Brain tissue echogenicity--implications for substantia nigra studies in parkinsonian patients.

The aim of the present study was to assess the origin of the substantia nigra hyperechogenicity in Parkinson disease patients. The cause of hyperechogenicity was tested on an animal model. Fresh porcine brains were injected consecutively with ferritin, apoferritin and water. Then, glioma samples were inserted into animal model. The echogenicity of the region of interest was assessed before and after experimental procedures. We observed the same echogenicity of porcine brain before and after injections of iron-loaded ferritin, apoferritin and water. Increased echogenicity of glioma samples compared to surrounding porcine brain tissue could be clearly seen. We postulate that the relative gliosis might be, at least partially, responsible for the increased echogenicity of the substantia nigra in Parkinson disease patients. Keeping in mind all limitations and inaccuracies of animal model used, it seems that hyperechogenicity of substantia nigra is caused rather by structural changes within the brain tissue than by increased iron concentration.