoring minor neurologic symptoms. Details concerning the episodes of vertigo are most critical, with careful scrutiny given to how random or provoked the episodes are, the precise duration of episodes, the exact episode frequency, and the temporal relationship of the episodes to other symptoms. Recording these details early in the course of the illness, even when the importance is not immediately obvious, may be critical later when symptoms of accompanying conditions can obscure details of past symptoms.

Episodic vertigo is commonly accompanied by the unpleasant vegetative symptoms of motion sickness. A history of childhood motion sickness is important because it often defines the severity of these symptoms in vestibular disorders. Vestibular symptoms in migraine include an altered visuospatial awareness, an ill-defined sense of dizziness or giddiness, lightheadedness, near-fainting sensation, ataxia or disequilibrium, or an illusion of motion. The vague description of these vestibular symptoms opens up the differential diagnosis to include transient cerebral ischemia, epilepsy, presyncope, and panic disorder. Complicating differentiation, some patients have features of both migraine and Meniere’s disease. Auditory symptoms are rare compared with vestibular symptoms but nevertheless there is evidence that hearing loss and tinnitus do occur.26 Hamed et al, on the other hand, found only minor changes of no significance in persons with migraine.²⁷ Tinnitus is common in migraine.

Many of the dietary and environmental triggers for migraineurs are the same as those for patients with nonmigrainous vestibular dysfunction (Table 16.3). Hormonal fluctuations, foods, and weather changes (barometric pressure variations) often exacerbate both conditions. If patients are examined acutely when vertiginous, there is usually minimal or no spontaneous nystagmus. This provides a differential feature from peripheral vestibular syndromes. When nystagmus is present, it is often directed vertically (e.g., up-beating or down-beating). Vertically directed spontaneous nystagmus is unusual in other contexts, providing another differential point.

Testing

There is no “test” for VM that by itself is specific and diagnostic. VM is diagnosed from the clinical pattern and by excluding alternatives. Neuroimaging studies, although rarely diagnostic, are helpful to rule out obscure pathologic entities.^28,29 A combination of audiologic and vestibular function tests is typically employed. These include positional testing with video-oculography, oculomotor and vestibuloocular reflex assessments with gaze stability and/or dynamic visual acuity testing, horizontal canal testing with video electronystagmography (VNG) with calorics, audiogram, and vestibular evoked myogenic potential (VEMP).

Nystagmus observed can have peripheral, central, or mixed features.³⁰ Vestibular test abnormalities usually cited in migraine patients include shorter vestibulo-ocular reflex (VOR) time constants, higher VOR gain, larger VOR bias, and more caloric asymmetry.^22,31 Audiometric testing in VM typically reveals no changes in function other than occasional hyperacusis, which usually is temporary and resolves shortly after the migraine event ends. However, there are also some reports of transient cochlear symptoms, usually a transient, mild, nonprogressive, low-frequency hearing loss.²⁷ There is no useful genetic test for ruling in or ruling out competing diagnoses.

Rather than seeking a specific test for migraine, consider narrowing the differential diagnosis of vestibular disorders causing episodic dizziness, with a careful process of inclusion or exclusion differentiating the clinical features of an otogenic source from neurogenic, cervicogenic, cardiogenic, or psychogenic sources. This is particularly important in chronic cases, where more than one source may be involved.

Table 16.3 Food triggers

Treatment

Pharmacologic treatment of migraine can be divided into two types: symptomatic and prophylactic. Symptomatic treatment of migraine vestibulopathy differs from migraine headache in two important ways. First, the headache phase is rarely the focus of symptom management. Second, the severe autonomic symptoms prevent the bioavailability of oral agents. Triptan medications used to abort migraine headache have yet to show promise in symptomatic treatment of vertigo associated with migraine.32 This is anticipated by the effect of triptans at vascular serotonergic receptors (5-HT1b-1d) only during the headache phase, not the aura phase, because of their activity in the trigeminal system and inhibition of dural vasodilation. They are contraindicated in the symptomatic treatment of basilar migraine.³³

Successful symptomatic management of the vertigo and the accompanying autonomic symptoms in migraine vestibulopathy does not differ from symptomatic management of episodic vertigo.³⁴ Several different vestibular suppressant medications are available with variability in their degree of sedation³⁵:

