Probable imaging diagnosis
Case 324
【Progress】
She is scheduled to routine follow-up whether a lesion is growing or not in our hospital.
【Discussion】
As ventricular tumors, choroid plexus papilloma, ependymoma, sub ependymoma, neurocytoma and choroid plexus cyst are listed (1, 2). Of these, neurocytoma has a potential of malignancy. ADC value of neurocytoma is reported to be 0.65 while that of ependymoma 1.20, cutoff value for differentiation between them is 0.87 (3). ADC values of other benign tumors are 1.20 or greater (3 - 6). In our case with choroid plexus cyst, ADC value was 1.037-1.269.
The present case with choroidal cyst was depicted high signal on MRI Diffusion WI. Diffusion WI represents not only water molecule motion restriction but also Diffusion WI is affected by signal intensity on T2WI. The lesion with higher signal intensity on T2WI tends to be higher on Diffusion WI. Water molecule restriction occurs in case of intracellular edema, cellular dense, mucin, abscess, fresh hematoma and fresh infarction. Vascular edema which leads high signal intensity on T2WI occurs in case of tumor edema, cyst, absorption process of infarction and abscess inducing less restriction of water molecules. ADC map plays a role to differentiate true-positive water molecule restriction from pseudo-restriction by vascular edema.
T2-shine-through is called in case of a lesion with high signal intensity on Diffusion WI due to pseudo-restriction whose ADC map is not lowering (dark) but elevating (7).
In our case, the lesion in lateral ventricle was depicted grey-whitish and ADC values of brain parenchyma were around 0.8 and ADC values of intraventricular lesion were around 1.2, implying that T2 shine through mechanism worked. The lesion with 1.2 of ADC values indicates a benign lesion probably choroid plexus cyst.
【Summary】
We presented a thirty-four-year-old female in our hospital for tightening and pulsating headache with a letter from a local clinic that she was suspicious of having intraventricular tumor. Brain MRI depicted lesions in bilateral lateral ventricle with high signal intensity on Diffusion WI whose ADC values were 1.037-1.269, indicative of being compatible with choroid plexus cyst. It is borne in mind that as intraventricular tumors, choroid plexus papilloma, ependymoma, sub ependymoma, neurocytoma and choroid plexus cyst are listed. Of these, neurocytoma whose ADC values are 0.8 level, is tended to be malignant, others are benign tumors whose values are 1.2 or greater. When a lesion is demonstrated higher on Diffusion WI despite of ADC values of the lesion being higher than those of brain parenchyma, T2 shine through mechanism works.
【References】
1.Danaila L, et al. Primary tumors of the lateral ventricles of the brain. Chirurgia (Bucur). 2013 Sep-Oct;108(5):616-30.
2.Delfini R, et al. Tumors of the lateral ventricles. Neurosurg Rev. 1991;14(2):127-33.
3.Sun PF et al. Application of diffusion-weighted imaging combined with apparent diffusion coefficient in differential diagnosis between central neurocytoma and ependymoma. Neuroradiology. 2020 Apr;62(4):439-445
4.Taheri H, et al. Measurement of Apparent Diffusion Coefficient (ADC) Values of Ependymoma and Medulloblastoma Tumors: a Patient-based Study. J Biomed Phys Eng. 2021 Feb 1;11(1):39-46.
5.Kennedy KA, et al. Choroid plexus cysts: significance and current management practices. Semin Ultrasound CT MR. 1993 Feb;14(1):23-30.
6.Sener RN, et al. Colloid cyst: diffusion MR imaging findings. J Neuroimaging. 2007 Apr;17(2):181-3.
7.Burdette J, et al. Acute cerebral infarction: quantification of spin-density and T2 shine-through phenomena on diffusion-weighted MR images. Radiology 1999; 212: 333-339.
2024.1.30