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The Causes of Epilepsy The Causes of Epilepsy
Common and Uncommon Causes in Adults and Children
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Chapter 44 - Hemimegalencephaly

from Section 3 - Symptomatic epilepsy

Published online by Cambridge University Press:  05 March 2012

Simon D. Shorvon
Affiliation:
National Hospital for Neurology and Neurosurgery, London
Frederick Andermann
Affiliation:
Montreal Neurological Hospital and Institute
Renzo Guerrini
Affiliation:
Child Neurology Unit, Meyer Pediatric Hospital, Florence
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Summary

Hemimegalencephaly often presents in early infancy with either cerebral hemisphere affected, and occurs in every ethnic group and both genders. Hemimegalencephaly may be the primary etiology of several epilepsy syndromes. In Ohtahara syndrome, tonic seizures, frequently asymmetric, present early in association with a burst suppression pattern. West syndrome is another frequently encountered epilepsy type with infantile spasms present in up to 50% of patients with hemimegalencephaly. The diagnosis of hemimegalencephaly is made definitively by magnetic resonance imaging (MRI) examination; however, early detection using postnatal cranial ultrasound and computed tomography (CT) is possible. Brain single photon emission computed tomography (SPECT) imaging often reveals hypoperfusion of the malformed hemisphere in the interictal state and hyperperfusion during the ictus. The choice of antiepileptic medication rests largely on the seizure type present in each case. Anatomic or functional hemispherectomy have been employed in patients with hemimegalencephaly and both show similar rates of postoperative seizure-freedom.
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The Causes of Epilepsy
Common and Uncommon Causes in Adults and Children
, pp. 289 - 292
Publisher: Cambridge University Press
Print publication year: 2011

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