Algorithm of approaching diagnosis of vestibular migraine 
2.4.1 Recognition and Confirmation of Vestibular Symptoms
When a patient presents with dizziness or other apparent vestibular symptoms, one should first determine if these symptoms are indeed vestibular related . The answers are often found in reviewing the patient’s history that needs to be comprehensive and detailed. The presenting symptoms are questioned from all possible aspects in order to understand their possible vestibular relevance and values in localization and diagnosis. For example, a vestibular relevance is strongly suggested when the symptoms include directional spinning and a sensation of self-motion or unsteadiness with directional pulsion. In contrast, the vestibular relevance is likely poor if the dizziness is reported as feeling lightheaded and fainting.
When the vestibular symptoms have been verified in reference to the recommended definitions and classifications , the patient should be further questioned regarding a few other symptoms that are frequently associated with vestibular disorders, such as gait disturbance, visual disturbance, nausea, tinnitus, hearing loss, earache, etc. These symptoms can be important for the differential diagnosis. Questions should cover the entire course of progression for each symptom starting from its onset.
Once the presenting vestibular symptoms and their related conditions are understood, the possibly involved neural structures need to be localized and a list of possible diagnoses formulated. For example, recurrent episodic vertigo, which is characterized as brief intense spinning attacks and only associated with head turning toward a certain side in supine position, is indicative of positional irritation of the ipsilateral posterior semicircular canal and is most likely related to canalithiasis or cupulolithiasis, i.e., benign paroxysmal positional vertigo. The concurrence of recurrent episodic spinning-type vertigo and unsteadiness with directional pulsion and ipsilateral ear fullness, loud tinnitus, and hearing loss suggests the involvement of ipsilateral peripheral vestibular and auditory components. In this case, Menière’s disease or acoustic neuroma should be considered. Meanwhile, the migraine-related vestibular symptoms are often poorly localized or grossly localized to the brainstem or cerebellum. As a matter of fact, when a relevant focal lesion is clearly indicated, migraine will unlikely be the diagnosis. However, migraine should be highly suspected when the dizziness is correlated with episodic headache attacks, sensitivity to light and/or noise, nausea, and poor tolerance to head motion. Such a possibility needs to be also considered when episodic headaches and other migraine-like symptoms are identified even when these symptoms may not coincide with the current dizziness.
2.4.2 Recognition and Confirmation of Migraine History
When the vestibular systems are confirmed, the patient should be asked for a possible previous or current history of headaches. If such a history does exist, detailed headache features should be inquired by means of the same approaches toward vestibular symptoms as previously discussed. Efforts are also made to explore headache-associated symptoms, such as visual aura, nausea, photophobia, and phonophobia. If these symptoms fulfill the ICHD-II criteria for diagnosing migraine with or without aura and alternative diagnosis can be excluded, the existence of migraine is recognized . All the patients with migraine headache should be asked for any vestibular symptoms and those symptoms, if present, should be further assessed for their vestibular relevance with the previously discussed criteria. Since sometimes a history of migraine can be difficult to clearly diagnose, a systemic approach following the clinician’s persistent efforts to identify and localize neurological symptoms and to formulate and refine the diagnostic hypothesis is again the key for uncovering the critical elements for migraine diagnosis.
2.4.3 Correlation Between Vestibular Symptoms and Migraine
After recognizing the coexistence of both vestibular symptoms and a history of migraine, the clinician should attempt to find out whether this coexistence is related to the same underlying etiology or is merely a coincidence. The diagnosis of vestibular migraine requires the recognition of a temporal correlation between vestibular symptoms and migraine . Once again, a careful review of all the relevant information from the entire history and physiological examination is essential to determine the relationship between these clinical symptoms. For example, a migraine patient may also suffer from vertigo related to a compressive meningioma at the cerebellopontine angle region on one side. In a case like this, both headache and vertigo can happen together at times.
