Attention should be paid to differentiating benign paroxysmal positional vertigo from vestibular migraine

Benign paroxysmal positional vertigo (BPPV) and vestibular migraine (VM) are different independent diseases with completely different treatment methods and the choice of treatment modality affects efficacy and prognosis
.
The former is peripheral vestibular disease, most patients present to otolaryngology, and the latter is a central vestibular disease, and most patients visit neurology
.
The two diseases have a high incidence, intersection of comorbidities and symptoms, spanning the two specialties of otolaryngology and neurology, and there is still a problem of low diagnosis rate in primary hospitals, and the key is the difficulty
of differential diagnosis of atypical patients 。 A retrospective study by the Multidisciplinary Center for Vertigo and Balance Disorders at the University of Zurich found that the proportion of 951 patients referred from the primary level was 25.
1% (< 65 years old), 37.
6% (≥ 65 years), and 20.
2% of patients with VM.
The diagnosis rate of primary doctors was 12.
7% (< 65 years old), 20.
7% (≥ 65 years old), and VM accounted for 1.
8%, the latter disease diagnosis rate was obviously low, suggesting that primary doctors have limited professional knowledge and diagnostic ability for BPPV and VM, and should
be popularized and strengthened.
VM is characterized by a diversity of clinical manifestations and signs, some patients with migraine are not synchronized with vestibular symptoms, and about 30% of patients with VM will have isolated episodic vertigo/dizziness and nystagmus, which is easily confused
with some atypical BPPV.
Patients with intractable BPPV who are clinically ineffective with some repeated repositioning therapy are eventually found to be VMs, so it is emphasized in the domestic and external diagnosis and treatment standards that the two need to be carefully distinguished
.
In recent years, the research in the field of vestibular science at home and abroad has made rapid progress, and only by fully grasping the constantly updated knowledge points can we correctly understand and implement the new diagnostic criteria and new practice guidelines for related diseases, so it is necessary to accurately distinguish
BPPV and VM in multiple dimensional planes.

Starting from symptomatology, we found similarities and differences

Previous habitual thinking believed that vertigo was a feature of peripheral vestibular disease, and dizziness was mostly associated with central or psychogenic diseases, guiding patients with vestibular disease to receive and refer patients with vestibular disease between otolaryngology and neurology
.
In the past, dizziness was defined as human disorientation dysfunction, vertigo was defined as the patient's own or external environment spinning sensation, dizziness is a general term for vertigo, presyncope, light headedness and balance disorder (disequilibrium), dizziness includes vertigo
。 In the international classification of vestibular symptoms issued by the Barany Association, the complex symptoms of balance system dysfunction are divided into four categories
: dizziness, vertigo, vestibule-visual symptoms and postural symptoms 。 Dizziness is defined as a feeling of impaired spatial orientation or dysfunction, an illusion of absence of movement; Vertigo is defined as an illusion of movement, the feeling of feeling one's own movement when there is no one's own movement, including rotation or non-rotation; Dizziness and vertigo are no longer subordinate but allele symptoms, and patients may develop both dizziness and vertigo during the course of the disease, each containing both induced and spontaneous and two subcategories
.
This suggests that when a patient has a change in position induced dizziness, it may be VM or BPPV, and in the 2015 version of the BPPV diagnostic criteria, patients may not only experience dizziness but also dizziness, and patients with BPPV with positional dizziness should be avoided
.

When some patients with BPPV and VM have similar clinical manifestations, which makes differential diagnosis difficult, the diversity of VM clinical manifestations is the key to
differentiation.
The vestibular symptoms of BPPV are single, and its characteristic dizziness/vertigo refers to transient dizziness/vertigo
induced by head movement to a new fixed position.
The diversity of vestibular symptoms in VM includes: (1) spontaneous dizziness/vertigo, including internal vertigo (self-motor illusion) and external vertigo (a sense of rotation or floatation of the surrounding environment); (2) positional-induced dizziness/vertigo; (3) Vision-induced dizziness/vertigo, induced by complex or large motor visual stimuli; (4) Dizziness/vertigo induced by head activity, which occurs during head activity, and the patient has head movement intolerance; (5) Head activity induces dizziness accompanied by nausea, which is characterized by feeling that spatial orientation is impaired
.
It can be seen that VM vestibular symptoms not only have dizziness but also vertigo, not only spontaneous symptoms but also predisposing symptoms; In addition to vestibular symptoms, typical VM must also have migraine or visual aura symptoms, but sometimes the relationship between dizziness/vertigo attacks and migraine attacks is not fixed, dizziness / vertigo can occur before, can also appear during or after migraine attacks, about 30% of patients vertigo attacks and headache or aura manifestations do not appear at the same time, so patients with vertigo symptoms caused by head movement and temporary lack of migraine and aura symptoms are not the same as the spontaneous remission in the 2015 version of the BPPV diagnostic criteria, Possible subtypes of BPPV are more likely to be confused
.

