Medically Unexplained Oral Symptoms

How common are medically unexplained symptoms?

MUS are extremely common, with reportedly around 80% of people experiencing them in any given week,⁷ although most will not seek medical attention. A systematic review of 996 studies found the point prevalence of at least one MUS in patients attending GPs to be 40.2%.⁸ A Danish study of consultations on a randomly chosen day classified 36% of reported symptoms as unexplained, with 50% expected by the GPs to remain so. The consultations with MUS patients were also felt to be more demanding.⁹ In specialist practice, up to 40% of ENT outpatient consultations relate to MUS,⁷ and in rheumatology, 20% had symptoms ‘somewhat explained’ and 8% ‘not at all explained’ by organic disease.¹⁰ MUS, therefore, constitute a large proportion of the clinical workload in both primary and secondary care, and are, in fact, the most common problem in some specialties with up to 50% of patient symptoms still unexplained at 3 months.¹¹ A recent estimate placed the total cost of managing MUS at 10% of National Health Service expenditure on the working age population.¹² The number of patients attending primary dental care with MUOS has not been well studied, and comparable figures are not available.

Causes/associations

MUS have been considered to arise due to predisposing, precipitating and maintaining factors¹³ and a number of causation models have been proposed. Genetic and environmental factors (eg early experiences of adversity, experience of parental ill health and self illness behaviours as a child) are postulated to predispose to MUS.^14,15 Other associated factors are high levels of health anxiety, reassurance-seeking behaviour, recent adverse life events and female gender.¹⁶ There is a relationship between MUS in adults and their children.¹⁷ Difficult or stressful events can then precipitate MUS: they are strongly linked with depression and anxiety.¹⁸ MUS are substantially higher among those on sick leave from work versus those in work.¹⁹ Many of these factors can also perpetuate symptoms. Social, cultural and societal influences are also important, because the incidence of different MUS varies widely between different groups and cultures.¹³

Related/confusable psychiatric conditions

It is clear that a significant proportion of patients suffer with a comorbid psychiatric disorder. Several psychiatric conditions have non-organic somatic symptoms as a core element and, therefore, provide a psychiatric explanation for symptoms that appear unexplained. Psychiatric assessment is generally needed to make many of these diagnoses, and clearly, it falls outside the remit of dentists and often of GPs. Nevertheless, such entities should be borne in mind and appropriate onward referral arranged if a psychiatric condition is suspected.

These psychiatric disorders, and the criteria for diagnosis, are clearly defined within two documents, each providing an alternative classification system – the International Classification of Diseases²⁰ and Diagnostic and Statistical Manual of Mental Disorders.²¹ In both cases, the content of previous editions was criticized and has been updated. Diagnostic entities and definitions of psychiatric conditions that overlap with/include MUS have, therefore, changed somewhat over the past few decades.

Both depression and anxiety (closely linked conditions that often co-exist) are known to be significantly more prevalent among those with MUS compared to both those with no symptoms at all, and those with explained physical symptoms.¹⁸ Somatic symptoms are common in these conditions. In depression, early morning wakening, loss of appetite and libido, weight loss and agitation/retardation may occur. In anxiety, a wide range of symptoms including palpitations, sweating, a ‘lump in the throat,’ nausea, dizziness, muscle aches, and many others can occur. These somatic symptoms (rather than low mood) are often the primary presenting complaint when attending a clinician and thus, it is particularly important for these diagnoses to be considered.²

The conditions, previously called somatization disorder and somatoform pain disorder, are now termed either bodily distress disorder²⁰ or somatic symptom disorder.²¹ The small subgroup of patients who have these disorders is distinguished from other MUS patients largely by the degree of distress, excessive attention given to, and persistence of, the symptoms, lack of response to reassurance, and degree of interference with daily life, work and social functioning. The International Classification of Diseases 11th Revision (ICD-11) describes the broad category of ‘bodily distress disorder,’ which ‘is characterized by the presence of bodily symptoms that are distressing to the individual and excessive attention directed toward the symptoms, which may be manifest by repeated contact with healthcare providers. If another health condition is causing or contributing to the symptoms, the degree of attention is clearly excessive in relation to its nature and progression. Excessive attention is not alleviated by appropriate clinical examination and investigations and appropriate reassurance. Bodily symptoms are persistent, being present on most days for at least several months. Typically, bodily distress disorder involves multiple bodily symptoms that may vary over time. Occasionally there is a single symptom—usually pain or fatigue—that is associated with the other features of the disorder'.²⁰ The Diagnostic and Statistical Manual of Mental Disorders 5th edition (DSM-V) employs a slightly different terminology and defines ‘somatic symptom disorder’ as the presence of one or more somatic symptoms, significantly disrupting daily life and eliciting disproportionate and persistent anxiety, to which excessive time and energy are devoted. The duration is typically longer than 6 months.²¹ The requirement for the lack of a medical explanation, which was a criticism of previous editions, has been removed.

