Answer of September 2011

Clinical History:

A 44 years old lady presented with progressive severe headache for few weeks. She also complained of transient double vision and unsteady gait. Plain CT brain showed suspicious sulcal space effacement near the vertex. She has history of radical subtotal gastrectomy for gastric carcinoma (signet ring adenocarcinoma) about half a year ago, and with adjuvant chemotherapy given. She does not have recent history of vaccination, fever or travel.

FLAIR (Se4)                                                          T2 (Se2)

T1 (Se3)                                                                  T1+c (Se5)

Diagnosis:

Leptomeningeal carcinomatosis

Discussion:

Malignant cells were found in patient's CSF. The diagnosis of leptomeningeal carcinomatosis was confirmed. On FLAIR (CSF suppressed) MR images, there was diffuse signal abnormality over the leptomeninges (most obviously seen near to the vertex) resembling the subarachnoid CSF space seen on the T2 weighted images. Increased leptomeningeal enhancement was also demonstrated on post-contrast images.

Leptomeningeal carcinomatosis (LC), also known as neoplastic meningitis, is a serious complication of cancer that carries substantial rates of morbidity and mortality. It may occur at any stage in the neoplastic disease, but is frequently associated with relapse of cancer elsewhere in the body. It can occur concurrently with CNS invasion or wide dissemination in the intraventricular spaces, or in association with CNS metastases. Adenocarcinomas are the most common tumors to metastasize to the leptomeninges.

The leptomeninges consist of the arachnoid and the pia mater; the space between the two layers contains CSF. Metastatic seeding of the leptomeninges may be explained by: (1) hematogenous spread to choroid plexus and then to leptomeninges, (2) primary hematogenous metastases through the leptomeningeal vessels, (3) metastasis via the Batson venous plexus, (4) retrograde dissemination along perineural lymphatics and sheaths, (5) centripetal extension along perivascular and perineural lymphatics from axial lymphatic nodes and vessels through the intervertebral and possibly from the cranial foramina to the leptomeninges, and (6) direct extension from contiguous tumor deposits. The CSF flow then seeds the tumor cells widely, with infiltration greatest at the basilar cisterns and dorsal surface of the spinal cord, particularly the cauda equina.

In general, imaging findings are consistent with or suggestive rather than diagnostic of LC.
Imaging findings are helpful to detect secondary complications of LC, such as hydrocephalus, periventricular edema, and gyral effacement; and also to delineate the extent of leptomeningeal disease where radiotherapy can be effectively targeted.