Leptomeningeal metastases

Leptomeningeal metastases, also know as carcinomatous meningitis, refers to the spread of malignant cells through the CSF space. These cells can be originated both in primary CNS tumours (e.g. drop-metastases), as well as from distant tumours that have metastasized (haematogenous spread).

This article has a focus on the brain's subarachnoid space involvement. Please refer on intradural extramedullary metastases for a particular discussion related to the leptomeningeal metastases in the spine. For other intracranial metastatic locations, please refer to the main article on intracranial metastases. 

Epidemiology

The demographics will follow those of the underlying malignancy.

Clinical presentation

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).

Pathology

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

• glioblastoma (GBM) and anaplastic astrocytoma
• medulloblastoma
• sPNET
• ependymoma
• germinoma
• choroid plexus carcinoma

The vast majority of leptomeningeal metastases originates from a widespread metastatic disease (haematogenic spread). The most common primary sites are: 

• breast cancer: most common
• lung cancer: most common
• melanoma 
• lymphoma and leukaemia

Radiographic features

MRI

• T1: usually normal
• T1 C+ (Gd): leptomeningeal enhancement is the primary mode of diagnosis. Scattered over the brain in a 'sugar coated' manner.
• T2: usually normal
• FLAIR
  • abnormally elevated signal within sulci ²
  • can be performed both non-contrast and post contrast, but is slightly less specific if performed post contrast ¹

Treatment and prognosis

Untreated leptomeningeal metastases have a poor prognosis with patients usually succumbing within a few months, whereas, with treatment, that time may be extended up to 6-10 months ^2-3. Treatment can consist of ³:

• intrathecal chemotherapy
• radiotherapy

Differential diagnosis

• leptomeningeal inflammation: leptomeningitis
• slow flow in vessels
• propofol, high oxygen tension, subarachnoid blood can all elevate sulcal FLAIR signal