Peripheral Vertigo
Vertigo is defined as a movement hallucination that is a symptom of an internal condition playing out through the misfiring of balance input [1]. Simply put, vertigo is a false sense of rotational movement. It is brought about by the misfiring or malfunctioning of signals coming from the inner ear, brainstem, cerebellum, and spinal cord being sent to the brain to help maintain postural control and balance. Postural balance (Figure 1) is maintained by the coordination of the peripheral sensory organs which are the eyes, muscles and joints, and two sides of the vestibular system [6].

Therefore, if the input coming from the inner ear, brainstem, cerebellum and spinal cord are inaccurate, then the body perceives things that are not true. This incorrect firing and misinterpretation of signals prominently displays the statement that “we do not see with our eyes or hear with our ears, but with our brain as it is capable of altering any signal that it receives for better or for worse” [3].
Figure 1.JPG
Figure 1: Integration of Sensory Input

There are different categories of vertigo classified as central and peripheral vertigo. They differ based upon the cause of the vertigo symptoms. Peripheral vertigo arises due to a malfunctioning of the vestibular organs of the inner ear, while central vertigo develops due brain or sensory nervous pathway disturbances. For clarity sake, this paper is going to focus on peripheral vertigo and the effect that the vestibular organs play in peripheral vertigo.


In a properly functioning ear, sensory input will send information to the brain about one’s movement. The vestibular organs will then help to rationalize, in a sense, the information that was provided to make sure that the information was accurate. They can be deemed as the double-checkers of postural balance. The problem with peripheral vertigo is that it affects the vestibular organs. Therefore, the vestibular organs are no longer able to accurately double-check the firing coming to the brain from the eyes, muscles and joints. Malfunctioning vestibular organs may themselves also send inaccurate signals, thus contributing or causing symptoms of peripheral vertigo to arise.

Anatomical of the Ear:
The ear is anatomically divided into three anatomical sections: the external, middle, and inner ear (Figure 2). The external ear is comprised of the auricle, which is the cartilage surrounding the external auditory canal that helps to funnel sound from outside into our ear [4]. The external ear terminates at the tympanic membrane. The intermediate ear portion is comprised of the eardrum, tympanic cavity, and malleus, incus, and stapes bones. It ranges from the tympanic membrane to the oval window. The final section of the ear is the inner ear which houses the cochlea, bony and membranous labyrinths. The cochlea allows for one to hear through the use of cells that translate vibration into impulses that are sent to the brain. The bony labyrinth stems from the temporal bone and provides structural support and protection to the inner ear. It encases the vestibule, the semicircular canals, and the cochlea. The membranous labyrinth is found within the bony labyrinth and is the location of the vestibule, semicircular canal, and cochlea fluid that provides for excitation or inhibition to occur. The signals sent from the vestibule and semicircular canal comprise the vestibular system.
Figure 2.JPG
Figure 2: Anatomy of External, Intermediate, and Inner Ear


Input Pathway of the Inner Ear:
The input pathway of the inner ear relies on the vestibular organs to provide information about the linear and angular acceleration of the head. The vestibular organs are the vestibule, which is comprised of the utricle and saccule, and three semicircular canals (Figure 3).
Figure 3.JPG
Figure 3: Inner Ear Displaying SCC and Otolithic Organs Influence by Endolymph


The vestibule, found within the membranous labyrinth, allows for detection of linear motion through the utricle and saccule organs. These two organs sit perpendicular to eachother so that the utricle is able to detect horizontal acceleration, while the saccule detects vertical acceleration. These two otolithic organs sense direction due to the linear movement through the movement of their macula. The macula of the utricle and saccule contains the hair cells, otolitihic membrane, and otocnoia. The hair cells are comprised of stereocilia, which are hair cells that sense and respond to fluid motion, and kinocilium, which is the tallest sterocilia in the macula. The hair cells are found within the otolitichic membrane, which is a gelatinous layer. On top of the otolithic membrane are otoconia which are ear stones or rocks comprised of calcium-carbonate protein granules. When linear acceleration occurs, the ear stones move due to gravities influence on their positioning and sends a signal through the utricle or saccular nerve.

