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Vertigo is recorded as a symptom of decompression sickness in 5.3% of cases by the US Navy as reported by Powell, 2008 It including isobaric decompression sickness.
Decompression sickness can also be caused at a constant ambient pressure when switching between gas mixtures containing different proportions of inert gas. This is known as isobaric counterdiffusion, and presents a problem for very deep dives. For example, after using a very helium-rich trimix at the deepest part of the dive, a diver will switch to mixtures containing progressively less helium and more oxygen and nitrogen during the ascent. Nitrogen diffuses into tissues 2.65 times slower than helium, but is about 4.5 times more soluble. Switching between gas mixtures that have very different fractions of nitrogen and helium can result in "fast" tissues (those tissues that have a good blood supply) actually increasing their total inert gas loading. This is often found to provoke inner ear decompression sickness, as the ear seems particularly sensitive to this effect.
Alternobaric vertigo is caused by a pressure difference between the middle ear cavities, usually due to blockage or partial blockage of one eustachian tube, usually when flying or diving underwater. It is most pronounced when the diver is in the vertical position; the spinning is towards the ear with the higher pressure and tends to develop when the pressures differ by 60 cm of water or more.
From 3% to 11% of diagnosed dizziness in neuro-otological clinics are due to Meniere's. The annual incidence rate is estimated to be about 15/100,000 and the prevalence rate is about 218/100,000, and around 15% of people with Meniere's disease are older than 65. In around 9% of cases a relative also had MD, signalling that there may be a genetic predisposition in some cases.
The odds of MD are greater for people of white ethnicity, with severe obesity, and women. Several conditions are often comorbid with MD, including arthritis, psoriasis, gastroesophageal reflux disease, irritable bowel syndrome, and migraine.
Ototoxic effects are also seen with quinine, pesticides, solvents, asphyxiants and heavy metals such as mercury and lead. When combining multiple ototoxins, the risk of hearing loss becomes greater.
Ototoxic chemicals in the environment (from contaminated air or water) or in the workplace interact with mechanical stresses on the hair cells of the cochlea in different ways. For organic solvents such as toluene, styrene or xylene, the combined exposure with noise increases the risk of hearing loss in a synergistic manner. Carbon monoxide, has been shown to increase the severity of the hearing loss from noise. Given the potential for enhanced risk of hearing loss, exposures and contact with products such as paint thinners, degreasers, white spirits, exhaust, should be kept to a minimum. Noise exposures should be kept below 85 decibels, and the chemical exposures should be below the recommended exposure limits given by regulatory agencies.
Drug exposures mixed with noise potentially lead to increased risk of ototoxic hearing loss. Noise exposure combined with the chemotherapeutic cisplatin puts individuals at increased risk of ototoxic hearing loss. Noise at 85 dB SPL or above added to the amount of hair cell death in the high frequency region of the cochlea In chinchillas. The American Academy of Audiology includes in their position statement that exposure to noise at the same time as aminoglycosides may exacerbate ototoxicity. The American Academy of Audiology recommends people being treated with ototoxic chemotherapeutics avoid excessive noise levels during treatment and for several months following cessation of treatment. Opiates in combination with excessive noise levels may also have an additive affect on ototoxic hearing loss.
Previous noise exposure has not been found to potentiate ototoxic hearing loss.
In most cases, the condition tends to be self-limiting. In 95% or greater, vestibular neuritis is a one-time experience with most people fully recovering.
Recovery from acute labyrinthine inflammation generally takes from one to six weeks, but it is not uncommon for residual symptoms (dysequilibrium and/or dizziness) to last for a couple of months.
Recovery from a temporary damaged inner ear typically follows two phases:
1. An acute period, which may include severe vertigo and vomiting
2. approximately two weeks of sub-acute symptoms and rapid recovery
In aviation and underwater diving, alternobaric vertigo is dizziness resulting from unequal pressures being exerted between the ears due to one Eustachian tube being less patent than the other.
This might have occurred due to barotrauma of descent, and/or the effects of nasal decongestants. It is due to unequal increase in middle ear pressures on ascent, is usually mild, and most often cleared by further ascent. When the pressures in both ears reach ambient levels, the stimulus for the dizziness stops. Although most often mild, the vertigo can persist until the diver reaches the surface continuing the unequal pressures, which can damage the inner ear or ear drum.
Alternobaric vertigo is most pronounced when the diver is in the vertical position; the spinning is towards the ear with the higher pressure and tends to develop when the pressures differ by 60 cm of water or more. Ear clearing may be a remedy. A similar vertigo can also occur as a result of unequal heating stimulation of one inner ear labyrinth over the other due to diving in a prone position in cold water - the undermost ear being stimulated.
