Advances in diagnosis and treatment of vestibular migraine and the vestibular disorders it mimics

Abstract

Dizziness is one of the most common chief complaints in both the ambulatory care setting and the emergency department. These symptoms may be representative of a broad range of entities. Therefore, any attempt at treatment must first start with determining the etiology. In this current perspective, we focus specifically on the diagnosis of and treatment of vestibular migraine, which is common and overlaps clinically with a variety of other diagnoses. We discuss the traditional treatments for vestibular migraine in addition to the recent explosion of novel migraine therapeutics. Because vestibular migraine can mimic, or co-exist with, a variety of other vestibular diseases, we discuss several of these disorders including persistent postural-perceptual dizziness, benign paroxysmal positional vertigo, post-concussive syndrome, Ménière's disease, and cerebrovascular etiologies. We discuss the diagnosis of each, as well as overlapping and distinguishing clinical features of which the reader should be aware. Finally, we conclude with evidence based as well as expert commentary on management, with a particular emphasis on vestibular migraine.

Introduction

According to the International Classification of Vestibular Disorders, vertigo is defined as a false sensation of motion when none is occurring, or an altered sensation of self-motion during normal movement. Dizziness is defined as a sensation of impaired or disturbed spatial orientation without a distorted sense of motion [1]. Although understanding whether the patient is experiencing “dizziness” or “vertigo” can sometimes have diagnostic value, it can also lead to misdiagnosis – e.g. assuming a patient with orthostasis or a cardiac arrhythmia has a vestibular disorder because they are experiencing vertigo. For the remainder of this manuscript, we will use the terms “dizziness” and “vertigo” interchangeably.

Dizziness is one of the most common complaints in a variety of healthcare settings, accounting for around 5% of ambulatory care visits [2], and between 2.5 and 4% of emergency department visits [3,4]. It is estimated to affect nearly 15–20% of adults yearly [5], yet patients often go undiagnosed for prolonged periods of time. In a variety of settings, vestibular migraine (VM) and benign paroxysmal positional vertigo (BPPV) are the most common causes of dizziness [6]. Vestibular migraine is a significantly underdiagnosed and underrecognized common cause of dizziness, especially elusive since it can present in a variety of forms and mimic other vestibular disorders. Herein we discuss VM with an emphasis on strategies to gather the salient features of the history to make the correct diagnosis and differentiate VM from its mimics (see Table 1). We discuss effective methods of treating VM and similar vestibular disorders.

Table 1.

Features of vestibular migraine and its vestibular mimics.

Disease	Diagnosis	Special Considerations	Disease Similarities to VM	Disease Differences from VM
Vestibular migraine (VM)	-Current or past history of migraine headaches -5+ attacks of vertigo between 5 ​min and 72 ​h -At least half associated with migraine headaches, photophobia and phonophobia, or visual aura	-Often triggered or exacerbated by visual stimuli or complex sensory cues -Associated with migraine specific triggers	N/A	N/A
Persistent postural-perceptual dizziness (PPPD)	-Sense of dizziness most days lasting at least hours each day -Ongoing 3+ months -Exacerbated by upright posture, active or passive motion -Exacerbated by exposure to complex visual stimuli	-Oftentimes a triggering event can be identified	-Exacerbated by passive motion, visual stimuli, complex visual cues -Anxiety symptoms may co-exist	-Symptoms typically present more often than not -Symptoms continuous and ongoing >3 months (VM more commonly episodic)
Benign paroxysmal positional vertigo (BPPV)	-Presents with attacks of vertigo lasting <1–2 ​min -Occurs with head movements -No other neurologic or otologic symptoms -Classic nystagmus patterns noted on positional testing	-Diagnosed by examination during positional testing -Treated with canalith repositioning maneuvers	-May present with positional episodic dizziness -May present with ongoing vertigo in certain positions (e.g., cupulolithiasis) -May present with geotropic or apogeotropic nystagmus (e.g., lateral canal BPPV)	-Associated with a crescendo-decresendo nystagmus pattern in positional testing -Not associated with neurologic or otologic symptoms -Typically triggered only by active motion
Post-concussive syndrome (PCS)	-Occurs after trauma -Continuous or episodic dizziness -Associated with headache, cognitive and/or emotional symptoms, sleep disturbance, initial LOC or amnesia, photophobia, phonophobia, visual focusing issues, fatigue	-May be associated with convergence insufficiency, abnormal smooth pursuit, and/or accommodative dysfunction	-Symptoms of headache, photophobia, phonophobia, visual complaints, fatigue	-Typically symptoms with a trend of improvement after traumatic event (VM more likely spontaneous and episodic)
Meniere's disease (MD)	-2+ attacks of vertigo between 20 ​min and 12 ​h -Audiogram demonstrating low to mid-frequency sensorineural hearing loss -Fluctuating aural symptoms in the affected ear	-May be associated with vestibular dysfunction ipsilateral to hearing loss	-May be associated with aural symptoms (fullness, tinnitus, subjective hearing loss) -may be associated with unilateral vestibulopathy	-Aural symptoms more commonly unilateral (VM symptoms more commonly bilateral) -Audiogram evidence of sensorneural hearing loss
Stroke/Transient ischemic attack (TIA)	-May present as AVS or EVS -May be associated with neurologic symptoms -May be associated with central ocular motor deficits	-Consider MRI and vascular imaging when ABCD2 >3 in AVS -Red flag features warrants MRI -Perform HINTS exam on patients presenting with AVS -Acute hearing loss warrants MRI	-May be associated with neurologic symptoms (VM may present as complex migraine) -May be associated with central ocular motor deficits	-Abnormal MRI

