T1- or T2-weighted magnetic resonance imaging: what is the best choice to evaluate atrophy of the hippocampus?

BACKGROUND AND PURPOSE: Magnetic resonance imaging is part of the diagnostic criteria for Alzheimer's disease (AD) through the evaluation of hippocampal atrophy. The objective of this study was to evaluate which sequence of T1-weighted (T1WI) and T2-weighted (T2WI) imaging allowed the best visual evaluation of hippocampal atrophy. METHODS: Visual qualitative ratings of the hippocampus of 100 patients with mild cognitive impairment (MCI) and 50 patients with AD were made independently by four operators according to the medial temporal lobe atrophy score based either on T1WI or T2WI. These two evaluations were compared in terms of interobserver reproducibility, concordance with a quantitative volumetric measure, discrimination power between AD and MCI groups, and correlation with several neuropsychological tests. RESULTS: The medial temporal lobe atrophy score evaluated on either T1WI or T2WI exhibited similar interobserver variability and accordance with quantitative volumetric evaluation. However, the visual evaluation on T2WI seemed to provide better discrimination power between AD and MCI groups for both left (T1WI, P = 0.0001; T2WI, P = 7.072 × 10-5 ) and right (T1WI, P = 0.008; T2WI, P = 0.001) hippocampus, and a higher overall correlation with neuropsychological tests. CONCLUSIONS: The present study suggests that T2WI provides a more adequate visual rating of hippocampal atrophy.

[The role of magnetic resonance angiography in the follow-up of intracranial arteriovenous malformations treated by an intravascular approach]. / Rôle de l'Angio-IRM dans la surveillance des malformations artério-veineuses intra-crâniennes traitées par abord endo-vasculaire.

The purpose of our work was to measure the accuracy and reliability of MR-Angiography in the study and follow-up of intracranial arteriovenous malformations, and in particular to evaluate the results of endovascular treatment. Over an 18-month period 4 patients with such malformations were examined by MR-Angiography. There was an angioma of the corpus callosum, a left parieto-rolandic angioma, a posterior thalamic angioma and a cerebellar angioma. All examinations were performed with a Magneton-Impact 1 Tesla machine (Siemens, Erlangen, Germany), using a head coil, MR-Angiography with time-of-flight sequences and differential arterial and venous saturations. Each patient was examined by MR-Angiography first at the beginning of treatment, then when ambulatory after embolization. The morphological study applied to the afferent vessels, the nidus and the efferent veins. MR-Angiography proved to be very good in identifying the arteries feeding the malformation, and this made it easier to evaluate the reduction of their input after treatment, without having recourse to any arteriography. Beside, analysis of the nidus was facilitated by the judicious arrangement of arterial and venous saturations. In fact, the systematic use of MR-Angiography in the follow-up of intracranial arteriovenous malformations makes it possible to measure, with full reliability, the efficacy of the endovascular treatment under conditions of comfort unequalled in these out-patients, and selective angiography sequences need to be performed only during therapeutic phases.

[Mucoid pseudocyst of the common peroneal nerve. Value of MRI (report of a case)]. / Pseudo-kyste mucoïde du sciatique poplité externe. Intérêt de l'IRM (rapport d'un cas).

The authors report a new case of ganglion cyst of the peroneal nerve. The rarity of this entity induced the authors to report this new case, emphasizing the value of MRI which constitutes a reliable non-invasive examination for the visualization of this lesion.

Necrosis and haemorrhage of the putamen in methanol poisoning shown on MRI.

Methanol, a highly toxic substance, is used as an industrial solvent and in automobile antifreeze. Acute methanol poisoning produces severe metabolic acidosis and serious neurologic sequelae. We describe a 50-year-old woman with accidental methanol intoxication who was in a vegetative state. MRI showed haemorrhagic necrosis of the putamina and oedema in the deep white matter.