A neurobiological model for Tourette syndrome centered on the nucleus accumbens

Enhanced reward-facilitating effects of d-amphetamine in rats in the quinpirole model of obsessive-compulsive disorder

The underlying neurobiology of addictive or repetitive behaviours, such as obsessive-compulsive disorder (OCD), involves dopaminergic dysregulation. While addictive behaviour depends strongly on mesolimbocortical dopaminergic responses, repetitive behaviours have been associated with dopaminergic dysregulation in the basal ganglia-thalamo-cortical circuitry. The present study investigates differences in brain stimulation reward in rats with quinpirole-induced compulsive checking behaviour, in order to examine if deficits in reward processing are also relevant for OCD. Rats were tested in the intracranial self-stimulation (ICSS) paradigm, which targets reward-related responses. After phenotype induction, animals were implanted with a monopolar stimulation electrode in the left medial forebrain bundle and trained to press a lever to self-administer electric stimulation of varying frequency. The curve-shift method was used to assess the reward-facilitating effects of d-amphetamine and the reward-attenuating effects of haloperidol (a D(2) antagonist). Thresholds for ICSS were estimated before and after drug/saline injection. The reward-facilitating effects of d-amphetamine were enhanced in quinpirole-treated rats in comparison to controls. This finding suggests that chronic quinpirole-treatment induces changes within the reward circuitry relevant for compulsive behaviour in the rat.

Deep brain stimulation therapy for treatment-refractory Tourette's syndrome: A review

Tourette's syndrome is a chronic neurobehavioral disorder that can demonstrate refractoriness to conservative treatments, or to invasive nonsurgical treatments such as botulinum toxin infiltration, or to psychobehavioral treatments. In these cases, the surgical option is often proposed, either with lesional interventions, or more recently with deep brain stimulation (DBS). This latter modality is currently preferred because of its reversibility and modularity. Some relevant issues, however, still persist in terms of appropriate indication to treatment, selection of target, and follow-up evaluation.

Long-term, post-deep brain stimulation management of a series of 36 patients affected with refractory gilles de la tourette syndrome

OBJECTIVES

  This study aimed to assess the long-term results of deep brain stimulation (DBS) for patients affected with Gilles de la Tourette syndrome, documenting refractoriness to conservative treatments.

MATERIAL AND METHODS

  Starting from November 2004, 36 patients diagnosed with a Tourette syndrome refractory to conventional and innovative treatments (refractory Tourette syndrome) were operated on for DBS positioning at our dedicated Tourette Clinic. A total number of 79 procedures were carried out: 67 at the thalamic intralaminar/ventralis oralis (Vo/CM-Pf) target, 2 at the posterior Gpi, and 10 at the nucleus accumbens. The target of the DBS procedure was chosen on the basis of clinical manifestations expressed by the single patient. Six out of the ten procedures centered at the Nucleus Accumbens were undertaken on the basis of a persistent behavioral comorbidity in spite of a good response over tic frequency and severity after a first DBS procedure (two interventions at the Vo/CM-Pf and one at the Gpi, bilaterally).

RESULTS

  All the patients were treated bilaterally except one, treated at the right Vo/CM-Pf because of vascular physiologic abnormalities at the left hemisphere. Two patients refused further treatments after DBS intervention (one of them requiring and obtaining complete removal of the DBS implant with no postsurgical complications documented) and were excluded from follow-up evaluation. Statistically significant improvements were reached for all the other patients concerning the evaluation scales used (Yale Global Tic Severity Scale, Beck Depression Inventory, State-Trait Anxiety Inventory, Yale-Brown Obsessive Compulsive Scale, and a 10-point visual analog scale for self-evaluation of the impact of TS on social integration of the patient).

CONCLUSIONS

  Gilles de la Tourette syndrome is a complex neuropsychiatric disorder with a significant prevalence in the general population. More than 50% of the patients with TS present a behavioral comorbidity, and anxiety and depression are, to various degrees, associated to this "waxing and waning" clinical picture. DBS in our experience proved to be a valid treatment modality for those patients who fail to respond to conservative treatment modalities. A multidisciplinary team is nevertheless necessary to properly handle this complex therapeutic option.

