Subependymal giant cell astrocytoma with high choline/creatine ratio on proton MR spectroscopy

Neuro 33.qxp 25.09.06 15:09 Page 877 Arq Neuropsiquiatr 2006;64(3-B):877-880 SUBEPENDYMAL GIANT CELL ASTROCYTOMA WITH HIGH CHOLINE/CREATINE RATIO ON PROTON MR SPECTROSCOPY Arnolfo de Carvalho Neto1, Emerson L. Gasparetto2, Isac Bruck3 ABSTRACT - Objective: To report a case of subependymal giant cell astrocytoma (SEGA) in a patient with tuberous sclerosis, emphasizing the proton MR spectroscopy (MRS) findings. Case: A three year-old boy with tuberous sclerosis presented with a 3-month history of mild headache. The physical examination showed discrete mental retardation and multiple hypomelanic macules in the legs and back. MRI showed many cortical tubers and subependymal nodules. At the left foramen of Monro, there was a 15 mm nodule, with heterogeneous signal on T1 and T2-weighted images, and strong enhancement after contrast administration. MRS study (multi-voxel PRESS, TE=144ms) showed the following ratios: a) left foramen of Monro nodule N-acetylaspartate (NAA)/creatine (Cr)=0.93 and Choline (Cho)/Cr=1.6 and b) at the right Monro foramen NAA/Cr=1.56 and Cho/Cr=1.29. Conclusion: The MRS performed at the SEGA may show high Cho/Cr and low NAA/Cr ratios, similar to the other brain neoplasms. As a consequence, MRS may be a valuable tool for the early detection of neoplastic transformation of subependymal nodules near the foramina of Monro in patients with tuberous sclerosis. KEY WORDS: subependymal giant cell astrocytoma, proton magnetic resonance spectroscopy, tuberous sclerosis. Astrocitoma subependimário de células gigantes com alta relação colina/creatina à espectroscopia de prótons por ressonância magnética RESUMO - Objetivo: Relatar caso de astrocitoma subependimário de células gigantes (ASCG) em paciente com esclerose tuberosa, enfatizando os achados de espectroscopia de prótons por ressonância magnética (EPRM). Caso: Um menino de três anos de idade apresentou-se com cefaléia por três meses. O exame físico demonstrou retardo mental discreto e múltiplas máculas hipomelanóticas no dorso e pernas. A ressonância magnética (RM) evidenciou múltiplos túberes corticais e nódulos subependimários. No forame de Monro esquerdo foi observado um nódulo de 15 mm, com sinal heterogêneo nas imagens ponderadas em T1 e T2, e realce intenso após a administração de contraste. A EPRM (multi-voxel PRESS, TE=144ms) demonstrou as seguintes relações: a) no nódulo no forame de Monro esquerdo N-acetilaspartato (NAA)/creatina (Cr)=0,93 e colina (Cho)/Cr=1,6 e b) no forame de Monro direito NAA/Cr=1,56 and Cho/Cr=1,29. Conclusão: A EPRM pode demonstrar relações altas de Cho/Cr e baixas de NAA/Cr em pacientes com ASCG, semelhante a outros tumores cerebrais. Sendo assim, a EPRM pode representar importante ferramenta diagnóstica na detecção precoce de transformação neoplásica de nódulos subependimários próximos ao forame de Monro em pacientes portadores de esclerose tuberosa. PALAVRAS-CHAVE: astrocitoma subependimário de células gigantes, espectroscopia de prótons por ressonância magnética, esclerose tuberosa. Subependymal giant cell astrocytoma (SEGA) is a tumor that typically occurs in the lateral ventricles near the foramina of Monro. The incidence of SEGA in tuberous sclerosis complex (TSC) varies from 5% to 14%1-3. Although this tumor is considered specific for TSC, there are reports of patients with SEGA who have none of the other stigmata of TSC. Usually these tumors grow slowly, but enlarge enough to cause increased intracranial pressure, seizures, and focal neurological signs3,4. The computed tomography (CT) and magnetic resonance imaging (MRI) are useful in non-invasive investigation of these tumors. Moreover, there are several reports of the CT and MRI aspects of the SEGA. Typically, the tumors are Departments of Diagnostic Radiology1,2 and Neuropediatrics3, University of Parana School of Medicine and DAPI - Diagnóstico Avançado por Imagem1, Curitiba PR, Brazil. Received 22 February 2006, received in final form 11 May 2006. Accepted 19 June 2006. Dr. Arnolfo de Carvalho Neto - DAPI, Diagnóstico Avançado por Imagem - Rua Brigadeiro Franco 122 - 80430-210 Curitiba PR - Brasil. E-mail: Neuro 33.qxp 878 25.09.06 15:09 Page 878 Arq Neuropsiquiatr 2006;64(3-B) described as heterogeneous lesions occurring near the Monro foramina, presenting with variable enhancement after intravenous contrast injection4-8. However, there are no reports of imaging features of SEGA regarding new advanced MRI techniques, such as proton magnetic resonance spectroscopy (MRS). MRS allows non-invasive biochemical evaluation of the brain, and it has been used in the investigation of several pathologies, such as brain tumors, degenerative diseases, metabolism born errors and developmental retardation9,10. In MRS, the most intense signal in the proton MR spectrum of brain originates from the N-acetyl groups, mainly N-acetylaspartate (NAA). Less intense signals arise from creatine plus phosphocreatine (Cr) and choline-containing compounds (Cho). N-acetylaspartate is localized exclusively in neurons and neuronal processes in the mature brain, and it can be used as a neuronal marker. Decreased NAA has been observed in areas of neuronal loss or dysfunction. creatine compounds, which may be more concentrated in glia than neurons, is relatively homogeneously distributed in normal brain and can be used as an internal standard in this circumstance. Choline is a component of phosphoglyceride and it is, therefore, a major constituent of cell membranes. As a result, the signal from Cho detected on MRS increases in conditions associated with high cell membrane turnover, such as tumors9,10. Although extensively applied as a differential diagno- sis tool in neuroimaging, to our knowledge there are no previous studies investigating the MRS findings in patients with SEGA. We present the MR findings of a patient with TSC and a SEGA near to the Monro foramina, emphasizing the MRS pattern of this tumor. CASE A three year-old boy with TSC presented with a 3-month history of mild headache. The physical examination showed discrete mental retardation and multiple hypomelanic macules in the legs and back. History of cardiac rhabdomyomas and West syndrome were also referred. The infantile spasms and EEG pattern of hipsarhythmia, present since he was eight months-old, were been controlled with vigabatrin. The parents signed the informed consent and agreed with the study. The patient underwent a MRI at the 1.5T GE LX echospeed plus (General Eletric Medical Systems, Milwaukee, Wis). Morphologic evaluation was performed and the following sequences were obtained (DFOV=24 cm and slice thickness=5.0 mm axial): “FLAIR” (TR=1100 ms, TI=2200 ms and TE=105 ms), coronal FSE T2-weighted (TR=8000 ms TE=102), axial GRE T2*-weighted (TR=667 ms, TE=25 ms and FA=20º), axial FSE T1-weighted (TR=500 ms TE=7.9 ms) before and after gadolinium IV injection (Fig 1) and GRE 3D T1-weighted (TR=10 ms TE=4.2 ms slice thickness=1.6 mm). The MRS was perf (...truncated)