Providing Expert Opinion on Olfactory and Gustatory Disorders
Summary
In discussing olfactory and gustatory disorders, it is often necessary to provide an expert legal opinion—a task that differs greatly from everyday clinical work. A series of factors makes a legal assessment difficult, particularly missing initial examinations and the limited possibilities to obtain objective examination results. The question of work-related causes of olfactory and gustatory disorders is of particular interest, despite the fact that these disorders are often not cited in lists of occupational diseases (e.g., in Germany). Presenting complaints depend greatly on their cause. In general, the patient reports a limited capability of smell as well as of taste. It is important to distinguish between a subjective gustatory dysfunction (generally an olfactory dysfunction) and a real dysfunction in terms of hypogeusia or ageusia.
A thorough medical history is the basis of every assessment, supplemented by clinical examinations, and completed by specific tests of olfactory and gustatory capabilities. For German-speaking countries, the Olfactology and Gustology Task Force of the German Society of Otolaryngology (Deutsche Gesellschaft für Hals-Nasen-Ohrenheilkunde) has published recommendations regarding the provision of expert opinion on olfactory disorders, which facilitate the assessment in practice.
Introduction
It is often necessary to provide an expert assessment on presumed or confirmed olfactory and gustatory disorders. In total, olfactory disorders outnumber gustatory disorders. A series of factors complicates the assessment of olfactory and gustatory disorders. Aside from missing initial examinations in almost all cases (convincing examinations of smelling and tasting capabilities are rarely conducted and are usually not among the screening examinations of the Employers’ Liabilities Insurance Association), this is mainly due to the lack of results from olfactory or gustatory examinations. In this chapter, we will demonstrate the assessor’s principal tasks as well as the obligatory examinations and basics of assessment in the authors’ view. Also, we will present recommendations for providing an expert opinion. Furthermore, this complex problem will be illustrated with two case studies from everyday practice.
Providing Expert Opinion
The task of providing an expert opinion is complex and differs greatly from the everyday activities of clinical practice. Within the framework of social legislation, a physician is often asked to function as an expert assessor for the Employers’ Liabilities Insurance Association, as well as for cases concerning compensation and the Severely Handicapped Persons Act. Private insurers have regulations of their own, which will not be discussed here. Finally, it might be necessary to take a stand in a liability suit if there are allegations of treatment errors and compensation claims (e.g., after nasal or sinus surgery). Iatrogenic olfactory disorders, for example, may be due to overzealous nasal surgery, most commonly polypectomy. These may be litigated as malpractice. Experts are required to testify that the nasal surgery was overzealous and so a departure from the standard of care. Defense experts testify the opposite.
Regarding the Employers’ Liabilities Insurance Association’s legislation, the question of work-related causes of olfactory and gustatory disorders is of utmost significance. Table 18.1 gives an overview, without claiming to be complete, of substances that are able to cause toxic olfactory disorders. In each case, an evaluation of the particular workplace is mandatory. Mixed exposures are numerous (e.g., chromates, bases and acids in electroplating). The precondition for toxic olfactory disorders is a substantial overstepping of critical values defined by occupational medicine. Most of today’s toxin exposures are therefore the result of an acute, intense injury. In the case of exposure to caustic or irritant agents in very high concentrations, the possibility of a toxic olfactory disorder and rhinitis must be considered.
Metals and their compounds | Organic solvents |
Lead | Inter alia several alloys, including benzenes |
Chromium | Esters (acetates) |
Cadmium | Carbon disulfide |
Nickel | Trichloroethylene |
Mercury | |
Aldehydes | |
Dust and smoke | |
Welding fumes | Acids and bases |
Cement | |
Hydrogen sulfide | |
Irritant gases | |
Inter alia ammonia | Carbon monoxide |
Nitrous gases | |
Sulfur dioxide | Cyanide |
Reproduced from Stuck and Muttray (2008)36; not all original papers were verified. | |
An overview of toxin-induced anosmia may be found in Smith et al 2009.1 This review points out that in the past, and prior to Occupational Safety and Health Administration protection, anosmia was seen as a result of chronic exposure to toxins such as formaldehyde and photo developing chemicals (see also Chapter 9: Miscellaneous Causes of Olfactory Dysfunction).
In addition, zinc gluconate nasal sprays, touted as a homoeopathic treatment for the common cold, are reported to cause anosmia based on numerous patient complaints to the Food and Drug Administration. Zinc gluconate nasal sprays have been removed from the market and presumably the flurry of current lawsuits will soon be resolved. Several scientific publications support the diagnosis of zinc-induced anosmia.2,3
In the case of a well-founded suspicion of an occupational disorder, it is usually mandatory (e.g., in Germany, Switzerland, or Austria) to report this to the Employers’ Liabilities Insurance Association, even if a reduction in earning capacity that may lead to retirement is not expected. The insured patient must be informed of this report by his physician. A comprehensive comment on the legal basis of assessment cannot be given here, as it differs substantially among different countries and social systems.