Vestibular Migraine

Overview

Descriptions of dizziness in association with migraine can be found in literature over 150 years ago [7]. However, the widespread awareness of dizziness as a major component of migraine symptomatology was not well elucidated until the emergence of several case series in the 1980s and 1990s [[8], [9], [10], [11]]. Numerous theories for the underlying pathophysiology of this dizziness have been proposed such as a spreading wave of depression, transient vasospasm, and release of neuroactive peptides leading to hyperexcitability of primary afferent neurons [9]. Since then, descriptions and studies of VM exploded, and in 2012, the Bárány Society published the first consensus diagnostic criteria for VM [12], a major victory for increased awareness, recognition, and accurate diagnosis of this condition.

Epidemiology

Based on the Bárány consensus criteria definition, a review of a large population-based survey revealed that the prevalence of dizziness in the general population meeting criteria for VM was 2.7%, which makes it the most common cause of spontaneous episodic vertigo [6]. Indeed, the prevalence over a one-year period was found to be 1.7x higher than that of benign paroxysmal positional vertigo (BPPV), and 5.4–13.5x higher than that of Ménière's disease [6]. Among those patients who meet the definition for VM, only 10% were told that migraine was likely the cause of their dizziness, and many of them were diagnosed with a mimic instead. Therefore, VM is likely both underdiagnosed and misdiagnosed. Another finding in this study was that nearly a quarter of all patients with dizziness in a one-year period may have VM, which would make it the most common cause of dizziness overall.

Diagnosis

The current updated and revised diagnostic criteria for definite VM published in 2022 consist of the following: either a current or past history of migraine with or without aura, at least five attacks of vertigo of moderate to severe intensity that last between 5 ​min and 72 ​h, at least half of these attacks must be associated with at least one of three migraine features including 1) migraine headaches, 2) photophobia and phonophobia, or 3) a visual aura, and finally the description of these attacks cannot better fit into an alternative vestibular disorder [13]. While VM is traditionally thought of as a spontaneous episodic dizziness, it is also known to be either triggered by or exacerbated by visual stimuli and/or self-motion [14]. Some common examples of visual stimuli include scrolling on a phone, prolonged exposure to computer screens, action movies, or certain stimulating environments such as grocery or department stores. Migraine specific triggers are especially useful to obtain including hormone-related (e.g. menstruation), sleep deprivation, stress or anxiety, specific foods, or sensory stimuli such as powerful smells, strobing lights, or excessive noise [15]. VM has even been described to present with a positional episodic vertigo very similar to BPPV [16]. Therefore, when BPPV is diagnosed but either does not have the classic nystagmus pattern in positional testing or does not respond to treatment maneuvers, the possibility of VM should be entertained. Although not included in the criteria, it is also important to note that up to 38% of patients complain of aural symptoms such as fullness, tinnitus, and subjective hearing loss [17]. Most VM patient complain of these aural symptoms bilaterally, although around one-third may experience these symptoms unilaterally, a history which mimics Ménière's disease.

Exam and laboratory testing findings

Ocular motor and vestibular abnormalities in VM patients including spontaneous nystagmus, saccadic pursuit, gaze-evoked nystagmus, and/or positional nystagmus can be seen during VM attacks [11,18]. Inter-ictally, the examination is typically normal, as is laboratory testing [19]. Mild vestibular testing abnormalities including unilateral vestibulopathy have occasionally been reported using electronystagmography, video head impulse test (vHIT), caloric testing, and/or rotary chair testing in VM patients that may also normalize inter-ictally [10,20]. It is unclear whether these abnormalities are related to VM itself or if the presentation of VM was triggered by an independent cause of unilateral vestibulopathy.