2.4.4 Exclusion of Alternative Causes of Vestibular Symptoms Besides Migraine
The final step in diagnosing vestibular migraine is to determine whether or not migraine is the only or the best explanation for the correlation between the identified vestibular symptoms and the migraine diagnosis. If the vestibular symptoms are clearly caused by, or are better related to, a recognized vestibular disorder, the diagnosis of vestibular migraine should be questioned. To do so, a careful differential diagnosis is needed and is usually not a significant challenge to an experienced clinician. However, difficulties are often encountered when a possible correlation between the vestibular symptoms and migraine cannot be completely rejected. For example, some migraine patients may also have vestibular symptoms that are clearly or reasonably believed to be not related to migraine. These vestibular symptoms may occur either by coincidence or due to aggravation during or between migraine attacks. In many cases, the underlying cause of vestibular symptoms can be a minor vestibular, visual, or cerebellar dysfunction that is normally asymptomatic but becomes unmasked or exacerbated during migraine attacks. In other words, despite independent mechanisms, vestibular symptoms and migraine may still interact and reciprocally influence each other. Further, a few neurological disorders in the spectrum of migraine can present with prominent vertiginous symptoms. Those disorders can be distinguished from vestibular migraine based on some of their unique clinical features. These conditions will be discussed later in differential diagnosis.
Having made all the above efforts, the gathered findings are examined against the recommended diagnostic criteria for vestibular migraine. A final diagnosis of vestibular migraine can be made if all the requirements are fulfilled .
A few important clinical aspects need to be further discussed. First, the inquiry of medical history should always include asking questions about all the medical conditions that can be relevant to vestibular function, such as cardiac and pulmonary functions, psychiatric and psychological status, childhood development, and, if any, previous diseases that involved peripheral and central nervous systems especially the vestibular system. Women should also be evaluated for their history of menstruation and possible complications with it. Patients should also be routinely asked for current or previous neurological and otological disorders such as motion sickness, gait and balance disorders, visual discomfort, eye misalignment, impaired control of ocular movement, auditory symptoms, head trauma, infection of brain or ear, etc. Relevant social history, such as previous and current medication and substance abuse, and family history, especially about migraine, vertigo, and unsteadiness, should be routinely obtained.
Second, one should keep it in mind that the diagnosis of vestibular migraine is entirely based on the subjective features of relevant clinical symptoms . In other words, the patients with vestibular migraine are not expected to have any significant finding on their physical examination. Although the physical examination is typically normal or unremarkable for the majority of those patients, subtle physical findings, such as brief episodic nystagmus and saccadic tracking, can be recognized during or between attacks of vestibular migraine [26, 27]. These findings are usually considered as benign and can be directly related to migraine. However, investigations are often made in order to prove that they are indeed not attributed to another disorder.
Finally, supplemental investigations in addition to history taking and physical examination are performed in some patients because of their individual conditions. Those clinical investigations include radiology (such as CT and MRI), vestibular laboratory (such as nystagmogram, vestibular evoked myogenic potentials, rotary chair, and posturography), and audiology laboratory (such as audiometry, auditory evoked potentials, and electrocochleogram). When used appropriately, these clinical tests may provide critical information to help with the differential diagnosis.
2.5 The Differential Diagnosis of Vestibular Migraine
When typical vestibular symptoms and migraine history are both identified and their temporal correlations confirmed in an otherwise healthy person with normal physical examination, the diagnosis of vestibular migraine may be not difficult. A diagnosis of vestibular migraine will be questioned if the identified vestibular symptoms can be explained by an alternative cause better than migraine. Meanwhile, ambiguous presentations or variations are often encountered. For example, an individual who presents with clear vestibular symptoms may have never experienced a headache despite having a typical migraine aura and associated phobia and nausea. In situations such as this, the judgment may heavily depend on the clinician’s knowledge and experience. In this section, a few vestibular disorders in which the clinical presentations can significantly overlap with vestibular migraine will be discussed.
