Third Ventricle Width: An Accessible Biomarker to Differentiate Between PD and PSP

Andrea Quattrone, MD

A recent study has developed a new biomarker to early differentiate between Parkinson disease (PD) and progressive supranuclear palsy (PSP) that is simple enough and generalizable for the majority of routine clinical practices as well as in patient selection for a variety of clinical trials.¹ The new biomarker uses only MRI images to measure the third ventricle/internal skull diameter ratio (3rd V/ID).

Among the study authors is Andrea Quattrone, MD, resident, neurology department, Magna Graecia University of Catanzaro. Quattrone and colleagues had previously identified another highly accurate biomarker, MRPI 2.0. However, assessment of MRPI 2.0 requires many measurements and expertise in taking these measurements and is therefore more suited to research centers than routine clinical practice.2 Following the identification of MRPI 2.0, the team set out to develop a simpler biomarker that could be easily and widely used to diagnose PSP.

NeurologyLive reached out to Quattrone to learn more about the development of the 3rd V/ID biomarker. He discusses the advantages of the new biomarker over previously developed ones, and how early differentiation between PSP and PD can help to improve patient care.

NeurologyLive: What prompted you to develop the 3rd V/ID biomarker after developing MRPI 2.0?

Andrea Quattrone, MD: MRPI 2.0 is a highly accurate biomarker to distinguish between PSP and PD, but it's very complex and includes the measurement of many brain structures involved in PSP in its calculations. So MRPI 2.0 is an excellent tool for research purposes and in research centers, but it is not suitable for clinical routine. We developed this new biomarker, which is based only on the measurement of the third ventricle width, to provide a simple and easy biomarker to help clinicians in distinguishing between PSP and PD. It can be used in clinical settings in which complex biomarkers such as MRPI or MRPI 2.0 are not available yet.

How will early differentiation between PSP and PD improve patient care?

Early differentiation between PSP and PD will absolutely improve patient care for many reasons. PSP is one of the most common atypical Parkinson types and shares several clinical signs with PD, but it is a more severe disease with a different prognosis, and usually also a worse response to many therapies. So, it is extremely important to distinguish between PSP and PD at the beginning of the disease, to benefit patient prognosis and therapy. Currently, diagnosis of PD and PSP is mostly based on clinical evaluation criteria. But the most specific signs of PSP, such as vertical ocular dysfunction, may appear late in the course of the disease, thus making that early diagnosis extremely challenging. Our new biomarker can impact clinical care of PD patients and PSP patients, leading to more accurate diagnosis in the early stages of the disease. This marker may also reduce the need for expensive or invasive diagnostic examinations, such as cerebral spinal fluid examination or PET imaging, which are not very accessible.

How does the assessment of the new biomarker compare to how other biomarkers are assessed?

This new biomarker can be manually measured on a single axial MR slice and does not require any reconstruction procedures. This is extremely important because it enables clinicians to directly use and calculate this biomarker in clinical settings using only their computer to visualize MRI images. This is one of the main strengths of our biomarker, because most other diagnostic biomarkers cannot be directly used by clinicians. They require a dedicated laboratory or MRI post-processing that is usually performed by engineers and not the clinicians themselves. These resources are usually available in research centers, but not in clinical settings. Thus, the potential use of many diagnostic biomarkers is limited in clinical care in relation to clinical research.

Transcript edited for clarity.

REFERENCES

1. Quattrone A, Antonini A, Vaillancourt DE, et. Al. A new MRI measure to early differentiate progressive supranuclear palsy from de Novo Parkin’s Disease in clinical practice: An international study. Movement Disord. Published online November 5, 2020. doi: 10.1002/mds.28364
2. Quattrone A, Morelli M, Vescio B, et al. Refining initial diagnosis of Parkinson's disease after follow-up: A 4 year prospective clinical and magnetic resonance imaging study. Movement Disord. 2019;34(4):487-495. doi: 10.1002/mds.27621.