Conversion/dissociative disorders occupy a status of confusing terminology, and, in the past, have been largely interchangeable terms. Dissociative disorder is defined as ‘the presentation of motor, sensory, or cognitive symptoms that imply an involuntary discontinuity in the normal integration of motor, sensory, or cognitive functions and are not consistent with a recognized disease of the nervous system, other mental or behavioural disorder, or other health condition'.²⁰ Symptoms can include paralysis, loss of speech, sensory changes, seizures and amnesia, may occur suddenly and be apparently triggered by a traumatic life event. They often represent the patient's perception of how a particular illness should present, thus, for example, an apparent stroke, but with sensory and motor changes inconsistent with stroke pathology. Conversion disorder is not included in ICD-11, whereas in DSM-V conversion and dissociative disorders are listed as separate entities.²¹

Adjustment disorder is a reaction to a psychosocial stressor causing significant and recurrent worry and impairment of functioning, which generally resolves within 6 months. Somatic symptoms, such as loss of appetite, sleep disturbance and fatigue, often occur. In one series it was the third most common psychiatric comorbidity in MUS patients after depression and anxiety.²²

Hypochondriasis and factitious disorder are both defined in ICD-11 only, and in DSM-V come largely under the umbrella of somatic symptom disorder. Hypochondriasis is a non-intentional belief of having an illness, despite negative test results and appropriate reassurance. The patient ruminates on this possibility and seeks medical attention regarding normal bodily functions, variants or insignificant minor ailments interpreted as a reflection of a serious underlying problem. This pre-occupation is typically in the form of an over-valued idea, but can be of an intensity to constitute a delusion and thus, a psychosis. There may be insight into the pre-occupation, although this does not stop the process.

Personality disorder is defined as an enduring disturbance of functioning of the self and/or interpersonal dysfunction with maladaptive cognitive, emotional and behavioural patterns manifesting across a range of personal and social situations.² Formerly, 10 subtypes were distinguished, whereas now, it is simply graded as mild, moderate or severe, with or without one or more prominent trait qualifiers. Around 12% of the general population has a diagnosable personality disorder²³ and in those, the prevalence of psychiatric comorbidity is high. Co-prevalence of personality disorder and MUS is high.²⁴

Post-traumatic stress disorder (PTSD) is a disorder that can follow exposure to an extremely threatening or horrific event, characterized by re-experiencing the event, avoidance of thoughts/memories of the event and persistent perception of heightened threat.²⁰ PTSD is strongly linked with increased incidence of MUS (and physical medical conditions).²⁵

Factitious disorder is the intentional fabrication of illness, either physical or psychological, without clear gain (thus distinguishing it from malingering or drug-seeking behaviour). This can be via induced or exaggerated signs or symptoms, deliberate non-compliance with treatment, interference with specimens, tests or wounds, or falsification of records. Formerly known as Munchausen syndrome, a ‘by proxy’ variant exists whereby illness is induced or prolonged in a dependent, thus introducing significant safeguarding concerns. It is significantly linked with certain personality disorder types, and has been recently reviewed in a dental context.²⁶

Rarely, a somatic delusion, as part of a range of delusional disorders including forms of schizophrenia, can manifest as, or include, oral symptoms. One particular example is ‘oral cenesthopathy’ – a delusional belief in the presence of an abnormal or strange body sensation, particularly an oral foreign body. This term is rarely used in the psychiatric literature and has received limited study in dentistry.²⁷

Why do primary care dentists need to know about MUS and MUOS?

It is recognized from studies of medical patients that the majority with MUS can be managed in primary care.¹³ The same could be true in primary dental care, but has never been adequately studied. Dentists may have patients presenting to them, as the first practitioner consulted, with MUOS. Managing these cases correctly from the earliest stage is crucial for a successful outcome. In some cases, the dentist will be able to determine the lack of cause and, therefore, presence of MUOS – in others patients may need evaluation by their GP or a hospital specialist. Certainly, dentists will see patients with MUS in other systems on a very regular basis.

Which MUOS are likely to be seen in dentistry?

Within the literature there is some disagreement on precisely what orofacial symptoms can be classified as MUOS, and some are no longer considered unexplained as research has provided a causal mechanism.

Chronic orofacial pain, as encompassing atypical facial pain, atypical odontalgia and burning mouth syndrome, has been considered MUOS by some authors.^28,29,30 However, this is now an outdated view because these pain syndromes are readily explainable through the proven pathophysiological mechanism of peripheral and central sensitization. This has been defined as ‘an amplification of neural signalling within the central nervous system (CNS) that elicits pain hypersensitivity'.³¹ Neurophysiological changes in neurones in the CNS lead to increased spontaneous neural activity, reduced activation threshold, increased synapse efficiency, reduced activity of inhibitory circuits and convergence of inputs from pain and non-pain sensory fibres. These neurophysiological changes, in practical terms, produce an autonomous and longer lasting perception of pain from a smaller (previously non-noxious) stimulus.³¹ All of the aforementioned pain syndromes, as well as temporomandibular disorder and phantom tooth pain, are now explainable in this way.³² Ways of explaining these symptoms to patients are discussed later.