Non-prescription medication treatment

Treatment options for VM are varied, and choice of treatment modality may depend on patient preferences. In 2023, a Cochrane review analyzed non-pharmacologic lifestyle modifications and concluded that there is a paucity of evidence in favor of these interventions for VM [21]. Therefore, until we find VM-specific evidence-based interventions, it may be reasonable to extrapolate data from the migraine headache studies. Evidence-based lifestyle modifications for standard migraines include minimizing stress, identification and avoidance of triggers (e.g., heat, loud sounds, strong odors, bright lights), proper sleep hygiene and having a regular sleep schedule, dietary change (e.g., avoiding hunger, dehydration, caffeine, alcohol), creating a headache diary to identify specific food triggers, regular physical activity, and maintaining a healthy body habitus [22]. The authors discuss the above interventions extensively with patients, especially those who prefer to avoid preventive medications. For certain patients, complementary therapy for migraine such as the herbal supplement feverfew as well as the natural supplements magnesium, riboflavin, and coenzyme q10 may be used for vestibular migraine, as all of these have some clinical trial evidence as preventives for migraines [23]. It should be noted that in 2015 the American Academy of Neurology (AAN) retracted their 2012 complementary therapy guidelines regarding safety concerns surrounding the supplement petasite (butterbur) [24].

Traditional preventive therapies

While there is a paucity of randomized controlled trials for medical management of VM [25], extrapolation of data of preventive medications from migraine headache trials is reasonable, and a common practical treatment strategy for VM (see Table 2). Common classes of medications that have been used to treat migraine for years include antiepileptics such as topiramate and valproic acid, tricyclic antidepressants such as amitriptyline and nortriptyline, serotonin norepinephrine reuptake inhibitors (SNRIs) such as venlafaxine and duloxetine, beta blockers such as propranolol and metoprolol, and calcium channel blockers such as verapamil [26]. Although there is a dearth of randomized controlled trials, there is evidence in the form of retrospective analyses to suggest the migraine preventive medications as a general class also work for VM [27,28]. Several of these individual agents including propranolol, venlafaxine [29], nortriptyline, topiramate [30], metoprolol, and valproic acid [27] have been individually studied and shown to be effective for VM. Finally, there is some evidence to suggest that medications such as acetazolamide and lamotrigine may be more effective for the vestibular symptoms than the headache symptoms in migraine patients [31]. The choice of agent to initiate may be based on side effect profile versus its utility in treating coexisting conditions.

Table 2.

Vestibular migraine preventive pharmacologic options.

Medication Class	Examples	Considerations	Diseases Medication may also Treat
Supplements	Feverfew, magnesium riboflavin, coenzyme q10	-Minimal side effects	N/A
Antiepileptics	Topiramate, valproic acid, lamotrigine, gabapentin	-Side effects variable but may include cognitive dysfunction, paresthesias, drowsiness, tremor, nausea, skin rash -Lamotrigine may be more effective for vestibular symptoms of migraine	Gabapentin: PCS
Tricyclic antidepressants	Amitriptyline, nortriptyline	-Side effects may include anticholinergic effects, drowsiness, confusion, hyponatremia, serotonin syndrome	PCS
Serotonin norepinephrine reuptake inhibitors (SNRIs)	Venlafaxine, duloxetine	-Side effects may include sexual dysfunction, bleeding, hypertension, hyponatremia, serotonin syndrome -Must titrate up and down slowly	PPPD
Beta blockers	Propranolol, metoprolol	-Side effects may include fatigue, bradycardia, bronchospasm	N/A
Calcium channel blockers	Verapamil	-Side effects may include bradyarrhythmias, headache, constipation	MD
Calcitonin gene-related peptide (CGRP) antagonists, subcutaneous	Erenumab, galcanezumab, fremanezumab	-Side effects may include injection site reactions, constipation, hypertension -Subcutaneous injections every 28 days	N/A
CGRP antagonist, intravenous	Eptinezumab	-Side effects may include anaphylaxis, angioedema -Intravenously administered every 3 months	N/A
CGRP receptor antagonist, oral	Rimegepant, atogepant	-Side effects may include gastrointestinal, hypersensitivity reactions -Rimegepant administered every 2 days and may be used as abortive	N/A
Onabotulinum-toxinA	Onabotulinum-toxinA	-Side effects may include sore neck or discomfort -Administered every 3 months	N/A

