Grégoire Dooms

Apparent diffusion coefficient measurements within intracranial epidermoid cysts in six patients

Abstract. The purpose was to determine whether a strong decrease in apparent diffusion coefficient (ADC) within epidermoid cysts (ECs) is actually responsible for their bright signal intensity on diffusion-weighted (DW) trace images. We studied six patients with surgically proven ECs in whom ADC calculation from T2-weighted DW-EPI-SE data were performed within the ECs and within the deep white matter and cerebrospinal fluid (CSF) as references. All ECs displayed highest signal intensity on the DW trace images. ADC values ranged from 1,280 to 807×10–6xa0mm2/s within cysts (with a mean value of 1,070), from 849 to 698×10–6xa0mm2/s within white matter (with a mean value of 764) and from 3,370 to 2,980×10–6xa0mm2/s within CSF (with a mean value of 3,185). ECs exhibited slightly higher ADC values than white matter, and not the strongly decreased ones which would have been expected if diffusion-weighting were the prominent mechanism for bright signal intensity of the ECs on DW images. However, the EC ADC values are much lower than those of the CSF. Other mechanisms must therefore be involved, i.e. the T2 shine-through effect. Reduced ADC is not the only explanation of the EC bright signal intensity on the DW trace images.

MRI assessment of unsuspected dural sinus thrombosis

SummaryIn three patients with clinically unsuspected diagnosis, MRI has afforded a positive and conspicuous demonstration of dural sinus thrombosis, allowing specific treatment and followed by improvement in the patients condition. Even in retrospect, CT examinations were nondiagnostic. Presenting symptoms were usual and nonspecific. CT and radionuclide scanning have proved valuable when performed on a clinically oriented basis. Angiography cannot be carried out without clear indications. MRI offers advantages in being a non-invasive technique without ionising radiation, allowing direct visualization and accurate delineation of the thrombus. MRI is definitely the method of choice to assess clinically suspected cerebral venous occlusion. As MR diagnosis relies on a routine examination protocol, we believe that it will detect other unsuspected cases of dural sinus thrombosis.

Hydrocephalus in Guillain-barre-syndrome

Hydrocephalus developed in a 16-year-old boy with a severe Guillain-Barré syndrome and was demonstrated by computerized tomography (CT) and magnetic resonance imaging. No papilledema was observed. The spontaneous resolution of hydrocephalus was achieved in a 6-month period. Ventricular changes were followed by CT scan.