White matter abnormalities associated with Alzheimer's disease and mild cognitive impairment: a critical review of MRI studies.

In this article, the authors aim to present a critical review of recent MRI studies addressing white matter (WM) abnormalities in Alzheimer's disease (AD) and mild cognitive impairment (MCI), by searching PubMed and reviewing MRI studies evaluating subjects with AD or MCI using WM volumetric methods, diffusion tensor imaging and assessment of WM hyperintensities. Studies have found that, compared with healthy controls, AD and MCI samples display WM volumetric reductions and diffusion tensor imaging findings suggestive of reduced WM integrity. These changes affect complex networks relevant to episodic memory and other cognitive processes, including fiber connections that directly link medial temporal structures and the corpus callosum. Abnormalities in cortico-cortical and cortico-subcortical WM interconnections are associated with an increased risk of progression from MCI to dementia. It can be concluded that WM abnormalities are detectable in early stages of AD and MCI. Degeneration of WM networks causes disconnection among neural cells and the degree of such changes is related to cognitive decline.

Coordinated and circumlocutory semantic naming errors are related to anterolateral temporal lobes in mild AD, amnestic mild cognitive impairment, and normal aging.

Naming difficulties are characteristic of Alzheimer's disease (AD) and, to a lesser extent, of amnestic mild cognitive impairment (aMCI) patients. The association of naming impairment with anterior temporal lobe (ATL) atrophy in Semantic Dementia (SD) could be a tip of the iceberg effect, in which case the atrophy is a marker of more generalized temporal lobe pathology. Alternatively, it could reflect the existence of a functional gradient within the temporal lobes, wherein more anterior regions provide the basis for greater specificity of representation. We tested these two hypotheses in a study of 15 subjects with mild AD, 17 with aMCI, and 16 aged control subjects and showed that coordinate and circumlocutory semantic error production on the Boston Naming Test was weakly correlated with ATL gray matter density, as determined by voxel-based morphometry. Additionally, we investigated whether these errors were benefited by phonemic cues, and similarly to SD, our AD patients had small improvement. Because there is minimal gradient of temporal lobe atrophy in AD or MCI, and, therefore, no basis for a tip of the iceberg effect, these findings support the theory of a modest functional gradient in the temporal lobes, with the ATLs being involved in the naming of more specific objects.

Postcraniotomy temporalis muscle atrophy: a clinical, magnetic resonance imaging volumetry and electromyographic investigation.

AIMS: To evaluate both cosmetic and functional effects of temporalis muscle atrophy, by means of clinical examination, magnetic resonance imaging (MRI), and electromyographic (EMG) activity in patients who underwent craniotomy in order to treat refractory mesial temporal lobe epilepsy (MTLE). METHODS: A total of 18 controls and 18 patients who underwent surgery for MTLE were investigated. The temporalis muscle volume of the patients was assessed by a 3D reconstruction. The image analysis software (ITK-SNAP) was used for the 3D reconstruction. In addition, the amplitude of the EMG signal during a maximum voluntary clench was recorded from both temporalis muscles by surface electrodes. The presence of temporomandibular disorder (TMD) signs was assessed by clinical examination that was performed only after surgery. Data were analyzed statistically by means of the Mann-Whitney U test, paired t-test, Pearson χ² and linear regression. RESULTS: The volume of the temporalis muscle of the operated side was significantly reduced (P = .004). The EMG results confirmed the presence of muscle atrophy, the amplitude of the EMG signal being significantly decreased on the operated side (P < .05). Also the patients' maximum mouth opening after surgery was significantly reduced compared to that of the controls (P < .0001). Patients presented facial asymmetry, signs of TMD (pain, disc displacement, and joint sounds), and masticatory abnormalities. CONCLUSION: These preliminary results showed that, despite the good control of seizures, some patients may experience cosmetic and functional abnormalities of temporalis muscle secondary to atrophy and fibrosis.

Dynamic changes in white and gray matter volume are associated with outcome of surgical treatment in temporal lobe epilepsy.

BACKGROUND: The reasons for surgical failure in 30% of patients with unilateral mesial temporal lobe epilepsy (MTLE) are still unclear. We investigated if different outcomes could be associated to different patterns of subtle gray matter atrophy (GMA) and white matter atrophy (WMA), and searched for postoperative magnetic resonance imaging (MRI) changes. METHODS: We studied 69 controls and 67 operated patients with refractory unilateral MTLE. Patients were grouped as seizure-free (SF) group (34 patients Engel's IA), worthwhile improvement group (23 patients, Engel's IB-IIA) and failure group (10 patients Engel's IIB-IV). We created a voxel-based morphometry/MATLAB code to mask the surgical lacuna, and performed t-test and paired t-test to evaluate preoperative and postoperative MRI scans. RESULTS: Failure group showed a widespread pattern of preoperative GMA. On SF and improvement groups we identified a more restricted pattern of GMA. The three groups presented a widespread, bilateral pattern of WMA. In contrast, postoperative analyses showed bilateral hemispheric recovery (a relative increase of WM concentration) on SF and improvement groups, but few changes on failure group. We also identified areas with relative postoperative increase of GM on both SF and improvement groups, more widespread on SF group. CONCLUSION: Areas of subtle GMA may be related to poorer surgical outcome. In addition, we demonstrated a postoperative relative increase of WM and GM concentration associated with seizure control. These changes may represent neuroplasticity related to improvement of brain function after seizure control. Further studies with a multimodal approach may help to predict surgical outcome and improve selection of patients for surgical treatment of MTLE.

