Postural+Control+II


 * //Age-related Vestibular Problems//**


 * Introduction**

As people grow older they tend to have more trouble with balance, which often results in injuries caused by falling [1]. When examining the greater cause of this, one will see that balance is mainly dependent on three systems: the vestibular system, vision, and the musculo-skeletal system [1]; [2], [3]. The presence of multiple systems working together allows a person to still be able to balance when one system fails to function [2]. Although all three systems are of great importance, this page will focus mainly on the importance of the vestibular system. Some of the most common reasons for older people to experience difficulties with balance are because of vestibular disorders, such as Benign Paroxysmal Positional Vertigo (BPPV), Meniere’s disease, and Labyrinthitis/vestibular neuritis [1]; [4]. Loss of hair cells in the vestibular system can also cause a loss of balance [1].


 * Functional Anatomy**

Before exploring how these difficulties lead to weakening or loss of vestibular function, it is important to first review the anatomy of the vestibular system, which is located in the inner ear. The saccule is a part of the inner ear located just above the cochlea, which is necessary for hearing [8]. Inside the saccule there are small calcium carbonate crystals, called oticonia, which sit on top of a membrane [3]. Inside of this membrane there are hair cells, one being the tallest (kinocelium) and gradually decreasing in height (sterocilia). When the person moves, the membrane moves, causing the hair cells to tilt in one direction or the other. When the hair cells tilt toward the kinocelium, channels open up, causing an increase in the firing rate of afferent fibers [8]. In the same way, when the hair cells tilt away from the kinocelium, there is a decrease in the firing rate of the afferent fibers [5]. This is one way that the vestibular system knows how the head is tilted.

The utricle is a part of the inner ear located above the saccule and at the ends of three different canals. Each utricle contains a slight bump (ampula), which holds an egg-shaped structure called the crista. Inside of the crista there is a gel (cupula) that hair cells touch [8]. Like with the hair cells in the saccule, these hair cells move as the person moves, creating another way for the vestibular system to know the direction of head tilt.

As briefly mentioned before, above the utricle there are three semicircular canals: the anterior, the posterior, and the horizontal). Each canal contains bone, perilymph, a membranous labyrinth, endolymph, another membranous labyrinth, another perilymph, and bone again. The perilymph is a fluid with a high sodium concentration and a low potassium concentration, while the endolymph is a fluid with a low sodium concentration and a high potassium concentration [5]; [6]. The endolymph in each of these canals flows towards a utricle when the person moves.

Attached to the utricles is a vestibular nerve, and attached to the cochlea is the cochlear nerve. These nerves connect to form the vestibulocochlear nerve [8], which communicates with other parts of the body about what is happening in the vestibular system.


 * Pathways**

As previously stated, there are multiple systems that are involved in controlling balance, and in the same way there are multiple pathways through the body to allow these systems to function. Although this page mainly focuses on the vestibular system, there will still be explanations for how the vestibular system is connected to the muscles, eyes, cerebellum, and cortex as a way of highlighting its overall importance.

All of these pathways first connect to the vestibular-cochlear nerve. This nerve makes up the eighth cranial nerve, which comes from the brain stem to the inner ear between the cochlea and the vestibular system [5].

//Connections to the muscles//

The vestibular system first connects to the muscles through the vestibular nerve, which enters the brainstem at the ventrolateral portion of the pontomedulliary junction [5]. It then moves on to the lateral vestibular nucleus, which divides dorsally and ventrally. The dorsal portion becomes the lateral vestibulo-spinal tract, which helps to keep postural balance and helps the extensor muscles [5]; [8]. The ventral portion becomes the medial vestibulo-spinal tract, the vestibulo-ocular pathway, and the vestibulothalamic pathway [5], but for now we will focus on the medial vestibulo-spinal pathway, which helps with gaze stabilization by assisting with contracting neck muscle to resist passive movements in the head and shoulders [5]; [8]. Each of these pathways goes on to connect to flexors and extensors, the lateral vestibulo-spinal tract descending all the way down the spinal cord and the medial vestibulo-spinal tract descending bilaterally to the mid-thoracic cord [7]; [8].

//Connections to the eyes//

To reach the eye muscles, the vestibular system first connects to the vestibular nerve, then to the pons, where it synapses onto the medial longitudinal fasciuli [8]. From here it divides, with part of it going to the trochlear nucleus and part continuing on to the midbrain [8]. At the midbrain, it synapses onto the oculomotor nucleus which then connects to the eye muscles [5]; [7]; [8]. This pathway is used for eye and head movements [5] and for the vestibular ocular reflex (VOR). As people age, there is a decrease in the speed of VOR [1], which can help to explain some of the balance difficulties because this would suggest that older people have more trouble adjusting their eye muscles appropriately as they move.

