138 Chapter 15
2 The stereotypies that are commonly seen in severe intellectual disability
and autistic spectrum disorders may look like complex motor tics, but it
is very rare to have complex tics without some simple tics too.
3 Compulsions cannot clearly be distinguished from complex tics preceded
by ‘urges’, but the latter are nearly always accompanied by simple
tics too.
Causation
Tourette syndrome, chronic tics and OCD often run together in families:
male relatives are more likely to have tic disorders than OCD, while the
reverse is true for female relatives. Not much progress has yet been made
in identifying the relevant genes at a molecular level, but ongoing genome-
wide searches may be more successful. Neuroimaging and neuropathology
studies have provided suggestive evidence for an imbalance between the
direct (excitatory) and indirect (inhibitory) pathways within the cortico-
striato-thalamo-cortical circuits.
While there is strong evidence for the involvement of striatal dopamin-
ergic systems in Tourette syndrome, there is less consistent support for
specific hypotheses linking tics to an excess of dopamine or increased
sensitivity of dopamine D2 receptors. In addition, there are many plausible
but unproven theories linking tics to imbalance in other neurotransmitter
systems, including cholinergic, noradrenergic, serotonergic, glutaminergic
or GABAergic systems.
Streptococcal infections have been associated with some cases of
sudden-onset tic disorders accompanied by other acute neuropsychiatric
symptoms such as obsessions, compulsions, emotional lability, disrup-
tive behaviour, attentional difficulties, depression, and sleep disturbance.
This has been designated PANDAS syndrome (PaediatricAutoimmune
NeuropsychiatricDisordersAssociated withStreptococcal infections) and
is described in more detail in Chapter 14.
Treatment
It is essential to explain to everyone involved – the affected family and
school as well as the affected individual – that Tourette syndrome is
a medical disorder. It is not deliberate disruptiveness or possession by
evil spirits. Mild tics may need no specific treatment. There is increasing
evidence that psychological treatments such as habit reversal may help
some children and adolescents. This may be an appropriate first line of
treatment for individuals with relatively mild tic disorders. It may also be
appropriate for individuals with more severe tic disorders who are strongly
motivated to try psychological approaches before considering medication.
The best established pharmacological approach to treating tics involves
neuroleptics, a family of drugs that are also sometimes described as