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Objective: To quantify spinal cord atrophy and its impact on clinical disability in spinocerebellar ataxia (SCA) type 3 and 6., Methods: Atrophy of the upper spinal cord was assessed by high resolution T1-weighted MRI of patients with SCA3 (n = 14) and SCA6 (n = 10). Furthermore, two groups of age- and sex-matched healthy control subjects (n = 24,) corresponding to the two SCA groups, were studied. Images were post-processed by a semi-automated volumetry method combining a marker based segmentation and an automatic histogram method facilitating highly reliable quantification and morphometry of the upper cervical cord in vivo., Results: We found a significant reduction of normalized mean crosssectional area of the spinal cord in SCA3 (p < 0.0005), whereas in SCA6 patients normalized mean crosssectional area was in the normal range (p = 0.379). No correlation was found between spinal cord atrophy and disease duration as well as CAG repeat length in both subtypes. In SCA6 a negative dependency between clinical disability, as expressed by the International Cooperative Ataxia Rating Scale as a well established ataxia score, and the mean cross-sectional area was found (p = 0.02). A similar correlation was observed in SCA3 but did not reach statistical significance., Conclusion: Our results quantify for the first time in vivo spinal cord atrophy as a non-cerebellar neurodegenerative process in SCA3. Our results suggest MR volumetry of the upper cervical cord as a marker of functional importance in SCA3 and SCA6.

Background and Purpose: In amyotrophic lateral sclerosis (ALS), fiber degeneration within the corticospinal tract (CST) can be quantified by diffusion tensor imaging (DTI) as an indirect marker of upper motor neuron involvement. A new method of measuring quantitative DTI parameters using a probabilistic mixture model for fiber tissue and background in the corticospinal tract of patients with ALS is evaluated., Materials and Methods: Axial echo-planar imaging (EPI) DTI datasets (6 gradient directions, 10 repetitions) were acquired for 10 patients and 20 healthy control subjects. The diffusion tensor was visualized in a multiplanar viewer using a unique color coding method. Pure fiber tissue inside a region is separated from background and mixture voxels using a probabilistic mixture model. This allows for a reduction of errors as a result of partial volume effects and measurement variability., Results: Fractional anisotropy (FA) was measured within the CST at levels ranging from internal capsule to pons. Mean coefficients of variation of intrarater, scan-rescan, and inter-rater reproducibility were 2.4%, 3.0%, and 5.7%, respectively. Optimal measurement positions along the CST with respect to minimum variability and maximum difference between patients and healthy subjects were identified in the caudal half of the internal capsule. Moreover, a negative correlation between the age-corrected FA and the disease duration but not the ALS Severity scale score was found., Conclusion: The new software for fiber integrity quantification is suited to assess FA in the corticospinal tract with high reproducibility. Thus, this tool can be useful in future studies for monitoring disease status and potential treatment efficiency.

Fast, reliable and easy-to-use methods to quantify brain atrophy are of increasing importance in clinical studies on neuro-degenerative diseases. Here, ILAB 4, a new volumetry software that uses a fast semi-automated 3D segmentation of thin-slice T1-weighted 3D MR images based on a modified watershed transform and an automatic histogram analysis was evaluated. It provides the cerebral volumes: whole brain, white matter, gray matter and intracranial cavity. Inter- and intra-rater reliability and scan-rescan reproducibility were excellent in measuring whole brain volumes (coefficients of variation below 0.5%) of volunteers and patients. However, gray and white matter volumes were more susceptible to image quality. High accuracy of the absolute volume results (+/-5 ml) were shown by phantom and preparation measurements. Analysis times were 6 min for processing of 128 slices. The proposed technique is reliable and highly suitable for quantitative studies of brain atrophy, e.g., in multiple sclerosis.