Nonenhancing Leptomeningeal Metastases: Imaging Characteristics and Potential Causative Factors

Abstract

The diagnosis of leptomeningeal metastasis (LM) has increased in frequency, as new therapies have lengthened the survival of patients with cancer. Early diagnosis and intervention help improve quality of life and prevent further neurological deterioration in LM. The detection of LM is often established by magnetic resonance imaging examinations, cerebrospinal fluid analysis, or both. We present a series of cases where LM was identified on fluid-attenuated inversion recovery or T2-weighted image but was nonenhancing on the traditionally more sensitive postcontrast T1-weighted sequences. Nonenhancing LM is unusual and not yet fully understood but should be considered in the appropriate clinical context and may become more common with increased utilization of antiangiogenic therapies.

Keywords: brain neoplasms; imaging; meningeal neoplasms; nervous system neoplasms; techniques.

Figure 1.

A 39-year-old male with an anaplastic oligodendroglioma. A, An axial FLAIR image demonstrates abnormal hyperintense signal representing leptomeningeal metastatic disease in the cerebellar folia, around the surface of the pons and along the medial right temporal lobe (arrows). B, There is no corresponding enhancement on the axial postcontrast T1WI. C, The patient’s spine MRI acquired on the same date demonstrates abnormal enhancement of the cauda equine nerve roots on this axial postcontrast T1WI. D and E, Axial FLAIR and contrast-enhanced T1WI images acquired 15 months later demonstrate progression of LM and new enhancement of the lesion in the left vermis (arrows). FLAIR indicates fluid-attenuated inversion recovery; T1W1, T1-weighted image; MRI, magnetic resonance imaging; LM, leptomeningeal disease.

Figure 2.

A 32-year-old male with a lumbar chordoma and neck pain. A and B, Sagittal postcontrast T1-weighted images of the cervical spine demonstrate no evidence of metastases. C and D, Sagittal short tau inversion recovery (STIR) images demonstrate hyperintense nodules in the CSF of the cervical spine and upper thoracic spine (arrows). A leptomeningeal metastasis is also noted at the craniocervical junction. D and E, CT myelography confirms the presence of space-occupying lesions in the CSF (arrows). CSF indicates cerebrospinal fluid; CT, computed tomography.