Supraphysiological doses of levothyroxine alter regional cerebral metabolism and improve mood in bipolar depression

Supplementation of standard treatment with high-dose levothyroxine (L-T(4)) is a novel approach for treatment-refractory bipolar disorders. This study tested for effects on brain function associated with mood alterations in bipolar depressed patients receiving high-dose L-T(4) treatment adjunctive to ongoing medication (antidepressants and mood stabilizers). Regional activity and whole-brain analyses were assessed with positron emission tomography and [(18)F]fluorodeoxyglucose in 10 euthyroid depressed women with bipolar disorder, before and after 7 weeks of open-label adjunctive treatment with supraphysiological doses of L-T(4) (mean dose 320 microg/day). Corresponding measurements were acquired in an age-matched comparison group of 10 healthy women without L-T(4) treatment. The primary biological measures were relative regional activity (with relative brain radioactivity taken as a surrogate index of glucose metabolism) in preselected brain regions and neuroendocrine markers of thyroid function. Treatment-associated changes in regional activity (relative to global activity) were tested against clinical response. Before L-T(4) treatment, the patients exhibited significantly higher activity in the right subgenual cingulate cortex, left thalamus, medial temporal lobe (right amygdala, right hippocampus), right ventral striatum, and cerebellar vermis; and had lower relative activity in the middle frontal gyri bilaterally. Significant behavioral and cerebral metabolic effects accompanied changes in thyroid hormone status. L-T(4) improved mood (remission in seven patients; partial response in three); and decreased relative activity in the right subgenual cingulate cortex, left thalamus, right amygdala, right hippocampus, right dorsal and ventral striatum, and cerebellar vermis. The decrease in relative activity of the left thalamus, left amygdala, left hippocampus, and left ventral striatum was significantly correlated with reduction in depression scores. Results of the whole-brain analyses were generally consistent with the volume of interest results. We conclude that bipolar depressed patients have abnormal function in prefrontal and limbic brain areas. L-T(4) may improve mood by affecting circuits involving these areas, which have been previously implicated in affective disorders.

Brain metabolic changes associated with symptom factor improvement in major depressive disorder

BACKGROUND

Symptoms of major depressive disorder (MDD) have been linked to regional brain function through imaging studies of symptom provocation in normal control subjects and baseline studies of subjects with MDD. We examined associations between change in depressive symptom factors and change in regional brain metabolism from before to after treatment of MDD.

METHODS

Thirty-nine outpatients with MDD underwent 18F-fluorodeoxyglucose positron emission tomography scanning before and after treatment with either paroxetine or interpersonal psychotherapy. Associations were determined between changes in regional brain metabolism and changes in four Hamilton Depression Rating Scale factors (anxiety/somatization [ANX], psychomotor retardation [PR], cognitive disturbance [COGN], and sleep disturbance) and two corresponding Profile of Mood States subscales (tension [TENS] and fatigue [FATIG]).

RESULTS

Improvement in ANX, PR, TENS, and FATIG factors was associated with decreasing ventral frontal lobe metabolism. Improvement in ANX and TENS was also associated with decreasing ventral anterior cingulate gyrus (AC) and anterior insula activity, whereas improvement in PR was associated with increasing dorsal AC activity. COGN improvement was associated with increasing dorsolateral prefrontal cortex metabolism.

CONCLUSIONS

Brain regions that show significant relationships with symptom provocation in normal control subjects have similar relationships with MDD symptoms as they improve with treatment.

