Selective frontal neurodegeneration of the inferior fronto-occipital fasciculus in progressive supranuclear palsy (PSP) demonstrated by diffusion tensor tractography.
BACKGROUND
The clinical presentation in progressive supranuclear palsy (PSP), an atypical parkinsonian disorder, includes varying degrees of frontal dysexecutive symptoms. Using diffusion tensor imaging (DTI) and tractography (DTT), we investigated whether diffusion changes and atrophy of the inferior fronto-occipital fasciculus (IFO) occurs in PSP and if these changes correlate with disease stage and clinical phenotype. The corticospinal tract (CST), which is often involved in PSP, was investigated for comparison.


METHODS
DTI of the whole brain was performed with a 3 T MR scanner using a single shot-EPI sequence with diffusion encoding in 48 directions. Scans were obtained in patients with PSP (n = 13) and healthy age-matched controls (n = 12). DTT of the IFO and CST was performed with the PRIDE fibre tracking tool (Philips Medical System). Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) were calculated and correlated with disease stage and clinical phenotype.


RESULTS
In patients with PSP, significantly decreased FA and increased ADC was found in the frontal part of IFO compared with the medial and occipital parts of IFO, as well as compared to controls. Four of the thirteen patients with PSP showed a marked decrease in the number of tracked voxels in the frontal part of IFO. These findings were most pronounced in patients with severe frontal cognitive symptoms, such as dysexecutive problems, apathy and personality change. There was a strong correlation (r2 = -0.84; p < 0,001) between disease stage and FA and ADC values in the CST.


CONCLUSIONS
DTT for identification of neuronal tracts with subsequent measurement of FA and ADC is a useful diagnostic tool for demonstrating patterns of neuronal tract involvement in neurodegenerative disease. In selected tracts, FA and ADC values might act as surrogate markers for disease stage.
Geriatric Psychiatry, Department of Clinical Sciences, Lund University, Klinikgatan 22, 22185 Lund, Sweden.
Pia
P
Kvickström
Bengt
B
Eriksson
Danielle
D
van Westen
Jimmy
J
Lätt
Christina
C
Elfgren
Christer
C
Nilsson
D000368:Aged; D016880:Anisotropy; D001284:Atrophy / Q000473:pathology; D003072:Cognition Disorders / Q000150:complications / Q000473:pathology; D056324:Diffusion Tensor Imaging / Q000379:methods*; D005260:Female; D005625:Frontal Lobe / Q000473:pathology*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D009434:Neural Pathways / Q000473:pathology; D009778:Occipital Lobe / Q000473:pathology*; D011712:Pyramidal Tracts / Q000473:pathology; D013494:Supranuclear Palsy, Progressive / Q000150:complications / Q000473:pathology*
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