Tuberculoma Versus Neurocysticercosis: Can Magnetic Resonance Spectroscopy and Diffusion Weighted Imaging Solve the Diagnostic Conundrum?
Dr. Ravishankar Pillenahalli Maheshwarappa,
724, Westgate Street, Apt 2, Iowa City, Iowa, USA.
Introduction: Tuberculoma and Neurocysticercosis (NCC) are the two most common infectious causes of intracranial ring enhancing lesions seen on CT and MRI in developing countries. They share common clinical and neuroimaging findings most of the times resulting in diagnostic conundrum. It is very important to differentiate these two conditions to avoid improper treatment. Magnetic Resonance Spectroscopy (MRS) and Diffusion Weighted Imaging (DWI) as additional imaging tools help to differentiate the two conditions when faced with diagnostic dilemma.
Aim: To evaluate the utility of MRS and DWI as an adjuvant in differentiating tuberculoma and NCC.
Materials and Methods: This was a retrospective study where the MRI of 30 subjects with clinical diagnosis of either tuberculoma or NCC were analysed. Imaging sequences included T1W, T2W, FLAIR, DWI, MRS images and post contrast T1W FS images. The data on MRS and DWI findings of both the conditions were collected. The correlation between the MRS and DWI findings with the lesions was studied. Finally, the data were pooled and analysed. Radiological diagnosis of the findings was confirmed by reasons to clinical trials (albendazole 15 mg/kg for one week for NCC and appropriate ATT for tuberculoma) in terms of remission of clinical symptoms and follow-up imaging for decrease in the size of the lesion and perilesionaloedema.
Results: NCC cases showed no lipid peak whereas tuberculoma lesions except one showed predominant lipid peaks. Both lesions showed reduced N-acetylaspartate (NAA) levels. NCC lesions showed acetate/succinate or both peaks whereas these metabolites were normal in tuberculoma lesions. Cho/creatinine ratio was normal in all cases of NCC. Seven out of 17 tuberculoma lesions showed increased Cho/creatinine ratio (greater than 1) and almost all the lesions showed elevated normalised Cho/Cr ratio reflecting increased membrane damage and cellularity tuberculoma. All tuberculoma lesions except three showed restricted diffusion whereas none of the NCC lesions showed restricted diffusion.
Conclusion: MRS and DWI are very useful imaging tools which when used along with conventional MRI imaging helps to differentiate tuberculoma from NCC and vice versa. These MR sequences when employed together will obviate the need for unnecessary biopsy thus helps in immediate clinical management and also follow-up.