//Connections to the cerebellum//

When connecting to the cerebellum, the vestibular system first connects to the vestibular nerve before splitting. Part of the nerve connects to the inferior cerebellar peduncle before moving on to the cerebellum, while the other part of the nerve connects the medial and inferior vestibular nuclei before connecting to the inferior cerebellar peduncle. This pathway is involved in controlling posture [7].

//Connections to the cortex//

The vestibular system connects to the cortex by first connecting to the vestibular nerve, which then connects to the vestibular nuclei and then to the ventral posterior nucleus of the thalamus [8]. From here it connects to the tempero-parieto-insular cortex [5]; [7]; [8]. This pathway, called the vestibulothalamic tract, is important because it is involved with visual processing and conscious perception of vertigo, self-motion, and the absence of visual stimulation [5].


 * Benign Paroxysmal Positional Vertigo**

Benign Paroxysmal Positional Vertigo (BPPV) is a medical condition where the oticonia detaches from the utricle and moves into a semicircular canal, and in so doing interferes with the movement of the endolymph [1]; [3]; [4]; [9]. This is because the endolymph does not move with gravity, but the oticonia does, forcing the endolymph to move at a time when it normally would not. As a result, the hair cells detect the movement and tell the brain that the head is moving when in reality it is not. This is especially difficult because the message from the ear does not match what the other ear, the visual system, and the muscles and joints are suggesting [3], and therefore results in temporary, but extreme, vertigo that usually lasts for about one minute [1]; [3]. BPPV most commonly occurs in the horizontal canal [1].

Two types of BPPV include canalithiasis and cupolithiasis. Canalithiasis occurs when the oticonia in the canal move freely in the endolymph [9]. With this type of BPPV, the feeling of vertigo stops when the crystals settle in the ear because it stops forcing the hair cells to move. However, with cupolithiasis the crystals get caught in nerves that sense the fluid movement, therefore causing the vertigo to continue until the head is moved to a different position, causing the hair cells to change their firing rate [9].

Both types of BPPV are diagnosed by putting the patient’s head in varying positions that will cause the crystals to move, forcing an episode of vertigo and conflicting messages sent to the brain [9]. When the brain thinks that the person is moving due to the signals from the hair cells, a nystagmus results, meaning that the eyes slowly move in one direction before quickly moving in the opposite direction [9]. This resulting nystagmus can then be observed by the doctors to help diagnose the patient with BPPV [9].

BPPV is treated with different physical therapy exercises depending on the type of BPPV displayed [1]; [9]. Canalithiasis is treated by putting the patient’s head in positions that will cause the crystals to fall out of the canal. Similarly, cupolithiasis is treating by first moving the head very quickly in an attempt to dislodge the crystals from the nerve before then using the treatment method for canalithiasis [9].

BPPV is the most common vestibular disorder, especially for adults and seniors [9].


 * Meniere’s disease**

Meniere’s disease is characterized by a very large amount of endolymph in the vestibular system, which forces the saccule to stretch until the membrane breaks, causing the endolymph and perilymph to mix together [3]; [4]; [10]. As mentioned earlier, the perilymph has a high sodium concentration and a low potassium concentration, while the endolymph has a low sodium concentration and a high potassium concentration [5]; [6]. The mixture of these two fluids results in regular levels of both sodium and potassium.

While the cause of the buildup in endolymph is unclear, triggers have been found including stress, fatigue, anxiety, strong emotions, illness, changes in pressure, and high amounts of salt intake [10].

This growing amount of endolymph results in attacks where they must deal with extreme vertigo. Before these attacks, people tend to experience imbalance, dizziness, lightheadedness, headaches, increased ear pressure, hearing loss, tinnitus, and sound sensitivity [3]; [10]. Upon the onset of an attack, patients face violent vertigo, sudden hearing loss, and tinnitus [3]; [10]. These symptoms grow stronger in later stages of Meniere’s disease [10]. Such attacks can last from twenty minutes to twenty-four hours, and the frequency of such attacks often varies. After an attack the patient will likely be so tired that they require several hours of sleep. However, it is important to move around shortly after the attack so that the brain can readjust to the changed balance signals [10). These signals changed because the body had been trying to adjust to the changed perception of the environment during the attack [10].