Novel preventive therapies

Despite these promising pharmacologic options, it is notable that even after trying some of the above medications, patients may fail due to lack of efficacy, inability to tolerate the side effects, or various socioeconomic factors such as a lack of access or cost [32]. Erenumab was the first calcitonin gene-related peptide (CGRP) antagonist to appear on the market in 2018, reducing weekly migraine days by greater than 50% [33]. Later that year, two other CGRP antagonists galcanezumab and fremanezumab were FDA approved, demonstrating similar efficacy [34,35]. All three are given as subcutaneous injections every 28 days and are considered well-tolerated since most patients report either no or mild side effects, the most common of which are injection site reactions, constipation, and hypertension. In 2020, the IV infusion CGRP antagonist eptinezumab and the oral disintegrating tablet CGRP receptor antagonist rimegepant were also approved for migraine prevention [36,37]. Eptinezumab has the advantage of only being given every three months, however it has the risk of hypersensitivity reactions such as anaphylaxis and angioedema [36]. Rimegepant is also well tolerated, however gastrointestinal side effects and hypersensitivity reactions are possible [37]. Finally, the oral CGRP receptor antagonist atogepant was approved for preventive treatment of migraine in 2021 as an alternative option to the injections [38]. Possible side effects include constipation and nausea. All these treatments have undergone intense scrutiny for the treatment of migraine, however there is a paucity of data on their effectiveness for VM, as no randomized controlled trials of these therapies exist. However emerging evidence suggests that these CGRP antagonists may be beneficial for VM in the same way they are effective for migraine headache [[39], [40], [41]]. In the author's experience, when patients have failed other migraine therapies, these appear anecdotally to be an effective option. A discussion on the newer preventives for the treatment of VM would not be complete without mention of onabotulinumtoxinA as treatment for prevention of chronic migraine. OnabotulinumtoxinA for migraine involves injecting 31 sites in 7 key areas of the head and neck. Since its approval by the FDA in 2010, this has emerged as an efficacious systemic drug-sparing option for migraine patients [42]. Side effects include sore neck or discomfort. Emerging evidence suggests it is likely to be an effective treatment option for VM [43]. The authors recommend that if some of the traditional migraine therapies fail to have a low threshold to attempt treatment with one of these newer migraine therapies.

Abortive therapies

While the future of preventive therapies for VM appears bright and largely seems to reflect the evolution of treatments for migraine headaches, there is inadequate evidence for VM abortive therapies. While triptans have shown clear benefit in aborting migraine headache [44], their effectiveness for VM was deemed inconclusive [45]. Currently, the default medications to relieve symptoms of vertigo in an acute attack are limited to anti-emetics such as meclizine, dimenhydrinate, benzodiazepines, and metoclopramide, all of which may be sedating [46]. We recommend trialing medications such as this sparingly and to instruct patients only to use them under circumstances when absolutely needed.

Persistent Postural-Perceptual Dizziness

In the 2010s, the Bárány society committee for the classification of vestibular disorders convened to better characterize similar disorders that had variably been referred to as phobic postural vertigo, chronic subjective dizziness, space motion discomfort, and visual vertigo [47]. This resulted in the description of a single disease entity now known as persistent postural-perceptual dizziness (PPPD). Importantly, this condition is more common than the structural vestibular disorders such as Ménière's disease and bilateral vestibular loss [47]. Thus, it is an important disorder for any clinician to be aware of when assessing dizzy patients.

In 2017, the Bárány society described the diagnostic criteria for PPPD [48]. The major features of this disease include a sense of dizziness, unsteadiness, or non-spinning vertigo on most days, lasting at least hours each day, and ongoing for at least 3 months. The symptoms can occur spontaneously, however are exacerbated by upright posture, active or passive motion, and exposure to moving or complex visual stimuli. Typically, the disease is triggered by an event that causes dizziness or vertigo and occasionally other neurological, medical, or psychiatric illnesses. The disease often causes significant distress or functional impairment and is not better accounted for by another disorder. A thorough neurological examination is warranted prior to making this diagnosis since a chronic sense of unsteadiness can occur secondary to diseases such as peripheral neuropathy, cerebellar ataxia, myelopathy, and Parkinsonism.

The underlying pathophysiology of PPPD is complex and theorized to be related to anxiety-related responses to triggering events, alteration in control of posture and gait, a dependence on visual input, poor spatial navigation and memory, alterations in the activity of the vestibular and visual cortices and frontal lobes, and a misperception of movement [49]. It is classified as a functional neurological disorder (FND), and like other FNDs, treatment involves patient education and counseling, psychotherapy, especially cognitive behavioral therapy (CBT), and treatment of co-existing anxiety and/or depression when present, vestibular rehabilitation, and medications [49,50]. Although currently large scale randomized-controlled treatment trials for PPPD are lacking, there is evidence to suggest that selective seroronin reuptake inhibitors (SSRIs), serotonin norepinephrine reuptake inhibitors (SNRIs), or sometimes these medications in conjunction with benzodiazepines are effective for PPPD [[51], [52], [53]]. Much of the evidence in favor of SSRIs and SNRIs comes from studies performed on the similar previously described disorders prior to the description of this disease [[54], [55], [56]].

A commonality between VM and PPPD is that both diseases may be triggered or exaggerated by passive motion (e.g. riding an escalator), visual stimuli (e.g. a bright computer screen), or complex visual cues (e.g. watching an action movie) [14,48]. Symptoms that are present more often than not and vary throughout the day (e.g., worse toward the end of the day) are suggestive of PPPD, whereas VM is an episodic condition lasting minutes, hours, or sometimes days in duration. Migraine specific associations such as headache or migraine triggers such as barometric pressure changes, menstruation, or specific foods may also make vestibular migraine more likely [15]. Anxiety symptoms commonly coexist with both VM and PPPD.

