This is a feasibility study to determine optimal thigh cuff design using a cephalad fluid shift protocol in patients who have an intraventricular catheter (such as Ommaya reservoir) placed for the delivery of central nervous system chemotherapy or for diagnosing potential elevation of ICP and monitoring its progression as part of standard medical care.

Inclusion Criteria:

• Male or female, 18-89 years old
• Willing and able to provide informed consent
• Patients who have an intraventricular catheter placed for the delivery of central nervous system chemotherapy or for diagnosing potential elevation of ICP and monitoring its progression as part of standard medical care
• KPS ≥ 70
• For patients on active anti-cancer (intra-thecal or IV) therapy, must be at least 2 weeks since last treatment; oral therapy is permitted

Exclusion Criteria:

• Less than 2 weeks since any prior surgery
• ICP > 20 mmHg that cannot be clinically stabilized
• Pregnant (Note: women of child-bearing potential must have a negative urine pregnancy test; women who are not of child-bearing potential are defined as: post-menopausal, age > 55 years with cessation of menses for 12 or more months; or less than 55 years with postmenopausal status confirmed by follicle-stimulating hormone in the post-menopausal range; or who have had a hysterectomy, bilateral salpingectomy, or bilateral oophorectomy)
• Existing cardiovascular disease, diabetes, syncope, ocular disease that, in the opinion of the investigator, may confound the study results
• Uncontrolled neurological symptoms such as headache, nausea or vomiting that, in the opinion of the investigator, will limit the patient's ability to participate in the study
• Injury, trauma, venous thromboembolism, peripheral arterial disease or any condition that, in the opinion of the investigator, will prevent the subject from tolerating the application of a thigh cuff; history of treated DVT is permitted

Data transfers or sharing is restricted to those JWCI study personnel identified on the site delegation log and/or per data use agreements. Data will be provided to the study sponsor.