Radioisotope CSF flow studies in leptomeningeal metastases

Background: Leptomeningeal metastases is a frequent neuro-oncologic complication in patients with cancer. Objective: Radionuclide CSF now studies provide a unique method of evaluating CSF compartments in patients with leptomeningeal metastases. Methods: Radionuclide CSF flow studies are performed by injecting (111)Indium-DTPA into either the ventricular or lumbar CSF compartment. (111)Indium-DTPA is entrained by CSF and flows through CSF compartments based on normal CSF physiology. Results: Normal times to appearance of (111)Indium-DTPA following intraventricular injection in either adults or children are as follows: ventricles (median 1 minute); cisterna magna/basal cisterns (5); cervical (15); thoracic (20); and lumbar (30) spinal subarachnoid spaces; and sylvian cisterns (50). Normal times to appearance of (111)Indium-DTPA following intralumbar injection are as follows: lumbar (1); thoracic (22.5); cervical (32.5) spinal subarachnoid spaces; cisterna magna/basal cisterns (37.5); sylvian cisterns (65); ventricles (1,440); and cerebral convexities (1,440). In 30 consecutive patients, 47% of patients had documented compartmentalization of CSF by (111)Indium-DTPA CSF flow studies. 13% had base of brain obstruction of whom 50% responded with re-establishment of normal CSF flow and 33% had spinal subarachnoid space block of whom 40% following therapy had reestablishment of normal CSF flow. In 61 consecutive patients, 33% of patients had abnormal spinal CSF flaw studies which better demonstrated interruption of CSF flow when compared to CT myelography and spine MR. In 40 patients, all with CSF block, 20 of whom responded to therapy with re-establishment of normal CSF flow as compared to 20 with refractory CSF block, significant differences were seen in median survival and cause of death favoring patients with normal or restored CSF flow. Conclusions: Radioisotope CSF flow studies in patients with leptomeningeal metastasis appear to have two practical uses. First, radioisotope CSF flow studies by documenting normal CSF flow predict for homogenous distribution of intra-CSF chemotherapy. Secondly, in patients with CSF flow obstruction refractory to site of obstruction therapy, limited survival, rapid leptomeningeal disease progression and death due to progressive CNS disease is predicted.