Expert Opinion in Olfactory Disorders
The symptoms involved in the assessment of olfactory disorders depend greatly on their cause. Persons who have lost their capacity to smell in an accident can normally define the circumstances and moment of the damage very clearly. They often experience the symptoms very vividly, as in the majority of these cases, an uninhibited ability to smell existed previously. If an olfactory disorder has evolved through the years because of occupational exposure to toxins or is claimed as a result of a medical intervention with a possibly preexisting impairment of smell, the situation clearly becomes more difficult for the assessor.
In general, not only an impairment of smell but also an impairment of taste is reported. The differentiation between a concomitant disorder of taste that occurs as a result of an olfactory disorder and a real gustatory dysfunction in terms of hypogeusia or ageusia is of substantial importance for an adequate assessment. This differentiation is often difficult to explain to the parties concerned. Factual gustatory disorders are relatively rare and will be discussed later. An appropriate medical history and a diligent gustatory examination ought to be part of every assessment of olfactory disorders. It must be pointed out, however, that disorders of the factual gustatory capabilities and subjective impairment of taste can both occur with a pre-existing olfactory disorder. Impaired sensitivity to flavors, as well as reduced trigeminal sensitivity in olfactory disorders,4–7 is ascribed to the loss of reinforcing neuronal interaction, and not to damage to receptive structures. A reduced reaction to trigeminal stimuli can be assessed as an indication, but not as proof, of an amplification of existing symptoms, or of malingering.
Medical History
At the beginning of the medical history, the nature and extent of the olfactory disorder must be established, and the origin and course must be ascertained. Qualitative olfactory disorders (e.g., parosmias and phantosmias) without an associated decline of olfactory capabilities (hyposmia or anosmia) are rare and not typically assessed for medicolegal purposes. For isolated qualitative olfactory disorders, concrete directives for action do not exist; compensation is, therefore, usually not provided.
In olfactory disorders that have developed over the years, a precise date of onset cannot be given quite frequently. Owing to their gradual onset, the symptoms often are not experienced or described as vividly as sudden onset disorders, and quite often olfactory disorders are noted as a secondary complaint to other disorders that are to be assessed. Questions regarding the accidental consumption of spoiled food, or occasions when smoke or hazardous materials that can be smelled were not recognized in time, can be helpful in chronological determination, as such occurrences are often remembered. This can be vital for the assessment of correlation, as toxic olfactory disorders develop in close chronological correlation with the causative exposure. Quite often, patients complain of a loss of appetite in association with the perceived taste disorders. However, some gain weight as a result of overeating to seek some taste. Change in body weight should be ascertained.
Additionally, special attention should be paid if the patient has previously seen a doctor for olfactory disorders or if appropriate examinations have already been performed. Generally, however, relevant examination results are not available. Patients are often assessed initially for other occupational disorders (e.g., hardness of hearing due to noise and disorders of the lung and the musculoskeletal system) and work-related olfactory disorders are not described until later in the process.
As a rule, traumatic damage resulting from accidents leads to an immediate defect in the fila olfactoria themselves, or in the brain areas responsible for processing olfactory stimuli. The majority of cases of post-traumatic anosmia are a result of frontal or occipital trauma, but are occasionally the result of temporal or parietal trauma. The generally accepted mechanism of injury is that the trauma results in an abrupt anterior or posterior movement of the brain. The thin olfactory fila of the cranial nerve are presumably stretched or torn as they exit the cribriform plate. If the fila are stretched, olfaction may recover; if torn, the olfactory disorder will usually persist. Some such patients will develop phantosmia, which may dissipate after several months. Loss of consciousness is not a prerequisite for post-traumatic anosmia. Isolated intracranial injury is uncommon.8 Although the onset is usually immediate, patients with severe cranial injuries or multiple trauma may not perceive the disorder until the acute phase of the injury has resolved, which can take up to several months depending on the severity of the injury. A gradual decrease in olfactory function in this period is not impossible, though very unlikely.
Obviously, a comprehensive review of the course of events and the resulting injuries must be attained and, if indicated, examination findings (e.g., magnetic resonance imaging [MRI] or paranasal sinus computed tomography [CT]) should be requested.
In cases of suspected occupational olfactory disorder due to exposure to toxic matter, the character, duration, and extent of the exposure must be evaluated thoroughly, including use of any protective measures. For example, mobile vacuum devices for welding outside the workshop are often not used, and paper screens do not protect from organic solvent fumes. Questions regarding work-related symptoms are also important. Such symptoms could be due to irritation of mucous membranes by irritant substances. Organic solvent fumes acutely affect the central nervous system depending on dosage. Typical symptoms are loss of appetite, nausea, dizziness, headaches, and intoxication (see Case Study 2). Older patients, in particular, have been “used” to such symptoms for many years and do not mention them spontaneously, so it is important that the assessor asks about them directly. Investigations into occupational disorders normally do not register these symptoms. An inquiry with the company medical officer could be helpful.
