Corticospinal tract involvement in spinocerebellar ataxia type 3: a diffusion tensor imaging study.

PURPOSE: The aim of this study was to evaluate the integrity of the corticospinal tracts (CST) in patients with SCA3 and age- and gender-matched healthy control subjects using diffusion tensor imaging (DTI). We also looked at the clinical correlates of such diffusivity abnormalities. METHODS: We assessed 2 cohorts from different Brazilian centers: cohort 1 (n = 29) scanned in a 1.5 T magnet and cohort 2 (n = 91) scanned in a 3.0 T magnet. We used Pearson's coefficients to assess the correlation of CST DTI parameters and ataxia severity (expressed by SARA scores). RESULTS: Two different results were obtained. Cohort 1 showed no significant between-group differences in DTI parameters. Cohort 2 showed significant between-group differences in the FA values in the bilateral precentral gyri (p < 0.001), bilateral superior corona radiata (p < 0.001), bilateral posterior limb of the internal capsule (p < 0.001), bilateral cerebral peduncle (p < 0.001), and bilateral basis pontis (p < 0.001). There was moderate correlation between CST diffusivity parameters and SARA scores in cohort 2 (Pearson correlation coefficient: 0.40-0.59). CONCLUSION: DTI particularly at 3 T is able to uncover and quantify CST damage in SCA3. Moreover, CST microstructural damage may contribute with ataxia severity in the disease.

[Diffusion tensor imaging of the corticospinal pathway and its association with the prognosis of acute cerebral infarction: experience with a cohort in Mexico]. / Imagen del tensor de difusión de la vía corticoespinal y su asociación con el pronóstico del infarto cerebral agudo: experiencia de una cohorte en México.

INTRODUCTION: Magnetic resonance diffusion tensor imaging through the fraction of anisotropy allows evaluation of the integrity of the motor pathways after cerebral infarction. AIMS: To correlate the fraction of anisotropy with the clinical scales and the prognosis of cerebral infarction. SUBJECTS AND METHODS: Prospective study of patients with cerebral infarction to compare the fraction of anisotropy in different regions of interest with functional evaluations and with controls free of infarction. A subgroup of subjects with rehabilitation underwent an initial MRI scan and another at three months, with clinical follow-up for six months. RESULTS: Thirty-eight consecutive patients with middle cerebral artery infarction were included. The fraction of anisotropy values were lower in the ipsilateral corticospinal pathway than the fraction of anisotropy of the corticospinal pathway of the controls. The values of the fraction of anisotropy in the ipsilateral corticospinal pathway were associated with the value of the functional scale on admission. Changes in the fraction of anisotropy values between the initial MRI and the scan performed at three months correlated with the score on the functional scale and the modified Rankin scale at three and six months. CONCLUSIONS: The value of the fraction of anisotropy in the ipsilateral internal capsule is associated with the presence of a lesion and with its presenting symptoms. Changes in the fraction of anisotropy at three months suggest long-term clinical recovery.

TITLE: Imagen del tensor de difusión de la vía corticoespinal y su asociación con el pronóstico del infarto cerebral agudo: experiencia de una cohorte en México.Introducción. La imagen del tensor de difusión por resonancia magnética a través de la fracción de anisotropía permite evaluar la integridad de las vías motoras después de un infarto cerebral. Objetivo. Correlacionar la fracción de anisotropía con las escalas clínicas y el pronóstico del infarto cerebral. Sujetos y métodos. Estudio prospectivo de pacientes con infarto cerebral para comparar la fracción de anisotropía en diferentes regiones de interés con evaluaciones funcionales y con controles sin infarto. En un subgrupo con rehabilitación, se realizó una resonancia magnética inicial y a los tres meses, con un seguimiento clínico durante seis meses. Resultados. Se incluyó a 38 pacientes consecutivos con infarto cerebral de la arteria cerebral media. Los valores de la fracción de anisotropía fueron menores en la vía corticoespinal ipsilateral que en la vía corticoespinal de los controles. Los valores de la fracción de anisotropía en la vía corticoespinal ipsilateral se asociaron con el valor de la escala funcional en el momento de su admisión. Los cambios en los valores de la fracción de anisotropía entre la resonancia magnética inicial y a los tres meses se correlacionaron con la puntuación en la escala funcional y en la escala de Rankin modificada a los tres y a los seis meses. Conclusiones. El valor de la fracción de anisotropía en la cápsula interna ipsilateral se asocia a la presencia de lesión y a su presentación clínica. Los cambios en la fracción de anisotropía a los tres meses sugieren la recuperación clínica a largo plazo.