Phantom bite syndrome, also termed occlusal dysaesthesia, has also been classed as MUOS.³⁰ Other authors, however, assert it to be a form of psychosis where a delusional belief is held of a problem with the bite (which is not improved by occlusal modification).³³ A further proposed explanation is of ‘dysproprioception,’ sometimes iatrogenic after dental treatment, and thus, an enhanced awareness of a change in occlusion.³⁴ Therefore, this syndrome should not be classified as MUOS.

No comprehensive study of all possible MUOS seen in dental primary care has yet been conducted, and reliable data on the prevalence of these symptoms in dentistry are not available. The exact symptoms that could occur have been poorly defined, although it is likely a wide range of MUOS occur, in common with the breadth of MUS across all other body systems.

How much investigation/testing should be done if MUS are suspected?

Where a clinician suspects MUS, deciding how far to investigate can be problematic. Clearly the risk of missing organic pathology is a concern, particularly disorders that are rare, vague or non-specific in their presentation. Among MUS patients, studies from the 1960s and 1970s reported very high rates of missed organic pathology of up to 40%; however, a more recent review put this figure at 4%.³⁵ A 19-month follow-up of 1095 patients diagnosed with MUS in a neurology service recorded only four cases (0.4%) where organic pathology was subsequently diagnosed and explained the original symptoms.³⁶ While the usual concern is missing organic pathology, actually misdiagnosing MUS as organic pathology is much more common.³⁷ Furthermore, clinicians were more likely to make diagnoses of organic pathology, later revised to MUS, in patients who were older, in employment, not receiving other therapies and when the clinician was satisfied with the consultation.³⁷

Therefore, there is a balance between extensive tests for organic pathology and rational use of resources. There is no doubt that over-investigation can cause iatrogenic harm.^2,13,38 Besides discomfort from the test itself, this includes direct risks as in diagnostic endoscopy, radiation exposure in X-ray-based tests, yielding of incidental findings leading to further tests/procedures and false positives, which can all generate further anxiety, harm and reinforce ‘illness behaviour’.² The degree of investigation pursued is, in fact, more related to the clinician's response to the patient's symptoms than the patient's ideas about the problem or demands.³⁹ Undertaking investigations ‘for reassurance’ is an often-quoted idea. A meta-analysis found investigations into symptoms with low risk of serious underlying illness did not provide significant reassurance, reduce anxiety or resolve symptoms, although subsequent primary care visits were slightly reduced.⁴⁰

Therefore, although many cases will require detailed investigations, it is not essential to exhaustively investigate in every case and exclude all possible organic diagnoses before reaching a conclusion of MUS. As above, there are negatives to investigations, and these must be balanced against the probability of yielding useful findings. With an index of suspicion, MUS can often be suspected from an early stage. Distinguishing these cases is a matter of clinical skill and experience. In these cases, where suspicion of MUS is high, it is not unreasonable to prudently investigate, but if initial tests are negative, then any further tests should be carefully planned to balance excluding organic pathology with the adverse effects of the tests, and with clear explanation to the patient as detailed below.

Assessment in primary dental care

When medically unexplained symptoms are suspected during a dental consultation, the following considerations may be useful during the assessment.

Management in primary dental care

Once it has been established that the symptoms of a patient in primary dental care are medically unexplained, likely to be following tests, information gathering and further consultations and reviews, the following management advice may be useful.

For patients with an underlying an psychiatric condition and referred to the GP, the following broad management strategies exist.

Prognosis

MUS improve in 50–75% of patients and deteriorate in 10–30% over a period of 6–15 months, and those with worse baseline symptoms have a worse prognosis.⁵³ Of those patients consulting primary care, 25% still have symptoms at ! year.⁵⁴ A 3-year study in the Netherlands found 36.4% of patients with MUS had persistent symptoms,⁵⁵ with parental psychopathology, increased medical comorbidities and reduced physical function being predictive of persistence

Various factors indicate a worse prognosis for MUS: the number, duration and frequency of symptoms, and involvement of multiple systems. Presence of mental illness is a weak prognostic factor. Psychological factors, such as negative illness perceptions, illness worry, maladaptive coping, catastrophizing, negative affect and childhood abuse, are also associated with a worse prognosis.⁵⁶

Conclusions

MUS are common in all areas of healthcare, and are likely to be common within patients presenting to dentists in primary care also. There are a number of reasons why managing patients with MUS can be challenging, but a good amount of clear guidance exists (aimed primarily at GPs) for such cases. Much of this is directly translatable from primary medical into primary dental care, where the majority of dentists work. Often, it can be suspected at an early stage that a symptom will not be explainable, and in such cases, judging how much investigation to perform can be difficult, although the risk of concluding MUS and missing organic pathology is low. Dentists have a role in the initial assessment and long-term care of such patients, but are likely to need to work closely with the patient's GP, and occasionally hospital specialists.