Publication: Brain A Journal of Neurology

Alexander G Murley, Matthew A Rouse, P Simon Jones, Rong Ye, Frank H Hezemans, Claire O’Callaghan, Polytimi Frangou, Zoe Kourtzi, Catarina Rua, T Adrian Carpenter, Christopher T Rodgers, James B Rowe

3 November 2020

Behavioural disinhibition is a common feature of the syndromes associated with frontotemporal lobar degeneration (FTLD). It is associated with high morbidity and lacks proven symptomatic treatments. A potential therapeutic strategy is to correct the neurotransmitter deficits associated with FTLD, thereby improving behaviour. Reductions in the neurotransmitters glutamate and GABA correlate with impulsive behaviour in several neuropsychiatric diseases and there is post-mortem evidence of their deficit in FTLD. Here, the researchers tested the hypothesis that prefrontal glutamate and GABA levels are reduced by FTLD in vivo, and that their deficit is associated with impaired response inhibition.

They measured glutamate and GABA levels using semi-LASER magnetic resonance spectroscopy in the right inferior frontal gyrus, because of its strong association with response inhibition, and in the primary visual cortex, as a control region. The stop-signal reaction time was calculated using an ex-Gaussian Bayesian model. Participants with frontotemporal dementia and progressive supranuclear palsy had impaired response inhibition, with longer stop-signal reaction times compared with controls. GABA concentration was reduced in patients versus controls in the right inferior frontal gyrus, but not the occipital lobe. There was no group-wise difference in partial volume corrected glutamate concentration between patients and controls. Both GABA and glutamate concentrations in the inferior frontal gyrus correlated inversely with stop-signal reaction time, indicating greater impulsivity in proportion to the loss of each neurotransmitter.

The researchers conclude that the glutamatergic and GABAergic deficits in the frontal lobe are potential targets for symptomatic drug treatment of frontotemporal dementia and progressive supranuclear palsy.

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Publication: Movement Disorders

Samuel Shribman, Carolin Heller, Maggie Burrows, Amanda Heslegrave,Imogen Swift, Martha S. Foiani, Godfrey T. Gillett, Emmanuel A. Tsochatzis, James B. Rowe et al

20 October 2020

Outcomes are unpredictable for neurological presentations of Wilson’s disease (WD). Dosing regimens for chelation therapy vary and monitoring depends on copper indices, which do not reflect end‐organ damage. The objective was to identify a biomarker for neurological involvement in WD.

Unlike copper indices, neurofilament light (NfL) concentrations were higher in neurological than hepatic presentations. They were also higher in those with active neurological disease when controlling for severity and correlated with neurological examination subscores in stable patients.

NfL is a biomarker of neurological involvement with potential use in guiding chelation therapy and clinical trials for novel treatments.

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Publication: Neurology

Beatrice Costa, Claudia Manzoni, Manuel Bernal-Quiros, Demis A Kia, Miquel Aguilar, Ignacio Alvarez, Victoria Alvarez, Ole Andreassen, Maria Anfossi, Silvia Bagnoli, Luisa Benussi, Livia Bernardi, Giuliano Binetti, Daniel Blackburn, Mercè Boada, Barbara Borroni, Lucy Bowns, Geir Bråthen, Amalia C Bruni, Huei-Hsin Chiang, James B Rowe et al

17 September 2020

The researchers sought to characterise C9orf72 expansions in relation to genetic ancestry and age at onset (AAO), and to use these parameters to discriminate the behavioural from the language variant syndrome, in a large pan-European cohort of frontotemporal lobar degeneration (FTLD) cases.

They found C9orf72 pathogenic expansions in 4% of all cases (56/1396). Expansion carriers differently distributed across syndromes: 12/101 FTLD-MNDs (11.9%), 40/800 bvFTDs (5%) and 4/495 of PPAs (0.8%). While addressing population-substructure through principal component analysis (PCA), we defined 2 patients groups with Central/Northern (n=873) and Southern European (n=523) ancestry. The proportion of expansion carriers was significantly higher in bvFTDs compared to PPAs (5% vs. 0.8% [p=2.17×10-5; OR=6.4; CI:2.31-24.99]), as well as in individuals with Central/Northern European compared to Southern European ancestry (4.4% vs. 1.8% [p=1.1×10-2; OR=2.5; CI:1.17-5.99]). Pathogenic expansions and Central/Northern European ancestry independently and inversely correlated with AAO. Their prediction model (based on expansions status, genetic ancestry and AAO) predicted a diagnosis of bvFTD with 64% accuracy.