VM and PPPD not only share certain clinical features (e.g., visual sensitivity), but also commonly co-exist [57]. In these cases, treatment may focus on either disease. When treating a patient who has both VM and PPPD, it may be reasonable to treat with an SNRI such as venlafaxine or duloxetine since both have evidence in migraine as well as PPPD [53,58,59]. Should this treatment fail, regular follow-ups to understand whether symptomatology is more VM or PPPD-related allows the clinician to tailor the treatment plan. If the patient has developed migraine triggers for symptoms and frequent headaches, migraine lifestyle modifications and a migraine preventive can be considered. Likewise, if the patient has developed constant symptoms that are worse when upright, then an SSRI and CBT may be considered.

Benign Paroxysmal Positional Vertigo

Benign paroxysmal positional vertigo (BPPV) is one of the more common causes of dizziness with a lifetime prevalence of 2.4% and accounts for 8% of individuals complaining of moderate or severe dizziness [60]. It is generally recognized as the most common cause of peripheral vertigo [61]. Robert Bárány, the namesake of the Bárány society, was the first to describe this condition over a century ago [62].

BPPV presents with attacks of vertigo lasting less than a minute or two, and it occurs with head movements including going from lying to sitting, sitting to lying, rolling over in bed, and looking up or down. They are not associated with any other neurologic or otologic symptoms. The Dix-Hallpike was the first positional maneuver described to diagnose posterior canal BPPV, which is characterized by a crescendo-decrescendo upbeat-torsional nystagmus that occurs after a brief latency [63].

The most common form of BPPV is canalithiasis, first described in 1979, where otoconia float freely as debris within the endolymphatic fluid of the semicircular canal [64]. The less common cupulolithiasis was the originally proposed mechanism behind BPPV, where otoconia are adherent to the cupula itself rather than free floating [65]. Beyond the above-mentioned posterior canal canalithiasis, we know the otoconia may end up in the lateral canal, which is characterized by a horizontal form of nystagmus in the supine position. This nystagmus may be geotropic, where there is a right-beat nystagmus on head to the right and a left-beat nystagmus with head to the left, or apogeotropic, which exhibits the opposite positional nystagmus pattern. Anterior canal involvement is rare, however the nystagmus associated with it is well described [66]. During positional changes to test for BPPV due to cupulolithiasis, symptoms could be persistently ongoing since these heavy otoconia will continue to displace the cupula with respect to gravity in certain positions. Since the above, a variety of descriptions and localization of BPPV have emerged [67].

Traditional treatment maneuvers for these conditions are well established and include the Epley or Semont maneuvers for posterior canal and the Gufoni or BBQ maneuvers for lateral canal BPPV patterns [68]. Even over the last couple of years, novel treatment maneuvers have emerged for the treatment of BPPV, including the Semont plus for posterior canal, the Zuma maneuver for lateral canal, and the modified Yacovino maneuver for anterior canal, all of which are suggested to be superior to previously described maneuvers [[69], [70], [71]]. For cases of cupulolithiasis in which the nystagmus pattern may be ongoing during positional testing, it is reasonable to perform the above maneuvers with the application of vibration applied to the ipsilateral mastoid [68,72].

Head trauma, prior infections of the ear, vascular risk factors, osteoporosis, and vitamin D deficiency have been associated with the development of BPPV [73,74]. Because of this association between low levels of vitamin D and BPPV, a randomized trial was performed that demonstrated that in patients with low levels of vitamin D, vitamin D and calcium supplementation helped prevent future attacks [75]. Thus, beyond the usual treatment maneuvers to treat active BPPV, obtaining vitamin D levels should be a routine part of any BPPV evaluation.

In theory, most BPPV cases are easily distinguished from VM because of the timing of the attacks, the triggers, and the classic positional nystagmus patterns. VM vertigo attacks typically last more than 5 ​min, whereas BPPV is most commonly less than a minute. BPPV is only triggered by head position changes, whereas VM may be spontaneous or triggered by complex visual stimuli and migraine specific triggers such as certain foods. However, the reality is that features of the history and exam overlap with VM or VM and/or BPPV may co-exist. For example, the above mentioned cupulolithiasis may have symptoms of vertigo ongoing in certain positions, which can be confused with the central positional nystagmus patterns described in VM patients [11,18]. While VM patients typically experience a spontaneous dizziness, 17–46% of patient may experience positional episodic dizziness [11,76]. Furthermore, because VM can present with a positional nystagmus, care must be taken when analyzing the nystagmus itself to see if it better matches with a BPPV localization. However, it is possible for patients with VM to have positional geotropic or apogeotropic nystagmus, especially ictally, which can mimic lateral canal BPPV [76].