At high doses, quinine, aspirin and other salicylates may also cause high-pitch tinnitus and hearing loss in both ears, typically reversible upon discontinuation of the drug.
The erectile dysfunction medications Viagra, Levitra, and Cialis have also been reported to cause hearing loss.
Within the labyrinth of the inner ear lie collections of calcium crystals known as otoconia or otoliths. In patients with BPPV, the otoconia are dislodged from their usual position within the utricle, and migrate over time into one of the semicircular canals (the posterior canal is most commonly affected due to its anatomical position). When the head is reoriented relative to gravity, the gravity-dependent movement of the heavier otoconial debris (colloquially "ear rocks") within the affected semicircular canal causes abnormal (pathological) endolymph fluid displacement and a resultant sensation of vertigo. This more common condition is known as canalithiasis.
In rare cases, the crystals themselves can adhere to a semicircular canal cupula, rendering it heavier than the surrounding endolymph. Upon reorientation of the head relative to gravity, the cupula is weighted down by the dense particles, thereby inducing an immediate and sustained excitation of semicircular canal afferent nerves. This condition is termed cupulolithiasis.
There is evidence in the dental literature that malleting of an osteotome during closed sinus floor elevation, otherwise known as "osteotome sinus elevation" or "lift", transmits percussive and vibratory forces capable of detaching otoliths from their normal location and thereby leading to the symptoms of BPPV.
It can be triggered by any action which stimulates the posterior semi-circular canal, including:
- Looking up or down
- Preceding head injury
- Sudden head movement
- Rolling over in bed
- Tilting the head
BPPV may be made worse by any number of modifiers which may vary between individuals:
- Changes in barometric pressure — patients may feel increased symptoms up to two days before rain or snow
- Lack of sleep (required amounts of sleep may vary widely)
- Stress
An episode of BPPV may be triggered by dehydration, such as that caused by diarrhea. For this reason, it commonly occurs in post-operative patients who have diarrhea induced by post-operative antibiotics.
BPPV is one of the most common vestibular disorders in patients presenting with dizziness; migraine is implicated in idiopathic cases. Proposed mechanisms linking the two are genetic factors and vascular damage to the labyrinth.
Although BPPV can occur at any age, it is most often seen in people over the age of 60. Besides aging, there are no major risk factors known for developing BPPV, although previous episodes of trauma to the head, or inner ear infections known as labyrinthitis, may predispose individuals to future development of BPPV.
Some people will report having an upper respiratory infection (common cold) or flu prior to the onset of the symptoms of vestibular neuronitis; others will have no viral symptoms prior to the vertigo attack.
Some cases of vestibular neuronitis are thought to be caused by an infection of the vestibular ganglion by the herpes simplex type 1 virus. However, the cause of this condition is not fully understood, and in fact many different viruses may be capable of infecting the vestibular nerve.
Acute localized ischemia of these structures also may be an important cause, especially in children, vestibular neuritis may be preceded by symptoms of a common cold. However, the causative mechanism remains uncertain.
This can also be brought on by pressure changes such as those experienced while flying or scuba diving.
Ménière's disease usually starts confined to one ear; it appears that it extends to both ears in about 30% of cases.
People may start out with only one symptom, but in MD all three appear with time. Hearing loss usually fluctuates in the beginning stages and becomes more permanent in later stages. MD has a course of 5–15 years, and people generally end up with mild disequilibrium, tinnitus, and moderate hearing loss in one ear.
Benign paroxysmal positional vertigo (BPPV) is a disorder arising from a problem in the inner ear. Symptoms are repeated, brief periods of vertigo with movement, that is, of a spinning sensation upon changes in the position of the head. This can occur with turning in bed or changing position. Each episode of vertigo typically lasts less than one minute. Nausea is commonly associated. BPPV is one of the most common causes of vertigo.
BPPV can result from a head injury or simply occur among those who are older. A specific cause is often not found. The underlying mechanism involves a small calcified otolith moving around loose in the inner ear. It is a type of balance disorder along with labyrinthitis and Ménière's disease. Diagnosis is typically made when the Dix–Hallpike test results in nystagmus (a specific movement pattern of the eyes) and other possible causes have been ruled out. In typical cases medical imaging is not needed.
BPPV is often treated with a number of simple movements such as the Epley maneuver or Brandt–Daroff exercises. Medications may be used to help with nausea. There is tentative evidence that betahistine may help with the vertigo but its use is not generally needed. BPPV is not a serious condition. Typically it resolves in one to two weeks. It however may recur in some people.
