Imaging of brain metastases

Abstract

Imaging plays a key role in the diagnosis of central nervous system (CNS) metastasis. Imaging is used to detect metastases in patients with known malignancies and new neurological signs or symptoms, as well as to screen for CNS involvement in patients with known cancer. Computed tomography (CT) and magnetic resonance imaging (MRI) are the key imaging modalities used in the diagnosis of brain metastases. In difficult cases, such as newly diagnosed solitary enhancing brain lesions in patients without known malignancy, advanced imaging techniques including proton magnetic resonance spectroscopy (MRS), contrast enhanced magnetic resonance perfusion (MRP), diffusion weighted imaging (DWI), and diffusion tensor imaging (DTI) may aid in arriving at the correct diagnosis. This image-rich review discusses the imaging evaluation of patients with suspected intracranial involvement and malignancy, describes typical imaging findings of parenchymal brain metastasis on CT and MRI, and provides clues to specific histological diagnoses such as the presence of hemorrhage. Additionally, the role of advanced imaging techniques is reviewed, specifically in the context of differentiating metastasis from high-grade glioma and other solitary enhancing brain lesions. Extra-axial CNS involvement by metastases, including pachymeningeal and leptomeningeal metastases is also briefly reviewed.

Keywords: Brain metastasis; computed tomography; diffusion weighted imaging; magnetic resonance imaging; magnetic resonance perfusion; magnetic resonance spectroscopy.

Figure 1

A 59-year-old smoker with headache and balance problems. (a) NECT demonstrates a right parietal mass at the gray–white junction with surrounding vasogenic edema. Postcontrast T1-weighted MRI (b) demonstrates ring enhancement, and FLAIR (c) confirms extensive vasogenic edema. (d) DWI demonstrates no restricted diffusion centrally, helping to differentiate this lesion from pyogenic abscess. Needle guided biopsy of a lung mass revealed nonsmall cell lung cancer. The patient underwent stereotactic radiosurgery of the brain mass for presumed lung cancer metastasis

Figure 2

A 61-year-old woman with endometrial cancer and new headache. T1-weighted MRI without (a) and with (b) contrast demonstrates a ring enhancing lesion causing mass effect on the fourth ventricle (arrowhead). FLAIR sequence shows surrounding vasogenic edema (c) and enlarged lateral ventricles (d) without transependymal CSF flow to indicate acute hydrocephalus. A second enhancing lesion within the pons (e, T1; f, T1 postcontrast, arrows) was presumed metastatic, and the patient was treated with whole brain irradiation. Pathologic evaluation of the cerebellar mass confirmed endometrial cancer

Figure 3

44 year-old found down. (a) NECT shows left frontal hemorrhage (arrow) with additional hyperdense lesions (arrowheads). (b) CECT shows enhancement, better delineating some of the masses (arrowheads). T1-weighted MRI without (c) and with (d) contrast shows multiple enhancing lesions. FLAIR (e) shows vasogenic edema surrounding the hemorrhage (arrow), but little edema associated with other lesions. T2* sequence (f) redemonstrates left frontal hemorrhage (arrow) but no blood within with the other lesions (arrowhead). Pathology revealed small cell lung cancer

Figure 4

A 67-year-old woman with recurrent ovarian cancer and 3 weeks of progressive difficulty walking. Nonenhanced CT (a and b) was normal. After contrast administration, multiple ill-defined nodules become evident (e.g., circles in c and d). Innumerable enhancing nodules are more conspicuous on contrast enhanced T1-weighted MRI (e and f)

Figure 5

A 59-year-old with pulmonary TB and word finding difficulty. Post-contrast MRI demonstrates two lesions, right frontal (a), and left parietal (d). Multivoxel MRS (b and c) demonstrates decreased NAA (red arrowhead) and elevated Cho/Cr ratio (Blue arrowhead) in the tumor (b) compared to normal white matter (c). Additionally, lactate is observed in the tumor (yellow arrowhead) but not in normal brain. Single voxel MRS at intermediate TE (e) and short TE (f) demonstrates abnormal metabolite ratios (e and f). Lipid peaks are evident on short TE spectra (green arrowhead) within the lesion. These findings indicate the lesions are metastases rather than tuberculomas

Figure 6

A 63-year-old male with known metastatic prostate cancer who presented with somnolence and word finding difficulty. NECT (a and b) demonstrates a hyperdense right parietal lesion (arrow) and equivocal fullness in the right middle cranial fossa. Contrast enhanced T1-weighted MRI clearly shows dural-based enhancing lesions in the right middle cranial fossa (c), and right parietal convexity (d). Lesions were new compared with MRI obtained 7 months prior and are consistent with pachymeningeal metastases

Figure 7

A 62-year-old with metastatic ocular melanoma who underwent staging CT. NECT demonstrates hyperdense material in a right frontal sulcus (a, arrow), which enhances (b). MRI obtained within 1 week demonstrates FLAIR hyperintense material in the subarachnoid space (c) that enhances (d), consistent with leptomeningeal carcinomatosis. Subsequent lumbar puncture confirmed malignant cells in the cerebral spinal fluid

Figure 8

A 57-year-old with recurrent renal cell carcinoma who presented with headaches. MRI revealed a lesion in the atrium of the right lateral ventricle, with areas of intrinsic T1 signal hyperintensity consistent with hemorrhage (a, arrowhead), and marked enhancement (b). Patient underwent gamma knife radiosurgery for solitary intraventricular metastasis