One method to distinguish the above is ruling in BPPV by positional testing and noting resolution with respective treatment, as well as a thorough history to investigate spontaneous dizziness history typical of VM. When the diagnosis remains uncertain, we recommend repeated examinations and treatment maneuvers targeted at BPPV. If the nystagmus is persistent for greater than a minute yet still a classic positional pattern for BPPV, one should still consider targeted treatment at BPPV with vibration applied to the mastoid for consideration of cupulolithiasis. The rationale for these recommendations is that BPPV treatment often leads to quicker results and is very low risk. Concurrent vitamin D supplementation should be considered if levels are low. Should these treatment maneuvers fail, consideration should be given to empiric migraine preventive therapy and lifestyle modifications. Patients should still be followed over time, and regular interval assessments of history (e.g., classic migraine associations such as photophobia and phonophobia or migraine triggers), and regular assessment of positional nystagmus should be made.

Post-Concussive Syndrome

Concussion is an acceleration-deceleration injury, and is a term often used to describe a mild form of traumatic brain injury (TBI). The symptoms of concussion may include headache, cognitive or emotional symptoms, sleep disturbance, and an initial loss of consciousness (LOC) or amnesia [77]. Symptoms typically resolved within 2 weeks, but symptoms that persist past 2 weeks are classified as the post-concussive syndrome (PCS), while the persistent post-concussive syndrome (persistent PCS) describes symptoms lasting longer than 3 months [78]. For the remainder of this manuscript, we will refer to both post-concussive syndrome and persistent post-concussive syndrome as PCS. While headache is the most common complaint of PCS, dizziness is the second most common complaint. Patient with PCS commonly also experience photophobia, phonophobia, visual focusing issues, and fatigue [78].

Dizziness due to PCS is typically described as either a continuous or episodic swaying or rocking sensation and it may be worse with movement or complex visual or overstimulating sensory cues [79]. The most common ocular motor abnormality in patients with concussion is convergence insufficiency in around 40% of patients, abnormal smooth pursuit in 40%, and accommodative dysfunction in around 20% of patients, although the ocular motor examination is often normal [80].

Treatment of PCS is variable, however a randomized controlled trial confirmed that early vestibular rehabilitation for post-concussive dizziness accelerates recovery [81]. Although there is a lack of randomized controlled trials for pharmacologic therapy targeting dizziness after concussion, trials have demonstrated a statistically significant decrease in headaches and the post-concussion symptom scale (PCSS) score with either gabapentin or a tricyclic antidepressant (TCA) [82]. While the PCSS does include dizziness, this scoring system groups together nausea, vomiting, balance problems, photophobia, phonophobia, fatigue, tingling, and a variety of cognitive, sleep related, and emotional symptoms with it. Therefore, the specificity of these medications' effects on dizziness in PCS remains uncertain. While there is evidence from animal studies that CGRP inhibitors may be effective for post-traumatic headaches, it is unclear whether this is also true in humans, and its generalizability to post-concussive dizziness remains uncertain [83].

While post-concussive dizziness is common, a variety of other treatable etiologies of dizziness should be considered including VM, BPPV, and PPPD [84]. It is recognized that post-traumatic headache can include migraine [85], and there can be significant overlap between PCS and VM given symptoms of headache, photophobia, phonophobia, fatigue, and visual complaints in both [13,14,78]. This makes the history especially important with particular attention to identifying classic migraine triggers and understanding the temporal relationship between dizziness, headaches, photophobia, and phonophobia. These symptoms occurring after concussion in a spontaneous episodic manner may more likely be VM, meanwhile a slow improvement over time with some fluctuations may more likely be PCS. It is also common that VM and PCS co-exist or cannot be teased apart.

Practically speaking, medications such as TCAs and gabapentin may be beneficial for both VM and PCS, and can be prescribed empirically even when the diagnosis is in question [26,82]. Otherwise, the potential risks and benefits should be weighed in each individual patient – e.g., avoid topiramate as a migraine preventive in a patient with cognitive dysfunction due to PCS or avoid propranolol as a migraine preventive in a patient with significant fatigue due to PCS. Inversely, a TCA may be considered in a patient with features of VM and PCS whose symptoms of dizziness are dominated by co-existing anxiety, insomnia, and headaches.

Ménière's Disease

Prosper Ménière first described a series of patients with episodes of vertigo and hearing loss in 1861 [86]. Prior to this it was assumed vertigo attacks originated in the brain in a mechanism akin to strokes or seizures, however included in this series of patients was the autopsy of a young girl with vertigo and hearing loss with an inner ear hemorrhage, the first account that convincingly demonstrated that vertigo could originate in the inner ear [87]. Classically, it has been theorized that Ménière's disease (MD) results from so-called endolymphatic hydrops, or and excessive buildup of endolymphatic fluid in the inner ear. More recently, this theory has been called into question since not all patients with endolymphatic hydrops (on temporal bone histopathology) have MD, although all patients with MD appear to have endolymphatic hydrops [88,89].

