Some considerations in Tourette syndrome diagnosis and cherished ideas


The arguments for viewing Tourette syndrome as a narrowly constrained disorder that consists of a discrete chronic tic disorder that may or may not be accompanied by one or more additional comorbid ‘disorders’, often appear not only unpersuasive but unsupported by evidence. The multi-disorder 'splitting' approach, for many, requires a more substantial symptomological and pathophysiological evidence-base to support it’s unquestioned use. Some would say it has become a set-in-stone ‘dogma’ and relies too much on anecdotal information and 'opinion'. It remains, possibly, as an over-valued legacy of psychological/psychiatric approaches to neuro-developmental medicine. In most cases physicians adhering to this approach, ‘fence off’ groups of symptoms from the overall symptomatology they encounter, or have presented to them in the ‘history’, and apply labels to those in a largely qualitative fashion. To illustrate this difference in approach, diagrams used in opthalmology include genuine or real patterns which are objectively recognisable within the complexity however complex 'blot' images, sometimes used in psychoanalysis can provoke perceptions of something meaningful based on looking for resemblances to known shapes/patterns but, in actuality, only the complex pattern itself exists. 'Significant' patterns may be 'teased' from complexity and much scope for interpretation exists depending on the observer's perception and recognition abilities. In the case of symptoms (or symptom groups) the danger lies in assuming they belong to one disorder or the other but not that they might be shared by several disorders and if the latter approach is accepted without discrimination it can be assumed that each of those disorders are present.



Ishihara (left) and Rorschach or random blot (right) diagram

 

 

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It is accepted, currently, that diagnosis of TS is relatively qualitative and hence somewhat subjective and that no definitive tests or investigations are appropriate. However recent research suggests that some quantitative techniques may be of value in the future. There are several diagnostic criteria-driven checksheet and scoring protocols, including the Yale Tic Severity Scale, and some neurophysiological, neurohormonal and neuroanatomical correlates have been identified. In the consulting room however, beyond observable tic behaviours, there are few ‘signs’ that can be elicited on examination and there are no investigations or laboratory analyses that can be ordered. Brain imaging technology has not yet revealed acceptably consistent structural characteristics but recent progress has been very encouraging. Work continues in refining understanding of the genetics of TS but this has, so far, proven to be complex and sufficiently specific markers have not been identified.

 

The use of scoring algorithms does not always ensure validity as the criteria those algorithms employ may be faulty especially when those diagnostic criteria are isolated subjectively in the first place. The definitions of disorders are often a product of the 'committtee consensus' approach that underlies the coding of diagnostic manuals such as the DSM and ICD rather than a process most would consider to be 'scientific' and include pathophysiological (e.g. neuro-biological) criteria. Unfortunately those criteria also form a basis for much of the data collection and categoristaion that underpins research studies. The specificity of scoring systems is often suspect. An example is the significant cross-over that occurs when such systems are used to 'diagnose' autistic spectrum disorder - a very large number of people with Tourette syndrome when undergoing these tests fall well inside the ASD criteria and are hence misdiagnosed. This illustrates the fallacy of symptoms domains being exclusive to one disorder or another. Such over-confident allocation of symptomatology would never be tolerated in other areas of evidence-based medicine where differential diagnosis would demand more rigorous elucidation. A spectrum disorder such as TS with diverse symptom domains will inevitably fall across a range of diagnostic categories that 'belong' to other disorders. Are those symptoms domains merely shared between several disorders or are they exclusive to them?

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The presentation of TS is seemingly complex and diverse, however careful exclusion of other possible differential diagnoses leaves a relatively unambiguous route to diagnosis. The combination of symptoms is difficult to misinterpret. TS may present in such a way that on the basis of observable symptoms alone it may be clear. Tic disorders may be transient and a significant proportion of all children do exhibit tic behaviours during their development. It is the continuous persistence of tics (e.g. motor and vocal) over a year or more that strongly suggests the diagnosis. Generally however a physician may not be able to, or fail to recognise tics during consultation. Patients are often able to suppress or hide tics under clinic conditions or may have tics that although present are not immediately noticeable. The clinical history is therefore, of principle importance, however good knowledge of TS presentation patterns is required in order to be able to ask the correct questions.

The severity of tics is not always indicative of the overall severity or 'disability' load of all TS domains combined. Motor tics may affect any skeletal muscle groups and muscles of the diaphragm and those under autonomic control may also be involved. Those in abdominal, pelvic-floor, gluteal or thigh muscles may not be noticed. Diaphragmatic tics are relatively common but usually unseen as are some of those of the pharynx, tongue or larynx. Motor tics may consist of tightening and relaxing of muscles, or the adoption of slow-onset postures and positions or interfere with gait on walking. Vocal tics may consist of very obvious vocalisations, tongue-clicking, grunting etc. or may occur as soft or barely noticeable blowing or inhalations through the mouth or nose. Many motor and vocal tics are easily disguised as ‘normal’ activities, a skill that some patients are able to develop to avoid drawing attention. This is usually a survival skill developed to negotiate the difficulties of social, work or school environments.