While the vestibule measures linear acceleration, the semicircular canals measure angular acceleration. They are composed of the anterior, posterior and horizontal canal. The anterior and posterior canal are positioned about 90 degrees from each other, while the horizontal canal is positioned about 45 degrees between them so that they can cummulatively provide input on the pitch, yaw, and roll of the head’s motion [2]. The right and left horizontal canals work together to provide angular acceleration information while the right and left anterior and posterior canals work synchronously with the opposite ear’s canals due to their parallel positioning. Therefore, the right posterior canal works with the left anterior canal and vice versa. These canals are rapidly adapting so that they are able to sense immediate motion, but their rapidly adapting state causes them to return to a tonic rate of firing if the motion is prolonged. The canals are able to provide input on the head’s angular acceleration because of the endolymph found within the canals. Endolymph is viscous fluid that is high in K+ and low in Ca2+ that flows within the ear canal over the hair cell bundles which are found on the crista within the canal. On the crista, there are hair cell bundling’s that are all oriented in a uniform direction with the tallest hair called the kinocilium located on the same edge of each hair bundling. The hair cells are found within a gelatinous cupula.
When angular acceleration occurs, the endolymph will lag for a second due to inertia, and then will flow in the opposite direction of the angular acceleration.

Depending on the positioning of the kinocilium, the endolymph will either pull the kinocilium away or push the kinocilium toward the other hairs. If the kinocilium is pushed away from the other hairs, it will allow for depolarization of the semicircular canal to occur. This means that the tip length will open the mechanoreceptors, K+ will flow intracellular and will open voltage gated Ca2+ channels. This will allow for Ca2+ to flood into the cell and release an excitatory input about the angular rotation of the head. The semicircular canal will become hyperpolarized if the endolymph causes the kinocilium to cover the hair cell bundles and thus block the mechanoreceptors and the K+ leakage channels sending an inhibitory input about the angular acceleration.

Output Pathway from the Inner Ear:
After a linear or angular acceleration occurs and is sensed by the vestibular organs, the information is then relayed to the brain and body in order to adjust for the motion. The descending output begins to travels together, but then ultimately diverges paths in order to innervate the intended location.


The 1st order vestibular afferent neuron is comprised of the inferior and superior vestibular nerve. The inferior nerve contains information from the posterior semicircular canal and the saccule, while the superior vestibular nerve carries information about the anterior semicircular canal, the horizontal semicircular canal, the utricle and saccule. The come together to form Scarpa’s Ganglion. The afferent nerves will join with the cochlear nerve to comprise the vestibulocochlear nerve (CN VIII). CN VIII will travel to the pontomedullary junction, which is located between the caudal pons and raustral medulla oblongata [2].

After synapsing with the 1st order vestibular afferents, the 2nd order vestibular nuclei diverges into four different nuclei branches. They are the lateral, medial, inferior, and superior vestibular nuclei. These vestibular nuclei provide input to help maintain body position, postural control, eye movement, and conscious perception of movement.


Body position is controlled by the lateral and medial vestibular nuclei (Figure 4) which travel through the lateral and medial vestibulospinal tract. The lateral vestibulospinal tract descends from the lateral nucleus through the inferior nucleus traveling ipsilateral down the length of the spinal cord to help with trunk and lumbar control, as well as extensor muscles. The medial vestibulospinal tract begins in the medial vestibular nucleus and travels bilaterally down the cervical spinal cord in order to innervate the neck and shoulder muscles [2].
figure 4.JPG
Figure 4: Medial and Lateral Vestibulospinal Tract

Postural control is coordinated by the medial and inferior vestibular nuclei through the vestibulo-cerebellar connections (Figure 5). These neurons arise through the inferior cerebellar peduncle to ultimately get to the cerebellum where they will terminate in the flocculonodular node [2].
figure 5.JPG
Figure 5: Vestibulo-Cerebellar Connections


Eye movement is regulated by the medial and superior vestibular nuclei which will send neurons to the occulomotor nuclei, as well as the abducens and trochlear nuclei [2]. Together they will help to coordinate eye movement through the vestibular ocular reflex (Figure 6).
Figure 6.JPG
Figure 6: Vestibular Ocular Reflex