The first medical description of the condition occurred in 1921 by Robert Barany. About 2.4% of people are affected at some point in time. Among those who live until their 80s, 10% have been affected. BPPV affects females twice as often as males. Onset is typically in the person's 50s to 70s.
These can be both congenital or develop over time with the thinning of the otic capsule by the persistent pulsations of the intracranial pressures against the bones of the skull. Finally, disease conditions—for example cholesteatoma—can result in a labyrinthine fistula. Traumatic events, with excessive pressure changes to the inner ear such as in scuba diving, head trauma, or an extremely loud noise can lead to rupture and leakage.
Endolymphatic hydrops is a disorder of the inner ear. It consists of an excessive build-up of the endolymph fluid, which fills the hearing and balance structures of the inner ear. Endolymph fluid, which is partly regulated by the endolymph sac, flows through the inner ear and is critical to the function of all sensory cells in the inner ear. In addition to water, endolymph fluid contains salts such as sodium, potassium, chloride and other electrolytes. If the inner ear is damaged by disease or injury, the volume and composition of the endolymph fluid can change, causing the symptoms of endolymphatic hydrops.
Endolymphatic hydrops may occur as a result of trauma such as a blow to the head, infection, degeneration of the inner ear, allergies, dehydration and loss of electrolytes or in rare circumstances a benign tumor. In many cases, it is not clear what causes the disorder. Meniere’s attacks occur when there is an increase in endolymphatic volume in the inner ear, causing a temporary leak in the membrane separating the perilymph (potassium poor fluid) and the endolymph (potassium rich fluid). The mix of these two fluids surrounding the vestibular sensory cells can lead to a temporary electrical blockade and loss of sensory function. The sudden change in the rate of the vestibular nerve firing results in a disturbance of signal processing in the corresponding brain regions, and thus to acute sensations of imbalance, otherwise known as vertigo.
When diagnosing, PLF should be differentiated from Ménière's disease. Tympanostomy has been reported to be a way to diagnose and cure PLF.
About 20–30% of the population report to have experienced dizziness at some point in the previous year.
According to current research, in approximately 2.5% of the general population the bones of the head develop to only 60–70% of their normal thickness in the months following birth. This genetic predisposition may explain why the section of temporal bone separating the superior semicircular canal from the cranial cavity, normally 0.8 mm thick, shows a thickness of only 0.5 mm, making it more fragile and susceptible to damage through physical head trauma or from slow erosion. An explanation for this erosion of the bone has not yet been found.
Brain related causes are less commonly associated with isolated vertigo and nystagmus but can still produce signs and symptoms, which mimic peripheral causes. Disequilibrium is often a prominent feature.
- Degenerative: age related decline in balance function
- Infectious: meningitis, encephalitis, epidural abscess, syphilis
- Circulatory: cerebral or cerebellar ischemia or hypoperfusion, stroke, lateral medullary syndrome (Wallenberg's syndrome)
- Autoimmune: Cogan syndrome
- Structural: Arnold-Chiari malformation, hydrocephalus
- Systemic: multiple sclerosis, Parkinson's disease
- Vitamin deficiency: Vitamin B12 deficiency
- CNS or posterior neoplasms, benign or malignant
- Neurological: Vertiginous epilepsy, abasia
- Other – There are a host of other causes of dizziness not related to the ear.
- Mal de debarquement is rare disorder of imbalance caused by being on board a ship. Patients suffering from this condition experience disequilibrium even when they get off the ship. Typically treatments for seasickness are ineffective for this syndrome.
- Motion sickness – a conflict between the input from the various systems involved in balance causes an unpleasant sensation. For this reason, looking out of the window of a moving car is much more pleasant than looking inside the vehicle.
- Migraine-associated vertigo
- Toxins, drugs, medications; it is also a known symptom of carbon monoxide poisoning.
Once diagnosed, the gap in the temporal bone can be repaired by surgical resurfacing of the affected bone or plugging of the superior semicircular canal. These techniques are performed by accessing the site of the dehiscence either via a middle fossa craniotomy or via a canal drilled through the transmastoid bone behind the affected ear. Bone cement has been the material most often used, in spite of its tendency to slippage and resorption, and a consequent high failure rate; recently, soft tissue grafts have been substituted.
The prevalence of migraine and vertigo is 1.6 times higher in 200 dizziness clinic patients than in 200 age- and sex-matched controls from an orthopaedic clinic. Among the patients with unclassified or idiopathic vertigo, the prevalence of migraine was shown to be elevated. In another study, migraine patients reported 2.5 times more vertigo and also 2.5 more dizzy spells during headache-free periods than the controls.
MAV may occur at any age with a female:male ratio of between 1.5 and 5:1. Familial occurrence is not uncommon. In most patients, migraine headaches begin earlier in life than MAV with years of headache-free periods before MAV manifests.