A Brain Marker for Developmental Speech Disorders.

OBJECTIVE: To characterize the organization of speech- and language-related white matter tracts in children with developmental speech and/or language disorders. STUDY DESIGN: We collected magnetic resonance diffusion-weighted imaging data from 41 children, ages 9-11 years, with developmental speech and/or language disorders, and compared them with 45 typically developing controls with the same age range. We used probabilistic tractography of diffusion-weighted imaging to map language (3 segments of arcuate fasciculus, extreme capsule system) and speech motor (corticobulbar) tracts bilaterally. The corticospinal and callosal tracts were used as control regions. We compared the mean fractional anisotropy and diffusivity values between atypical and control groups, covarying for nonverbal IQ. We then examined differences between atypical subgroups: developmental speech disorder (DSD), developmental language disorder, and co-occurring developmental speech and language disorder. RESULTS: Fractional anisotropy in the left corticobulbar tract was lower in the DSD than in the control group. Radial and mean diffusivity were higher in the DSD than the developmental language disorder, co-occurring developmental speech and language disorder, or control groups. There were no group differences for any metrics in the language or control tracts. CONCLUSIONS: Atypical development of the left corticobulbar tract may be a neural marker for DSD. This finding is in line with reports of speech disorder after left corticobulbar damage in children and adults with brain injury. By contrast, we found no association between diffusion metrics in language-related tracts in developmental language disorder, and changes for language disorders are likely more complex.

Pyramidal and Proprioceptive Dysfunctions as the Main Neurologic Features in Symptomatic Type I Chiari Malformation Patients

Objective Broader access to magnetic resonance imaging (MRI) has increased the diagnosis of tonsillar ectopia, with most of these patients being asymptomatic. The early diagnosis and treatment of type I Chiari malformation (CM I) patients has impact on the prognosis. This study supplements information about the neurologic exam of symptomatic patients with CM I. Methods The sample was composed of 32 symptomatic patients with CM I diagnosed by a combination of tonsil herniation of more than 5 mm below the magnum foramen (observed in the sagittal T2 MRI) and at least one of the following alterations: intractable occipital headache, ataxia, upper or lower motor neuron impairment, sensitivity deficits (superficial and deep) or lower cranial nerves disorders. Results Occipital headache was the most frequent symptom (53.12%). During the physical exam, the most common dysfunctions were those from the pyramidal system (96.87%), followed by posterior cord syndrome (87.5%). Discussion In this study, patients became symptomatic around the fifth decade of life, which is compatible with previous descriptions. Patients withmore than 2 years of evolution have worse responses to treatment. Occipital headache, symptoms in the upper limbs, gait and proprioceptive disorders are common findings in patients with CM I. Conclusion Deep tendinous reflexes and proprioception disorders were the main neurologic features found in symptomatic CM I patients.

Wallerian Degeneration Beyond the Corticospinal Tracts: Conventional and Advanced MRI Findings.

Wallerian degeneration (WD) is defined as progressive anterograde disintegration of axons and accompanying demyelination after an injury to the proximal axon or cell body. Since the 1980s and 1990s, conventional magnetic resonance imaging (MRI) sequences have been shown to be sensitive to changes of WD in the subacute to chronic phases. More recently, advanced MRI techniques, such as diffusion-weighted imaging (DWI) and diffusion tensor imaging (DTI), have demonstrated some of earliest changes attributed to acute WD, typically on the order of days. In addition, there is increasing evidence on the value of advanced MRI techniques in providing important prognostic information related to WD. This article reviews the utility of conventional and advanced MRI techniques for assessing WD, by focusing not only on the corticospinal tract but also other neural tracts less commonly thought of, including corticopontocerebellar tract, dentate-rubro-olivary pathway, posterior column of the spinal cord, corpus callosum, limbic circuit, and optic pathway. The basic anatomy of these neural pathways will be discussed, followed by a comprehensive review of existing literature supported by instructive clinical examples. The goal of this review is for readers to become more familiar with both conventional and advanced MRI findings of WD involving important neural pathways, as well as to illustrate increasing utility of advanced MRI techniques in providing important prognostic information for various pathologies.