The results indicate correlation between pathogenic C9orf72 expansions, AAO, PCA-based Central/Northern European ancestry and a diagnosis of bvFTD, implying to complex genetic risk-architectures differently underpinning the behavioural and language variant syndromes.

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Publication: NeuroImage

Catarina Rua, William T. Clark, Ian D. Driver, Olivier Mougin, Andrew T. Morgan, Stuart Clare, Susan Francis, Keith W. Muir, Richard G. Wise, T. Adrian Carpenter, Guy B. Williams, James B. Rowe, Richard Bowtell, Christopher T.Rodgers

9 September 2020

The researchers present the reliability of ultra-high field T2* MRI at 7T, as part of the UK7T Network’s “Travelling Heads” study. T2*-weighted MRI images can be processed to produce quantitative susceptibility maps (QSM) and R2* maps. These reflect iron and myelin concentrations, which are altered in many pathophysiological processes. The relaxation parameters of human brain tissue are such that R2* mapping and QSM show particularly strong gains in contrast-to-noise ratio at ultra-high field (7T) vs clinical field strengths (1.5–3T). The study team aimed to determine the inter-subject and inter-site reproducibility of QSM and R2* mapping at 7T, in readiness for future multi-site clinical studies.

Mean susceptibility (χ) and R2* values agreed broadly with literature values in all ROIs. The inter-site within-subject standard deviation was 0.001–0.005 ppm (χ) and 0.0005–0.001 ms−1 (R2*). For χ this is 2.1–4.8 fold better than 3T reports, and 1.1–3.4 fold better for R2*. The median ICC from within- and cross-site R2* data was 0.98 and 0.91, respectively. Multi-echo QSM had greater variability vs single-echo QSM especially in areas with large B0 inhomogeneity such as the inferior frontal cortex. Across sites, R2* values were more consistent than QSM in subcortical structures due to differences in B0-shimming. On a between-subject level, theirr measured χ and R2* cross-site variance is comparable to within-site variance in the literature, suggesting that it is reasonable to pool data across sites using our harmonised protocol.

The harmonized UK7T protocol and pipeline delivers on average a 3-fold improvement in the coefficient of reproducibility for QSM and R2* at 7T compared to previous reports of multi-site reproducibility at 3T. These protocols are ready for use in multi-site clinical studies at 7T.

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Publication: Clinical Neuropathology

Melanie P Jensen, Olivera Spasic-Boskovic, James B Rowe, Clare Galton, Kieren S J Allinson

1 September 2020

The researchers presented the clinicopathological findings of a case of combined Fahr’s disease (FD) and dementia with Lewy bodies (DLB), associated with a novel pathogenic mutation. The patient presented with visual hallucinations, fluctuating confusion and parkinsonism, leading to a presumptive diagnosis of DLB. CT scan showed extensive bilateral parenchymal calcifications, suggestive of FD. DNA sequencing identified a novel missense variant (c.92A>T p.(Asn31Ile)) in the SLC20A2 gene, a gene known to be associated with FD. This change has not been previously recorded in genetic repositories, and in silico analyses classified it as likely to be disease-causing.

Neuropathological examination revealed, macroscopically and microscopically, extensive calcification in the striatum, globus and cerebellar white matter. There was also neuronal loss in the substantia nigra and residual neurones contained alpha-synuclein-positive Lewy bodies. The neuropathology was therefore consistent with DLB and FD.

A literature review identified 3 other cases of co-existing Fahr’s and Lewy body pathology, thus the frequency of dual pathology (44%) is higher than expected by random association. Further studies are needed to determine whether alpha-synucleinopathy is linked mechanistically to FD and/or represents a phenotypic subtype.

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