Midbrain Area Measurements Can Be Used to Distinguish Parkinson’s From PSP, Study Says

Midbrain area measurements can be used to distinguish patients with Parkinson’s disease from those with progressive supranuclear palsy, a study finds.

The study, “Midbrain area for differentiating Parkinson’s disease from progressive supranuclear palsy,” was published in Clinical Neurology and Neurosurgery.

Progressive supranuclear palsy (PSP), the second most common Parkinsonian syndrome after Parkinson’s disease, is characterized by gait, balance, speech, vision, behavioral, and cognitive impairments. Despite recent advancements in brain imaging techniques, distinguishing people with Parkinson’s from those with PSP at the earliest stages of the disorders is still challenging for clinicians.

To learn more, researchers from the Iran University of Medical Sciences and the Tehran University of Medical Sciences set out to assess whether midbrain area measurements could be used to differential people with Parkinson’s from those with PSP. The midbrain is the region connecting the spinal cord to the brain, and plays key functions in motor movement, and in auditory and visual processing.

The team used a technique called transcranial sonography (TCS) — a non-invasive, fast, and inexpensive procedure used to visualize brain structures in people unable to undergo magnetic resonance imaging (MRI).

The study enrolled a total 35 patients, 18 of whom had been diagnosed with Parkinson’s, and 17 with PSP. Participants had an average age of 67.2 years, and had been living with their disorder for approximately five years before enrolling in the study.

The results showed that patients with Parkinson’s tended to have larger midbrain areas compared with those with PSP (average of 4.86 cm² vs. 3.61 cm²). The differences in midbrain size between those with Parkinson’s and PSP remained significant even after researchers normalized the midbrain area values to each patient’s disease duration.

Further analyses demonstrated that using the midbrain area as a diagnostic tool to identify people with Parkinson’s disease had higher sensitivity and specificity compared with other regions of the brain, such as the diameter of the third ventricle. Specifically, the sensitivity was 83.3% vs. 38.9%, while the specificity was 70.6% vs. 18.0%, respectively.

The third ventricle is one of the cavities in the center of the brain that is filled with cerebrospinal fluid (the liquid that circulates in the brain and spinal cord).

However, the diameter of the third brain ventricle showed higher sensitivity and specificity compared with the midbrain area in identifying PSP patients (sensitivity of 82.0% vs. 29.0%; specificity of 62.0% vs. 17.0%, respectively).

“Midbrain area in patients with PD was wider than those with PSP that was not affected by disease duration. In comparison with SN [substantia nigra] hyperechogenoicity [higher response during transcranial sonography ] and third ventricle size, midbrain area was the most accurate index for differentiating PD and PSP by [transcranial sonography],” the scientists said.