Doctors have found several treatments for Meniere’s disease. To prevent attacks, some patients must use a diet low in sodium to help reduce the pressure of the endolymph [10]. During the attacks, some medications have been found to assist with reducing vertigo. When these methods don’t work, doctors might try intratympanic gentamicin, the destruction of vestibular tissue through the injection of gentamicin in the ear [10]. A last option is also surgery, where the doctors block the flow of information from the inner ear to the brain by destroying the vestibular nerve [10]. Although this would not normally be desired because the body would no longer receive as much information about the head’s position, this method can work for those with Meniere’s disease because the vestibular nerve is no longer sending accurate information to other parts of the body.

Meniere’s disease most commonly affects people between the ages of forty and sixty [1]; [10].


 * Ventral Neuritis/Labyrinthitis**

Vestibular neuritis occurs when the vestibular nerve is infected by a virus or bacteria, resulting in inflammation of part of the vestibular-ocular nerve and vertigo that can last for hours or days [3]; [4]; [11]. Often times this can lead to the slow deterioration of the vestibular epithelium, the superior and inferior vestibular nerves, and the vestibular ganglion [4].

Labyrinthitis is just like vestibular neuritis except that it involves the infection of both branches of the vestibular-cochlear nerve, rather than just the vestibular nerve [11]. This involves the infection of the labyrinth, the name for all of the fluid filled tubes and sacs involved with hearing and balance [11].

Labyrinthitis can be divided into serous labyrinthitis and suppurative labyrinthitis. Serous labyrinthitis occurs when bacteria affect the middle ear and release toxins into the oval or rounded window of the cochlea [11]. On the other hand, suppurative labyrinthitis involves bacteria that infect the middle ear or cerebrospinal fluid, which then spread through the cochlea [11].

Whether for vestibular neuritis or labyrinthitis, the inner ear can be infected by viruses, which are more common, or by bacteria. These viruses can include the herpes virus, influenza, hepatitis, measles, rubella, mumps, polio, and Epstein-Barr, with some viruses affecting the entire body and others specifically infecting the labyrinth [11]. Unfortunately, these viruses can go dormant before becoming active again. When a virus infects the labyrinth, symptoms can include dizziness, vertigo, vomiting, nausea, imbalance, and difficulties with vision and concentration [11]. Symptoms of bacterial infection include these symptoms as well as difficulty walking, tinnitus, and hearing loss. Furthermore, these symptoms often appear rather suddenly [11].

In order to diagnose these vestibular problems, doctors must use the process of elimination. To do so, machines such as the audiogram, electronystagmography (ENG), videonystagmography (VNG), or vestibular evoked myogenic potential (VEMP) may be used to test muscles, vision, and the inner-ear [11]. Through this process, more symptoms can be collected to help rule out other vestibular problems.

Once the diagnosis is made, medications can be used to help calm the symptoms. If the symptoms do not go away after treatment, vestibular rehabilitation exercises can be used, which can also help to avoid permanent damage [11].

Vestibular neuritis and labyrinthitis most often occur for people between the ages of forty and fifty [1].


 * Hair Loss**

Sometimes vestibular difficulties for the aging are not caused by a specific disorder, but instead are caused by the slow loss of hair cells in semicircular canals and the cochlea. It has been shown that hair cells and neurons in the vestibular system do not regenerate [1]. The slow decrease in the number of hair cells begins around age 20, and continues so that when the person is older they will not be able to hear as well because there is a significant loss in hair cells [1]. The loss of hair cells means that fewer hair cells can send messages about body position or sound to the rest of the body, causing the person to be less prepared to respond to their environment.


 * Conclusion**

As shown above, there are several different causes and treatments for imbalance in the aging population in addition to the visual and musculo-skeletal causes not discussed here. Although people may be at risk for experiencing difficulties with balance, precautions can be taken to avoid vestibular difficulties. These include eating a healthy diet, exercising regularly, getting a geriatric physical, and checking the surrounding environment for any possible damaging factors [3]. With continued research and practiced prevention, more can be learned about causes and methods of treatment of vestibular disorders so as to make life more enjoyable for the aging population.

