Whole brain and localized magnetization transfer measurements are associated with cognitive impairment in patients infected with human immunodeficiency virus

BACKGROUND AND PURPOSE

Patients infected with human immunodeficiency virus (HIV) are susceptible to cognitive deterioration. This study investigated the utility of magnetization transfer (MT) imaging for quantification of brain tissue alterations associated with cognitive deficits in patients with HIV.

MATERIALS AND METHODS

MT ratios (MTR) were derived for whole brain and for regions of interest (ROIs) in the basal ganglia and white matter in 11 HIV and 12 control subjects. Relationships with severity of cognitive impairment and specific neuropsychological deficits were also evaluated.

RESULTS

MTR values for normalized whole brain histogram peak height, whole brain histogram mean, and all examined ROIs were reduced in the HIV subjects. Normalized histogram peak height and mean for whole brain, as well as means for the corpus callosum, basal ganglia, and frontal white matter (FWM), were significantly correlated with severity of cognitive impairment. MTR values for white matter regions (corpus callosum, FWM, and centrum semiovale) were correlated with specific cognitive deficits.

CONCLUSION

Quantitative MTR measurements, determined for the whole brain and for vulnerable ROIs, are sensitive to neuropathologic changes associated with cognitive impairment in HIV-infected patients.

Monocyte chemoattractant protein-1 correlates with subcortical brain injury in HIV infection

Various biomarkers have been suggested as associative or predictive of HIV-associated neurocognitive impairment. Plasma levels of monocyte chemoattractant protein 1 (MCP-1), tumor necrosis factor alpha (TNF-alpha), and hematocrit were evaluated for relationships with diffusion tensor imaging measurements of centrum semiovale, caudate, and putamen. MCP-1 levels correlated with tissue status (mean diffusivity) in all examined regions. Plasma markers were also significantly correlated with anisotropy measurements in centrum semiovale (TNF-alpha) and putamen (hematocrit).

Diffusion alterations in corpus callosum of patients with HIV

BACKGROUND AND PURPOSE

Diffusion alterations have been identified in the corpus callosum and frontal white matter of patients infected with human immunodeficiency virus (HIV), though the relevance of these findings to cognitive deterioration has not yet been determined. This study tested the hypothesis that diffusion tensor imaging can detect tissue status alterations in these regions in cognitively impaired patients infected with HIV and the acquired measurements correlate with the severity of cognitive impairment.

METHODS

Fractional anisotropy (FA) and mean diffusivity (MD) were determined for corpus callosum (genu and splenium) and frontal white matter (FWM). The DTI measurements were compared in 11 HIV and 11 control participants. Patterns of relationship were examined with cognitive status measures from concurrent neurologic and neuropsychologic evaluations.

RESULTS

FA values for the splenium were significantly reduced in the patients infected with HIV and correlated with dementia severity and deficits in motor speed. MD values for the splenium were significantly increased in the patients infected with HIV and correlated with deficits in motor speed. FA measurements were also significantly correlated with performance on visual memory (genu), visuoconstruction (FWM), and verbal memory (FWM) tasks.

CONCLUSION

Diffusion abnormalities were identified in the splenium of the corpus callosum in patients infected with HIV, and these alterations were associated with dementia severity and motor speed losses. In vivo assessment of callosal integrity by using quantitative neuroimaging may have potential utility as a marker of brain injury in patients infected with HIV.

Bone marrow diffusion measures correlate with dementia severity in HIV patients

BACKGROUND AND PURPOSE

Escalation in monocyte trafficking from the bone marrow into the brain may play a critical role in central nervous system injury and cognitive deterioration in patients with HIV infection. This study tested the hypothesis that the mean diffusivity is sensitive to marrow changes in HIV patients and that these quantitative imaging measurements correlate with the severity of dementia.

METHODS

The mean diffusivity (MD), determined for clival and calvarial marrow regions, was compared in 11 HIV-infected patients and 9 control subjects. The imaging measurements were also evaluated for relationships with dementia severity and markers of disease progression (CD4 and viral load in plasma).

RESULTS

The MD was significantly reduced in both clival and calvarial marrow in HIV-infected patients (P =.006). Diffusion measurements for clival (P =.02) and for calvarial (P =.03) regions were significantly correlated with the severity of dementia.

CONCLUSION

The results of this investigation support the utility of diffusion strategies for monitoring the marrow and provide further evidence of a relationship between marrow status changes and neurologic progression in HIV patients.

