Neuroimaging techniques

Schweitzer I, Tuckwell V, Ames D and O Brien J (2001). Structural neuroimaging techniques in late-life depression. World Journal of Biological Psychiatry, 2, 83-88. 

In this chapter we review extant data on the neurobiology of unipolar and bipolar depressive disorders in children and adolescents. A complement to two recent reviews (Kaufman and Ryan, 1999 Kaufman et ah, 2001), this chapter places primary emphasis on those studies in which neuroimaging techniques have been used. Unfortunately, such studies are few and far between. Preclinical models that have guided research on the neurobiology of affective disorders in adults are discussed, and, given the limits in the application of these models to juvenile samples, especially in the case of unipolar disorder, the need for more developmentally focused preclinical work is emphasized. 

Unipolar and bipolar depressive disorders in children and adolescents are serious conditions. The pathophysiology of these disorders is poorly understood. The new tools available through neuroimaging techniques will help to unravel the neuroanatomical systems involved in the onset and recurrence of these disorders. There is a need for more developmentally informed predinical research and more studies of the normal development of the neural systems implicated in emotional regulation. 

Neuroimaging techniques assessing cerebral blood flow (CBF] and cerebral metabolic rate provide powerful windows onto the effects of ECT. Nobler et al. [1994] assessed cortical CBE using the planar xenon-133 inhalation technique in 54 patients. The patients were studied just before and 50 minutes after the sixth ECT treatment. At this acute time point, unilateral ECT led to postictal reductions of CBF in the stimulated hemisphere, whereas bilateral ECT led to symmetric anterior frontal CBE reductions. Regardless of electrode placement and stimulus intensity, patients who went on to respond to a course of ECT manifested anterior frontal CBE reductions in this acute postictal period, whereas nonresponders failed to show CBF reductions. Such frontal CBF reductions may reflect functional neural inhibition and may index anticonvulsant properties of ECT. A predictive discriminant function analysis revealed that the CBF changes were sufficiently robust to correctly classify both responders (68% accuracy] and nonresponders (85% accuracy]. More powerful measures of CBF and/or cerebral metabolic rate, as can be obtained with positron-emission tomography, may provide even more sensitive markers of optimal ECT administration. 

Research on the alterations in consciousness caused by sleep has re-centiy been greatly augmented by two sources of evidence that we can scrutinize for instances of complementary enhancement and disruption of function. They are studies of selective brain activation utilizing PET and fMRI neuroimaging techniques, already mentioned in chapters 6 and 7, and the close questioning regarding dreaming of patients who have... 

Neuroimaging technique for measuring cerebral blood flow, cerebral blood volume, metabolic rate, oxygen utilization and the oxygen extraction volume. 

Neuroimaging techniques can be broadly classified by the information content of the images. Morphological information can be obtained from MRI and CT, sensitivity and specificity... 

Lang CJ The use of neuroimaging techniques for clinical detection of neurotoxicty a review. Neurotoxicology 21 847-855, 2000 Lee S-H, Lee SH A study on the neurobehavioral effects of occupational exposure to organic solvents in Korean workers. Environ Res 60 227-232,1993 Lidberg L, Tael T, Wiklund N Violent crime and occupational exposure to organic solvents (letter). Lancet 2 1080, 1987... 

Fortunately, widely available neuroimaging techniques have helped us to understand the clinical response to reperfusion, and thus are useful in patient selection. This chapter will discuss the following imaging questions in order of importance that guide patient selection for lAT [18-20] (Table 12.1) ... 

---