(1) Benign Paroxysmal Positional Vertigo (BPPV): when the oticonia detaches from the utricle and moves into a semicircular canal, and in so doing interferes with the movement of the endolymph (2) Canalithiasis: when the oticonia in the canal move freely in the endolymph; feeling of vertigo stops when the crystals settle in the ear because it stops forcing the hair cells to move (3) Cupolithiasis: when the oticonia get caught in nerves that sense the fluid movement, therefore causing the vertigo to continue until the head is moved to a different position, causing the hair cells to change their firing rate (4) Labyrinthitis: when the vestibular nerve is infected by a virus or bacteria, resulting in inflammation of the entire vestibular-ocular nerve and severe vertigo (5) Meniere’s disease: characterized by a very large amount of endolymph in the vestibular system, which forces the saccule to stretch until the membrane breaks, causing the endolymph and perilymph to mix together (6) Nystagmus: when that the eyes slowly move in one direction before quickly moving in the opposite direction (7) Vestibular neuritis: when the vestibular nerve is infected by a virus or bacteria, resulting in inflammation of part of the vestibular-ocular nerve and vertigo that can last for hours or days
 * Glossary**

Multiple Choice
 * Quiz Questions**
 * 1) The gel inside of the crista is called
 * 2) a. Ampula
 * 3) b. Cupula
 * 4) c. Oticonia
 * 5) d. Endolymph
 * 6) 2. Which pathway involves the oculomotor nucleus?
 * 7) a. Pathway to the muscles
 * 8) b. Pathway to the eyes
 * 9) c. Pathway to the cerebellum
 * 10) d. Pathway to the cortex
 * 11) 3. Which vestibular problem mentioned involves a nystagmus?
 * 12) a. BPPV
 * 13) b. Meniere’s disease
 * 14) c. Labyrinthitis
 * 15) d. Hair cell loss
 * 16) 4. Which of the following is not a symptom during an attack for those with Meniere’s disease?
 * 17) a. Tinnitus
 * 18) b. Hearing loss
 * 19) c. Blindness
 * 20) d. Loss of balance
 * 21) 5. Which of the following is not true for labyrinthitis?
 * 22) a. The labyrinth is made up of the fluid filled tubes and sacs involved with hearing and balance.
 * 23) b. The viruses involved can go dormant before becoming active again.
 * 24) c. It is diagnosed through the process of elimination.
 * 25) d. It is just like vestibular neuritis except that it involves the infection of only one branch of the vestibular-cochlear nerve, rather than both branches.
 * 1) a. The labyrinth is made up of the fluid filled tubes and sacs involved with hearing and balance.
 * 2) b. The viruses involved can go dormant before becoming active again.
 * 3) c. It is diagnosed through the process of elimination.
 * 4) d. It is just like vestibular neuritis except that it involves the infection of only one branch of the vestibular-cochlear nerve, rather than both branches.

True/False
 * 1) Decrease in the number of hair cells in the vestibular system begins around age 30.
 * 2) Suppurative labyrinthitis involves bacteria that infect the middle ear or cerebrospinal fluid, which then spread through the cochlea.
 * 3) BPPV is generally treated by putting the patient’s head in positions that will cause the crystals to fall out of the canal.
 * 4) The medial vestibulo-spinal pathway helps to keep postural balance and helps the extensor muscles.
 * 5) After those with Meniere’s disease experience an attack, they will likely be so tired that they require several hours of sleep.

Short answer
 * 1) Fill in the blank: Perilymph has a high sodium concentration and a low potassium concentration, while the endolymph has a low sodium concentration and a high potassium concentration.
 * 2) In what age range do vestibular neuritis and labyrinthitis most commonly occur?
 * 3) Name the two types of BPPV.
 * 4) Which vestibular difficulty is characterized by a very large amount of endolymph in the vestibular system, which forces the saccule to stretch until the membrane breaks, causing the endolymph and perilymph to mix together?
 * 5) For which vestibular difficulty does the endolymph not move with gravity, but the oticonia does, forcing the endolymph to move at a time when it normally would not.

//Vestibular Health// [] Explains some of the vestibular problems which older adults may face. Gives a brief overview of the causes and treatment methods for these health issues.
 * Suggested Readings**

//Benign Paroxysmal Positional Vertigo// [] Specifically talks about what happens in the vestibular system of those experiencing BPPV. Further talks about the causes, methods of diagnosing, and treatment methods.

//Meniere’s Disease// [] Specifically talks about what happens in the vestibular system of those experiencing Meniere’s disease. Further talks about the causes, methods of diagnosing, and treatment methods.

//Labyrinthitis and Vestibular Neuritis// [] Specifically talks about what happens in the vestibular system of those experiencing Labyrinthitis and Vestibular Neuritis. Further talks about the causes, methods of diagnosing, and treatment methods.

//Senior Health// [] Discusses the importance of balance, especially as one gets older. Also briefly talks about the most common vestibular disorders and their causes, methods of diagnosis, and treatment methods.

//American Hearing Research Foundation// [] Gives a list of hearing and balance disorders.

//Benign Paroxysmal Positional Vertigo// [] Talks about the causes, methods of diagnosis, treatment methods, and some research behind the disorder.

