Posterior fossa in primary microcephaly: relationships between forebrain and mid-hindbrain size in 110 patients
Yuko Adachi1, Ganeshwaran Mochida2, Christopher Walsh2
1Department of Radiology and Biomedical Imaging, University of California, San Francisco, California, United States.
Insights
In microcephaly patients, brain structure proportions vary. A disproportionately large cerebellum was observed in 45.5% of cases, potentially aiding genetic cause identification.
Area of Science:
- Neuroscience
- Genetics
- Pediatric Neurology
Background:
- Microcephaly presents with diverse clinical severity and morphology.
- Understanding brain structure disproportion is key to diagnosing microcephaly subtypes.
- Genetic factors significantly influence brain development and microcephaly etiology.
Purpose of the Study:
- To determine the frequency of disproportion between cerebrum and hindbrain/midbrain structures in microcephaly.
- To explore how these disproportions correlate with microcephaly severity.
- To assess the utility of relative brain size analysis in identifying genetic causes of microcephaly.
Main Methods:
- Visual analysis of relative forebrain, brain stem, and cerebellum sizes on magnetic resonance (MR) images.
- Study included 110 infants and children diagnosed with microcephaly.
- Categorization of cerebellar size relative to cerebrum as disproportionally large, proportional, or disproportionally small.
Main Results:
- A disproportionally large cerebellum was found in 45.5% of patients.
- A proportional cerebellum was observed in 44.5% of cases.
- Disproportionately small cerebella were present in 10% of patients, primarily in severe and moderate microcephaly.
Conclusions:
- Relative cerebellar size analysis is a valuable tool for categorizing microcephaly.
- Observed disproportions may assist in pinpointing specific genetic causes of microcephaly.
- Cerebellar and brain stem size analysis on MR imaging can aid in initial microcephaly assessment.
Abstract:
Microcephalies vary widely in clinical severity and in morphology. The purpose of this study is to determine the frequency of disproportion between the size of the cerebrum and the size of midbrain and hindbrain structures in infants and children with microcephaly, as analysis of such disproportions might aid understanding of these disorders and facilitate testing for specific genetic causes. The relative sizes of the forebrain, each component of the brain stem, and vermis and hemispheres of the cerebellum were analyzed visually on magnetic resonance (MR) images of 110 microcephalic patients. A disproportionally large cerebellum, compared with the cerebrum, was found in 50 cases (45.5%), a proportional cerebellum in 49 cases (44.5%), and a disproportionally small cerebellum in 11 cases (10%). Proportional cerebella were most common in mild (86%) and moderate (55%) microcephaly patients, whereas disproportionately large cerebella were most common in severe (57%) and moderate (32%) microcephaly. Disproportionately small cerebella were seen only in moderate (13%) and severe (9%) microcephaly. As genes are expressed at different times in cerebral and cerebellar development, it is postulated that analysis of relative cerebellar and brain stem size may be useful in the initial analysis of microcephaly by MR images both to categorize and to help determine likely genetic causes.
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