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a
Department of Neuroradiology, Pontchaillou University Hospital, 2, rue Henri-Le-Guilloux, 35000 Rennes, France b Department of Neurology, Pontchaillou University Hospital, 2, rue Henri-Le-Guilloux, 35000 Rennes, France ∗
Corresponding author. E-mail address:
[email protected] (J.-C. Ferré). doi:10.1016/j.neurad.2010.12.001
Magnetic resonance spectroscopy of a cerebral parasitic cyst Spectroscopie par résonance magnétique d’un kyste cérébrale parasitaire Figure 3 Axial-view T1-weighted image with gadolinium enhancement shows no enhancement either within the cyst or in its wall.
A 9-year-old boy, living in France under substandard conditions of hygiene, presented with right hemiparesis and left oculomotor nerve palsy that had progressively worsened over 3 weeks. Magnetic resonance imaging (MRI) disclosed a well defined, round 6-cm lesion in the left frontoparietal region with cerebrospinal fluid (CSF)-like signal intensity and a mass effect (Fig. 1). A thin hypointense peripheral rim was noted on T2-weighted images, and there was no diffusion restriction, peripheral edema or enhancement (Figs. 2 and 3). Magnetic resonance spectroscopy ([MRS]; Fig. 4) revealed a succinate peak (2.4 ppm), an inverted lactate peak (1.3 ppm), a smaller alanine peak (1.48 ppm) and an acetate peak (1.9 ppm). These features suggested an infectious cyst. However, hydatidosis and cysticercosis serology and hepatic ultrasound examination were negative. Figure 1 Axial-view FLAIR (fluid-attenuated inversion recovery) MRI (1.5 Tesla units) reveals a rounded cystic mass in the left frontal lobe with cerebrospinal fluid-like signal intensity exerting a mass effect on the falcorial sinus and temporal lobe.
Surgical removal via a left frontal craniotomy and hydrodissection of the cyst was performed to avoid rupture (Fig. 5). The postoperative recovery was complete,
Figure 2 Diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) mapping: (a) DWI shows no bright area in the cyst; and (b) no restricted diffusion on the ADC map.
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Figure 4 Monovoxel MRS within the cyst at (a) short and (b) long echo times reveals the presence of a succinate peak at 2.4 ppm, an inverted lactate peak at 1.3 ppm, a smaller alanine peak at 1.48 ppm and a smaller acetate peak at 1.9 ppm, but no choline, creatine or N-acetylaspartate peak.
Figure 5 Macroscopic view of hydrodissection of the cyst reveals a translucent fluid cyst.
and albendazole treatment for 1 month was prescribed. No recurrence was observed. Anatomopathological examination revealed a sterile parasitic cyst containing no protoscoleces, and ruled out neuroglial cyst and tumor. Although histopathological examination failed to identify tapeworm, we consider this lesion to be a sterile hydatid cyst rather than neurocysticercosis because of the patient’s age; the location of the lesion within the white matter; its size; the lack of rim enhancement, peripheral edema or calcification; and the features seen on MRS. Hydatid echinococcosis (HE) is a worldwide zoonosis, albeit rarely seen in Western countries [1]. Most patients (80%) have single-organ involvement mainly affecting the liver or lungs. Cerebral involvement is seen in only 2% of patients, most commonly children and affecting the middle cerebral artery territory [1,2]. ‘Daughter’ vesicles are considered pathognomonic, but these are seldom identified, even on MRI [1,2].
HE usually presents as a single, well-defined, rounded cystic lesion with CSF-like signal intensity, and no perilesional edema or contrast enhancement [1]. The hypointense rim observed on T2-weighted images is due to a pericyst (a fibrous capsule derived from reactive host tissue) [1]. Misdiagnosis may occur in Western countries because other causes of cystic lesions, such as neuroglial cyst, giant perivascular spaces, cystic glioma and abscesses, are more frequently encountered than this disease. However, MRS in vivo may be added to the usual MRI protocol for a more accurate etiological diagnosis of a cystic lesion. The most specific metabolite of HE reported at a peak of 2.4 ppm by Jayakumar et al. [3] was pyruvate, although other studies have assigned this peak to succinate [4—6], as confirmed by mass spectroscopy. In addition to HE, a succinate peak at 2.4 ppm has also been seen in pyogenic abscesses and neurocysticercosis [6]. Other less-specific metabolites, such as lactate and acetate, are suggestive of infectious diseases [4]. MRS studies ex vivo have found malate (4.3 ppm) and fumarate (6.5 ppm) in fertile cysts [4,5]. These metabolites are not found in cysticercosis cysts, but the presence of a creatine peak is specific in that case [6]. In conclusion, MRS is a useful addition to the MRI workup of a cystic lesion of unknown cause, as it can help to identify a parasitic origin in non-endemic countries.
Conflict of interest statement None.
References [1] Tüzün M, Altinors N, Adra IS, Hekimo˘ glu B. Cerebral hydatid disease CT and MR findings. Clin Imaging 2002;26(5):353—7. [2] Basraoui D, El Idrissi I, Jalal H, Hiroual M, Essadki O, Ousehal A, et al. Intracranial hydatis cysts in children: a report of 9 cases. J Radiol 2010;91:293—6. [3] Jayakumar PN, Srikanth SG, Chandrashekar HS, Kovoor JM, Shankar SK, Anandh B. Pyruvate: an in vivo marker of cesto-
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dal infestation of the human brain on proton MR spectroscopy. J Magn Reson Imaging 2003;18(6):675—80. [4] Garg M, Gupta RK, Prasad KN, Sikora SS, Pal L, Chawla S, et al. Fertility assessment of hydatid cysts by proton MR spectroscopy. J Surg Res 2002;106:196—201. [5] Hosch W, Junghanss T, Stojkovic M, Brunetti E, Heye T, Kauffmann GW, Hull WE. Metabolic viability assessment of cystic echinococcosis using high-field 1H MRS of cyst contents. NMR Biomed. 2008;21(7):734—54. [6] Garg M, Chawla S, Prasad KN, Roy R, Sikora SS, Kumar R, et al. Differentiation of hydatid cyst from cysticercus cyst by proton MR spectroscopy. NMR Biomed 2002;15(5):320—6. a,∗
E. Ukkola-Pons S. Ferrand-Sorbet b E. Banayan a M. Polivka c
J. Savatovsky a F. Heran a a Service de radiologie, fondation ophtalmologique Adolphe-de-Rothschild, 25, rue Manin, 75940 Paris cedex 19, France b Service de neurochirurgie, fondation ophtalmologique Adolphe-de-Rothschild, 75940 Paris cedex 19, France c Service d’anatomie et cytologie pathologiques, hôpital Lariboisière, 2, rue Ambroise-Paré, 75475 Paris cedex 10, France ∗
Corresponding author. 46, rue de l’Église, 75015 Paris, France. E-mail address:
[email protected] (E. Ukkola-Pons). doi:10.1016/j.neurad.2010.07.002
