Nadine Girard

Pituitary MRI characteristics in 297 acromegaly patients based on T2-weighted sequences

Responses of GH-secreting adenomas to multimodal management of acromegaly vary widely between patients. Understanding the behavioral patterns of GH-secreting adenomas by identifying factors predictive of their evolution is a research priority. The aim of this study was to clarify the relationship between the T2-weighted adenoma signal on diagnostic magnetic resonance imaging (MRI) in acromegaly and clinical and biological features at diagnosis. An international, multicenter, retrospective analysis was performed using a large population of 297 acromegalic patients recently diagnosed with available diagnostic MRI evaluations. The study was conducted at ten endocrine tertiary referral centers. Clinical and biochemical characteristics, and MRI signal findings were evaluated. T2-hypointense adenomas represented 52.9% of the series, were smaller than their T2-hyperintense and isointense counterparts (P<0.0001), were associated with higher IGF1 levels (P=0.0001), invaded the cavernous sinus less frequently (P=0.0002), and rarely caused optic chiasm compression (P<0.0001). Acromegalic men tended to be younger at diagnosis than women (P=0.067) and presented higher IGF1 values (P=0.01). Although in total, adenomas had a predominantly inferior extension in 45.8% of cases, in men this was more frequent (P<0.0001), whereas in women optic chiasm compression of macroadenomas occurred more often (P=0.0067). Most adenomas (45.1%) measured between 11 and 20 mm in maximal diameter and bigger adenomas were diagnosed at younger ages (P=0.0001). The T2-weighted signal differentiates GH-secreting adenomas into subgroups with particular behaviors. This raises the question of whether the T2-weighted signal could represent a factor in the classification of acromegalic patients in future studies.

Pediatric Neuroimaging: Fetal MR Imaging

Ultrasonography (US) is currently the primary imaging method for routine examination of the fetal brain (Monteagudo and Timor-Tritsch 1997; Economides and Braithwaite 1998; Economides et al. 1998; Levi 1998; Isaksen 1998) and specially by using three-dimensional ultrasonography (Kelly et al. 1994; Hata et al. 1998; Kurjak et al. 1998). However,magnetic resonance imaging (MRI) constitutes a useful procedure when ultrasonography is inadequate or equivocal and is also a powerful tool to illustrate the morphological changes of the developing brain as well as fetal abnormalities (Girard and Raybaud 1992; Girard et al. 1992, 1993, 1995, 1996; Sonigo et al. 1996). Fetal MRI is becoming a valuable adjunct to the evaluation of an abnormal fetus because of the developments in fast imaging and in fetal surgery (Farmer 1998). MRI is also becoming a potential and contributive tool in perinatal autopsy (Langer et al. 1998), for in vitro study (Brisse et al. 1997; Woodward et al. 1997) as well as in fetal volume estimations (Garden And Roberts 1996).

Malformations of the Telencephalic Commissures

“Callosal agenesis” is a misnomer. Modern imaging with magnetic resonance (MRI) allows for a detailed anatomic study of the malformation, and demonstrates that in at least 90% of the cases, absence of the corpus callosum is only part of the disorder: typically, the hippocampal commissure is also missing or incomplete. Therefore, the term “commissural agenesis,” or “agenesis of the (forebrain) commissures” should rather be used [1].

Central Nervous System Vasculitis in Children

Central nervous system (CNS) vasculitis in children may develop as a primary condition, or secondary to an underlying systemic disease. Accurate and early diagnosis is mandatory in order to prevent severe neurological complications. Neuroimaging play an important role in advancing the diagnosis. Cerebral digital subtraction angiography (DSA), MRI, and MRA are the most useful examinations for vasculitis. MRI appears as the modality of choice for diagnosis and follow-up evaluation of cerebral involvement with vasculitis. MRA will be the first angiographic examination in the diagnostic workup of suspected cerebral vasculitis. DSA remains an indispensable tool in some cases for the investigation of medium and small brain artery stenosis. The infectious causes of vasculitis, including bacterial, viral, and fungal infections, are only a small component of the overall list of etiologies but among the more treatable causes if diagnosed early and treated effectively. Cerebral complications associated with systemic vasculitis can occur from hypertensive encephalopathy secondary to renovascular hypertension, or direct intracranial vessel involvement. Childhood primary CNS vasculitis (PVCNS) includes two distinct and actually well-recognized subtypes: angiography-positive PVCNS affecting large-and medium-sized vessels with a progressive and non-progressive forms, and angiography-negative PVCNS involving small-sized vessels. These subtypes are defined by clinical features, neuroimaging characteristics, and brain biopsy findings and each mandates a distinct therapeutic approach. Therefore the diseases that must be considered in children presenting with features suggesting angiography-positive PVCNS are distinctly different from those in suspected angiography-negative PVCNS.