Abstracts

Recently, abnormalities of the shape and positioning of the hippocampal formation have been recognized increasingly on MRI. The significance of this finding is not well known since it can be detected in patients investigated for various reasons. Few data exists in the literature regarding the presence of this abnormality in patients with seizures. We aimed to investigate the clinical and EEG findings in patients with seizures whose cranial MRI revealed the presence of hippocampal shape abnormalities., We retrospectively analyzed the clinical and laboratory findings of patients who were investigated at our epilepsy clinic for seizures between 1995-2006 and had cranial MRI that clearly demonstrated abnormalities of the shape of the hippocampus. Patients with any accompanying lesions (malformation of cortical development, tumor, encephalomalacia, etc) were excluded., Twenty one patients [11M, 10F; age: 17-69 years (mean 33)] were included in the study. Seizure onset varied between 1-58 years (mean 21.5) and occurred in adulthood in 15 (71 %) patients. Seizure characteristics were as follows: simple partial (n=9), complex partial (n=17) and secondary generalized tonic-clonic (n=10). Twelve (57.1 %) patients were seizure free on monotherapy with anticonvulsants. Eight (38.1 %) patients reported risk factors for seizures (febrile convulsion, head trauma, perinatal injury, family history of epilepsy). Cranial MRI was initially reported as normal in 11 (52.4 %) patients. Abnormal shape of the hippocampus was evident on the left side in 16 (76.1 %), right side in 3 (14.3 %) and bilaterally in 2 patients (9.5 %). Eight (38.1 %) patients had normal or non-specific EEG recordings. Pathological EEG findings were concordant with MRI results in 9 (42.8 %) patients., Although uncommon when compared to hippocampal sclerosis, hippocampal shape abnormalities may be associated with epilepsy. Seizure onset is usually late in this group and more than half of the patients are seizure free on single anticonvulsant. EEG may fail to demonstrate pathological findings in a considerable number of patients. The occurrence of this abnormality mostly on the left side may somehow be related to development of the dominant hemisphere and deserves further attention. Radiologists should be aware of hippocampal shape abnormalities since half of the cases may be overlooked on MRI.,