The effects of an alpha-2 adrenergic agonist, guanfacine, on rCBF in human cortex in normal controls and subjects with focal epilepsy

Alpha-2 noradrenergic agonists may have wide applicability in the treatment of pre-frontal cortex deficits in primates and behavioral dysfunction in man. We have undertaken this study to determine the effect of an alpha-2 agonist, guanfacine, on regional cerebral blood flow (rCBF) in humans. Three subject groups were evaluated: normal controls, subjects with frontal lobe epilepsy (FLE), and subjects with temporal lobe epilepsy (TLE). All underwent a number of PET scans using 15O-water, with half before and half after a single dose of guanfacine. A wide area of increased rCBF was seen in the frontal lobe, maximal at the central region, following guanfacine in controls and subjects with TLE. Smaller areas of decrease in rCBF were seen in the posterior temporal-occipital cortex. In the FLE group a decrease in rCBF was seen in the dorsal prefrontal cortex on the epileptogenic side with only small increases seen in the mid- to anterior temporal perisylvian areas. The ability of alpha-2 agonists to enhance performance of tasks reliant on prefrontal cortex, without improving tasks believed to rely on intact temporal-hippocampal function, may be explained by these results. Epileptogenic zones appear to create both direct and indirect changes in patterns of drug response. Further studies on the cognitive properties of these agents in humans should be encouraged.

Dementia with leukoaraiosis: clinical differentiation by temporoparietal hypometabolism on (18)FDG-PET imaging

Patients with dementia and leukoaraiosis may have either Alzheimer's disease (AD) with cerebrovascular changes or a form of vascular dementia (VaD). The presence or absence of the characteristic AD pattern of bilateral temporoparietal hypometabolism on (18)FDG-PET was used to differentiate 30 patients with progressive dementia and severe leukoaraiosis. Compared to 18 patients with the typical AD pattern (group I), the remaining 12 (group II) had better recognition memory, and greater difficulty with sustained attention and serial reversals. Better recognition memory, confluent periventricular leukoaraiosis, and poorer sustained attention distinguished all group II patients from group I. Dementia patients with severe leukoaraiosis and bilateral temporoparietal hypometabolism may have predominant AD; those who lack this pattern and have confluent leukoaraiosis may have a greater contribution from VaD. Copyrightz1999S.KargerAG,Basel

Positron emission tomography: the contribution of cognitive activation paradigms to the understanding of the epilepsies

Cognitive activation paradigms coupled with positron emission tomographic techniques may aid in the identification of functional and epileptogenic zones for presurgical evaluation. More work is needed to determine the most clinically efficacious paradigms for different seizure types. The real strength of activation positron emission tomography lies in the ability to study shifts in cognitive circuitry that accompany a fixed neuropathologic entity for both groups of similar subjects and individuals. These techniques are enhancing our understanding of the fundamentals of brain plasticity and may be used in the future to predict precise surgical risks.

The role of positron emission tomography in occult primary head and neck cancers

PURPOSE

To evaluate the utility of positron emission tomography (PET) fluorodeoxyglucose (FDG) imaging in the workup of unknown primary head and neck tumors.

METHODS

Fourteen patients with squamous cell carcinoma of cervical lymph node metastasis of unknown primary origin (clinical stage N2-N3) were studied prospectively. The patients underwent conventional workup, including physical examination, computed tomography, and random biopsies of the potentially suspected sites. If no primary site was found, 8 to 13 mCi of FDG was given intravenously, and whole-body scans with standardized uptake values were obtained. The results of FDG-PET imaging were compared with clinical, CT, and histopathologic findings. To eliminate bias, PET scans were reviewed by nuclear medicine physicians who had no previous knowledge of the other findings.

RESULTS

PET identified the location of primary tumor in three patients: lung hilum, base of tongue, and pyriform sinus. These lesions were pathologically confirmed. All these primary sites were not visualized on CT or physical examination, except for a pyriform sinus lesion, which was seen on CT, but initial biopsy result was negative. In one patient, the initial PET did not identify a primary tumor, but a nasopharyngeal carcinoma was identified in post-radiation therapy follow-up PET. In the remaining nine patients, a primary lesion was never found. All cervical lymph nodes detected by CT were identified by PET.

