Texasdizziness.com5018 NE 15TH AVE · PORTLAND, OR 97211 · FAX: (503) 229-8064 · (800) 837-8428 Vestibular Injury
Compensation, De-compensation, and Failure to Compensate
By Thomas E. Boismier, MPH, with contributions by Kamran Barin, PhD The vestibular system includes the inner not successful, vestibular rehabilitation ear balance organs and the parts of the therapy may be required. brain that coordinate and process balance information. The balance organs ACUTE (IMMEDIATE) contribute vital sensory information about motion, equilibrium, and spatial When a sudden injury occurs to the orientation. In addition, the vestibular balance organs on one side, the patient system helps maintain clear vision during may feel very sick for hours to a few days movements via an automated function with vertigo (a spinning feeling), called the vestibulo-ocular reflex (VOR). lightheadedness (dizziness), and unsteadiness, often accompanied by The vestibular system can be sweating, nausea, and vomiting. This compromised in many ways. Viral or is because the spatial orientation signals bacterial infections (labyrinthitis and sent to the brain from both ears vestibular neuritis), disorders that affect are no longer equal and opposite, and inner ear fluid levels (Ménière's disease the brain interprets the difference as and secondary endolymphatic hydrops), constant movement. trauma from head injury (mild traumatic brain injury or mTBI), benign tumors Researchers theorize that after this initial (vestibular schwannoma), and age- period, the brain recognizes that the related degeneration can all cause signals being received from the ears permanent damage to the vestibular are incorrect and turns the signals down through a process called the cerebellar clamp. When the clamp is in place, the The body has limited ability to repair vertigo and much of the sick feelings damage to the vestibular organs. improve. However, the patient feels However, the body can compensate for unsteady while standing, because the the vestibular injury by recalibrating the vestibular signals normally used to part of the brain that controls balance. maintain balance have been reduced. This compensation process occurs naturally in most people, but when it is Vestibular Disorders Association ◦ vestibular.org ◦ Page 1 of 4 The patient may also report disorientation inner ear to pass to the brain. The brain or blurred vision during head movements can then fine-tune its calculations in because the VOR no longer functions order to account for differences between properly. In addition to the vestibular the signals received from damaged system, proprioception (the sensors in versus undamaged vestibular organs. the muscles, joints and at the bottom of Such compensation can't occur if the the feet) and vision provides information cerebel ar clamp remains in place. that is necessary for maintaining balance. So without vestibular input, the patient For most patients, the movements made can still walk but will feel unsteady and during normal daily activities are enough may fall in the dark or on soft or bumpy to achieve chronic (long-term) compensa- surfaces such as a thickly carpeted floor, tion, usually in two to four weeks after the grass lawn, or gravel path. injury has occurred. Once this chronic compensation process is complete, the At this point, most patients are well patient is essentially symptom-free. If enough to get out of bed and visit a unsteadiness and/or motion-provoked doctor. The doctor sees a person who is dizziness persist after that time, compen- not experiencing dizziness or vertigo but sation is not complete and the physician whose gait is ataxic, meaning awkward may prescribe a program of vestibular and uncoordinated. If the patient is not rehabilitation therapy (VRT). given an opportunity to clearly describe what has happened, he or she may be VRT is a treatment program administered immediately referred to a neurologist to by a specially-trained physical or rule out stroke because of this ataxic gait. occupational therapist. It is designed to (1) desensitize the balance system to The cerebel ar clamp may persist for days problematic movements and (2) enhance after the initial injury. If balance testing the fine-tuning required for long-term is performed during this phase, test compensation. This is accomplished with results may incorrectly suggest that the exercises that involve small, controlled, patient has damage to both sides of the and repeated "doses" of the movements balance system, because the cerebellar and activities that provoke dizziness. VRT clamp reduces the eye movements (VOR) is most effective when administered by a that are typically evaluated during therapist who has specific training and balance testing. experience in this specialized form of CHRONIC (LONG-TERM) After the initial compensation phase, It's important to remember that even the cerebellum slowly releases the clamp, after symptoms go away, the balance gradually allowing more signals from the system remains injured, the brain has Vestibular Disorders Association ▪ ▪ Page 2 of 4 simply adapted to the injury. For many compensation is exactly like the recovery patients, dizziness and