• Meclizine 12.5–50 mg po every 6 hours

• Dimenhydrinate 50 mg po every 4–6 hours, 100 mg prn every 12 hours

• *Diphenhydramine 25–50 mg every 4–6 hours

• Lorazepam 0.5–1.0 mg sublingually every 4 hours

• *Lorazepam 0.5–2 mg IM/IV every 6–8 hours

• *Diazepam 2–10 mg po/IV/IM every 6–8 hours

• Droperidol 2.5–5 mg IV/IM every 3–4 hours

• Promethazine 12.5–25 mg po/pr/IV/IM every 4–6 hours

• Prochlorperazine 5–10 mg po/pr/IV/IM every 6–8 hours

• Scopolamine patch 0.5 mg per 24 hours every 3 days

* (An asterisk denotes off-label usage, not FDA approved. po = by mouth; pr = per rectum; prn = pro re nata, when necessary; IV = intravenously; IM = intramuscularly)

The nonbenzodiazepine medications useful in treating episodic vertigo include meclizine, dimenhydrinate, and diphenhydramine. They often are given chronically yet have no proven prophylactic benefit in migraine. Scopolamine is a potent parenteral vestibular suppressant, yet it is a slow-acting agent more effective for motion sickness than for vertigo. Its chronic use (more than 9 days) and withdrawal often produce significant neurologic symptoms. The off-label use of benzodiazepines has been the mainstay of treatment for episodic vertigo, yet their chronic daily usage is complicated by uncertain pharmacokinetics, exacerbation of migraine headache, abuse potential, and significant neurologic risks of withdrawal. The parenteral administration of benzodiazepines is appropriate in the emergency department or hospital setting for the acute reduction in vertigo intensity. Sublingual lorazepam to reduce the intensity of the vertigo attack, leading to less provocation of the autonomic and emotional effects, has also proved useful, although no evidence-based confirmation of its efficacy exists.

Migraine occurring more than once a week or persisting more than 24 hours may benefit from migraine prophylaxis. There is no clinical evidence to suggest a preferential efficacy of one medication or class over another in the treatment of migraine. The first medication chosen should be a result of collaboration between doctor and patient. A return visit to assess efficacy requires waiting ~ 2 months after reaching therapeutic dosage. For appropriate treatment of migraine, the American Academy of Neurology (AAN) has published treatment guidelines, dividing prophylactic medications into various groups, defined by evidence of proven efficacy.³³ Because these medications are drawn from a diverse group of agents released for other indications, patients often become confused. It is important for the doctor to discuss this prior to beginning therapy, as the patient’s confusion can polarize the therapeutic relationship. Fortunately, the diversity of effective migraine prophylactic medications usually does not require trials of medications without proven efficacy. These agents include antihypertensives, antidepressants, and neuroleptics (Fig. 16.1).

All of these medications require titration from a low, nontherapeutic dosage to therapeutic dosage. The dose is advanced slowly over a course of weeks to months. This allows for considerable accommodation to side effects but delays expected outcomes. Patience is required, as often side effects are a poor predictor of eventual outcome. Weight changes and psychiatric, cardiopulmonary, and other side effects complicate compliance and treatment outcome. Each drug has different side effects. A trial should not be considered adequate until a therapeutic dose is reached and maintained for a minimum of 2 to 3 months.³⁶ Once stabilized, effective treatment requires at least 6 months of continued administration before consideration is made to taper off the medication. Withdrawal from these agents too early can produce relapse. Evidence confirming the efficacy of migraine prophylaxis in migraine vestibulopathy is complicated by the lack of standardized diagnostic criteria. However, several case series have been reported, usually with medications that are not AAN group 1 agents. These studies find 33 to 92% improvement using β-blockers, calcium channel blockers, tricyclic antidepressants, acetazolamide, and clonazepam.

There are certain caveats to treatment of VM. Chronic daily headache or head pain suggests the patient will do best to address the headache control first. These patients will require a headache clinic approach to management of their head pain before any promise of a response to migraine prophylaxis for their vestibular complaints. In refractory cases, it is important to reconsider disorders that masquerade as migraine. These include the early stages of Meniere’s disease, superior semicircular canal dehiscence syndrome, and a myriad of sporadic and familial neurodegenerative disorders.

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