DISCUSSION

A previously unknown primary tumor can be identified with FDG-PET in about 21% of the patients in our prospective series. PET can be of value in guiding endoscopic biopsies for histologic diagnosis and treatment options.

Dynamic [18F]fluorodeoxyglucose positron emission tomography and hypometabolic zones in seizures: reduced capillary influx

We performed dynamic [18F]fluorodeoxyglucose ([18F]FDG) positron emission tomographic (PET) analyses in 8 patients. Rate constants of influx (K1*), efflux (k2*), phosphorylation (k3*), and dephosphorylation (k4*) were derived for the regions of interest (ROIs), which included (1) the hypometabolic epileptogenic regions and (2) the homologous regions in the contralateral hemispheres. In addition, the four constants were determined from at least one clearly defined (control) ROI from the same plane and its homologous contralateral ROI. Influx (K1*) in the epileptogenic region was reduced in comparison with the contralateral ROI. Reductions in influx (K1*), which averaged 18 +/- 13% (mean +/- SD), [18F]FDG phosphorylation (k3*) (25 +/- 20%), and brain glucose utilization rates (26 +/- 10%) were observed in the epileptogenic region. Reductions in efflux were not statistically significant (k2* = 13 +/- 28%) but were comparable in magnitude to the average reduction in K1*. No ipsilateral versus contralateral differences were seen for any rate constants measured outside the epileptogenic region. Influx correlated highly with phosphorylation in the epileptogenic region. Our data suggest that the hypometabolic epileptogenic focus seen in [18F]FDG-PET studies is also a region of reduced blood-brain barrier glucose transporter activity and that reductions in phosphorylation are proportional to reductions in [18]FDG influx.

Functional electrical stimulation effect on skeletal muscle blood flow measured with H2(15)O positron emission tomography

OBJECTIVE

To test the hypothesis that the limitation in muscle power development with functional electrical stimulation (FES) results from an insufficient increase in muscle blood flow (MBF) in response to activity.

SUBJECTS AND METHODS

Five subjects with neurologically complete spinal cord injury (SCI) were tested to measure the MBF response to FES-induced knee extension. The MBF response to voluntary knee extension was measured in five age-matched, able-bodied controls. MBF was measured with positron emission tomography (PET) using H2(15)O as a tracer. Three scans were performed with muscle at rest (baseline), immediately after 16min of FES-induced or voluntary knee extension (activity), and 20min after the second scan (recovery).

RESULTS

In SCI subjects, mean +/-SE MBF (mL/100g/min) values were: baseline = 1.85 +/- .48; post-FES = 31.9 +/- 5.65 (p = .0058 vs baseline); recovery = 6.06 +/- 1.52 (p = .0027 vs baseline). In able-bodied controls, mean +/-SE MBF values were: baseline = 8.52 +/- 3.24, post-voluntary exercise = 12.62 +/- 3.03 (p = .023 vs post-FES in SCI subjects); recovery = 10.7 +/- 6.01.

CONCLUSIONS

MBF does not appear to be the limiting factor in muscle power generation with FES. The greater increase in MBF observed with FES in SCI subjects when compared with able-bodied subjects performing a similar task (unloaded knee extension against gravity) may relate to abnormal metabolism in FES-stimulated muscle.

Mnemonics usage and cognitive decline in age-associated memory impairment

To determine predictors of cognitive deterioration, the authors performed baseline and 1- to 5-year follow-up (mean +/- SD = 2.5 +/- 1.2 years) neuropsychological assessments on 36 persons (mean age +/- SD = 62.1 +/- 8.0; range = 50 to 81 years) with age-associated memory impairment. Subjects were recruited from a larger group of volunteers, had minimal medical comorbidity, and 25 of them had a family history of Alzheimer's disease. Baseline age and a subjective memory measure indicating reported frequency of mnemonics usage were significant decline predictors. Subjects reporting more frequent mnemonics use at baseline were more likely to show objective cognitive decline at follow-up. Baseline full-scale IQ, educational level, and family history of Alzheimer's disease failed to predict decline. These findings suggest that although age is the strongest decline predictor in some people with age-associated memory impairment, self-perception of memory function may also predict subsequent cognitive loss.

