Leptomeningeal metastases

Last revised by Bahman Rasuli on 8 Dec 2023

Leptomeningeal metastases, also known as carcinomatous meningitis and meningeal carcinomatosis, refers to the spread of malignant cells through the CSF space. These cells can originate from primary CNS tumors (e.g. in the form of drop metastases), as well as from distant tumors that have metastasized via hematogenous spread.

This article has a focus on subarachnoid space involvement. Refer to intradural extramedullary metastases for a discussion of leptomeningeal metastases in the spine. For other intracranial metastatic locations, please refer to the main article on intracranial metastases

The demographics follow those of the underlying malignancy. Meningeal metastases were found in 8% of patients with systemic cancer in cadaveric studies 22.

Clinical presentation is varied, but most commonly includes a headache, spine or radicular limb pain or sensory abnormalities, nausea and vomiting, and focal neurological deficits 3. Meningism is only present in a minority of patients (13% 3).

The primary intracranial malignancies that may cause metastases to the subarachnoid space are:

The vast majority of leptomeningeal metastases occur in the context of widespread metastatic disease, likely by hematogenous spread. Over 50% of cases have concurrent brain (parenchymal) metastases 13.  The most common primary sites are: 

Less common reported primary sites include:

  • T1: usually normal

  • T1 C+ (Gd): leptomeningeal enhancement is the primary mode of diagnosis, often scattered over the brain in a 'sugar coated' manner

  • T2: usually normal; may show hyperintensity (including the bloomy rind sign in the brainstem 23)


    • abnormally elevated signal within sulci 2 and rarely within the parenchymal surface (including the bloomy rind sign in the brainstem 23)

    • can be performed both non-contrast and post-contrast but is slightly less specific if performed post-contrast 1

Leptomeningeal metastases have a poor prognosis with patients usually succumbing within a few months (median overall survival 2.4 months 13).  Treatment may extend survival to 6-10 months 2,3. Treatment can consist of 3:

  • intrathecal chemotherapy

  • radiotherapy

Resection is usually inappropriate due to the presence of widespread metastases at the time of diagnosis.

  • leptomeningeal inflammation: leptomeningitis

  • slow flow in vessels

  • propofol, high oxygen tension, and subarachnoid blood (hemorrhage) can all elevate sulcal FLAIR signal

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