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Metastases, CSF Disseminated


KEY FACTS

Terminology

  • Spread of malignant tumor through subarachnoid spaces of brain and spinal cord

Imaging

  • Smooth or nodular enhancement along cord, cauda equina

  • Located at any point along CSF pathway

  • 4 basic patterns

    • Solitary focal mass at bottom of thecal sac or along cord surface

    • Diffuse, thin, sheet-like coating of cord/roots (“carcinomatous meningitis”)

    • Rope-like thickening of cauda equina

    • Multifocal discrete nodules along cord/roots

Top Differential Diagnoses

  • Multifocal primary tumor

  • Meningitis (pyogenic, granulomatous > chemical)

  • Neurosarcoidosis (diffuse or nodular enhancement)

  • Recent lumbar puncture

  • Thick nerve roots/cauda equina

    • Guillain-Barré

    • Congenital hypertrophic polyradiculoneuropathies

    • Neoplasm (e.g., lymphoma)

Pathology

  • Hematogenous dissemination from solid tumors (1-5%)

  • “Drop” metastases from patients with primary CNS tumor (1-2%)

  • Leukemia, lymphoma (5-15%)

  • Falsely negative CSF cytology in up to 40%

Clinical Issues

  • Typically seen in advanced cancer cases

  • Prevalence increasing as cancer patients living longer

  • Median patient survival of 3-6 months with treatment

Diagnostic Checklist

  • MR more sensitive than CSF cytology

Sagittal T1WI C+ MR shows a mixed nodular
and smooth
leptomeningeal tumor along the distal cord and conus medullaris due to drop metastases from glioblastoma multiforme.

Sagittal T2WI shows multiple nodular, low signal intensity, rounded, drop metastases
involving roots of the cauda equina, spreading from an intracranial glioblastoma multiforme.

Sagittal T1WI C+ MR shows bulky, nodular, drop metastases
from a pineal germinoma along the conus and cauda equina.

Sagittal T1WI C+ MR shows cerebrospinal fluid metastasis from small cell lung carcinoma with a bulky enhancing dural mass compressing the cervicomedullary junction
and linear enhancing metastases along the dorsal pial surface of the cord from C7 caudally
. An additional enhancing focus is seen in the region of the gracile tubercle
.

TERMINOLOGY

Synonyms

  • Leptomeningeal carcinomatosis

  • Carcinomatous meningitis

  • Neoplastic meningitis

  • Drop metastases

Definitions

  • Spread of malignant tumor through subarachnoid spaces of brain and spinal cord

IMAGING

General Features

  • Best diagnostic clue

    • Smooth or nodular enhancement in basilar cisterns, along cord (especially dorsally) and cauda equina

  • Location

    • Any point along CSF pathways

  • Size

    • Variable

  • Morphology

    • 4 basic patterns

      • –

        Solitary focal mass at bottom of thecal sac or along cord surface

      • –

        Diffuse, thin, sheet-like coating of cord/roots (carcinomatous meningitis)

      • –

        Rope-like thickening of cauda equina

      • –

        Multifocal discrete nodules along cord/roots

    • Intramedullary nodule(s)

      • –

        Rarely due to CSF spread, impossible to distinguish from hematogenous metastatic disease

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