In the Barany Society's overview of the International Classification of Vestibular Disorders (ICVD), BPPV and VM are both episodic vestibular syndromes (EVS).

EVS is defined as a group of syndromes
characterized by transient episodes of vertigo/dizziness and unsteady standing.
It is characterized by provoked or spontaneous multiple, recurrent attacks lasting seconds to hours, occasionally days
.
VM and BPPV are both EVS, indicating that their clinical features have some commonalities, which are easy to misdiagnose in atypical states and need to be carefully screened
.
The main points of differentiation are: (1) time of
onset.
The duration of BPPV episodes is calculated in seconds and minutes; VMs vary greatly from 5 minutes to 72 h, of which about 30% last a few minutes, about 30% have seizures for a few hours, about 30% can have seizures for a few days, and the remaining 10% last only a few seconds
.
(2) Frequency of
seizures.
Studies have shown that the frequency of VM vertigo attacks is significantly higher than BPPV, the former is measured in daily scales, the latter is measured in weeks, and VM seizures are more frequent, especially in the case of repeated recurrence of probable BPPV that requires repeated reduction treatment, and even patients with poor response to repeated reduction treatment for a single episode need to consider excluding VM.

Master the characteristics of nystagmus and seek accurate identification

Nystagmus is an important sign of vestibular disease and a key indicator of
the differential diagnosis of related diseases.
The 2019 Barany Association ICVD defines nystagmus as an involuntary, fast-rhythmic eye oscillation movement with at least 1 slow phase
in the Nystagmus Examination and Classification 。 It divides nystagmus into physiologic nystagmus and pathologic nystagmus, the latter including spontaneous nystagmus, gaze-evoked nystagmus, and triggered nystagmus
。 Triggered nystagmus includes benign paroxysmal positional nystagmus (BPPN) and central positional nystagmus (CPN), and related diseases are localized peripheral and central
, respectively.
BPPV is a specific nystagmus induced by head movement to a new position, associated with a specific semicircular canal plane, with short onset time, latency, fatigue, angular acceleration movement correlation, and is characteristic of
peripheral vestibular disease nystagmus.
The nystagmus of VM is CPN, which is characterized by diversity, variability, and is not characterized by fixed semicircular canals, and is characteristic of
nystagmus in central vestibular disease.
The detection of nystagmus with different characteristics is an important basis for differentiating BPPV and VM, but the nystagmus examination in clinical work will be limited by the experience and equipment of the examiner, so correct clinical diagnosis ideas are required to reduce deviations
.

The judgment of BPPV must meet the description of its diagnostic criteria, and the clinical diagnosis idea is: (1) There is a false negative in the induction process of BPPV, and the patient's head is moved to the semicircular canal to be measured at the beginning of the positional induction test in a vertical position and parallel
to the gravity line 。 During the inspection, keep the head rotating on the plane where the semicircular canal to be measured can record the maximum intensity of BPPV, which is helpful to identify the side and responsibility of BPPV; (2) In the BPPV position induction test of the posterior semicircular canal, the patient had a twisted jumping nystagmus in the overhanging position, and the direction of the nystagmus was reversed when returning to the seat, that is, the twisted jumping nystagmus, if the nystagmus is not reversed, it may be VM; (3) BPPV does not appear spontaneous nystagmus, and BPPV of horizontal semicircular crest cap stones may produce nystagmus in the middle of the gaze eye position when looking directly, which is called pseudospontaneous nystagmus
.
Tilt the head forward 30°, the nystagmus will disappear, and when the head is tilted forward, the direction of the nystagmus will be reversed, which is essentially another form of triggered nystagmus; (4) In the horizontal semicircular canal BPPV position-induced test, the patient has horizontal directional positional nystagmus (DCPN), which assists in judging the side of the responsible semicircular canal according to the strength of the nystagmus, and judges the tube stone or crest stone
according to the direction of the nystagmus 。 If non-DCPN occurs in the diagnosis and treatment of BPPV, or the nystagmus changes from terrestrial to dorsal, it may be related to otolith ectopia, or it may indicate VM or light crest; (5) Anterior semicircular canal and most semicircular canal BPPV are rare, especially in the face of repeated reduction effect is not good, induced vertical nystagmus is recommended as refractory BPPV patients, need to exclude central diseases including VM, vestibular paroxysmal, congenital skull base malformation and fourth ventricle tumor.