The diagnostic criteria for MD were most recently updated in 2015 and are separated into definite MD and probable MD [90]. Definite MD is characterized by at least two episodes of vertigo lasting between 20 ​min and 12 ​h, an audiogram demonstrating low to mid-frequency sensorineural hearing loss in the affected ear, fluctuating aural symptoms such as hearing loss, tinnitus, or fullness in the affected ear, and the symptoms should not be better accounted for by another disorder. Probable MD allows for attacks to last up to 24 ​h instead of 12 and excludes the audiogram criteria. Vestibular testing – including vestibular-evoked myogenic potential testing, electrocochleography, head impulse testing, and especially calorics may demonstrate vestibular dysfunction ipsilateral to the hearing loss, although abnormal results do not contribute to the diagnostic criteria of MD [91].

Treatment of MD includes interventions such as restricting salt and caffeine intake, and the use of diuretics or betahistine (although not FDA-approved in the U.S.) [92]. In patients who do not respond to these measures, intratympanic steroids injections can be an option. For intractable cases, surgeries such as endolymphatic sac surgery or shunt, intratympanic gentamicin injections, labyrinthectomy, and vestibular neurectomy may be offered [92]. Because of a prior theory about the etiology of MD being due to reduced cochlear blood flow, verapamil was also utilized in MD with some mild evidence of efficacy [93]. The efficacy of surgery for MD is debated amongst experts in the field, although new surgical techniques are being studies in patients with medically refractory MD [94,95].

Whether a particular patient is suffering from VM or MD is a common diagnostic conundrum given several overlapping features, particularly the aural symptoms that may be present in both [17]. Although aural symptoms are typically bilateral in VM, they can be unilateral in both MD and VM. The 20 ​min to 12 ​h timing for definite MD is well within the 5 ​min to 72 ​h timing in the VM criteria. To capture the extent of shared features in these conditions, the Ménière's disease/vestibular migraine overlapping syndrome (VM/MD-OS) was described based on a series of 10 patients who fulfilled diagnostic criteria for both [96]. Furthermore, a case-control study analyzed the association between MD and migraine and found that those patients with MD had a 2.22x higher risk of migraine and those with migraine had a 1.95x higher risk of MD [97]. Based on this analysis, the authors suggested that migraine therapies may help MD. Recent literature has gone as far as to suggest that MD may be a presentation of migraine [98]. After all, endolymphatic hydrops is a finding that has been demonstrated in patients with VM who do not meet criteria for MD both on MRI and histopathologically, and while an estimated 12% of the general population suffers from migraine headaches, 51–60% of MD patient have migraine headaches [98,99]. However, others contend that MD is primarily an inner ear disorder based on genetic and histologic findings as well as the efficacy of target MD treatments (including ablation of the end organ) [100]. It seems the brain origin theory to MD is mirroring the original controversy from 1861.

Regardless of underlying pathophysiology, if a patient meets diagnostic criteria for MD, starting with MD treatments is reasonable. Should they have features of VM however, tailoring treatment to either MD or VM is sensible. If there is symptomatic overlap between VM and MD, conservative and medication options should always be pursued prior to going to surgical route. Because verapamil has demonstrated efficacy in both MD and VM [26,93], its use was studied in VM/MD-OS with promising results [101]. Therefore, it may be reasonable to start with verapamil as a first line migraine preventive agent in the overlap disease or MD with some VM features. Interestingly, others have studied the utility in treating definite MD patient with migraine preventives after they have failed diuretic therapy with favorable results [102]. Therefore, if an MD patient has failed multiple lines of therapy targeting MD, it may be reasonable to pursue migraine preventive medications prior to surgical approaches.

Stroke and Transient Ischemic Attack

In our last section, we would like to make a few comments on when to think about stroke and transient ischemic attack (TIA), or generally, when is neuroimaging indicated in the acutely dizzy patient? Other disorders, such as mass lesions and demyelinating disease, should remain on the differential for more long-standing dizziness.

When obtaining a history, the TiTrATE method has emerged as a powerful history-taking tool to assess the etiology of an acutely dizzy patient in the emergency department [103]. We believe this tool is still practical and useful for the ambulatory clinician as well assessing these patients >2 weeks out from their initial episode of dizziness. By assessing timing and triggers of a patient's dizziness, patients with the episodic vestibular syndrome (EVS) can be subcategorized into spontaneous and triggered, and patients with acute vestibular syndrome (AVS) can be subcategorized into spontaneous and post-traumatic or toxic.

