Lecture 7
Tourette syndrome
Tourette syndrome
Tourette syndrome (TS)
- TS is a neurodevelopmental disorder characterized by the presence of chronic vocal and
motor tics.
- These tics are involuntary, repetitive, stereotype behaviors than can occur many times in a
single day.
- Motor tics can range from simple repetitive movements to complex coordinated action
sequences, such as repetition of another’s actions (echopraxia).
- Verbal tics can consist of:
o Grunting
o Repetition of words or utterances (palilalia).
o Production of inappropriate or obscene utterances (coprolalia, actually only 10 to
15%).
o Repetition of another’s words or actions (echolalia).
- There is an increase in the risk of suicide for individuals with TS.
- The life expectancy of someone with TS -> there seems to be a 7 to 8-year reduction in life
expectancy.
Co-morbidity of neurodevelopmental disorders
- OCD occurs in 40-60% of individuals with TS.
- ADHD occurs in approximately 50% of TS cases.
- Both disorders have been linked to the basal ganglia.
- ASD is highly co-occurring with TS, and individuals with ASD often have tics, obsessions,
and compulsive behaviors.
Co-morbidity of neuropsychiatric conditions
- Most individuals with TS also have have OCD or ADHD, followed by affective disorder,
anxiety disorder, and conduct/oppositional disorder.
- Age of onset of co-morbid disorder is slightly different -> the physician will often focus on
one of the diagnosis, depending on the complaints.
Developmental time course of Tourette syndrome
- TS affects ~1% children.
- Typically presents during childhood (onset ~3-6 years).
- 4:1 ratio of boys to girls in child samples but 1:1 in adults.
- Tic severity at its maximum between 8-12 years and often decreases in early adulthood.
- 70% of children with TS have very mild tics or are free of tics by the age of 18 years -> they
can still be ticking, but do not have the same clinical severity.
- Suggests some degree of compensatory adaptation -> the brain is adapting to the disorder.
1
, Neuropathological basis for TS
Cortical-striatal-thalamic circuits
- Circuits in which information goes from
the cortex through the basal ganglia,
particular part of the basal ganglia called
the striatum, the information goes to the
thalamus, and back up to the cortex.
- These circuits seem to be organized as
separate parallel circuits.
- Motor circuit -> motor tics.
- Associative circuit -> cognition.
- Limbic circuit -> motivation
- Cognition and motivation (associative
and limbic) together lead to
ADHD/OCD complex tics.
Impaired cortico-striatal-thalamo-cortical circuit (CSTC) function in TS
- Typically developing individual:
o Cortical inputs produce a focus of neural activation within the striatum.
o This leads to selection of a desired motor output through:
▪ Disinhibition in the globus pallidus.
▪ Increased thalamic activation.
- In TS:
o Subset of striatal neurons become abnormally active in inappropriate contexts
(reduced inhibition).
o Disinhibition in thalamo-cortical circuits.
o Activity-dependent dopamine may inappropriately reinforce such activity leading to
stereotype repetition of behavior.
Cortical hyper-excitability and echophenomena
Echophenomena and impaired mirror neuron system
- Echophenomena (e.g., echopraxia and echolalia) as core feature of TS.
o Echolalia: repetition of sounds or words escaping explicit awareness.
o Echopraxia: automatic repetition of actions.
- Echophenomena part of the behavioral repertoire of OCD patients with tics, but not OCD
patients without tics.
- Also seen in early childhood, and in autism, schizophrenia, dementia, frontal lobe epilepsy,
and aphasia.
Echophenomena study
- TS patients and controls presented with video clips showing spontaneous facial movements
of healthy controls or facial tics of other TS patients.
- TS patients echoed not only tics but also spontaneous movements.
- Importantly, 81% of echoed movements were part of the patient’s tic repertoire.
- Suggests TS patients largely echo what they tic.
2
Tourette syndrome
Tourette syndrome
Tourette syndrome (TS)
- TS is a neurodevelopmental disorder characterized by the presence of chronic vocal and
motor tics.
- These tics are involuntary, repetitive, stereotype behaviors than can occur many times in a
single day.
- Motor tics can range from simple repetitive movements to complex coordinated action
sequences, such as repetition of another’s actions (echopraxia).
- Verbal tics can consist of:
o Grunting
o Repetition of words or utterances (palilalia).
o Production of inappropriate or obscene utterances (coprolalia, actually only 10 to
15%).
o Repetition of another’s words or actions (echolalia).
- There is an increase in the risk of suicide for individuals with TS.
- The life expectancy of someone with TS -> there seems to be a 7 to 8-year reduction in life
expectancy.
Co-morbidity of neurodevelopmental disorders
- OCD occurs in 40-60% of individuals with TS.
- ADHD occurs in approximately 50% of TS cases.
- Both disorders have been linked to the basal ganglia.
- ASD is highly co-occurring with TS, and individuals with ASD often have tics, obsessions,
and compulsive behaviors.
Co-morbidity of neuropsychiatric conditions
- Most individuals with TS also have have OCD or ADHD, followed by affective disorder,
anxiety disorder, and conduct/oppositional disorder.
- Age of onset of co-morbid disorder is slightly different -> the physician will often focus on
one of the diagnosis, depending on the complaints.
Developmental time course of Tourette syndrome
- TS affects ~1% children.
- Typically presents during childhood (onset ~3-6 years).
- 4:1 ratio of boys to girls in child samples but 1:1 in adults.
- Tic severity at its maximum between 8-12 years and often decreases in early adulthood.
- 70% of children with TS have very mild tics or are free of tics by the age of 18 years -> they
can still be ticking, but do not have the same clinical severity.
- Suggests some degree of compensatory adaptation -> the brain is adapting to the disorder.
1
, Neuropathological basis for TS
Cortical-striatal-thalamic circuits
- Circuits in which information goes from
the cortex through the basal ganglia,
particular part of the basal ganglia called
the striatum, the information goes to the
thalamus, and back up to the cortex.
- These circuits seem to be organized as
separate parallel circuits.
- Motor circuit -> motor tics.
- Associative circuit -> cognition.
- Limbic circuit -> motivation
- Cognition and motivation (associative
and limbic) together lead to
ADHD/OCD complex tics.
Impaired cortico-striatal-thalamo-cortical circuit (CSTC) function in TS
- Typically developing individual:
o Cortical inputs produce a focus of neural activation within the striatum.
o This leads to selection of a desired motor output through:
▪ Disinhibition in the globus pallidus.
▪ Increased thalamic activation.
- In TS:
o Subset of striatal neurons become abnormally active in inappropriate contexts
(reduced inhibition).
o Disinhibition in thalamo-cortical circuits.
o Activity-dependent dopamine may inappropriately reinforce such activity leading to
stereotype repetition of behavior.
Cortical hyper-excitability and echophenomena
Echophenomena and impaired mirror neuron system
- Echophenomena (e.g., echopraxia and echolalia) as core feature of TS.
o Echolalia: repetition of sounds or words escaping explicit awareness.
o Echopraxia: automatic repetition of actions.
- Echophenomena part of the behavioral repertoire of OCD patients with tics, but not OCD
patients without tics.
- Also seen in early childhood, and in autism, schizophrenia, dementia, frontal lobe epilepsy,
and aphasia.
Echophenomena study
- TS patients and controls presented with video clips showing spontaneous facial movements
of healthy controls or facial tics of other TS patients.
- TS patients echoed not only tics but also spontaneous movements.
- Importantly, 81% of echoed movements were part of the patient’s tic repertoire.
- Suggests TS patients largely echo what they tic.
2