Conscious perception occurs due to the superior vestibular nuclei’s bilateral ascension to the thalamus in order to innervate the lateral lemniscus or the reticular formation (Figure 7). This conscious perception control depends primarily on the vestibular system [2]. Detailing regarding the exact pathway of the superior vestibular nuclei’s 2nd order neurons is controversial as many have differencing opinions due to a lack of clarity of the location that it ultimately innervates.
figure 7.JPG
Figure 7: Possible Pathway to Vestibular Cortex


Peripheral Vertigo:
Peripheral vertigo is caused by a disturbance in the balance organs of the inner ear, also known as the vestibular system. Another form of vertigo is central vertigo which is due to a disturbance to parts of the brain that deal with the interaction between the sense of vision, balance, or sensory messages to and from the thalamus [3]. Although central vertigo displays itself in similar ways as peripheral vertigo, it’s symptoms arise due to migraines, strokes, transient ischemic attack, cerebellar brain tumors, acoustic neuroma, and multiple sclerosis [3]. Peripheral vertigo symptoms may arise due various factors, but the three most common causes of peripheral vertigo are Benign Paroxysmal Positional Vertigo (BPPV), Meniere’s Disease, and Vestibular Neuronitis and Labyrinthitis.

Causes
Benign Paroxysmal Positional Vertigo (BPPV) is the most common cause of vertigo, affecting about 2.4% of people over their life time, most commonly in one’s late adult years [6]. BPPV gives the false feeling of spinning or movement due to a disturbance to the otolith particles found within the utricle. The utricle has a gelatinous layer covering its hair cells that has calcium carbonate crystals onto of the gel. In BPPV, the calcium carbonate crystals become unattached from the gel and relocate to one or more of the semicircular canals. When enough of the crystals build up in the semicircular canals they hinder the endolymph from flowing properly. This hinders the semicircular canals from sending accurate signals about head rotation (Figure 8). Symptoms are normally felt for short durations that on set due to specific head positions or movements.
Figure 8.jpg
Figure 8: BPPV conditions of the relocation of otoconia

Meniere’s Disease is an inner ear disorder caused by the buildup of fluid and changing pressure in the inner ear, as seen in Figure 9 [3]. This disease plays out through symptoms of vertigo, ringing in the ears called tinnitus, and hearing loss in most cases in only one ear. The cause of Meniere’s disease is not fully known, but it is believed that contributors could be improper fluid drainage, an abnormal immune response, allergies, viral infection, genetic predisposition, head trauma, or migraines that cause the pressure within the ear to fluctuate [5]. Symptoms normally last anywhere from twenty minutes to up to four hours and typically affects men and women between the ages of 20 to 50 years old [5].
Figure 9.jpg
Figure 9: Effects of Meniere’s Disease


Vestibular Neuritis and Labyrinthitis is the inflammation of the nerves connecting the inner ear to the brain and the inner ear labyrinth [6]. This viral infection interrupts the transmission of sensory information to the brain and thus vertigo, dizziness, and trouble seeing, hearing, and maintaining one’s balance. The vestibular neuritis becomes inflamed when the vestibular ganglion becomes infected (Figure 10). This affects one’s balance, without causing hearing loss. The labyrinth becomes inflamed when the vestibule-cochlear nerve is infected, resulting in changes of hearing, dizziness, and vertigo while [6]. Symptoms of vestibular neuritis and labyrinthitis can be acute, setting on quickly, or can be chronic and long lasting due to the damage to the vestibular nerve.
Figure 10.jpg
Figure 10: Effects of Vestibular Neuritis and Labyrinthitis


Diagnosis
Although these three different symptoms of peripheral vertigo are different, doctors are able to diagnosis them for the most part through similar qualitative and quantitative examinations and tests. They are able to gain insight about the type and cause of vertigo through information about the patient’s symptoms, duration, severity, triggers, and possible compensations to decrease vertigo sensations. Information regarding symptoms of hearing loss, tinnitus, nausea, vomiting or feeling of fullness in ear also help to doctors to decipher the root cause of vertigo. Doctors are also able to explore a patient’s medication use, family history of migraines or Meniere’s disease, and recent ear infections or head injuries to gain insight to causes of symptoms and type of vertigo one is suffering from [3]. They can also gain more clarity by examining one’s inner ear, performing maneuver tests, or through MRI or CT scans.
Figure 11.jpg
Figure 11: Diagnosis Steps of Vertigo