De novo and rescue DBS leads for refractory Tourette syndrome patients with severe comorbid OCD: a multiple case report

Invasive treatment for Gilles de la Tourette syndrome has shown interesting results in a number of published reports; it seems to be evolving into a promising therapeutic procedure for those patients demonstrating disabling clinical pictures who are refractory to conservative treatments. There are important issues concerning the stimulated brain target, with different nuclei currently under investigation. Our group asked in this pilot study whether Tourette syndrome could be treated by tailoring specific brain targets for specific symptoms. Deep brain stimulation for Tourette syndrome may thus in the future be tailored and patient specific, utilizing specific target regions for individual clinical manifestations. In our early experience we did not adequately address non-motor clinical symptoms as we only used a thalamic target. More recently in an obsessive compulsive disease cohort we have had success in using the anterior limb of the internal capsule and nucleus accumbens region as targets for stimulation. We therefore explored the option of a "rescue" procedure for our Tourette patients with persistent obsessive-compulsive disorder following ventralis oralis/centromedianus-parafascicularis (Vo/CM-Pf) deep brain stimulation. Following two cases where rescue anterior limb of internal capsule/nucleus accumbens leads were employed, we performed two additional procedures (anterior limb of the internal capsule plus ventralis oralis/centromedianus-parafascicularis and anterior limb of the internal capsule alone) with some mild improvement of comorbid obsessive-compulsive disorder, although the number of observations in this case series was low. Overall, the effects observed with using the anterior limb of the internal capsule either alone or as a rescue were less than expected. In this report we detail our experience with this approach.

DBS in tourette syndrome: rationale, current status and future prospects

Tourette syndrome is a neuropsychiatric disorder with onset in early childhood and characterized by tics, often associated with behavioural abnormalities. Symptoms often disappear before or during adulthood. Treatment consists of psychotherapy or pharmacotherapy. A small percentage of patients is treatment refractory. After the introduction of deep brain stimulation (DBS) of the thalamus as a new therapeutical approach in 1999, several other brain nuclei have been targeted in a small number of patients, like the globus pallidus internus, anteromedial and ventroposterolateral part, and the nucleus accumbens. In the published reports, a tic reduction rate of at least 66% is described. The effects of DBS on associated behavioural disorders are more variable. The number of treated patients is small and it is unclear whether the effects of DBS are dependent on the target nucleus. The pathophysiology of Tourette syndrome is not well understood. On the basis of our current knowledge of cortico-basal ganglia-thalamocortical circuits, an explanation for the beneficial effects of DBS on tics is proposed. It is concluded that a meticulous evaluation of the electrode position, and a blinded assessment of the clinical effects on tics and behavioural disorders, is absolutely mandatory in order to identify the best target of DBS for Tourette syndrome.

Does an imbalance between the dorsal and ventral striatopallidal systems play a role in Tourette's syndrome? A neuronal circuit approach

Tourette's syndrome is characterized by simple, involuntary muscle contractions and/or more complex movements or stereotyped behaviors, including vocalizations. There are strong indications that the basal ganglia play an important role in the pathophysiology of Tourette's syndrome. The present account reviews the functional anatomy of the basal ganglia, with an emphasis on the prefrontal cortex-ventral striatopallidal system. Different parts of the basal ganglia and thalamocortical system, with a focus on the premotor and prefrontal cortices, are connected with each other via parallel, functionally segregated basal ganglia-thalamocortical systems. These parallel circuits, representing sensorimotor, cognitive and emotional-motivational behavioral processes, are connected with each other through specific pathways that serve to integrate these various functions. In the context of the discussion on the pathophysiological mechanisms that lead to the expression of tics, emphasis is placed on the pathways that lead from the ventral striatum via the dopaminergic substantia nigra to the dorsal striatum. The dorsal striatum is crucial for habit formation. A conclusion of this overview of the anatomical organization of the basal ganglia is that via dopaminergic pathways limbic-relation information can influence the expression of (fragments of) motor and behavioral repertoires. Whether such mechanisms indeed play a role in the expression of tics in Tourette's syndrome remains to be established.

Mind from genes and neurons: a neurobiological model of Freudian psychology

A hypothetical neurobiological model of Freud's architecture of the mind is presented in an attempt to unify concepts and data derived from molecular biology (e.g., genomic imprinting), systems neuroscience (e.g., neuroanatomochemical circuitries), evolutionary psychology (e.g., human mating strategies), and Freudian psychology. The model posits that events related to genomic imprinting can be regulated in a tissue-specific manner over the course of neural development such that imprinting along the matriline would favor the development of corticostriatal structures whereas imprinting along the patriline would favor the development of limbic-subcortical structures. A neuropsychological analysis of the brain requirements for successful mating presumably would put an evolutionary premium on the corticostriatal system (matrilineal) in men and limbic-subcortical systems (patrilineal) in women. Additionally, the model emphasizes that the ego and the super-ego of Freudian psychology are dependent on corticostriatal mechanisms (matriline-related), while the id is dependent on brainstem processes (patriline-related). It is hoped that the model herein presented has heuristic value for a rapprochement of psychoanalysis and neurobiology.

Tic disorders: new developments in Tourette syndrome and related disorders

The constellation of motor and vocal tics and certain of the other neuropsychiatric symptoms seen in Tourette syndrome are thought to have an organic basis, although the nature of the neurobiological lesion is uncertain. The syndrome is usually familial but the presumed genetic substrate has not been identified. A number of models currently under debate include a proposed autoimmune contribution.