Hippocampal abnormalities in malformations of cortical development: MRI study.

Area of Science:

• Neuroimaging
• Neurology
• Developmental Neuroscience

Background:

• Hippocampal abnormalities can co-occur with malformations of cortical development (MCD).
• Understanding the spectrum and clinical impact of these co-occurrences is crucial for patient management.
• Previous studies have indicated a potential link, but large-scale categorization is needed.

Purpose of the Study:

• To categorize hippocampal abnormalities in patients with MCD using MRI.
• To compare the clinical characteristics of MCD patients with and without hippocampal abnormalities.
• To identify specific MCD subtypes associated with particular hippocampal changes.

Main Methods:

• A cross-sectional MRI study involving 220 patients diagnosed with MCD and epilepsy.
• Visual assessment of hippocampal anatomy, rotation, size, internal structure, and signal alterations by three independent raters.
• Classification of four hippocampal abnormality types: partially infolded/hypoplastic hippocampus (HH), hippocampal sclerosis (HS), malrotated hippocampus (MH), and enlarged hippocampus (EH).

Main Results:

• Hippocampal abnormalities were identified in 31% (69/220) of patients.
• The most frequent abnormalities were HH (49%), HS (26%), and MH (22%).
• Periventricular nodular heterotopia (PNH) and polymicrogyria (PMG) were most commonly associated with hippocampal abnormalities.
• Patients with hippocampal abnormalities showed higher rates of learning disability and delayed developmental milestones compared to those without.

Conclusions:

• A significant proportion of patients with MCD present with coexisting hippocampal abnormalities.
• Partially infolded/hypoplastic hippocampus (HH) is linked to a more severe clinical phenotype, including epilepsy, learning disability, and developmental delays.
• These findings highlight the importance of evaluating hippocampal structure in patients with MCD for comprehensive clinical assessment.