Conventional MRI

Conventional magnetic resonance imaging (MRI) allows for a detailed noninvasive visualization/examination of posterior fossa structures and represents a fundamental step in the diagnostic workup of many cerebellar disorders. In the first part of this chapter methodologic issues, like the correct choice of hardware (magnets, coils), pro and cons of the different MRI sequences, and patient management during the examination are discussed. In the second part, the MRI anatomy of the cerebellum, as noted on the various conventional MRI sequences, as well as a detailed description of cerebellar maturational processes from birth to childhood and into adulthood, are reported. Volumetric studies on the cerebellar growth based on three-dimensional MRI sequences are also presented. Moreover, we briefly discuss two main topics regarding conventional MRI of the cerebellum that have generated some debate in recent years: the differentiation between cerebellar atrophy, hypoplasia, and pontocerebellar hypoplasia, and signal changes of dentate nuclei after repetitive gadolinium-based contrast injections. The advantages and benefits of advanced neuroimaging techniques, including ¹H magnetic resonance spectroscopy, diffusion-weighted imaging, diffusion tensor imaging, and perfusion-weighted imaging are discussed in the last section of the chapter.

"Growing" cerebellum in an infant after shunt insertion

INTRODUCTION

Supratentorial cortical mantle growth after shunt surgery in infants with posthemorrhagic hydrocephalus is common. However, cerebellar growth and Chiari are rare.

PATIENT DESCRIPTION

We describe a term newborn with an intraventricular hemorrhage and posthemorrhagic hydrocephalus who underwent endoscopic third ventriculostomy followed by shunt placement at age 4 months.

RESULTS

After shunt placement, her head circumference growth rate rapidly decreased from the ninety-seventh percentile to the third percentile. Six months after a shunt placement, cerebellar disproportional growth was noticed. Five years after surgery, her cerebellar volume had increased by 300% whereas the cerebral hemispheres volume by 150%, and Chiari 1 appeared. She manifested early hemiparetic cerebral palsy, but, did not develop clinical evidence of increased intracranial pressure or brainstem abnormalities.

CONCLUSION

This term newborn exhibited apparent cerebellar "growth" and posterior fossa crowding after shunt surgery for posthemorrhagic hydrocephalus. Our patient's findings may have resulted from shunt-related alterations in pressure dynamics, leading to decreased head growth rate with a relatively smaller posterior fossa, in face of a normal brain growth. The timing of intraventricular hemorrhage at term, beyond the vulnerable period of cerebellar development, may have been a contributing factor to the craniocerebellar disproportion and posterior fossa crowding cerebellar development may have been relatively spared and was a contributing factor to the craniocerebellar disproportion and posterior fossa crowding.