The most common maneuver test is the Dix-Hallpike maneuver. A doctor can chose to perform this maneuver if they believe that a patient has BPPV. In this test, the doctor will have the patient sit on the examining table, holding the patient’s head at a 45-degree angle. The doctor will then quickly reposition the patient into the horizontal lying down position, allowing their head to go off the edge of the table and end 30 degrees below the horizontal position of the patient’s body. Throughout the maneuver, the doctor will be analyzing the patient’s eye movement to see if the inner ear fluid continues to produce stimulation to the eyes after the head motion has ceased. This would convey that there is a buildup of otoconia within the semicircular canals causing the delay of motion sense.


https://www.youtube.com/watch?v=RNBJLed_Slc

Treatment
Once one is diagnosed with peripheral vertigo, depending on the cause, there are numerous options that one is able to take to decrease symptoms. There is no guaranteed cure for peripheral vertigo, but doctors are able to control almost all vertigo cases through pharmaceutical options, maneuver treatments, or surgery.

Pharmaceutical Options
The most common pharmaceutical options used to treat peripheral vertigo are vestibular suppressant and antimetic drugs. The medications prescribed are most commonly antibiotics to treat infections, antihistamines to decrease inflammation, and benzodiazepines to decrease physical symptoms of vertigo such as anxiety and nausea [1]. These medications are most commonly used to help decrease symptoms of vertigo due to Meniere’s Disease and Vestibular Neuritis and Labyrinthitis. After beginning medication, recovery usually takes about three to four weeks to be symptom free. After symptoms cease, it is unlikely that one will suffer from vestibular Neuritis and Labyrinthitis vertigo again [1].

Maneuver Treatment
BPPV is treated mechanically through Canalith Repositioning Maneuvers that utilize gravity to help reposition the otoconia back in the utricle [1]. This maneuver treatment allows patients to be about 90% vertigo symptom free after one to three treatments. After one has BPPV, the likelihood of symptoms reoccurring is about 50% within the following five years [1].


Surgery
In the rare case that vertigo symptoms do not improve, surgery is the final option that is only utilized by a minority of patients who suffer from Meniere’s Disease. There are three surgery procedures that are available to patients to relieve vertigo symptoms. Doctors are able to perform an endolymphatic sac shunt which will decrease the feeling of ear fullness, a selective vestibular neurectomy which entails the surgeon cutting the vestibular nerve in order to prevent misfiring to the brain, and a labryrinthectomy which entails destroying the inner ear of one side. These surgeries are only used in extreme cases and have a high risk of damaging one’s hearing function [4].


Vertigo Prevention:
Although vertigo is common, there are numerous ways that individuals can help prevent vertigo symptoms from occurring or progressing. One is able to maintain a strong immune system by living a healthy and active life style. This will help to strengthen their immune system and reduce susceptibility to inflammation in the ears. The consumption of anti-inflammatory foods and plenty of fluids also helps to decrease one’s susceptibility to vertigo as inflammation and dehydration can cause one to feel dizzy or increase one’s blood pressure. Striving to decrease stress, excess salt ingestion, caffeine, smoking and alcohol, as well as get plenty of sleep, can also decrease one’s likelihood of developing symptoms of vertigo. A deficiency of vitamin B12, lower blood pressure, anemic symptoms, heart complications, and anxiety can increase one’s likelihood of dizziness, which may lead to vertigo. If one has suffered from BPPV or other vestibular imbalances, there is vestibular rehabilitation therapy (VRT) that one is able to attend to help prevent symptoms from reoccurring. These exercises focus on head rotation exercises that utilize gravity to help to prevent otonica from resettling in one’s semicircular canal.


https://www.youtube.com/watch?v=iP-UYhAk6tA

If one feels dizzy for an abnormal duration of time or is suffering from other symptoms of vertigo, they are advised to see a doctor immediately. Peripheral vertigo is a manageable symptom that one should not be afraid of, but it is important that one takes proper care of their body and acts appropriately when symptoms arise.

