Numbers
- Prevalence of 1-3% of the population
Clinical features
- Characterized by recurrent, intrusive anxious thoughts (obsessions) accompanied by repetitive stereotyped behaviours or mental routines (compulsions) that are frequently performed in an effort to reduce distress caused by obsessions.
- Can affect quality of life
- Interpersonal relationships, social and occupational functioning
- Ability to carry out basic activities of daily living;
- Associated with a higher lifetime risk of
- Suicide (up to 27% of patients)
- Major depression.
Mechanism
- Functional neuroimaging studies:
- Corticostriatal-thalamocortical circuitry abnormalities
- In the form of
- Failure of inhibition within basal ganglia–thalamocortical loops
- Abnormal signalling of dopamine and GABA.
- Subsets of projection neurons become active in inappropriate contexts as a result of dysfunctional inhibitory GABA interneurons within the striatum → disinhibition of thalamocortical projections and increased excitability of both motor and limbic regions → inappropriate expression of sensory and motor phenomena, i.e. tics.
- Increased metabolic activity in the
- Orbitofrontal cortex (OFC)
- Caudate nucleus (particularly its ventral division)
- OFC and caudate hyperactivity are directly correlated with symptom severity, and these changes partially normalize with successful treatment.
- Anterior cingulate cortex (ACC)
- Medial prefrontal cortex
Treatment
- Non-surgical
- Pharmacotherapy
- SSRI
- Psychotherapy
- CBT
- Exposure and response prevention).
- Outcome
- 50% of OCD patients do not obtain adequate benefit with standard treatment approaches
- 10% experience severe treatment-refractory symptoms.
- DBS
- Target
- From
- Lesional psychosurgery procedures
- Following observations of response to surgery for other conditions (e.g. STN DBS for PD)
- Gradual target refinement following ongoing evaluation of clinical outcomes in relation to lead location.
- Anterior limb of the internal capsule
- Nucleus accumbens
- Ventral capsule/ventral striatum
- STN
- Inferior thalamic peduncle
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