Psychiatry 2008 - September 2008 - (Page 27)

FIGURE 1. Neural circuitry of OCD and DBS target. Hyperactivity in the CT loop or hypoactivity of the C-S-T-C loop may produce OCD symptoms. DBS targets the C-T loop and normalizes activity in the circuit. KEY: PFC: prefrontal cortex; OFC: orbitofrontal cortex; C-T: corticothalmic; C-S-T-C: cortico-striatal-thalamic-cortical; ACG: anterior cingulate gyrus; OCD: obsessive compulsive disorder; DBS: deep brain stimulation for this is the lack of sophisticated animal models for these disorders, in part, because they are uniquely situated in our conscious subjectivity as humans. Analogous to neurological disorders, our understanding of the neurobiology of psychiatric disorders began with lesioning studies. Based on the seminal work of neurologists studying aphasias and movement disorders, researchers attempted to localize psychiatric syndromes to specific neuroanatomic regions. Once so defined, in theory the “abnormal” brain area could be surgically modulated for clinical benefit. However, it has become clear that psychiatric syndromes cannot be localized in a single, so-called “abnormal” brain region. OCD and MDD are not located in a specific region of the brain. Rather, mood and anxiety disorders involve immensely complex interconnected systems or networks of organization within the brain. The current approach in treating psychiatric disorders neurosurgically is to modulate specific targets or nodes within these networks in an effort to produce symptom relief.2 OCD. OCD is an often-debilitating psychiatric disorder that is characterized by anxiety-provoking intrusive thoughts (obsessions) leading to compulsive behaviors or mental rituals to temporarily decrease the anxiety provoked by the obsessions. The 12-month prevalence of OCD in the US is approximately one percent.5 Symptoms generally begin in childhood and adolescence and often result in severe impairments in social and occupational functioning. Currently, behavioral psychotherapy and high-dose serotonergic antidepressant medications are considered to be the standard of care (APA Practice Guidelines, 2007). Follow-up studies, however, suggest suboptimal outcomes with current treatments with complete sustained remission of symptoms occurring in only 12 to 20 percent of patients receiving standard care.6 With more aggressive or optimized pharmacotherapy and behavioral therapies, an estimated 10 percent of OCD patients still manifest severe, intractable illness.7 Etiology. The etiology of OCD is currently hypothesized to relate to a combination of genetic and environmental factors. Epidemiological studies, including family and twin studies, strongly support a genetic component for OCD.8 Recent evidence highlights an abrupt onset of OCD symptoms in some cases in the context of group A beta-hemolytic streptococcal (GABHS) infection, implying that environmental factors may also contribute to the etiology of this disorder.9 Many authors have commented on obsessions and compulsions as being similar to involuntary motor behaviors. Freud hypothesized this connection in his psychoanalytic case report of the “Rat Man” stating, “a thought-process is obsessive or compulsive when, in consequence of an inhibition (due to a conflict of opposing impulses) at the motor end of the psychical system, it is undertaken with an expenditure of energy which is normally reserved for actions alone.”10 Other observers have also commented on the relationship of OCD to movement disorders, including Sydenham’s chorea, Tourette’s syndrome, Huntington’s disease, and involuntary tics.11 Recent studies have highlighted genetic links between Tourette’s syndrome and OCD, suggesting a similar neurological substrate for these disorders, specifically in the basal ganglia.8 Metabolic and volumetric neuroimaging studies of patients with OCD reveal abnormalities in several areas of the brain, including the caudate nucleus of the basal ganglia, as well as the orbitofrontal cortex.7 The cingulate gyrus also has demonstrated hypermetabolism in patients with OCD.12 Circuitry. Based on these findings, distinct neuronal circuits [SEPTEMBER] Psychiatry 2008 27

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Psychiatry 2008 - September 2008 Editor’s Message Editorial Advisory Board Contents Psych Rx Letters to the Editor Use of Benzodiazepines in the Treatment of Anxiety Functional Neurosurgery in the Treatment of Severe Obsessive Compulsive Disorder and Major Depression: Overview of Disease Circuits and Therapeutic Targeting for the Clinician Treatment of Comorbid Adolescent Cannabis Use and Major Depressive Disorder Risperidone Long-acting Injections: Successful Alternative Deltoid Muscle Injections for Refractory Schizophrenia Alcohol/Substance Misuse and Treatment Nonadherence: Fatal Attraction Transforming the Psychiatric Inpatient Unit from Short-term Pseudo-asylum Care to State-of-the-art Treatment Setting Journal Watch Classified Advertising Information for Authors

Psychiatry 2008 - September 2008

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