vertigo will return that occurs during the chronic months or years after compensating for compensation phase. Movements and a balance system injury. It is critical for activities are the stimuli the brain needs the physician to find out what type of to fine-tune the system. We recommend dizziness and vertigo the patient has. that patients keep their VRT exercise program instructions available even after If the patient describes another severe they recover so that they can begin the attack of spinning with unsteadiness exercises immediately if symptoms and nausea lasting hours to days, this return. Usually recovery after de- suggests that a second injury has compensation is quicker than the occurred to the balance system, such time it takes to recover after the initial as another viral infection or an attack injury to the balance system. of Ménière's disease or secondary endo- lymphatic hydrops. These conditions Failure to compensate
require diagnosis and medical treatment. Two things are required in order to compensate for an injury. First, the brain If the patient reports that dizziness must continue to receive signals from the occurs after particular head movements balance organs so that it can learn how to and lasts seconds to a few minutes, interpret different head movements. Thus, this suggests one of two things. It is movements must not be avoided, because possible that the patient has developed they create the signals the brain needs to benign paroxysmal positional vertigo compensate for the injury. Second, the (BPPV), which is common after some areas of the brain that are responsible for vestibular injuries. BPPV can be compensation must not be damaged. diagnosed and treated effectively using simple procedures. If the patient's During the early stages of dizziness, symptoms turn out to be unrelated to patients may avoid quick movements and BPPV, then the most likely explanation is reduce their activities. Most patients will that de-compensation has occurred. De- also be prescribed one or more anti- compensation simply means that the dizziness medications such as Antivert brain has ‘forgotten' the fine-tuning it (meclizine), Valium (diazepam), Xanax developed during the chronic (alprazolam), Phenergan (promethazine), compensation phase described above. or Compazine (prochlorperazin). This is fine during the acute stages of dizziness. Events that can provoke de-compensation However, once the acute phase is past, include a bad cold or the flu, minor inactivity and medications can interfere surgery, or anything that interrupts with the long-term compensation process. normal daily activity for a few days, such as long trips. Recovery after de- Vestibular Disorders Association ▪ ▪ Page 3 of 4 Any medication that makes the brain sleepy, including all of the anti-dizziness medications, can slow down or stop the process of compensation, so they are often not appropriate for long-term use. Most patients who fail to compensate are found to either be strictly avoiding certain movements, using anti-dizziness medications daily, or both. Treatment includes VRT and gradual reduction and eventual elimination of these medications. Brain damage caused by stroke, head injury, or other causes can slow down or stop the natural compensation process. It is difficult to predict which patients with brain injury will improve or to what degree, so all patients should be given the chance to improve through a VRT program. There are several different measures of symptoms and functional capabilities used to assess progress repeatedly as treatment goes on. As long as a patient continues to show improvement, even if it is gradual, treatment should be continued.
Other helpful resources available from the VEDA's publications are protected under Vestibular Disorders Association include: copyright. For more information, see our Vestibular Rehabilitation – An Effective permissions guide a Evidence-Based Treatment, and Benign Paroxysmal Positional Vertigo. This document is not intended as a substitute for professional health care. 2015 Vestibular Disorders Association Vestibular Disorders Association ▪ ▪ Page 4 of 4 5018 NE 15TH AVE · PORTLAND, OR 97211 · FAX: (503) 229-8064 · (800) 837-8428 Did this free publication from VEDA help you?
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BEWARE OF OVERCLAIMING, FEDERAL COURT OF CANADA WARNS Alexandra Steele* LEGER ROBIC RICHARD, Lawyers ROBIC, Patent & Trademark Agents Centre CDP Capital 1001 Square-Victoria – Bloc E – 8th Floor Montréal, Québec, Canada H2Z 2B7 Tel.: (514) 987-6242 - Fax (514) 845-7874 [email protected] –www.robic.ca INTRODUCTION The Applicant's application for a writ of prohibition preventing the Canadian Minister of National Health and Welfare from issuing a Notice of Compliance to the Respondent in respect of anti-depression medication was denied, the Court having ruled that the Respondent's al egations that the proposed drug would not infringe the Applicant's patents were sufficient. [Biovail Pharmaceuticals Inc. et al v. Minister of National Health and Welfare at al,  F.C.J. No. 7, Harrington J., January 6, 2005] BACKGROUND
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