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Abstract : This article comments on challenging aspects of the phenomenology of Tourette syndrome and obsessive–compulsive disorder and suggests a reductionistic clinical approach.
Résumé : Remettre en question la phénoménologie du syndrome de la Tourette et du trouble obsessif–compulsif : les avantages du réductionnisme
Cet article commente les aspects controversés de la phénoménologie du syndrome de la Tourette et du trouble obsessifBcompulsif, et propose une approche clinique réductionniste.
Key Words : Tourette syndrome, obsessive–compulsive disorder, phenomenology, reductionism
Psychiatrist: “Are the compulsions like the tics?”
Patient: “Yes”
Psychiatrist: “Are they different?”
Patient: “Yes”
Tourette syndrome (TS) and obsessive–compulsive disorder (OCD) share similar neurobiological mechanisms and, by virtue of that, demonstrate intriguingly interrelated clinical features.
Their etiologies remain unknown. Cooccurrence of the two conditions is common and occurs well beyond what one would expect from chance (1). Association is apparent at the hereditary level in that probands with one condition have a higher incidence of the other condition in family members (2,3). Secondary forms of each condition can independently be caused by neurological disorders of the basal ganglia, such as stroke or tumour (4,5). Functional brain scan studies demonstrate abnormal function of components of corticostriatothalamo-cortical (CSTC) neuronal circuits in both conditions (6,7). Specifically, TS involves the premotor circuit, and OCD involves the lateral orbitofrontal circuit. The CSTC circuits appear to be important as mediators of highly preserved and evolutionarily useful motor and cognitive programs (8). Examples of such programs include those for making common movements (for example, blinking), as well as more complex behaviours such as checking the security of one’s domain, cleaning and grooming the body, cleaning one’s surroundings and, even counting, exploring or collecting objects. Appropriate activity of these circuits allows the individual to perform common actions with maximal efficiency when they are necessary. Dysregulation of these circuits may lead to decreased inhibition of these motor or cognitive programs, with resultant unwanted, senseless, physical and mental overactivity. The symptoms of TS, OCD and related disorders result.
The behaviours, cognitions and affective symptoms seen in these conditions are often complex and difficult to analyze. Distinctions are important because therapeutic direction may depend on them.
In their “pure” forms, the core symptoms of TS and OCD are relatively easily differentiated. A tic is a rapid and nonrhythmic repetitive movement. It is preceded by a physical sensation (a sensory premonitory phenomenon) in more than 80 per cent of patients (9). There is no associated cognition or anxiety. A compulsion, in contrast, is a stereotyped and intentional movement that is performed in response to an obsession (an intrusive thought that is perceived to be senseless to the affected individual). There is a mental anxiety present prior to the compulsion, with temporary relief after the act. There is no associated sensory phenomenon. Patients who suffer both of these pure forms are often eloquent in their ability to differentiate the phenomena as being respectively “physical” and “mental.”
Tics, however, can also consist of coordinated patterns of sequential movements, in which case they are called “complex tics” and may be challenging to differentiate from compulsions. They may appear goalless or may be incorporated into apparently useful actions.
The exact definition of a compulsion still appears to be unclear. Some think that only acts resulting from obsessions should be called compulsions; others, however, only require anxiety or even an urge (10) to call an associated complex movement a compulsion.
Various epiphenomena are associated with the core behaviours, thus each deserves
separate consideration.
Sensory phenomena may be localized, as with a sense of building pressure in
the shoulder prior to a shoulder elevation tic. Indeed, 75 per cent
of individuals with this phenomenon report that resultant tics are
voluntary movements that are aimed at relieving this sensation.
Other sensory phenomena are nonlocalizable (10) and may be challenging
to differentiate from mental dysphoria—more so when they may be
coexistent. These symptoms have some features reminiscent of akathisia
and likely share neurobiological mechanisms with other causes of
that condition.
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“Just-right phenomena” are actions that have to be performed over
and over until something about them is judged to be completed (11).
They commonly involve acts such as placing a drinking glass onto
a surface. There are no specific associated cognitions. The action
usually has to appear right in one of the sensory modalities: it
has to feel, look or sound right to achieve the desired endpoint.
The exact criteria for the endpoint are often beyond the patient’s
descriptive capacities. These repetitive behaviours would be called
“compulsions” if they had associated cognitions and “tics” if they
did not involve objects outside the body. They are reminiscent of
both, but they are neither. They may be labelled “compulsions” by
those who only require an urge as the origin of a compulsion.
Other variations confound matters further—in severe forms of OCD, individuals may lose insight into their compulsions, see them as necessary and then technically be suffering delusions. Some patients with comorbid Asperger’s-spectrum syndromes demonstrate unusual thought content that is best characterized as preoccupations but easily confused with obsessions. Some individuals with TS describe urges that may have overlap with sex drive (for instance, the urge to touch a stranger in the genital area). Some behaviours may involve pain as a desired endpoint and may be self injurious. Movements may occur with no specific associated affective state or with mental dysphoria (anxiety or irritability) that may alter once an action is completed.
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In the clinical setting, a reductionistic
approach makes most sense. Describe the action as accurately
as possible, calling complex behaviours "intentional
repetitive behaviours" (12) if they are not definite
pure forms.
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As if these descriptive issues were not enough, there are also purely semantic challenges. Words such as “compulsive” and “obsessive” are widely used in the English language in ways that differ from their clinical definitions. Someone may be labelled a “compulsive” shopper or an “obsessive” gardener. In a related sense, most psychiatrists will eventually have the experience of being referred a patient for assessment of OCD, only to find that the individual is someone who has a degree of neatness and organization about their lives that is substantially more prominent than that of the referring clinician. Thus, obsessiveness has been mistaken for obsessions and compulsions, the distinguishing feature being that the former is not seen as senseless by the patient.
In the clinical setting, a reductionistic approach makes most sense. Describe the action as accurately as possible, calling complex behaviours “intentional repetitive behaviours” (12) if they are not definite pure forms. Describe all epiphenomena including sensory phenomena, cognitions, affective state, changes with the completion of the action, how endpoint is judged, senselessness and so on. Treatment, therefore, focuses on the most disabling symptoms, with the aim to improve overall quality of life rather than to eliminate all symptoms. Medication choice is based on knowledge of how parsed phenomena best respond to specific current therapies. For the purpose of diagnosis, certain labels may be applied (“OCD” or “Tourette”), but the therapeutic path will more closely relate to the pattern of phenomena than will the broad labels which, by nature, will lose resolution when it comes to understanding the individual’s unique situation.
Faced with related phenomenology dilemmas, the TS Classification
Study Group (13) used a reductionistic approach when it said of
its numerous tic syndromes, “Although some of these separate entities
may ultimately be shown to be caused by the same etiology (or even
the same gene), until that is established it is considered best
to divide the condition into distinct entities.” “(This classification)
can both expand and consolidate, as (etiological factors) are identified
(13).” One promise of reductionism is that accurate description
of the variations of phenotype will lead to the best chance of correlating
such variation with neurobiological underpinnings, as the latter
become elucidated. We may find that phonic tics are simply motor
tics of noise-making musculature; however, we may find that they
are somehow neurobiologically distinct from other tics. We do not
yet know, and until we do, we should continue to subdivide them.
An approach such as this one has already led to the description
of two likely biologically distinct types of OCD (10).
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