RADIOISOTOPE CSF FLOW STUDIES IN LEPTOMENINGEAL METASTASES

Background: Leptomeningeal metastases is a frequent neuro-oncologic co mplication in patients with cancer. Objective: Radionuclide CSF now st udies provide a unique method of evaluating CSF compartments in patien ts with leptomeningeal metastases. Methods: Radionuclide CSF flow stud ies are performed by injecting (111)Indium-DTPA into either the ventri cular or lumbar CSF compartment. (111)Indium-DTPA is entrained by CSF and flows through CSF compartments based on normal CSF physiology. Res ults: Normal times to appearance of (111)Indium-DTPA following intrave ntricular injection in either adults or children are as follows: ventr icles (median 1 minute); cisterna magna/basal cisterns (5); cervical ( 15); thoracic (20); and lumbar (30) spinal subarachnoid spaces; and sy lvian cisterns (50). Normal times to appearance of (111)Indium-DTPA fo llowing 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 cerebr al convexities (1,440). In 30 consecutive patients, 47% of patients ha d 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 sp ace block of whom 40% following therapy had reestablishment of normal CSF flow. In 61 consecutive patients, 33% of patients had abnormal spi nal CSF flaw studies which better demonstrated interruption of CSF flo w when compared to CT myelography and spine MR. In 40 patients, all wi th CSF block, 20 of whom responded to therapy with re-establishment of normal CSF flow as compared to 20 with refractory CSF block, signific ant differences were seen in median survival and cause of death favori ng patients with normal or restored CSF flow. Conclusions: Radioisotop e CSF flow studies in patients with leptomeningeal metastasis appear t o have two practical uses. First, radioisotope CSF flow studies by doc umenting normal CSF flow predict for homogenous distribution of intra- CSF chemotherapy. Secondly, in patients with CSF flow obstruction refr actory to site of obstruction therapy, limited survival, rapid leptome ningeal disease progression and death due to progressive CNS disease i s predicted.