MRF Imaging Predicts Gait Improvement in Normal Pressure Hydrocephalus Patients
A non-invasive imaging technique called magnetic resonance fingerprinting (MRF) is showing promise in predicting which patients with normal pressure hydrocephalus (NPH) will benefit from shunt surgery, potentially reducing the need for more invasive diagnostic procedures. The findings, published in the Journal of Magnetic Resonance Imaging, center on the ability of MRF to assess cerebrospinal fluid (CSF) dynamics and correlate them with improvements in gait – a key symptom of NPH.
Understanding Normal Pressure Hydrocephalus
Normal pressure hydrocephalus is a brain condition most often seen in people over 65, where CSF builds up inside the skull, disrupting brain function. Symptoms often mimic dementia, including difficulties with walking, cognitive impairment and urinary incontinence. According to the Cleveland Clinic, NPH is sometimes reversible, typically through the surgical implantation of a shunt to drain excess fluid. However, determining which patients will respond to shunt placement remains a clinical challenge.
Currently, the standard approach involves an extended lumbar cerebrospinal fluid drainage (ELD) trial, where CSF is temporarily drained to see if symptoms improve. While effective, this requires a hospital stay and can be burdensome for patients. MRF offers a potential alternative – a faster, non-invasive assessment that could help clinicians make more informed decisions about shunt surgery.
How MR Fingerprinting Works
MRF is a relatively new quantitative imaging technique that generates maps of T1 and T2 relaxation times – parameters reflecting the composition and structure of brain tissue. The process involves matching the signal evolution at each point in the brain (voxel) against a database of known signal patterns, known as the “MRF dictionary.” This allows for a detailed characterization of brain tissue properties without the need for contrast agents or lengthy scan times. The technique received FDA approval for clinical use in 2023.
Researchers at the Cleveland Clinic, led by Stephen E. Jones, MD, PhD, conducted a prospective cohort study involving 20 individuals with presumed NPH. Participants underwent initial MRF scans and clinical assessments, followed by a 36-hour ELD trial. Walking tests were performed before and after drainage to measure gait improvements. The study utilized a 3T MRI scanner with a 2D MRF sequence.
Key Findings: T1 and T2 Relaxation Times
The study revealed significant associations between MRF-derived T1 and T2 relaxation-time measures and gait assessment metrics. Specifically, changes in T1 times in gray matter appeared to correlate with treatment response. Responders – those who showed gait improvement after ELD – tended to have lower T1 times after treatment, while non-responders often had higher T1 times.
While most participants showed reduced T2 relaxation times in both gray and white matter after drainage, regardless of clinical improvement, higher pre-treatment peak T1 and T2 relaxation times in gray or white matter were associated with less post-treatment gait improvement. This suggests that baseline relaxation times could serve as a predictive biomarker.
Implications for Patient Care and Cost
The potential benefits of MRF extend beyond simply reducing the need for invasive testing. As Dr. Jones explains, “The holy grail might be that one day we don’t have to do any (invasive) testing.” Currently, a two-day inpatient stay is often required for the ELD trial. If MRF can reliably predict shunt responsiveness, it could streamline the diagnostic process, reduce healthcare costs, and expedite treatment for appropriate patients.
The researchers acknowledge that further validation is needed. The current study involved a relatively modest sample size, and the findings need to be replicated in larger cohorts. They also plan to investigate the durability of shunt performance over time and whether MRF can predict long-term outcomes.
Beyond NPH: Expanding the Applications of MRF
Developed at Case Western Reserve University by physicist Mark Griswold, PhD, MRF is gaining traction in other neurological applications. Cleveland Clinic is currently using the technology in clinical trials for epilepsy, exploring its potential to identify seizure foci and guide surgical planning. The versatility of MRF stems from its ability to provide quantitative information about brain tissue composition and function, opening up possibilities for a wide range of diagnostic and therapeutic applications.
Challenges and Future Directions
While MRF holds significant promise, several challenges remain. Clinical application requires not only access to the MRF technology but also advanced analytic tools and expertise in image processing. As Dr. Jones notes, “We had to receive the pictures and then put them onto a laboratory computer, and I wrote the program that analyzes them.” Standardizing the analysis pipeline and making it accessible to a wider range of clinicians will be crucial for widespread adoption.
The researchers are also exploring the use of higher-resolution imaging techniques to further refine the MRF analysis. “We also need a great high-resolution image of brain structure volumetrics. That is going to be something that has like one-millimeter isotropic resolution, so it looks at the brain with very fine detail,” Dr. Jones stated.
Looking ahead, the team plans to expand the inquiry with a larger cohort and a longer follow-up period to assess the long-term impact of MRF-guided shunt surgery. They hope to determine whether the technique can identify patients who are unlikely to benefit from shunting, preventing unnecessary procedures and improving overall patient care. The ultimate goal is to personalize treatment for NPH, ensuring that the right patients receive the right intervention at the right time.
You can uncover more information about hydrocephalus on the Cleveland Clinic website.