Regional cerebral activity in normal and pathological perception of visceral pain

BACKGROUND & AIMS

To characterize the cerebral processing of noxious visceral events, changes in regional cerebral blood flow associated with perception of intestinal pain were examined.

METHODS

The effects of rectal pressure stimuli on regional cerebral blood flow were assessed with 15O-water positron emission tomography (PET) in 12 subjects, half with irritable bowel syndrome (IBS). PET scans were obtained at baseline and during both actual and simulated delivery of anticipated stimuli. Changes in regional cerebral blood flow were interpreted using statistical parametric mapping and region of interest methods of analysis.

RESULTS

In healthy subjects, perception of pain during actual or simulated delivery of painful stimuli was significantly associated (P < 0.01) with activity of the anterior cingulate cortex (ACC; Brodmann's areas 24 and 32), whereas no ACC response to perception of nonpainful stimuli was observed. In patients with IBS, the ACC failed to respond to the same stimuli, whereas significant activation (P < 0.01) of the left prefrontal cortex (maximal in Brodmann's area 10) was seen.

CONCLUSIONS

The perception of acute rectal pain is associated with activation of the ACC in healthy subjects, and patients with IBS show an aberrant brain activation pattern both during noxious rectal distention and during the anticipation of rectal pain.

PET scans of abdominal malignancy

Positron emission tomography (PET) with fluorine-18-2-d-deoxyglucose (FDG) currently is being integrated into clinical oncology because it provides unique functional information that can be applied to the management of cancer. In particular, it is useful for assessing tumor activity and growth, evaluating efficacy of therapy, and detecting tumor recurrence. Studies have demonstrated the value of whole-body PET-FDG imaging when staging and managing abdominal malignancy.

Predictors of cognitive change in middle-aged and older adults with memory loss

OBJECTIVE

Previous longitudinal studies of age-related memory loss have focused on objective neuropsychological measures that predict subsequent cognitive change, yet brain metabolic function, self-perception of memory loss, and other measures may also be sensitive indicators of cognitive change. To determine such baseline predictors of change, the authors made longitudinal assessments of middle-aged and older adults with memory loss.

METHOD

Forty-two persons (mean age = 60 years, range = 43-81) with memory complaints received comprehensive baseline assessments, including subjective neuropsychological measures, objective measures of visual-spatial memory (the Benton Visual Retention Test) and verbal memory (the Buschke-Fuld Selective Reminding Test), and positron emission tomography scans to determine neocortical glucose metabolism. At an average follow-up of 3 years, the objective neuropsychological measures were again used to quantify the degree of cognitive change.

RESULTS

Multiple regression analyses indicated that parietal asymmetry, sex of the subject, and baseline visual-spatial memory score were significant predictors of change in visual-spatial memory; level of education and baseline verbal memory score predicted change in verbal memory. Other neocortical asymmetry scores, age, family history of Alzheimer's disease, cerebral atrophy, and self-ratings of use of mnemonics were not significant predictors of change.

CONCLUSIONS

Measures of cerebral metabolism, objective memory performance, sex, and education may predict subsequent cognitive change in middle-aged and older persons with memory loss. Also, the parietal asymmetry found in persons with questionable dementia that progresses to probable Alzheimer's disease may be present very early in the course of age-related cognitive decline.

Apolipoprotein E type 4 allele and cerebral glucose metabolism in relatives at risk for familial Alzheimer disease

OBJECTIVE

Cerebral parietal hypometabolism and left-right asymmetry occur early in the course of Alzheimer disease (AD), and the apolipoprotein E type 4 allele (APOE epsilon 4) is a risk factor for familial AD. To determine if APOE epsilon 4 is associated with lowered brain function in nondemented relatives at risk for familial AD, we studied 12 relatives with APOE epsilon 4 and 19 relatives without APOE epsilon 4. We also compared them with seven patients with probable AD.