In a diary study, the 1-month prevalence of MAV was 16%, frequency of MAV was higher and duration longer on days with headache, and MAV was a risk factor for co-morbid anxiety.
The disease is an inherited autosomal dominant disease, but the physiological cause of the dysfunction is still unclear. An acidophyllic mucopolysaccharide-containing substance was discovered, especially in cochleas, maculas, and crista ampullaris of patients with DFNA9 (a chromosome locus), as well as severe degeneration of vestibular and cochlear sensory axons and dendrites. It is suggested that the mucopolysaccharide deposit could cause strangulation of nerve endings.
The maculas and crista ampullaris are what allow for non-visual sensation of head movements. The crista ampullaris resides in the semicircular canals of the inner ear and detects angular acceleration, while the maculas are housed within the vestibule of the inner ear and detect linear acceleration. When affected, these organs can lead to vertigo and nausea because the body would always feel off-balance.
Causes of dizziness related to the ear are often characterized by vertigo (spinning) and nausea. Nystagmus (flickering of the eye, related to the Vestibulo-ocular reflex [VOR]) is often seen in patients with an acute peripheral cause of dizziness.
- Benign Paroxysmal Positional Vertigo (BPPV) – The most common cause of vertigo. It is typically described as a brief, intense sensation of spinning that occurs when there are changes in the position of the head with respect to gravity. An individual may experience BPPV when rolling over to the left or right, upon getting out of bed in the morning, or when looking up for an object on a high shelf. The cause of BPPV is the presence of normal but misplaced calcium crystals called otoconia, which are normally found in the utricle and saccule (the otolith organs) and are used to sense movement. If they fall from the utricle and become loose in the semicircular canals, they can distort the sense of movement and cause a mismatch between actual head movement and the information sent to the brain by the inner ear, causing a spinning sensation.
- Labyrinthitis - An inner ear infection or inflammation causing both dizziness (vertigo) and hearing loss.
- Vestibular neuronitis - an infection of the vestibular nerve, generally viral, causing vertigo
- Cochlear Neuronitis – an infection of the Cochlear nerve, generally viral, causing sudden deafness but no vertigo
- Trauma – Injury to the skull may cause either a fracture or a concussion to the organ of balance. In either case an acute head injury will often result in dizziness and a sudden loss of vestibular function.
- Surgical trauma to the lateral semicircular canal (LSC) is a rare complication which does not always result in cochlear damage. Vestibular symptoms are pronounced. Dizziness and instability usually persist for several months and sometimes for a year or more.
- Ménière's disease - an inner ear fluid balance disorder that causes lasting episodes of vertigo, fluctuating hearing loss, tinnitus (a ringing or roaring in the ears), and the sensation of fullness in the ear. The cause of Ménière's disease is unknown.
- Perilymph fistula – a leakage of inner ear fluid from the inner ear. It can occur after head injury, surgery, physical exertion or without a known cause.
- Superior canal dehiscence syndrome – a balance and hearing disorder caused by a gap in the temporal bone, leading to the dysfunction of the superior canal.
- Bilateral vestibulopathy – a condition involving loss of inner ear balance function in both ears. This may be caused by certain antibiotics, anti-cancer, and other drugs or by chemicals such as solvents, heavy metals, etc., which are ototoxic; or by diseases such as syphilis or autoimmune disease; or other causes. In addition, the function of the semicircular canal can be temporarily affected by a number of medications or combinations of medications.
Otitis is a general term for inflammation or infection of the ear, in both humans and other animals.
It is subdivided into the following:
- "Otitis externa", external otitis, or "swimmer's ear" involves the outer ear and ear canal. In external otitis, the ear hurts when touched or pulled.
- "Otitis media" or middle ear infection involves the middle ear. In otitis media, the ear is infected or clogged with fluid behind the ear drum, in the normally air-filled middle-ear space. This very common childhood infection sometimes requires a surgical procedure called "myringotomy" and tube insertion.
- "Otitis interna" or labyrinthitis involves the inner ear. The inner ear includes sensory organs for balance and hearing. When the inner ear is inflamed, "vertigo" is a common symptom.
The following factors increase some people's susceptibility to airsickness:
- Fatigue, stress, and anxiety, are some factors that can increase susceptibility to motion sickness of any type.
- The use of alcohol, drugs, and medications may also contribute to airsickness.
- Additionally, airsickness is more common in women (especially during menstruation or pregnancy), young children, and individuals prone to other types of motion sickness.
- Although airsickness is uncommon among experienced pilots, it does occur with some frequency in student pilots.