Standardized diagnosis and treatment is the basis of differential diagnosis

The treatment of the disease is mainly aimed at its pathogenesis
.
VM is a central vestibular disease, but can be secondary to peripheral vestibular damage, so there is a variety of clinical manifestations and signs
.
Possible mechanisms of VM include: (1) vascular theory: pain stimulation through the trigeminal neurovascular reflex system can increase the vascular permeability of the inner ear, resulting in plasma protein exudation and affecting the function of the inner ear; (2) Cortical diffusion inhibition theory: cell depolarization affects the corresponding cortical region, and nerve cell dysfunction activates the trigeminal neurovascular reflex system; (3) Neural pathway theory: vestibular migraine is the intersection of vestibular pathway and pain pathway at different levels of the central nervous system; (4) Neurotransmitter theory: serotonin, norepinephrine, calcitonin, dopamine and gene-related peptides are involved in the activity of peripheral and central vestibular neurons, and may be involved in the pathogenesis of VM; (5) Ion channel theory: VM may be an ion channel disease, which is related to the gene defect of voltage gate calcium channel; (6) VM has an obvious family history, indicating that it may be related to genetic factors, but the causative gene is not clear
.
The treatment of VM includes patient management and drug treatment, rational selection of therapeutic drugs, which has become the key to the treatment and prevention of repeated dizziness/vertigo in VM, otolith reduction therapy is ineffective for positional vertigo and nystagmus in patients with VM, when there is a high clinical suspicion of BPPV repeated treatment is ineffective, or recurrent patients need to be carefully evaluated to exclude VM.

In the process of BPPV diagnosis and treatment, standardized diagnosis and treatment is very important
.
In the 2015 version of the BPPV diagnostic criteria and the 2017 version of the BPPV clinical practice guidelines, there is no breakthrough in the understanding of the pathogenesis of BPPV, the otolithith theory (including the theory of tube stones and the theory of crest stone disease) is still a generally accepted theory, the otolith detached from the cyst plaque falls into the semicircular canal or adheres to the ampullary crest of the semicircular canal, when the head moves in the plane of the affected semicircular canal, due to the change of the gravity direction of the otolith, the vestibular peripheral receptors are stimulated, and the excitatory vestibular signal is transmitted from the periphery to the center, Causes dizziness/vertigo and nystagmus
.
In specific position-evoked tests (Dix-hallpike or head roll test), dizziness/vertigo symptoms and nystagmus specific to the semicircular canal involved are key
to diagnosing BPPV 。 The main points of BPPV treatment include: (1) During BPPV reduction, keep the head to rotate at the plane of the semicircular canal to be measured, which not only induces positional nystagmus of maximum intensity, which is also the key to the success of manual reduction operation; (2) The treatment of BPPV needs to be standardized, that is, for typical BPPV, once the diagnosis is clear, manual reduction therapy can be carried out in time, and pure tone audiometry, vestibular function, and inner ear and cranial imaging examinations are not considered for the time being; (3) After manual reduction treatment, the patient's original positional vertigo/dizziness and nystagmus disappeared, which supported the diagnosis
of BPPV.