DESIGN

After grouping subjects according to diagnosis and genotype, brain function measures were compared among groups.

SETTING

University medical center.

PATIENTS

At risk subjects had mild memory complaints, normal cognitive performance, and at least two relatives with AD. Subjects with APOE epsilon 4 did not differ from those without APOE epsilon 4 in mean age at examination (56.4 vs 55.5 years) or in neuropsychological performance (mean Mini-Mental State Examination score, 28.8 vs 29.3).

MAIN OUTCOME MEASURES

Cerebral glucose metabolism was measured using positron emission tomography and fludeoxyglucose F 18.

RESULTS

Parietal metabolism was significantly lower and left-right parietal asymmetry was significantly higher in at-risk subjects with APOE epsilon 4 compared with those without APOE epsilon 4. Patients with dementia had significantly lower parietal metabolism than did at-risk subjects with APOE epsilon 4.

CONCLUSIONS

These results suggest that the inheritance of APOE epsilon 4 is associated with reduced cerebral parietal metabolism and increased asymmetry in non-demented relatives at risk for probable AD. Longitudinal study will determine if glucose metabolic measures provide a means to monitor experimental treatment responses during the early phases of the disorder.

The relationship between psychiatric symptoms and regional cortical metabolism in Alzheimer's disease

Cognitive and noncognitive psychiatric symptoms were systematically evaluated in 21 patients with Alzheimer's disease by using the Neurobehavioral Rating Scale. Regional cerebral metabolic activity was measured in each patient by [18F]fluorodeoxyglucose PET. Significant correlations emerged between global cortical metabolic activity and the Agitation/Disinhibition factor score, Cognition factor score, and total score. Relationships between noncognitive symptoms and metabolic activity were regionally specific, with significant correlations between Agitation/Disinhibition factor score and metabolism in the frontal and temporal lobes, between Psychosis factor score and metabolism in the frontal lobe, and between Anxiety/Depression factor score and metabolism in the parietal lobe. These results suggest that psychiatric symptoms are fundamental expressions of the cortical dysfunction of Alzheimer's disease.

Cerebral metabolic change in patients with AIDS: report of a six-month follow-up using positron-emission tomography

The authors examined change in cerebral metabolic function over time by using PET in HIV-infected individuals diagnosed with AIDS. Ten subjects with AIDS received [18F]2-fluoro-2-deoxy-D-glucose PET scans and completed a comprehensive neuropsychological battery. The scan and test battery were repeated after 6 months. Over time, the subjects showed increased relative basal ganglia metabolism as well as increased parietal lobe metabolism. There were no statistically significant changes in neuropsychological performance. These results suggest that PET may be more sensitive than traditional neuropsychological evaluation to subtle central nervous system changes in AIDS.

Markedly increased mesiotemporal lobe metabolism in a case with PLEDs: further evidence that PLEDs are a manifestation of partial status epilepticus

The pathophysiologic and clinical significance of periodic lateralized epileptiform discharges (PLEDs) is unclear; whether PLEDs represent an ictal condition that should be treated remains uncertain. We performed FDG-positron emission computed tomography (FDG-PET) in a patient with PLEDs at 3 days, 18 days, and 10 weeks after onset. During left temporal PLEDs, the initial scan showed intense hypermetabolism of the left mesiotemporal region. The second scan, performed when PLEDs were resolving, displayed reduced hypermetabolism. The follow-up scan, when PLEDs had resolved, showed left temporal hypometabolism. These findings, together with clinical evidence from the literature, are compatible with the interpretation that PLEDs represent partial status epilepticus (SE); whether vigorous therapy is required to prevent neuronal damage from this focal seizure activity remains uncertain.