Glossary of Terms:
  • Benign Paroxysmal Positional Vertigo (BPPV)- Recurrent vertigo and nystagmus occurring when the head is placed in certain positions
  • Central vertigo- disorder due to the central nervous system
  • Endolymph- the fluid contained within the membranous labyrinth; resembles intracellular fluid in composition
  • Labyrinthitis- inflammation of the inner ear that is often a complication of otitis media. It is caused by the spread of bacterial or viral infections from the head or respiratory tract into the inner ear.
  • Meinere’s Disease- condition characterized by recurrent vertigo, hearing loss, and tinnitus
  • Otoliths- crystalline particles of calcium carbonate and a protein adhering to the gelatinous membrane of the maculae of the utricle and saccule
  • Peripheral vertigo- vertigo due to disturbances of the vestibular centers
  • Vertigo- sensation of rotation or movement of one’s self or surroundings in any plane
  • Vestibular Neuritis- condition marked by vertigo, nausea and vomiting, and gait disturbance of relatively acute onset, usually caused by the inflammatory processes within the bony labyrinth of the ear.
  • Vestibular organs- consists of the bony labyrinth containing a membranous labyrinth of the inner ear. The vestibular organ consists of the membranous saccule, utricle, and semicircular canals.

Suggested Readings:
  • Brandt-Daroff exercises to help improve BPPV and labyrinthitis vertigo symptoms
http://www.webmd.com/brain/brandt-daroff-exercise-for-vertigo-16844
  • Discussion about the causes and physiological differences between central and peripheral vertigo
https://www.ncbi.nlm.nih.gov/pubmed/9674515
  • Oschner Journal article about vertigo and the disorders that causes it
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3096243/
http://homeremedyshop.com/11-easy-home-remedies-for-the-treatment-of-vertigo/

Quiz:
1. What does BPPV stand for?
a. Body Positioning Paroxysmal Vertigo
b. Benign Paroxysmal Positional Vertigo
c. Benign Positioning for People Vertigo
d. Body Part Positional Vertigo
2. Which Vestibular Nuclei is responsible for the Vestibulo-Cerebellar Connections?
a. Superior
b. Inferior
c. Medial
d. Lateral
e. A&B
f. B&C
g. C&D
3. The Canalith Repositioning Maneuver is used to help alleviate which type of vertigo?
a. BPPV
b. Meniere’s Disease
c. Vestibular Neuritis
d. Labyrinthitis
4. The outer ear becomes the middle ear at what junction?
a. Oval window
b. Eardrum
c. Tympanic membrane
d. Semicircular Canals
5. Otoconia are ear stones or rocks found in the utricle and saccule comprised of what granule?
a. carbon-carbonate
b. sodium-carbonate
c. potassium-carbonate
d. calcium-carbonate
True/False:
1. Vertigo is a disease that arises from only three causes
2. The most common way to alleviate vertigo is through a surgical procedure
3. The kinocilium is the tallest hair in the ear
4. Endolymph is vicious fluid, high in Ca+
Short Answer:
1. What is the difference between central and peripheral vertigo?
2. How might the integration of vestibular, visual and proprioceptive information allow for one to compensate vertigo symptoms in order to remain balanced?
3. Compare and contrast the three main causes of peripheral vertigo symptoms.

Text References:
[1] Dispenza, Francesco, and Alessandro De Stefano. Textbook of Vertigo: Diagnosis and Management. New Delhi: Jaypee Brothers Medical, 2014. Print.
[2] Gray, Lincoln, Ph.D. "Vestibular System: Pathways and Reflexes." Vestibular System: Pathways and Reflexes (Section 2, Chapter 11) Neuroscience Online: An Electronic Textbook for the Neurosciences | Department of Neurobiology and Anatomy - The University of Texas Medical School at Houston. Neuroscience Online, n.d. Web. 24 Nov. 2016. <http://neuroscience.uth.tmc.edu/s2/chapter11.html>.
[3] MacGill, Markus. "Vertigo: Causes, Symptoms, and Treatment." Medical News Today. MediLexicon International, 8 Apr. 2016. Web. 22 Nov. 2016. <http://www.medicalnewstoday.com/knowledge/160900/vertigo-causes-symptoms-treatments>.
[4] Ratini, Melinda, DO, MS. "Vertigo: Causes, Symptoms, and Treatment." WebMD. WebMD, 23 Dec. 2014. Web. 22 Nov. 2016. <http://www.webmd.com/brain/vertigo-symptoms-causes-treatment#1>.
[5] Taylor, Danette C., DO, MS, FACN. "Vertigo Symptoms, Treatment, Causes - What Causes Vertigo? - MedicineNet." Vertigo. MedicineNet, 7 Oct. 2016. Web. 24 Nov. 2016. <http://www.medicinenet.com/vertigo_overview/page2.htm>.
[6] Vestibular Disorders Association. "The Human Balance System." Vestibular Disorders Association. VEDA, 05 May 2016. Web. 24 Nov. 2016. <http://vestibular.org/understanding-vestibular-disorder/human-balance-system>.

