Tourette
syndrome also known as Gilles de la Tourette’s syndrome or Tourette disorder
can be a neurodevelopmental disorder characterized by involuntary motor
(chronic presence of multiple motor and phonic tics, i.e. involuntary movements
and utterances) and vocal tics; that is closely correlated with the spectrum of
obsessive-compulsive disorders [1]. Tics can be defined as sudden,
intermittent, repetitive vocalizations (phonic tics) or movements (motor tics)/
also defined as stereotyped motor responses originating from an abnormal
sensitivity to stimuli coming from within the body or from the outside world
[3]. Simple motor tics consist of brief twitches or jerks, such as eye
blinking, facial grimacing or head jerks. Simple phonic tics are inarticulate
noises or sound such as throat clearing, sniffing and grunting [3]. Chronic
motor or vocal tic disorder can be defined by the presence of either motor or
vocal tics (but not both) and shares a similar clinical phenomenology and
disease course with Tourette syndrome [4]. Tourette syndrome is a
phenomenologically heterogeneous neuropsychiatric disorder comprised of
multiple motor and vocal tics that commence in early childhood and persist for
at least a yr. The pathophysiology of Tourette syndrome involves an abnormality
in the central dopaminergic system either excess amounts of dopamine or a
hypersensitivity of dopamine-2 receptors. Additionally, there is growing
evidence that certain dysfunction in the central mono-aminergic systems
involving serotonin or serotonin 5-hydroxytryptamine-2 receptors may also play
a role [5,6].
Risk factors
Genetic,
examination of disease patterning by socio-economic status and environmental
factors are likely to play a role in the development of Tourette syndrome. The
strong correlation between childhood socio-economic conditions and stomach
cancer mortality, independent of adult status, suggests the potential role of
Helicobacter pylori infection as an etiological factor given its correlation
with overcrowding in childhood [7].
Genetic
vulnerability is the common risk factors for Tourette syndrome; for example
gestational and perinatal risk factors such as severe nausea and vomiting
during the first trimester, severe psychosocial stress of the mother during
pregnancy, maternal usage during pregnancy of coffee more than two per days,
cigarette smoking more than ten per days, or alcohol consumption, identical
twin with a lower birth weight, low birth weight children with evidence of
parenchymal lesions, ventricular enlargement, or both, and transient hypoxia or
ischaemia during birth (labour greater than 24 hrs), use of forceps, nuchal
cord, evidence of fetal distress. High heritability’s, twin and family studies
have consistently demonstrated a significant role for additional, non-genetic
factors in the pathogenesis of Tourette syndrome. Low birth weight, maternal
nausea and vomiting in the first trimester, maternal life stress and maternal
smoking during pregnancy have also been correlated with elevated tic severity
[8-10].
Severe
psychosocial trauma, recurrent daily stresses
(eg, teasing by peers), or extreme emotional excitement; recurrent
streptococcal infections with post-infectious autoimmune response, drug abuse
are implicated as the frequently cause of Tourette syndrome [11].
Exposure
to androgenic drugs such as chronic intermittent use of cocaine and other
psycho stimulants are the etiological factors of Tourette syndrome [12].
Co-existing
medical or psychiatric disorders such as hyperkinetic disorders, earning
disabilities, depression and manic depression are the commonly implicated
causes of Tourette syndrome [13].
Conclusion
Tourette
syndrome is a chronic neuropsychiatric disorder that starts in childhood and is
characterized by motor and vocal tics persisting for more than 1 yr and varying
in frequency. Tourette syndrome is a phenomenologically heterogeneous
neuropsychiatric disorder comprised of multiple motor and vocal tics that
commence in early childhood and persist for at least a yr. The pathophysiology
of Tourette syndrome involves an abnormality in the central dopaminergic system
either excess amounts of dopamine or a hypersensitivity of dopamine-2 receptors.
Additionally, there is growing evidence that certain dysfunction in the central
mono-aminergic systems involving serotonin or serotonin 5-hydroxytryptamine-2
receptors may also play a role. Maternal prenatal smoking, complications during
pregnancy, birth weight, gestational age, Apgar scores at five minutes after
birth, number of prenatal visits, younger maternal age and older paternal age
have all been reported to be correlated with risk of Tourette syndrome.
Acknowledgments
The
author would be grateful to anonymous reviewers for the comments that increase
the quality of this manuscript.
Funding
None
Competing Interests
The
author has no financial or proprietary interest in any of material discussed in
this article.