Brain Magnetic Resonance Imaging Techniques in the Diagnosis of Parkinsonian Syndromes

Unraveling neurological diseases: the contribution of neuroimaging

The 21st Meeting of the European Neurological Society (ENS) was held on 28-31 May 2011 in Lisbon, Portugal. Over 3400 participants attained the meeting. The ENS meeting is an international event, which offers an exclusive opportunity for excellent continuous education, as well as an update of cutting-edge research in all fields of neurology. Among the key themes of this year's conference, the contribution of magnetic resonance-based techniques to unravel the physiopathology of neurological diseases and improve our knowledge of the way they progress was highlighted in several sessions. This article summarizes the major neuroimaging findings of the 21st ENS Meeting.

Diffusion tensor magnetic resonance imaging tractography in progressive supranuclear palsy

BACKGROUND

Diffusion tensor magnetic resonance imaging tractography allows quantification of in vivo white matter tract damage.

METHODS

Using tractography, diffusion tensor magnetic resonance imaging metrics were obtained from the superior and middle cerebellar peduncles and major cerebral white matter tracts in 5 patients with progressive supranuclear palsy and 13 controls.

RESULTS

Patients showed severe intrinsic damage to the superior cerebellar peduncle, corpus callosum, and cingulum bilaterally. Only decreased axial diffusivity was found in the left middle cerebellar peduncle.

CONCLUSIONS

Diffusion tensor magnetic resonance imaging tractography holds promise for providing accurate in vivo cartography of progressive supranuclear palsy tissue damage.

Diagnostic accuracy of the magnetic resonance Parkinsonism index and the midbrain-to-pontine area ratio to differentiate progressive supranuclear palsy from Parkinson's disease and the Parkinson variant of multiple system atrophy

Using magnetic resonance (MR) planimetry, both the midbrain-to-pontine area ratio (m/p-ratio) and the MR parkinsonism index (MRPI) have been shown to assist in the differential diagnosis of progressive supranuclear palsy (PSP) from Parkinson's disease (PD) and the Parkinson variant of multiple system atrophy (MSA-P). The aim of this study was to determine the diagnostic accuracy of the MRPI compared with the m/p-ratio in a large cohort of 123 patients with neurodegenerative parkinsonism including patients with PSP, PD, and MSA-P. Patients with PSP had significant higher MRPI values and significant smaller m/p-ratios compared with the other groups with overlapping individual values. Overall predictive accuracy was similar for the m/p-ratio (87.0%) and the MRPI (80.5%) with a predictive accuracy for PSP from MSA-P being significantly better for the MRPI (87.5%) compared with the m/p-ratio (75%) as well as a predictive accuracy for PSP from PD being significantly better for the m/p-ratio (87.6%) compared with the MRPI (77.3%). Both the m/p-ratio and the MRPI may assist the clinical differential diagnosis in neurodegenerative parkinsonism.

Idiopathic Parkinson disease effect of levodopa on apparent diffusion coefficient value of the brain

PURPOSE

To evaluate the effect of levodopa on apparent diffusion coefficient (ADC) value of the brain parenchyma in patients with idiopathic Parkinson disease (PD).

MATERIAL AND METHODS

Prospective study was conducted on native PD without treatment (n = 25) and patients receiving levodopa (L-Dopa) (n = 25). Diffusion magnetic resonance-weighted imaging was done using a single-shot spin echo type of echo planar imaging. The apparent diffusion coefficient (ADC) value at different regions of the brain on both sides was calculated.

RESULTS

The ADC value of the putamen in patients with native PD was 0.732 ± 0.15 × 10-3 mm2/seconds and in patients receiving levodopa was 0.789 ± 0.24 × 10-3 mm2/second. There was a statistically significant difference in the ADC value at the putamen (P = .001) between patients with native PD and patients receiving levodopa. When ADC value of the putamen at 0.745 × 10-3 mm2/second was used as a threshold value for differentiating native PD patients and patients receiving L-Dopa, the best results were obtained with an accuracy of 82%, sensitivity of 92%, specificity of 72%, positive predictive value of 77%, negative predictive value of 90%, and area under the curve of 0.955.

CONCLUSION

ADC value of the putamen is a promising parameter for predication of effect of levodopa on brain parenchyma in patients with PD.

Magnetic resonance imaging in progressive supranuclear palsy

Progressive supranuclear palsy (PSP) is a tauopathy, presenting clinically most often with a symmetrical akinetic-rigid syndrome, postural instability, supranuclear gaze palsy and frontal dementia. In the absence of reliably validated biomarkers, the diagnosis of PSP in vivo is presently based on clinical criteria, which to date do not include supporting imaging findings, as is accepted for other neurodegenerative diseases. However, data from conventional magnetic resonance imaging (MRI) and various advanced MRI techniques including magnetic resonance volumetry, voxel-based morphometry, diffusion-weighted and diffusion-tensor imaging, magnetization transfer imaging and proton resonance spectroscopy suggest that MRI can contribute valuable information for the differential diagnosis of PSP. We review here the presently published literature concerning MRI in PSP and discuss the potential role of MRI in differentiating PSP from other parkinsonian syndromes.