Neuropsychiatric implications of basal ganglia dysfunction

Schizophrenia

To provide the most effective care for this difficult patient population, it is helpful to remember that patients with schizophrenia have disease-intrinsic limitations that limit their ability to participate in their care. These limitations are symptoms of a disease and not volitional. For the physician to substitute for these deficits, a certain degree of flexibility as well as the willingness to use unorthodox interventions is necessary. Good medical care is as important for the patient with schizophrenia as for any other patient.

Neural models of schizophrenia

Hallucinations and delusions - two diagnostic features of psychosis shared across the spectrum of heterogeneous schizophrenia constructs - can be described in terms of the pathophysiology of sensory information processing: hallucination is the impaired ability to classify representations as internally or externally generated, while delusion is the immutable linking of representations with each other in the absence of external dependency. The key anatomical systems in higher-order information processing are the cortex, thalamus, basal ganglia, and medial temporal lobe, each of which is modulated by neurotransmitter projection systems. Preliminary evidence, concentrating to date on the dorsolateral prefontal cortex, thalamus, and hippocampal region of the medial temporal lobe, points to neural circuitry dysfunction within and between each system in psychosis. This may account for specific symptoms and associated cognitive deficits such as memory impairment, attention deficit, and language disturbance.

Caudate size in first-episode neuroleptic-naive schizophrenic patients measured using an artificial neural network

BACKGROUND

Structural brain imaging studies have demonstrated an increase in caudate volume in schizophrenic patients medicated with typical neuroleptics and a volume decrease following treatment with atypical neuroleptics. The measurement of striatal volume in patients who have never been treated with neuroleptics may indicate whether these changes are superimposed on intrinsic basal ganglia pathology in schizophrenia or are solely neuroleptic-induced.

METHODS

We studied 36 first-episode, neuroleptic-naive schizophrenic patients and 43 control subjects using an artificial neural network (ANN) to identify and measure the caudate nucleus. The resulting volumes were analyzed using an ANCOVA controlling for intracranial volume, age, gender, and socioeconomic status.

RESULTS

The mean volume difference between the caudate nuclei of patients and control subjects was .297 mL, the caudate nuclei of the patients being smaller than those of controls. When we covaried for intracranial volume, this was a statistically significant difference in caudate volume (n = 79; df = 1,75; F = 4.18; p > .04).

CONCLUSIONS

Caudate nuclei of neuroleptic naive schizophrenic patients are significantly smaller than those of controls. This suggests that patients suffering from schizophrenia may have intrinsic pathology of the caudate nucleus, in addition to the pathology observed as a consequence of chronic neuroleptic treatment.