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Whether adhering to the splitting or integrated disorder perspective, it is important to determine a complete clinical picture of all symptom domains present. Around 90% of individuals have so-called comorbid disorders which strongly suggests that many symptoms, thought of as belonging to one disorder or another, might actually be symptoms of TS itself. The intricacies of attempting to separate or group these symptoms into a plethora of discrete disorders, is fraught with pitfalls. A specific danger of the comorbidity concept is that it logically leads on to a fragmented approach to management, therapy and supportive provision. There has been a tradition among many physicians to treat each presumed disorder as a discrete entity. This, unfortunately, has lead, in many cases to ineffective treatment regimes which can actually exacerbate some symptoms or introduce new ones and so further complicate the clinical picture. It is very easy to become lost in a seemingly intractable maze of symptoms and continual drug adjustments/substitutions.

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A particular difficulty comes with attempting to separate obsessive, compulsive, impulsive behaviours, emotional reactivity, hyperactivity and the difficulties that manifest as attention deficit, poor concentration and impaired sensory processing/hypersensitivity. Labelling these as OCD, ADD/ADHD, SPD does not represent well the complex interaction between these and so-called Tourette or tic behaviours. Additionally differences have been noted between OCD and Tourette-related obsessive-compulsive behaviours (OCB). Some tics are undoubtedly beyond conscious control in younger patients but many have a very strong conscious and compulsive origin. Indeed if they were not compulsions the individual would not be ‘compelled’ to express them. Some researchers/clinicians have coined the term ‘premonitory urges’ to explain what they feel the TS patient is trying to convey to them. It is merely a intellectual exercise to make a distinction between tic urges that ‘need’ to be fulfilled and an action that is born of a compulsion. There is an established distinction perceived between simple and complex tics and obsessive and compulsive behaviours but those with TS do not always share this perspective. Many individuals are mystified by the certainties expressed by expert physicians regarding how their ‘disorder’ is divided neatly into discrete components. They may not accept, or may disbelieve, that they are so unfortunate as to be inflicted simultaneously with so many troublesome disorders. Unless you are both physician and TS sufferer it would seem extraordinary that such an ‘internalised’ and existential disorder could be adequately perceived with insight by another even if they are clinically qualified.

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Another area of contention arises from the ‘social difficulties’ that many with TS experience. When these are described by the patient of their carers, the response is often that TS does not include such issues. Frequently the conclusion will be that the individual may also have an autistic spectrum disorder: ASD or Asperger Syndrome. However it is quite common for symptoms, usually thought to be typical of ASD, to occur in those with TS but with several of the definitive autistic triad of impairments being entirely absent.

 

In TS there may be difficulties with ‘theory of mind’ perceptions. An example is being unable to read other’s intentions effectively and to detect deception. Conversational difficulties occur in the form of ‘perseverating’ excessively on a particular favoured topic, speaking rapidly and expansively without knowing when to stop, change topic or allow the other conversee to respond (poor turn-taking or reciprocity). Difficulties also occur with speech volume, overuse of particular 'favoured' words or phrases and in knowing what is socially-appropriate to say, to whom and when and if it touches upon a taboo subject. As is well known, taboos and rules have another special place in TS in that they frequently provoke a desire, or need, to transgress. Difficulties also occur in initiating conversation or social relationships, and maintenance and breaking-off can be equally challenging. Yet these and other difficulties may coexist without other defining autistic characteristics. People with TS are often beset by a sometimes overwhelming emotional responsiveness and concern for the well-being of others (empathy/compassion). Autonomy, a greater preference for material rather than living ‘things’ and language difficulties such as understanding the contextual meaning of words and phrases are usually more common in autism.

Use of language, even though vocabularly may be substantial, is often subtly different in Tourette and Asperger Syndromes. In Asperger's there can be a tendency to ‘lecture’ didactically rather than conversing 'conventionally'. A seeming lack of expression is often noticed and the material may seem to ignore context or the social-setting. In TS, there can be a tendency to use overly expressive and expansive phraseology and a to explore and elucidate, with great zeal, all possible connections and avenues with bewildering rapidity and imagination, and often not with immediately-apparent consistency.

 

Both TS and ASD may include obsessive thinking, reluctance to change a favoured way of doing things or a situation, as well as tactile problems with the texture and feel of clothing etc and hypersensitivity to and avoidance of ‘unpleasant’ environmental sensory stimuli such as noises, bright or flickering lighting, smells etc. A marked difference in the reasons for avoidance of social situations, due to stress can often be seen. In ASD, unwillingness, or absence of a need to socialise can prevail and others may be regarded as intimidating, too forward and willing to invade personal space making the individual uncomfortable. Many with TS are extremely gregarious and want to immerse themselves in the social environment and may even crave more interaction and enjoy close and tactile contact. They may however, paradoxically and reluctantly, go to considerable lengths to avoid social contact because of fears of ridicule, saying or doing the wrong thing (committing social ‘faux pas’) or due to the stress of holding in or hiding their tics and other behaviours. They are often painfully aware of what others think of them and fear embarrassment or criticism or, worse, ridicule.

The diagnosis of ASD in those with TS is frequently made but it is a diagnosis that should be made with careful consideration of any shared traits between the disorders and not made simply because there is a perceived requirement to fence-off symptoms to ‘account for everything’ and apply a discrete label within the comorbidity paradigm. It is becoming more common to use the term TS-Plus (or TS+) to denote the majority of cases (around 90%) in which non-tic symptoms are present. Whether the plus bit represents the greater part of the overall 'condition' or not, it is important to account for it's presence and consider all symptom domains ('comorbidities'). Only a small subset of cases of Tourette syndrome appear to involve just overt tics and should therefore, be seen as unrepresentative of the disorder.