Regeneração de atrofia de substância branca após a cirurgia de epilesia: evidências estruturais através da morfometria baseada em voxel / Recovery of white matter atrophy after epilepsy surgery: structural evidences through voxel-based morphometry

OBJECTIVES: To study pre and postoperative WMA in MTLE patients. METHODS: We performed Voxel-Based Morphometry (VBM) with volume of interest (VOI) in 69 controls (mean age, 34.3±11.1 years) and 67 operated patients (mean age, 34.1±10.4 years) with unilateral MTLE. 34 became seizure-free (SzFree-Group), 23 improved (Engel IB-IIA [Partial recovery-group]) and 10 did not improve (Engel III-IV [Failure-Group]). All had pre and postoperative MRIs (one year minimum). We flipped MRIs of right MTLE patients in order to avoid right-to-left analysis cancelation. VBM was performed on SPM2/MATLAB7.0 with individual masks for surgical lacunae and 1 percent false-discovery-rate to control for multiple comparisons. We used MARSbar routine to select ROIs and t-test for statistical analyses. RESULTS: Mean postoperative follow-up was 60.2 (±SD 30.7) months. On baseline MRI, SzFree-Group showed White Matter Atrophy (WMA) involving temporal lobes [TL], ipsilateral occipital, parietal and frontal regions, with areas of significant recovery of WMA on postoperative MRI. Partial recovery-Group presented a more restricted pattern of WMA, involving ipsilateral temporal lobe, contralateral superior temporal gyrus and few areas in bilateral cingulated and orbitofrontal areas. In this group we also identified areas with relative increase of WM after surgery. By contrast, Failure-Group showed more widespread bi-hemispheric areas of WMA on baseline MRI without postoperative improvement. CONCLUSIONS: Although we have identified some differences in baseline WMA, we were unable to correlate a more widespread pattern with a worse prognosis, as SzFree-Group, also presented a bilateral distribution of WMA. The recovery of WMA in SzFree-Group and Partial recovery-group is in agreement with previous MRS and PET studies and suggests that a network of neuronal dysfunction in MTLE can be, at least in part, reversible after successful postoperative ...

Avaliação computacional da impressão plantar. Valores de referência do índice do arco em amostra da população brasileira / Computational evaluation of the footprint. Reference values of the plantar arch index in a sample of the Brazilian population

A presença do arco longitudinal medial (ALM) é característica dos pés humanos e através dele o pé tem sido classificado como normal, cavo e plano. A literatura permite escolher entre variados métodos e técnicas de mensuração do ALM, cada qual com vantagens e desvantagens. Optou-se pelo método da impressão plantar com medida do índice do arco (IA) para avaliar indiretamente a altura do ALM. A escolha foi motivada por ser a impressão plantar exeqüível com baixo custo e não invasiva. Seguiu-se o princípio básico do método de mensuração do IA proposto por Cavanagh & Rodgers, modificado pela introdução do escaneamento da impressão plantar e pelo cálculo do IA através de programa computacional elaborado por um dos autores. Foram avaliadas 100 impressões plantares de 25 homens e 25 mulheres sadios, não obesos, com média de idade de 34,7 anos, extremos de 10 a 59 anos. Obtiveram-se os valores de referência do IA de amostra da população brasileira: 0,21< IA < 0,25. A comparação estatística dos valores nacionais com os da amostra americana não mostrou diferença estatística significativa.

The presence of medial longitudinal arch (MLA) is characteristic of the human feet and has been used for the classification of a normal, cavus and flat foot. The literature provides informations about several methods and different techniques of measurement the MLA, each one having advantage and disadvantage. We choose the footprint method and the measuring of arch index (AI) as an indirect evaluation of the MLA height. We preferred this method because it is simple, cost-effective and noninvasive. We followed the basic principles of the IA measurement proposed by Cavanagh & Rodgers, but modified because we introduced footprint scan and AI calculation using a software program elaborated by one of the authors. A total of 100 footprints were analyzed in healthy, non obese subjects, 25 males and 25 females, with mean age of 34.7 years, extreme of 10 and 59 years. The AI reference values obtained in a sample of the Brazilian population were 0.21< IA < 0.25. There was no significant statistical difference between Brazilians values and Americans ones.