Proton magnetic resonance spectroscopy in focal cortical dysplasia at 3T.

PURPOSE

Focal cortical dysplasia (FCD) type II is a frequent cause of medically intractable epilepsy. On conventional MRI diagnosis may be difficult. The purpose of our study was to assess the metabolic characteristics of MRI-typical or neuropathologically confirmed FCD II lesions at 3T.

METHODS

In a prospective study, 13 patients with drug-resistant epilepsy and MRI diagnosis of FCD II (seven neuropathologically confirmed) were investigated by single-volume proton magnetic resonance spectroscopy ((1)H MRS). We performed an intra-individual comparison placing spectroscopic volumes of interest in the lesion and in the apparently normal contralateral hemisphere. Spectroscopic results were correlated with clinical data.

RESULTS

Matched pair analysis revealed a significant increase in absolute choline (Cho) concentration in the lesion volume (+32%, p=0.015) compared to the control volume. This increase was associated with a significant decrease in N-acetyl-aspartate (NAA) concentration (-13%; p=0.008). Mean myo-inositol (Ins) levels were distinctly (+36%) but not significantly (p=0.051) elevated. Lesional creatine (Cr) concentration correlated significantly with the frequency of seizures (Spearman-Rho r=0.898; p=0.002), while concentrations of NAA, Cho and Ins did not correlate with clinical or imaging parameters.

CONCLUSION

MR spectroscopy revealed a characteristic metabolic pattern in FCD II lesions that helps to distinguish normal from epileptogenic tissue.