2.5.1 Benign Paroxysmal Vertigo of Childhood (BPVC) (See Also Chap. 4)
As first described by Basser in 1964 , BPVC is a paroxysmal pediatric disorder that has been regarded as a migraine equivalent, or a precursor of migraine, in children. Together with migraine, BPVC is a common cause of vertigo in pediatric population [28, 29] and the most common cause of episodic vertigo in children between ages 2 and 5 years . It is classified as one of the childhood periodic syndromes in ICHD-II. It is defined as a probably heterogeneous disorder with at least five episodic severe vertigo attacks that occur suddenly without warning, last for minutes to hours, and resolve spontaneously in otherwise healthy young children. The disorder has a typical onset younger than 4 years and usually resolves after age 7–8 years . Clinically, the child may suddenly appear frightened, may exhibit pallor, and has to stop playing. The child may also report having a spinning sensation or may be witnessed with nystagmus. The child may also cry, vomit, and stagger during attacks. The neurological examination is usually normal between attacks and so are the encephalogram, vestibular laboratory, and auditory measures between attacks. However, some abnormalities with auditory and vestibular functional tests within a few days after attacks have been reported . A more complete review of this topic is discussed in Chap. 4.
2.5.2 Basilar-Type Migraine
It has been estimated that more than 60 % of patients with basilar-type migraine may experience vertigo during their attacks . Vestibular migraine and basilar-type migraine are different disorders by their definitions and diagnostic criteria. These two disorders can be differentiated from each other by the more complicated focal neurological deficits with basilar-type migraine. Historically, in the development of the concept of vestibular migraine, all patients with vestibular symptoms were thought to manifest basilar-type migraine; see Chap. 3.
In addition to vertigo, patients with basilar-type migraine also describe complicated migraine auras, such as dysarthria, diplopia, binocular and symmetric visual field disturbances, decreased consciousness, ataxia, bilateral paresthesia, tinnitus, and hypacusia . These symptoms are generally considered as manifestations of transient ischemia involving the brainstem, cerebellum, and bilateral posterior hemispheres. Vestibular migraine is much more common in adults than basilar-type migraine that usually affects adolescents and usually resolves by adulthood .
2.5.3 Menière’s Disease (See Also Chap. 6)
Menière’s disease is an idiopathic syndrome of endolymphatic hydrops . The diagnosis of definite Menière’s disease requires fulfillments of all the following criteria: (1) at least two definitive spontaneous episodes of vertigo lasting from 20 min to 24 h, (2) hearing loss on at least one occasion documented by audiometry, (3) tinnitus and ear fullness on the affected side, and (4) exclusion of other causes.
Despite the apparent differences in their pathologies and clinical presentations, a possible link between Menière’s disease and vestibular migraine has been suggested . Migraine has been found to be more common than usual in patients with Menière’s disease [3, 35]. Those two conditions may be even genetically related [15, 36, 37]. Similar symptoms, such as vertigo, headache, phobia, and even alternation of hearing, may present in both disorders . Migraine may also facilitate the development of Menière’s disease . The differentiation between Menière’s disease and vestibular migraine can be difficult when Menière’s disease presents with predominantly vestibular symptoms. However, its association with significant fullness and pressure, roaring tinnitus, and progressive sensorineural hearing loss in the affected ear is not the characteristics of migraine.
2.5.4 Benign Paroxysmal Positional Vertigo (BPPV)
Vestibular migraine may present with prominent positional vertigo that can be confused with BPPV. Migraine has been found to be more common in patients with idiopathic BPPV than those with BPPV secondary to other causes [3, 39]. In BPPV, the stereotype association of characteristic spinning vertigo and nystagmus with specific head position leads to a localization at the peripheral vestibular end organ. The absence of intense migraine features and the brief duration of vertigo with each episode lasting only for seconds favor the diagnosis of BPPV rather than vestibular migraine. Many references, including comprehensive review articles , are available for the diagnosis of BPPV. The definitive finding of rotary nystagmus when performing the Dix-Hallpike test confirms the diagnosis of BPPV.
2.5.5 Psychiatric Dizziness
The association of migraine with some psychiatric disorders, such as anxiety, panic attacks, and depression, has been well recognized [19–21]. Vestibular symptoms and signs are common in patients with anxiety . Patients with vestibular migraine often also suffer from anxiety [23, 42]. Furman et al.  has described a disorder named migraine-anxiety-related dizziness (MARD) which is a combination of dizziness, migraine, and anxiety.