Exploring the pattern and neural correlates of neuropsychological impairment in late-life depression.

BACKGROUND: Neuropsychological impairment is a key feature of late-life depression, with deficits observed across multiple domains. However, it is unclear whether deficits in multiple domains represent relatively independent processes with specific neural correlates or whether they can be explained by cognitive deficits in executive function or processing speed. METHOD: We examined group differences across five domains (episodic memory; executive function; language skills; processing speed; visuospatial skills) in a sample of 36 depressed participants and 25 control participants, all aged ≥ 60 years. The influence of executive function and processing speed deficits on other neuropsychological domains was also investigated. Magnetic resonance imaging correlates of executive function, processing speed and episodic memory were explored in the late-life depression group. RESULTS: Relative to controls, the late-life depression group performed significantly worse in the domains of executive function, processing speed, episodic memory and language skills. Impairments in executive function or processing speed were sufficient to explain differences in episodic memory and language skills. Executive function was correlated with anisotropy of the anterior thalamic radiation and uncinate fasciculus; processing speed was correlated with anisotropy of genu of the corpus callosum. Episodic memory was correlated with anisotropy of the anterior thalamic radiation, the genu and body of the corpus callosum and the fornix. CONCLUSIONS: Executive function and processing speed appear to represent important cognitive deficits in late-life depression, which contribute to deficits in other domains, and are related to reductions in anisotropy in frontal tracts.

Dual task performance in early Alzheimer's disease, amnestic mild cognitive impairment and depression.

BACKGROUND: The dual task paradigm (Baddeley et al. 1986; Della Sala et al. 1995) has been proposed as a sensitive measure of Alzheimer's dementia, early in the disease process. METHOD: We investigated this claim by administering the modified dual task paradigm (utilising a pencil-and-paper version of a tracking task) to 33 patients with amnestic mild cognitive impairment (aMCI) and 10 with very early Alzheimer's disease, as well as 21 healthy elderly subjects and 17 controls with depressive symptoms. All groups were closely matched for age and pre-morbid intellectual ability. RESULTS: There were no group differences in dual task performance, despite poor performance in episodic memory tests of the aMCI and early Alzheimer's disease groups. In contrast, the Alzheimer patients were specifically impaired in the trail-making test B, another commonly used test of divided attention. CONCLUSIONS: The dual task paradigm lacks sensitivity for use in the early differential diagnosis of Alzheimer's disease.

White matter hyperintensities in late life depression: a systematic review.

BACKGROUND: White matter hyperintensities in MRI scans are age related but appear to be more prevalent in depressed patients. They may be more pronounced in late onset depression. This finding, if confirmed, would potentially illuminate the heterogeneity of depression in elderly subjects. METHODS: We conducted a systematic literature search of studies investigating white matter changes in late life depression, identifying 98 studies. The 30 remaining eligible studies were scrutinised for the presence and severity measures of periventricular and deep white matter changes in late life, late onset and, if available, early onset depression as well as in controls. Comparisons between groups were entered into random effects meta-analyses using odds ratios and Cohen's d, as appropriate. Correlations with potential confounders, such as age difference between groups, were explored. RESULTS: Late life depression and, to a greater extent, late onset depression in late life were characterised by more frequent and intense white matter abnormalities. In particular, the odds of having white matter changes were over 4 for late compared with early onset depression. Similarly, on severity scales, late onset depression had scores of 0.7-0.8 standard deviations above early onset patients. CONCLUSIONS: Significant differences between early and late onset depression suggest different aetiological mechanisms, in accordance with a theory of "cerebrovascular" depression of late onset. Greater duration of depressive symptoms, signs and treatment does not appear to have a measurable impact on white matter signal in MRI scans.

Cavernous malformation within a schwannoma: review of the literature and hypothesis of a common genetic etiology.

The finding of cavernous malformations within tumors of the central or peripheral nervous system is a rare occurrence. We report a case of a histologically proven cavernous malformation found within an eighth cranial nerve schwannoma in a 76-year-old man. The patient presented with progressive loss of hearing on the left, facial pain and dysesthesia. Symptoms improved significantly after the tumor was subtotally resected through a left retrosigmoid craniotomy. Including the present report, 34 cases of cavernous malformations associated with tumors of nervous system origin, 24 cases (71%) involving tumors of Schwann cell origin, and 9 cases (26%) involving gliomas have been published. The cases were classified into two forms based on the type of association. Conjoined association, in which the cavernous malformation is located within the tissue of the nervous system tumor, and discrete association, in which the cavernous malformation and nervous system tumor are in separate locations. We explore the etiology of this association and hypothesize that a common genetic pathway may be involved in a majority of these cases.