How Does the Cerebellum Differ in Children with Tourette Syndrome and OCD?

What you need to know

• The cerebellum shows structural and functional differences in children with Tourette syndrome and OCD compared to healthy children
• Children with Tourette syndrome show increased structural connectivity in cerebellar white matter tracts, while children with OCD show decreased connectivity
• Both disorders show altered functional connections between the cerebellum and other brain regions involved in movement and cognition
• The findings suggest the cerebellum plays an important role in the underlying brain changes associated with Tourette syndrome and OCD

Cerebellum structure shows differences

This study examined the structure and function of the cerebellum in children with Tourette syndrome, OCD, or both conditions, compared to healthy children. The researchers used advanced brain imaging techniques to look at cerebellar gray matter volume, white matter tract integrity, and functional connections with other brain regions.

When examining the structure of cerebellar white matter tracts, the researchers found some key differences between the groups:

• Children with Tourette syndrome (with or without OCD) showed increased structural connectivity in the cerebellar peduncles compared to healthy controls. The cerebellar peduncles are white matter tracts that connect the cerebellum to other parts of the brain.

• In contrast, children with OCD showed decreased structural connectivity in these same cerebellar tracts compared to both healthy controls and children with Tourette syndrome.

These opposite patterns suggest the cerebellum may be affected differently in Tourette syndrome versus OCD. The increased connectivity in Tourette syndrome could represent the brain adapting to help control tics. Meanwhile, the decreased connectivity in OCD may relate to difficulties controlling compulsive behaviors.

Functional connections are altered

The researchers also examined the functional connections between a key region of the cerebellum called the dentate nucleus and the rest of the brain. They found that both Tourette syndrome and OCD were associated with altered functional connectivity patterns compared to healthy children.

Some key findings on functional connectivity:

• Children with Tourette syndrome and OCD both showed decreased connectivity between the cerebellum and regions like the thalamus, sensorimotor cortex, and temporal lobe compared to healthy controls.

• Children with Tourette syndrome showed decreased connectivity between the cerebellum and prefrontal cortex.

• Children with OCD showed increased connectivity between the cerebellum and prefrontal/orbitofrontal cortex.

• The strength of some of these altered connections correlated with symptom severity in both disorders.

These findings suggest the cerebellum has disrupted communication with brain networks involved in movement, sensation, and cognitive control in both Tourette syndrome and OCD. However, the specific patterns differ between the two disorders.

Implications for understanding the disorders

By studying children who have not yet received any treatments, this research provides insight into how Tourette syndrome and OCD may affect brain development and function early in the course of the disorders. The findings highlight the cerebellum as an important brain region involved in both conditions, beyond the traditional focus on basal ganglia circuits.

Some key implications of the results:

• The cerebellum likely plays a role in the underlying neurobiology of both Tourette syndrome and OCD, but in distinct ways.

• Increased structural connectivity in Tourette syndrome may represent compensatory changes to help control tics.

• Decreased structural connectivity in OCD could contribute to difficulties controlling compulsive behaviors.

• Altered functional connections between the cerebellum and other regions may relate to various symptoms in both disorders.

• Examining cerebellar structure and function could potentially help distinguish between Tourette syndrome and OCD in some cases.

Conclusions

• The cerebellum shows clear differences in structure and function in children with Tourette syndrome and OCD compared to typically developing children.
• Opposite patterns of structural connectivity changes were found - increased in Tourette syndrome but decreased in OCD.
• Both disorders show altered functional connections between the cerebellum and brain networks involved in movement and cognitive control.
• These findings suggest the cerebellum plays an important role in the brain basis of both Tourette syndrome and OCD, but in distinct ways for each disorder.