Clinical practice is carried out according to diagnostic and treatment guidelines

Since 2012, the Barany Association and the International Headache Society (IHS) have successively issued new diagnostic criteria for VM and BPPV, and in 2017, the BPPV clinical practice guidelines
have been revised.
In 2018, IHS published the International Classification of Headache Disorders (ICHD-3) with new revisions
to the diagnostic criteria and characteristics of VM.
In 2019, the English Edition of the Chinese Medical Journal issued the VM China Expert Consensus
.
In the above domestic and foreign consensus and diagnosis and treatment guidelines, it is emphasized that we should pay attention to the differential diagnosis
of BPPV and VM.

In the diagnosis and treatment of BPPV, the concept of atypical BPPV and subjective BPPV (SBPPV) is easily confused
with VM.
A controlled study of dizziness in patients with uninduced nystagmus and dizziness who could induce typical nystagmus found that the presence of atypical BPPV was no significant difference in
treatment from typical BPPV.
Haynes et al.
have proposed the concept of subjective BPPV, and they call patients with typical symptoms, BPPN negative, but good manual reduction effect SBPPV; Patients with typical symptoms, positive BPPN, and good manual reduction are called objective BPPV (OBPPV).

In the 2015 new diagnostic criteria for BPPV, the duration of onset < 1 minute and SBPPV excluding other vestibular disorders was defined as spontaneously remitting, probable BPPV
.
The pathogenesis of BPPV is the otolith theory, and the current examination methods can not directly show how otolith shedding causes vertigo and nystagmus, manual reduction treatment how to make otolith return to cause vertigo and nystagmus disappear, according to the characteristics and direction of inducing nystagmus in the position test, judge the responsibility semicircular canal for otolith shedding, so as to choose the correct reduction method
。 Nystagmus is an objective basis for diagnosis and treatment, and spontaneous remission, possible BPPV subtypes are missing this only objective indicator, which is easy to affect doctors' judgment, clinical diagnosis and treatment has risks and challenges, therefore, in the 2015 version of the BPPV standard notes and comments, especially emphasize this type of BPPV and VM screening, so as to avoid misdiagnosis and mistreatment
.

In the 2017 edition of the BPPV clinical practice guidelines, "observation therapy" was proposed, suggesting that some patients with acute BPPV can be given sufficient observation time before manual reduction therapy, and at the same time give popular science guidance to avoid position-inspired vertigo attacks and falls, especially for patients with severe cervical spondylosis, unstable heart disease, cerebrovascular disease and adverse reactions after the first otolith reduction, the basis for this plan is that BPPV is a benign self-limited disease, and 27% to 38% of patients can heal themselves This is different from the previous view that BPPV should be treated in time once it is diagnosed, but it is full of wisdom
.
At the same time, the guidelines suggest that BPPV patients should be re-examined after 1 week and 1 month after repositioning treatment, respectively, to revise the disease diagnosis to avoid other diseases such as VM being misdiagnosed as BPPV
.
The frequency of dizziness/vertigo episodes is different in patients with BPPV and VM, the former on a weekly scale and the latter on a daily basis, with VM episodes more frequent, repeated recurrence after otolith reduction therapy, or BPPV with suboptimal treatment response to repeated treatment that requires the exclusion of VM.

In the face of intractable BPPV, especially in patients with intractable BPPV who are ready for surgery, VM needs to be excluded
before surgery.
Leveque et al.
found that the significant decrease in the number of cases of refractory BPPV treated by surgery after 1990 is due to the recognition of the existence of horizontal semicircular canal and upper semicircular canal BPPV in the late 80s of the 20th century, and the mastery of their clinical characteristics and effective manual reduction methods that are different from posterior semicircular canal BPPV, so that those patients who are misdiagnosed as posterior semicircular BPPV due to the limitation of diagnosis and treatment level are not difficult to treat
。 Reflections and lessons learned in the clinical practice of BPPV are sometimes worth waiting and observing for self-limited diseases, especially benign diseases, when treatment options or potentially harmful patients are to avoid radical surgical treatment or destructive treatment
.

Currently, imaging tests in the diagnosis of BPPV and VM are used to rule out other diseases
.
Studies have found that some patients with VM have abnormal T1 and long T2 signals such as multiple spots in the center of the subcortical white matter and semi-oval center such as T1 and long T2 or high signal on FLAIR, which provides a relevant reference
for exploring the imaging markers of BPPV and VM differentiation.