Patients with triggered EVS and a classic nystagmus pattern for BPPV do not require MRI, however those with unusual nystagmus patterns should get an MRI. Those with triggered EVS as well as a history that meets criteria for VM probably do not need an MRI unless there are any red flag features. Red flags may include description of neurological deficits (e.g., aphasia, hemiparesis, dysarthria, etc) or headaches that are new or different from normal, severe, or sustained. Vertebral artery dissection should always be considered in patients with dizziness and acute head/neck pain. Patients with a spontaneous EVS who do not clearly have VM or MD should be risk stratified by ABCD2 score for TIA [103]. Those with spontaneous EVS and ABCD2 score equal to or less than 3, and a history that is typical for VM or MD probably do not need an MRI unless there are any red flags. Meanwhile those with a score above 3 usually warrant MRI with vascular imaging (CT or MR angiography of the head and neck), although normal neuroimaging still cannot exclude TIAs. While it is traditionally thought that a room-spinning vertigo cannot be cardiac, this has proven to be a misconception [104]. Therefore, in patients who present to clinic with a spontaneous EVS, have multiple vascular risk factors, do not clearly fit neatly into either VM or MD, and have a normal MRI study, we recommend considering a more thorough cardiac and stroke workup, which may include continuous heart monitoring, structural heart assessment (i.e. echocardiogram), vascular imaging, and blood work. If the AVS is preceded by head trauma (especially when hearing loss is present), a CT brain and temporal bones and/or CT angiogram should be considered to look for skull fractures or a vertebral artery dissection, respectively.

Recently, the Academy of Emergency Medicine published the GRACE-3 guidelines for the management of acute dizziness and vertigo in the ED [105]. These guidelines cover the dizzy patient who presents within 2 weeks of symptom onset, regardless of whether symptoms are consistent with AVS or EVS. Because this article is more directed at the outpatient provider, we would like to briefly touch on when to suspect stroke or TIA when patients present to clinic >2 weeks after symptom onset.

Importantly, the outpatient clinician should be aware that for acutely dizzy patients, MRI is estimated to miss 15–20% of acute posterior fossa ischemic strokes up to 48 ​h after symptom onset [106]. Therefore, if suspicion for a stroke is high and an MRI brain was performed <48 ​h after symptom onset, a repeat MRI should be considered. As a result of this lack of sensitivity of MRI early on, the HINTS examination was first described in 2009, where a 3-step bedside test was found to have higher sensitivity early on in patients with the AVS. For a peripheral vestibular disorder (i.e., vestibular neuritis) to be diagnosed, the following findings must be present: an abnormal (ipsilesional) head impulse test, unidirectional (contralesional) horizontal or horizontal-torsional nystagmus, and a negative test of skew [107]. Any other pattern must be considered central until proven otherwise. A few years later, HINTS was addended to include a test of hearing, now known as HINTS plus [108,109]. Because the labyrinthine artery is a branch of the anterior inferior cerebellar artery (AICA), an AICA stroke can present with unilateral hearing loss. Thus, if a patient presents with a peripheral HINTS exam and hearing loss (with normal otoscopy), this is suggestive of an AICA or labyrinthine artery stroke, and a cerebrovascular event should be assumed. For the clinician seeing these patients weeks to months later, if a patient has had no loss of hearing and a clearly documented HINTS exam that is consistent with a peripheral lesion, and a patient is recovering as expected, then no MRI is indicated. The diagnostic criteria for vestibular neuritis includes an acute onset of vertigo lasting at least 24 ​h, a peripheral HINTS examination, an absence of otologic or neurologic symptoms, and it is not better accounted for by another condition. Patients will slowly improve over time, however that time varies quite a bit and can occur over days to months [110]. If there are any atypical historical features (e.g., focal neurological deficits) or examination findings, a contrast-enhanced MRI with internal auditory canal protocol is indicated, which evaluates for central and peripheral structural lesions such as a vestibular schwannoma.

Conclusion

Migraine has long-been known to mimic other disorders such as stroke, and often the term “complex migraine” has been utilized in migraines with associated neurological deficits such as hemiplegia or aphasia [111]. Analogously, as the criteria for VM has emerged, it is clear this disease may mimic a variety of other vestibular disorders. VM may also coexist with these disorders. A detailed history elucidating classic migraine triggers or associations, and a detailed physical examination to rule out mimics almost always leads to the proper diagnosis. Many effective treatment modalities exist, and when the diagnosis remains uncertain or VM coexists with another vestibular disorder, there are many overlap treatment strategies that can be utilized. However, just as how atypical headache histories warrant neuroimaging, an atypical VM history or abnormal ocular motor or neurologic examination findings warrants neuroimaging to exclude structural lesions [112].

Author contributions

Wrote most of the article, Edited the article: NEFH, DRG.

Declaration of competing interest

The authors have no declarations of interest to disclose.