Epidermoid Cyst with a Metabolite Pattern Mimicking a Brain Abscess. A Magnetic Resonance Spectroscopy Study

Abstract

Intracranial epidermal cysts are benign uncommon lesions. Such lesions arise from an inclusion of an ectodermal element during neural tube closure, in which dermal elements become trapped in the suture line, diploe, meninges, or scalp. Reports have extensively demonstrated the typical magnetic resonance (MR) spectra with the presence of large lactate signals with a virtual absence of healthy brain metabolites. A 20-year-old male patient with a parietal lobe brain lesion was studied by magnetic resonance imaging and magnetic resonance spectroscopy in a 1.5-T Philips scanner. The lesion presented atypical MR spectra with presence of alanine (1.46 ppm), lactate (1.31 ppm), and amino acids such as valine, isoleucine (0.97 ppm), and glicine (3.52 ppm). No evidence of normal parenchyma tissue metabolites (N-acetylaspartate, creatine, and choline) or succinate and acetate signals was observed. This spectral pattern was unexpected being proposed the differential diagnosis of brain abscess versus epidermoid cyst. Finally, surgical total excision biopsy confirmed the diagnosis of epidermal cyst. In this report, we describe a case of an epidermal cyst with an unusual metabolic pattern observed by magnetic resonance spectroscopy mimicking a brain abscess.