How to Measure Substantia Nigra Hyperechogenicity in Parkinson Disease

Abstract

The detection of an enlarged echogenic size ("hyperechogenicity") of the substantia nigra on transcranial sonography is increasingly used for the early and differential diagnosis of Parkinson disease. However, the diagnostic value of substantia nigra sonography depends on the quality of its execution. This article with an accompanying video presents a step-by-step description and demonstration of ultrasound system settings, typical errors in assessment of the substantia nigra, planimetric measurement of substantia nigra echogenicity according to current guidelines, and its diagnostic implications in 2 exemplary patients with parkinsonism. Published cutoff values for grading substantia nigra hyperechogenicity with different ultrasound systems and novel technologies are reviewed.

Transcranial Brain Parenchymal Sonography in Neurodegenerative and Psychiatric Diseases

“…For the insonation of the brain parenchymal structures, it is suggested to perform transcranial sonographic scanning through the anterior or middle temporal acoustic bone windows, as suggested for transcranial vascular sonography. Guidelines suggest using modern clinical ultrasound systems equipped with 2.0–3.5‐MHz phased array transducers 11 – 13 . For the optimal insonation of brain structures, transcranial sonographic parameters should be set as follows: dynamic range between 45 and 60 dB, insonation depth of 14 to 16 cm, and individualized adaptation of the time‐gain compensation and brightness of the sonogram to achieve the best possible visualization.…”

“…At this axial scanning level, the echogenicity of the ipsilateral substantia nigra, red nucleus, and brain stem raphe can be evaluated (Figure 1). 13 , 14 The best‐validated method for measuring and grading substantia nigra echogenicity is planimetric measurement of the substantia nigra echogenic area in the axial plane. The hyperechoic area is measured by encircling the outer circumference and is automatically displayed in square centimeters.…”

“…The hyperechoic area is measured by encircling the outer circumference and is automatically displayed in square centimeters. Other substantia nigra echogenicity scoring methods, such as semiquantitative visual grading, volumetry, semiautomatic substantia nigra detection, and complex mathematical echo signal analysis, were less reliable and are not validated 11 – 13 …”

“…In normal conditions, the brain stem raphe is depicted as a highly echogenic continuous line, which has echogenicity similar to that of the red nucleus or surrounding cerebral white matter (Figure 1). 13 – 15 Based on the transcranial sonographic guidelines, brain stem raphe echogenicity is rated semiquantitatively. A 3‐point grading system (1, raphe invisible; 2, hypoechoic or interrupted brain stem raphe; and 3, hyperechoic brain stem raphe) or, better, a 2‐point grading system (0, invisible, hypoechoic, or interrupted brain stem raphe representing a pathologic finding; and 1, a highly echogenic continuous brain stem raphe, as a normal finding) is suggested 13 – 15 .…”

“…A very important landmark of the thalamic or ventricular level is the usually highly echogenic pineal gland (Figure 2). 13 , 14 At this insonation plane, the thalami, the anatomic site of the basal ganglia, and the ventricular system (third ventricle and frontal horns of the lateral ventricles) are displayed.…”