Disease burden in HIV-associated cognitive impairment: a study of whole-brain imaging measures

OBJECTIVE

To study whole-brain MR measures derived from diffusion tensor imaging and magnetization transfer imaging (MTI) for the in vivo assessment of cumulative neuropathologic changes in HIV and to evaluate the quantitative imaging strategies with respect to cognitive status measures including the severity of dementia and the degree of impairment in specific cognitive domains including attention, memory, constructional abilities, and motor speed.

METHODS

Quantitative whole-brain measurements, including fractional anisotropy (FA), apparent diffusion coefficient (ADC), and magnetization transfer ratio (MTR), were derived from histograms and compared in HIV and control participants. Relationships between the MR and cognitive status measures were examined.

RESULTS

Whole-brain FA and MTR were reduced in patients with HIV and correlated with dementia severity. Whole-brain MTR and ADC were correlated with psychomotor deficits. Evaluation of relationships between the studied MR measures indicated a correlation between ADC and MTR; FA was not correlated with either ADC or MTR.

CONCLUSIONS

Findings from this investigation support the use of quantitative whole-brain MR measures for evaluation of disease burden in HIV. Reductions in whole-brain fractional anisotropy and magnetization transfer ratio (MTR) distinguished HIV and control subjects, and these measures were associated with dementia severity. Relationships were identified between whole-brain MTR and apparent diffusion coefficient and psychomotor deficits. Combining these quantitative strategies in neuroimaging examinations may provide more comprehensive information concerning ongoing changes in the brains of HIV patients.

Changes in auditory-vocal reaction times within and across experimental sessions: preliminary observations

Changes in auditory-vocal reaction times (AVRTs) within and across experimental sessions were studied in 13 healthy university students, all females. Subjects were required to listen to a series of synthesized vowels and utter each of the vowels as soon as they heard it. The vowels were /i/, /u/, /a/, /o/, and /ae/, each presented 14 times and all presented in random order and at irregular intervals (2.5-4.5 sec). The stimuli and the instructions were prerecorded and presented to the subjects binaurally at a comfortable intensity level via headphones in an IAC booth. Each subject performed the experimental task twice, a week apart. The stimuli and the vocal responses were tape recorded and later digitized and computer analyzed. Serial analysis of successive AVRTs revealed significant intra- and intersession decreases in AVRTs in the majority of the subjects. Increases in AVRTs were also seen, but much less frequently. The implications of these findings are discussed.

Poverty of speech in schizophrenia and depression during in-patient and post-hospital periods

Poverty of speech, a prominent feature of the negative symptom construct in schizophrenia, was assessed longitudinally in 12 schizophrenic and 13 depressed subjects at hospital admission and about seven months after discharge in order to evaluate hypotheses concerning course and diagnostic specificity. Multiple measures of the poverty of speech construct were employed, including both clinical and quantitative indices. During the in-patient period, poverty of speech was more pronounced among depressed than schizophrenic subjects. Examination of this specific negative symptom across in-patient and follow-up evaluations indicated that poverty of speech increased among schizophrenic subjects, but remained relatively stable or declined among depressed subjects. These results suggest that the processes underlying poverty of speech may differ in schizophrenia and depression.

Communicability and thought disorder in schizophrenics and other diagnostic groups. A follow-up study

To evaluate qualitative differences in the nature of thought disorder, the 'cloze' procedure and the Scale for the Assessment of Thought, Language and Communication were used to compare speech samples from schizophrenic, depressive, manic, schizo-affective and normal subjects at two different times. At the acute phase, thought-disordered subjects (schizophrenics, manics and schizo-affectives) were less communicable than non-thought-disordered subjects (depressives and normals). Communicability increased with remission of the more flagrant features of disturbance. Comparison of the thought-disordered diagnostic groups in the rate and pattern of remission of specific features of thought disorder indicated that factors reflecting goal-disrupted cognition distinguished the groups.

Predictability as an index of impaired verbal communication in schizophrenic and affective disorders

The cloze procedure was used to examine predictability in speech samples from schizophrenic, depressive, manic, schizoaffective and normal subjects. Each speech sample was also rated for particular indices of thought disorder using the Andreasen Scale for the Assessment of Thought, Language and Communication. Schizophrenics were found to be less predictable than other patient groups or normals. Depressives were found to be the most predictable. Correlational analyses of cloze scores and specific thought disorder ratings suggest that reduced predictability is associated with traditional indicators of thought disorder.