Regional brain metabolite abnormalities in inherited prion disease and asymptomatic gene carriers demonstrated in vivo by quantitative proton magnetic resonance spectroscopy

INTRODUCTION

Inherited prion diseases are caused by mutations in the gene which codes for prion protein (PrP), leading to proliferation of abnormal PrP isomers in the brain and neurodegeneration; they include Gerstmann-Sträussler-Scheinker disease (GSS), fatal familial insomnia (FFI) and familial Creutzfeldt-Jakob disease (fCJD).

METHODS

We studied two patients with symptomatic inherited prion disease (P102L) and two pre-symptomatic P102L gene carriers using quantitative magnetic resonance spectroscopy (MRS). Short echo time spectra were acquired from the thalamus, caudate region and frontal white matter, metabolite levels and ratios were measured and z-scores calculated for individual patients relative to age-matched normal controls. MRS data were compared with structural magnetic resonance imaging.

RESULTS

One fCJD case had generalised atrophy and showed increased levels of myo-inositol (MI) in the thalamus (z=3.7). The other had decreased levels of N-acetylaspartate (z=4) and diffuse signal abnormality in the frontal white matter. Both asymptomatic gene carriers had normal imaging, but increased frontal white matter MI (z=4.3, 4.1), and one also had increased MI in the caudate (z=5.3).

CONCLUSION

Isolated MI abnormalities in asymptomatic gene carriers are a novel finding and may reflect early glial proliferation, prior to significant neuronal damage. MRS provides potential non-invasive surrogate markers of early disease and progression in inherited prion disease.

Short TE Quantitative Proton Magnetic Resonance Spectroscopy in Variant Creutzfeldt-Jakob Disease

Variant Creutzfeldt-Jakob disease (vCJD) is a fatal neurodegenerative disorder. Clinical diagnosis is difficult in the early stages as the disease often presents with non-specific psychiatric and neurological symptoms. To investigate the diagnostic potential of quantitative short TE in vivo MRS, and the nature and anatomical distribution of biochemical abnormalities in vCJD, localised single-voxel spectra (TE/TR 30 ms/2,000 ms) were acquired from three brain regions: thalami, caudate nuclei and frontal white matter. Metabolite concentrations and ratios from three patients with definite or probable vCJD were compared with eight normal age-matched controls. Abnormal signal on T2-weighted MRI was apparent in the pulvinar region in all vCJD patients; this region also showed greatly increased myo-inositol [MI] (mean 2.5-fold, P=0.01) and decreased N-acetyl-aspartate (NAA; mean 2-fold, P=0.01). Two patients also showed increased [MI] (z=17, 11; one with decreased NAA, z=-12) in normal-appearing caudate nuclei. The magnitude of metabolite abnormalities in the thalami in moderately advanced vCJD suggests a potential role in earlier diagnosis. Short TE protocols allow the measurement of MI, which adds discriminant power to the MRS examination.

Maffucci's syndrome with extensive gastrointestinal involvement

A 10-year-old girl with cutaneous, oral and gastrointestinal vascular lesions was referred for consideration of laser treatment of her skin lesions. She was noted to have multiple venous malformations predominantly affecting the hands and feet, some of which had been present from birth. Her right hand was deformed by multiple venous malformations, and X-rays of this hand revealed enchondromata within metacarpal and phalangeal bones. She was known to have extensive involvement of her gastrointestinal tract by venous malformations, resulting in refractory iron-deficiency anaemia. In view of the multiple cutaneous and gastrointestinal vascular lesions, a diagnosis of blue rubber bleb naevus syndrome had been made many years earlier. However, after recognition of the characteristic enchondromata, this diagnosis has been revised to Maffucci's syndrome. In addition to her ongoing dermatological and paediatric follow up, she has now been referred to the orthopaedic surgeons for surveillance of her skeletal lesions.

Frontotemporal lobar degeneration with ubiquitin-only-immunoreactive neuronal changes: broadening the clinical picture to include progressive supranuclear palsy

The frontotemporal lobar degenerations (FTLDs) are a group of disorders in which the clinical picture is not necessarily predictive of the underlying neuropathology. The FTLD with ubiquitin-only-immunoreactive neuronal changes (FTLD-U) subtype is pathologically characterized by ubiquitin-positive, tau and alpha-synuclein-negative neuronal cytoplasmic inclusions in the frontotemporal cortex and hippocampal dentate fascia. When similar pathological changes are accompanied by histological features of motor neuron disease (MND), the term FTLD-MND is used. The latter pathological changes may be found in patients with or without clinical evidence of MND. We retrospectively reviewed the clinical details of three patients with a rapidly progressive, levodopa-unresponsive bradykinetic-rigid syndrome and frontal cognitive impairment. A diagnosis of progressive supranuclear palsy (PSP) had been considered in all three cases at initial presentation. Two of the cases fulfilled clinical diagnostic criteria for PSP, which was the final clinical diagnosis during life. Pathological analysis showed typical histological appearances of FTLD-MND in two cases and of FTLD-U in one case. Semi-quantitative analysis of pathological load seemed to correlate with the clinical phenotype. FTLD-U or FTLD-MND should be considered in the differential diagnosis of progressive frontal dementia with an akinetic rigid syndrome and supranuclear gaze palsy or Steele-Richardson-Olszewski disease.