Age-associated memory loss: initial neuropsychological and cerebral metabolic findings of a longitudinal study

To determine the relationships between clinical and brain function in persons with a familial risk for Alzheimer's disease, the authors assessed subjective and objective cognitive abilities, mood state, and cerebral glucose metabolism (using positron emission tomography) in 43 persons with age-associated memory impairment, with and without first-degree relatives with a clinical diagnosis of Alzheimer's disease. Subjective complaints of memory loss, mood state ratings, and objective memory measures were similar in persons with a family history of Alzheimer's disease (n = 29) compared to those without such a history (n = 14). Metabolic ratios in the frontal regions correlated with a decrease in a specific type of subjective memory complaint (mnemonics usage; p < .001) and some mood state ratings. These results indicate that parietal and temporal hypometabolism is not evident in persons with mild age-related memory complaints, even when such subjects have a familial risk for Alzheimer's disease. Moreover, self-reports of mnemonics usage may be sensitive indicators of decreased frontal lobe function. Longitudinal study will determine whether such clinical and metabolic measures will predict eventual disease progression.

Clinical, neuroimaging, and environmental risk differences in monozygotic female twins appearing discordant for dementia of the Alzheimer type

OBJECTIVE

The study of monozygotic twins can elucidate possible environmental causes for a disease in genetically identical subjects. To this end, we studied a pair of monozygotic female twins appearing discordant for dementia of the Alzheimer type (DAT).

DESIGN

Clinical and neuroimaging findings were compared in terms of potential environmental risk factors.

SETTING

University referral center.

PARTICIPANTS

An 81-year-old female monozygotic twin pair.

OUTCOME MEASURES

Clinical assessments, standardized rating scales, and brain imaging studies, including magnetic resonance imaging, positron emission tomography, and electroencephalography, were performed. Neuropsychological tests were performed initially and after 1 year.

RESULTS

Although DAT was confirmed clinically in only one twin, neuropsychological and brain imaging studies suggested that the unaffected twin may be developing the prodrome of DAT. The twins' varied life histories suggest that environmental risk factors may contribute to apparent discordance for DAT and possible delay in disease onset for the currently nondemented twin.

CONCLUSIONS

These results suggest that both genetic and nongenetic factors influence disease onset and expression. Moreover, review of previous reports of monozygotic twin pairs concordant or discordant for Alzheimer's disease, with adequate family history data, suggest a pattern indicating interactions among age at dementia onset, sex, and familiarity. Such patterns point to hypotheses regarding neurobiologically meaningful Alzheimer's disease subgroups.

Reliability of drawing regions of interest for positron emission tomographic data

We determined interrater reliability for two raters who independently used a standard protocol to draw regions of interest (ROIs) on F-18 fluorodeoxyglucose positron emission tomographic data acquired from eight patients with mild to moderate memory impairment. Intraclass correlation coefficients for region sizes (total pixel number) varied among anatomical ROIs (RIs from 0.324 to 0.935). However, correlations calculated from relative metabolic rates (normalized average counts) were consistently high (RI > or = 0.954). The raters also showed high agreement for region recognition on each image plan (kappa = 0.978). These results suggest that rater disagreements in ROI margins have minimal impact on average count densities used to calculate metabolic rates.

Cerebral metabolic dysfunction in AIDS: findings in a sample with and without dementia

Positron-emission tomography was coupled with neurological and neuropsychological evaluation to study regional cerebral activity and neurologic status in two groups. Seventeen patients with full-blown AIDS and 14 seronegative control subjects were studied using [18F]2-fluoro-2-deoxy-D-glucose in a resting state. The AIDS group had relative regional hypermetabolism in the basal ganglia and thalamus; stepwise multiple-regression analyses revealed a significant relationship for the AIDS group between temporal lobe metabolism and severity of dementia on the AIDS Dementia Complex Rating Scale. These results suggest that the basal ganglia, thalamus, and temporal lobes are differentially affected in AIDS.