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AJNR Awards, New Junior Editors, and more. Read the latest AJNR updates

Case of the Week

Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada

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Submit a Case Previous Cases ASPNR Pediatric Cases

March 3, 2008
  • Description
  • Diagnosis
  • Brain Teaser
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Parahippocampal Gray Matter Heterotopias, Dysplastic Left Cerebellum

  • Most common causes of recognizable hippocampal lesions causing seizures: sclerosis, developmental abnormalities (cortical dysplasias, gray matter heterotopias), vascular malformations (cavernous or arteriovenous malformations) or insults (infarctions), tumors (glial, oligodendroglial, ganglion cell)
  • In one study, 7.2% of patients with temporal lobe epilepsy had malformations: heterotopia, neocortical malformation, abnormal shape/configuration and other complex malformations
  • Parahippocampal heterotopias are amenable to surgery only when unilateral and not present elsewhere (patients who also have periventricular heterotopias will most likely have recurrent seizures)
  • Regardless of underlying lesion, shortly after seizures (particularly prolonged ones) the hippocampi may be T2 bright and show restricted diffusion

Suggested Reading

Lehericy S, Dormont D, Semah F, et al. Developmental abnormalities of the medial temporal lobe on patients with temporal lobe epilepsy. AJNR Am J Neuroradiol 1995;16:617-26.

Chan S, Chin SS, Kartha K, et al. Reversible signal abnormalities in the hippocampus and neocortex after prolonged seizures. AJNR Am J Neuroradiol 1996;17:1725-31.

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American Journal of Neuroradiology: 46 (6)
American Journal of Neuroradiology
Vol. 46, Issue 6
1 Jun 2025
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Print ISSN: 0195-6108 Online ISSN: 1936-959X

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