Current concepts in the diagnosis and therapy of vertigo
The maintenance of balance is the most complex of all biological systems. The vestibular system in conjunction with many other biological systems of the body is responsible for the maintenance of balance. Derangement of vestibular function leads to vertigo, which is a rotating or spinning sensation and/or imbalance. Over and above this, vertigo and imbalance also have an impact on the psychic and cognitive systems and induce a sense of insecurity, fear , frustration and mental depression, all of which have a profound impact on the quality of life of the patient. Vertigo and imbalance, (just like fever or headache) are symptoms or manifestations of an underlying medical disorder and to correct the vertigo or imbalance the underlying cause has to be diagnosed and treated. Unfortunately however, vertigo / imbalance is most commonly treated by using symptom relieving anti-vertigo drugs or vestibular sedatives which only camouflage the symptom of vertigo without correcting the cause. Both vertigo as well as imbalance can be caused by more than 100 diverse types of medical disorders some of which are very sinister and life-threatening. Hence leaving the underlying causative medical disorder undiagnosed and untreated and merely camouflaging the symptom of vertigo by the symptom relieving vestibular suppressants is unethicaland illogical to say the least. Treating vertigo or imbalance by the anti-vertigo drugs is like trying to treat malaria or typhoid with paracetamol.
However, trends are now changing and the updated clinician of today, is aware of the futility as well as the deleterious effects of the anti-vertigo drugs. The current consensus and the medical teaching of today is never to use these anti-vertigo drugs or vestibular sedatives for more than 3 to 5 days; some authorities even denounce using such medications for more than a day. Nevertheless, even today it is very common to find patients using these drugs for weeks and months together and not uncommonly on medical advice. This is deplorable. It is high time clinicians treating vertigo patients updated themselves on the current concepts in the diagnosis and therapy of vertigo and offered an ethical treatment that tries to correct the underlying disorder rather than suppressing the symptom of vertigo / imbalance by prescribing anti-vertigo medications.Diagnosis of the cause of the vertigo or imbalance is not at all difficult today as there has been tremendous advancements in diagnostic neurotology in the past two decades and neurotology today is no longer an occult science as it was thought to be. Medical science has now reached a stage where neurotologists can diagnose the nature and site of lesion in a patient of vertigo or imbalance with utmost precision by the modern vestibular function tests. Neurotology (the medical speciality for diagnosis and treatment of vertigo / imbalance) is now a complete evidence based medical discipline and today there is no excuse for not being able to diagnose the underlying cause of vertigo or imbalance in any patient. Hence the common practice of doctors trying to camouflage the symptom of vertigo by prescribing the symptom relieving anti-vertigo drugs in spite of their known deleterious effects, and not correcting the underlying medical disorder which is causing the vertigo/ imbalance is completely unjustified today. In fact, many of these anti-vertigo drugs that are sold in our country are not approved by the FDA in the US.
The vestibular labyrinth which is the main organ of balance situated deep inside the ear and connected to the brain has different sensors that can sense movement in different directions in whatever angle the movement takes place; it also senses in the side to side, front – back and up – down directions. Each sensor of the vestibular labyrinth is very specific and senses one specific type of movement in a specific plane of movement. After the movement is sensed by the sensors in the vestibular labyrinth, the brain carries out some corrective measures by contracting some specified body muscles so that the subject does not feel imbalanced or vertiginous. If any one of these sensors are defective, the movement of the body in that plane is not sensed adequatelyand hence the requisite correction by the brain is not effected due to which the subject gets head spinning or feels imbalanced. If there is any defect in the brain or in the neural pathways that carry down the corrective impulse from the brain to the body muscles then also the same thing can happen and so all the individual sensors as well as the parts of the brain and the neural pathways need to be thoroughly tested. The sensors are the 3 semicircular canals (lateral, anterior and posterior) that sense movement in 3 different angular planes, the utricle that senses movement in the side to side and front to back directions and the saccule that senses movement in the up and down axis. The adjoining figure shows the different sensors in the vestibular labyrinth. The videonystagmography or VNG test helps to identify lesions in the lateral semicircular canal at low frequencies of vestibular stimulation, the video head impulse test or VHIT helps to identify lesions in the superior, lateral and posterior semicircular canals individually at different high frequencies of vestibular stimulation. These sensors of the balance system need to be evaluated at different high frequencies of vestibular stimulation to ascertain how these sensors function at different types of stimulation. The vestibular evoked myogenic potential or VEMP test helps to identify lesions in the otolith organs namely the utricle and the saccule. The ocular VEMP or oVEMP identifies lesions in the utricle and the cervical VEMP identifies lesions in the saccule. The static and dynamic subjective visual vertical test or SVV helps to diagnose otolithic lesions and the faculty of the visual vertical which is a function of the vestibular system. The Dynamic Visual Acuity test or DVA assesses the functial status of the vestibuloocular reflex. There is so much precision in the current Vestibular Function Tests (VFT) that we can today ascertain the functional status of each of these different sense organs inside the vestibular labyrinth and not only that, also evaluate vestibular function at different frequencies of vestibular stimulation. Advancements in the hearing tests too have sharpened the diagnostic skills of neurotologists. Electrocochleography or ECochG helps to identify and confirm Ménière’s disease, the advanced hearing tests like CHIRP BERA and ASSR in addition to the detailed multipoint DPOAE test can evaluate lesions in the auditory system with pinpoint precision. Instruments like the Auricle that can carry out real ear measurements or REM has brought tremendous amount of precision in the fitting of hearing aids, and the fitting of hearing aids is no longer a trial and error method as it used to be some years back. The age-old pure tone audiometry or PTA, Tympanometry and Eustachian tube function tests or ETF still retain their pride of place but the new audiological tests have added precision to audiological diagnosis. All these different high precision vestibular function tests and audiological tests combined with a very detailed history of the patient’s complaints alongwith the chronology of the symptoms and a through clinical examination of the patient, though pretty time consuming, has made it possible to accurately diagnose the cause of the vertigo or imbalance in nearly all patients presenting with such problems. This is just for information sake and the treating clinician is of course the best judge to decide on the diagnostic tests and treatment that is relevant for each particular patient at a particular time. Some details of the different tests for evaluating the vestibular (i.e., the balance system) and the auditory system can be had from the page titled ‘Services’ in this website.
Facilities for these advanced tests are available in all modern neurotology clinics including Vertigo and Deafness Clinic at BJ 252, Salt Lake, Kolkata – 700091, India. The reader is referred to the relevant pages like ‘Services’, ‘An Insight into the Therapy of Vertigo’ and ‘About Vertigo Deafness Clinic’ in this website for more details on the current concepts of diagnosis and management of vertigo.
For an update on the current scenario on ethical and rational management of vertigo please see the post in the same heading in the blog space of vertigoclinic.in