As with any assessment, other possible causes for the disorder (e.g., inflammatory or structural sinonasal causes, or nonsinonasal or neurodegenerative causes) must be excluded. If the patient suffers from acute inflammatory disorders (such as acute rhinitis or rhinosinusitis) at the time of examination, the required olfactory tests should be postponed until the acute inflammation has resolved. The existence of chronic paranasal sinus inflammation can impede the assessment significantly, as recovery often is either not possible or prolonged, and this must always be considered as a differential diagnosis. On the other hand, there is the possibility that toxin exposure could also be responsible for the development of chronic inflammation of the nose or the paranasal sinus.9,10 If this is definitely the case, then the olfactory disorder would rank as a direct result of an occupational disorder.
When taking the medical history of a patient presenting with an olfactory disorder, it is important to ask about previous surgical interventions on the nose or the cranium. Olfactory disorders can exist that are not primarily reported, particularly in patients with chronic inflammation of the paranasal sinuses.11 After surgical intervention, these patients often ascribe their (quite frequently persisting) olfactory disorder to the surgery. In view of subsequent legal claims based on an assumed malpractice on the part of the surgeon (which normally entails an expert opinion), the authors recommend performing olfactory testing before surgery (e.g., before septal surgery or surgery of the paranasal sinuses), and explaining to the patient the possible (potentially permanent) disorders associated with the intervention. Postinfectious anosmia is also a common cause of olfactory dysfunction.
Examination
Clinical and Technical Examinations
During the clinical examination of the nose, special attention must be paid to inflammatory changes, chronic inflammatory or atrophic changes of the mucous membranes, relevant structural abnormalities (obstructing deviations of the septum, significant hyperplasia of the nasal concha), and signs of acute or chronic inflammation of the paranasal sinuses, including nasal polyposis. As well as anterior rhinoscopy, endoscopy should be included in the examination; special attention should be paid to the fossa olfactoria. Furthermore, signs of previous surgical interventions (e.g., synechias or perforations of the septum) should be sought. However, the latter can also be attributed to chronic damage of the mucous membranes due to occupational exposure to toxic substances such as chromates or acids.
Purely structural changes with reduced nasal airflow are very rarely the sole cause for a relevant olfactory disorder, and rhinomanometric findings do not show any causal relationship with olfactory capability. (Here, the previously mentioned inspection of the fossa olfactoria using angular optics is the most significant test.) However, owing to its minimal invasiveness and its widespread use, rhinomanometry is used frequently to determine nasal airflow. If, in the course of the medical history or clinical examination, signs of a chronic disorder (e.g., chronic rhinosinusitis) are discovered, additional tests might be necessary, such as CT of the paranasal sinuses. These, however, should be discussed beforehand with the commissioning party. Additional images of the cranium (CT or MRI) are required to rule out a space-occupying intracranial process or tumor of the skull base if there are no relevant radiological findings.
If there are complaints of disorders of taste (which usually exist), the clinical examination and assessment of gustatory disorders should also be applied as described on p. 168–178.
Olfactory Testing
Quantitative validated tests of olfactory function are mandatory in all cases. In Europe, the authors recommend the extended “Sniffin’ Sticks” test battery.12 Other test systems that are recommended (especially for the USA) are the University of Pennsylvania Smell Identification Test (UPSIT) or the test of the Connecticut Chemosensory Clinical Research Center (for further details see Chapter 6: Smell Testing).
A test of retronasal olfactory capability can also be performed if the relevant resources are available. Qualitative olfactory disorders cannot be tested to date. They must be specified in detail, in particular the frequency of their occurrence. Testing with mainly trigeminal substances such as acetic acid or ammonia can give clues regarding an amplification of existing symptoms, or simulation of such symptoms.
In this context, we would like to point out that even a patient with anosmia can score a minimal number of points in the Sniffin’ Sticks test because of the probability of guessing correctly in the “forced choice” test. Conspicuously low results, or a TDI (threshold, discrimination, and identification score) of 0, points to simulation of symptoms (malingering). The probability for a TDI score of 0 is 0.002%; a TDI score of 1 has a probability of 0.02%. The UPSIT is a 40-item multiple-choice test. Malingering in this test is defined as a score of 5 correct, as it is statistically extremely improbable for a patient with anosmia to score 5. Nevertheless, malingering is still possible for both tests.
In all cases of doubt and to rule out simulation, in the authors’ opinion, the assessment of olfactory disorders should also include an objective examination, primarily using olfactory and trigeminal event-related potentials (ERPs). The assessment may need to be performed by a specialized institution if essential technical equipment is not available. Lack of ERPs with preserved responses to trigeminal stimuli substantiates the diagnosis of anosmia (even if it does not answer the question of its cause). The persistence of olfactory potentials, however, clearly speaks against the presence of anosmia. Despite the publication of standard parameters for latencies and amplitudes,13 a reliable verification of hyposmia is not possible at the time.14
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