//Meniere’s Disease// [] Talks about the causes, methods of diagnosis, treatment methods, and some research behind the disorder.

//Labyrinthitis and Vestibular Neuritis// [] Talks about the causes, methods of diagnosis, treatment methods, and some research behind the disorder.

(1) Shinichi, I., & Tatsuya, Y. (2015). Dizziness and Imbalance in the Elderly: Age-related Decline in the Vestibular System. //Aging & Disease//, //6//(1), 38-47. doi:10.14336/AD.2014.0128 (2) Toledo, D., & Barela, J. (2014). Age-related differences in postural control: effects of the complexity of visual manipulation and sensorimotor contribution to postural performance. //Experimental Brain Research//, //232//(2), 493-502. doi:10.1007/s00221-013-3756-1 (3) Shupert, C. (2015). Age-related dizziness and imbalance. Retrieved December 22, 2015, from [] (4) Hong, S. M., Yeo, S. G., Kim, S. W., & Cha, C. I. (2008). The results of vestibular evoked myogenic potentials, with consideration of age-related changes, in vestibular neuritis, benign paroxysmal positional vertigo, and Meniere's disease. //Acta Oto-Laryngologica//, //128//(8), 861-865. doi:10.1080/00016480701784981 (5) Lysakowski, A., McCrea, R. A., & Tomlinson, R. D. (1998). Anatomy of vestibular end organs and neural pathways. //Otolaryngology Head and Neck Surgery. 3rd ed. St Louis: Mosby//, 2561-84. (6) HHTM. (2013). The Fluids of the Inner Ear–Hearing Health. Retrieved December 23, 2015, from [] (7) Gray, L. (n.d.). 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. Retrieved December 23, 2015, from [] (8) Wolfe, J. M., Kluender, K. R., Levi, D. M., Bartoshuk, L. M., Herz, L. M., Klatzky, R. L., … Merfeld, D. M. (2012). Spatial Orientation and the Vestibular System. In //Sensation & Perception// (3rd ed.). Sunderland, Massachusetts: Sinauer Associates. (9) Woodhouse, S. (2015). Benign Paroxysmal Positional Vertigo (BPPV). Retrieved December 22, 2015, from [] (10)Haybach, P. (2015). Ménière's Disease. Retrieved December 22, 2015, from [] (11)Shupert, C. (2015). Labyrinthitis and Vestibular Neuritis. Retrieved December 22, 2015, from []
 * References**

(1) Scicurious. (2011). SCIENCE 101: The Vestibulo part of Cranial Nerve VIII, the Vestibulocochlear Nerve. Retrieved December 23, 2015, from [] (2) Gray, L. (n.d.). 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. Retrieved December 23, 2015, from [] (3) Wolfe, J. M., Kluender, K. R., Levi, D. M., Bartoshuk, L. M., Herz, L. M., Klatzky, R. L., … Merfeld, D. M. (2012). Spatial Orientation and the Vestibular System. In //Sensation & Perception// (3rd ed., pp. 359). Sunderland, Massachusetts: Sinauer Associates. (4) Wolfe, J. M., Kluender, K. R., Levi, D. M., Bartoshuk, L. M., Herz, L. M., Klatzky, R. L., … Merfeld, D. M. (2012). Spatial Orientation and the Vestibular System. In //Sensation & Perception// (3rd ed., pp. 352). Sunderland, Massachusetts: Sinauer Associates. (5) Wolfe, J. M., Kluender, K. R., Levi, D. M., Bartoshuk, L. M., Herz, L. M., Klatzky, R. L., … Merfeld, D. M. (2012). Spatial Orientation and the Vestibular System. In //Sensation & Perception// (3rd ed., pp. 357). Sunderland, Massachusetts: Sinauer Associates. (6) Benign Paroxysmal Positional Vertigo (BPPV). (2015). Retrieved December 23, 2015, from [] (7) Meniere’s Disease. (2015). Retrieved December 23, 2015, from [] (8) Vestibular Neuritis. (n.d.). Retrieved December 23, 2015, from http://vestibularneuritis.com/
 * Image References**

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 * Video References**


 * Quiz Answers**
 * 1) 1. B
 * 2) 2. B
 * 3) 3. A
 * 4) 4. C
 * 5) 5. D
 * 6) 6. F
 * 7) 7. T
 * 8) 8. T
 * 9) 9. F
 * 10) 10. T
 * 11) 11. High; high
 * 12) 12. 40-60
 * 13) 13. Canalithiasis and cupolithiasis
 * 14) 14. Meniere’s disease
 * 15) 15. BPPV