Pathognomonic MRI and MR spectroscopy findings in cerebral hydatid cyst.

Abstract

A 14-year-old girl presented with features of raised intracranial pressure. MRI brain revealed a large, well defined, T2 hyperintense, cystic lesion in the right frontoparietal region with an imperceptible wall and a small anterior daughter cyst (Fig. 1). There was no significant perilesional oedema or abnormal enhancement. No similar thoracic or abdominal involvement was noted. MR spectroscopy (TE 144 ms) showed a large peak at 2.4 ppm (pyruvate/succinate). Smaller peaks of alanine (doublet 1.48 ppm), lactate (inverted, 1.3 ppm), and myoinositol (3.5 ppm) were also seen. NAA peak was reduced, choline peak was mildly elevated (Fig. 2). Conventional and spectroscopic findings were consistent with hydatid cyst. She underwent right parietal craniotomy with total cyst excision. Intraoperatively the cyst showed a fragile wall and daughter cysts. Histopathology confirmed the pre and intraoperative diagnosis of hydatid cyst with secondary granulomatous inflammation. Hydatid disease is a zoonotic disease caused by the larval stage of echinococcus, more commonly by E. granulosus and rarely by E. multilocularis [1]. The central nervous system is affected in 1–2 % of cases, more commonly in children [1]. They usually present with a single cyst in the middle cerebral artery territory. Multiple daughter cysts can be seen within the large cyst. MR spectroscopy helps in the noninvasive diagnosis of the hydatid cyst. The 2.4 ppm peak has been described as a very specific marker for intracranial cestodal infection. Although Jaykumar et al. attributed this 2.4 ppm peak to pyruvate, other authors believe it is a succinate peak [2, 3]. Peaks at 2.4 ppm have been found as a noninvasive marker of cestodal cysts [2]. Alanine and acetate peaks have also been reported [2]. Creatine is usually absent, unlike cysticercal cysts [4].