Image References:
[Figure 1] Vestibular Disorders Association. "The Human Balance System." Vestibular Disorders Association. VEDA, 05 May 2016. Web. 24 Nov. 2016. <http://vestibular.org/understanding-vestibular-disorder/human-balance-system>.
[Figure 2] "The Anatomy of the Human Ear (Outer Ear)." Health Life Media. Health Life Media Team, 25 June 2016. Web. 28 Nov. 2016. <http://healthlifemedia.com/healthy/the-anatomy-of-the-human-ear-outer-ear/>.
[Figure 3] Hawkins, Joseph E. "Human Ear - Inner Ear." Encyclopedia Britannica Online. Encyclopedia Britannica, 18 Dec. 2015. Web. 28 Nov. 2016. <https://www.britannica.com/science/ear/Inner-ear#ref531798>.
[Figure 4] "The Spinal Cord (Organization of the Central Nervous System) Part 4." Whatwhenhow RSS. The-Crankshaft Publishing, n.d. Web. 29 Nov. 2016. <http://what-when-how.com/neuroscience/the-spinal-cord-organization-of-the-central-nervous-system-part-4/>.
[Figure 5] Gray, Lincoln, Ph.D. "Vestibular System: Pathways and Reflexes." Vestibular System: Pathways and Reflexes (Section 2, Chapter 11) Neuroscience Online: An Electronic Textbook for the Neurosciences | Department of Neurobiology and Anatomy - The University of Texas Medical School at Houston. Neuroscience Online, n.d. Web. 24 Nov. 2016. <http://neuroscience.uth.tmc.edu/s2/chapter11.html>.
[Figure 6] OpenStax. "Anatomy and Physiology." 16.3 The Cranial Nerve. OpenStax, 06 Mar. 2013. Web. 29 Nov. 2016. <https://opentextbc.ca/anatomyandphysiology/chapter/16-3-the-cranial-nerve-exam/>.
[Figure 7] Gray, Lincoln, Ph.D. "Vestibular System: Pathways and Reflexes." Vestibular System: Pathways and Reflexes (Section 2, Chapter 11) Neuroscience Online: An Electronic Textbook for the Neurosciences | Department of Neurobiology and Anatomy - The University of Texas Medical School at Houston. Neuroscience Online, n.d. Web. 24 Nov. 2016. <http://neuroscience.uth.tmc.edu/s2/chapter11.html>.
[Figure 8] Vestibular Disorders Association. "The Human Balance System." Vestibular Disorders Association. VEDA, 05 May 2016. Web. 24 Nov. 2016. <http://vestibular.org/understanding-vestibular-disorder/human-balance-system>.
[Figure 9] Publications, Harvard Health. "Meniere's Disease - Harvard Health." Harvard Health. Brooks Digital, n.d. Web. 29 Nov. 2016. <http://www.health.harvard.edu/diseases-and-conditions/menieres-disease->.
[Figure 10] "Labyrinthitis and Vestibular Neuritis." Summit Medical Group. Relay Health, 2014. Web. 29 Nov. 2016. <http://www.summitmedicalgroup.com/library/adult_health/aha_vestibular_neuritis_and_labyrinthitis/>.
[Figure 11] Labuguen, Ronald H., M.D. "Initial Evaluation of Vertigo." American Family Physician. University of Southern California, 15 Jan. 2006. Web. 29 Nov. 2016. <http://www.aafp.org/afp/2006/0115/p244.html>.

Answer Key: B,F,A,C,D False, False, True, False