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Unilateral megalencephaly: correlation of MR imaging and pathologic characteristics
1Department of Radiology, University of California School of Medicine, San Francisco 94143.
Abstract:
Unilateral megalencephaly is a rare and poorly understood malformation resulting in the enlargement of all or part of a cerebral hemisphere. The clinical and radiologic features of 12 patients with unilateral megalencephaly are presented; pathologic correlation was available in four. All patients had seizures and developmental delay. Two were in congestive heart failure as a result of arteriovenous shunting through the abnormal hemisphere. The affected hemispheres showed a wide spectrum of involvement. Anomalies of neuronal migration were present, and there was a roughly inverse correlation between the severity of hemispheric involvement and the magnitude of enlargement. This correlation is explained via a proposed mechanism of a mild hemispheric insult in the middle-to-late second trimester. One patient had an extremely anomalous hemisphere that did not have characteristics of a neuronal migration anomaly and may have been a hamartomatous malformation. Our correlation of the clinical, radiologic, and pathologic features of unilateral megalencephaly, together with a theory of pathogenesis, should help elucidate this rare malformation.
Insights
Unilateral megalencephaly, a rare brain malformation causing hemisphere enlargement, is linked to seizures and developmental delays. Pathogenesis may involve early second-trimester insults, explaining varied severity.
Area of Science:
- Neuroscience
- Developmental Biology
- Pediatric Neurology
Background:
- Unilateral megalencephaly is a rare congenital brain malformation characterized by enlargement of one cerebral hemisphere.
- Its etiology and pathogenesis remain poorly understood, necessitating further research into its clinical and pathological features.
Purpose of the Study:
- To present the clinical, radiological, and pathological findings in 12 patients diagnosed with unilateral megalencephaly.
- To propose a mechanism for the pathogenesis of unilateral megalencephaly based on observed correlations.
Main Methods:
- Retrospective review of clinical and radiological data from 12 patients with unilateral megalencephaly.
- Pathological correlation was available for four patients.
- Analysis of hemispheric involvement, clinical presentation, and developmental outcomes.
Main Results:
- All 12 patients exhibited seizures and developmental delay.
- Two patients presented with congestive heart failure due to arteriovenous shunting.
- A spectrum of hemispheric involvement was observed, with anomalies of neuronal migration noted in most cases.
- An inverse correlation between severity of involvement and degree of enlargement was observed, suggesting a mid-to-late second-trimester insult.
Conclusions:
- Unilateral megalencephaly is consistently associated with significant neurological deficits, including seizures and developmental delay.
- The proposed pathogenesis involving a mild second-trimester insult provides a framework for understanding the observed clinical and radiological spectrum.
- Further research is warranted to fully elucidate the diverse presentations and underlying mechanisms of this rare malformation.