A new assessment tool for Parkinson disease: the nigral lesion load obtained by transcranial sonography.

Objectives: A sonographic method that provides for the measurement of a single frozen image and ignores the remaining portions of the midbrain has been used recently as a biological marker of Parkinson disease. We propose a new approach to evaluating the midbrain: obtaining the nigral lesion load, with which it is possible to acquire an estimate of the real damage to the substantia nigra.

Methods: We studied 60 patients with Parkinson disease and classified them according to the Hoehn and Yahr scale (Neurology 1967; 17:427-442). Magnetic resonance imaging of the brain, ioflupane-labeled single-photon emission computed tomography, and technetium Tc 99m-labeled single-photon emission computed tomography were performed. Assessment of the midbrain parenchyma was performed with transcranial sonography to quantify the extent of hyperechoic signals on 2 different scans (upper and lower substantia nigra).

Results: In 90% of patients (54), we found pathologic hyperechoic substantia nigra signals (>0.25 cm(2)). These data were similar to those described previously by other authors. However, the sum of the values obtained from each measurement (total of 4 per patient) showed that patients with severe disease had larger nigral lesion loads. In most cases, the study showed impairment of the nigrostriatal dopaminergic system when the hyperechoic pattern was more pronounced.

Conclusions: Transcranial sonography is a useful tool for Parkinson disease workup. A single measurement of substantia nigra echogenicity may be insufficient for an optimal definition of the stage of the disease. A study of the entire midbrain may deliver more information than a single measurement.