Coronal Transcranial Sonography and M-Mode Tremor Frequency Determination in Parkinson's Disease and Essential Tremor

Background and purpose: The axial mesencephalic transcranial sonography plane is an established and sensitive diagnostic tool for the differentiation of Parkinson's disease and essential tremor. However, the substantia nigra can also be depicted in a second coronal examination plane, whose diagnostic value has not yet been evaluated. Furthermore, the M-mode tremor frequency determination represents another sonographic tool, which might yield additional diagnostic value.

Methods: We included patients with diagnosed Parkinson's disease (n = 31), essential tremor (n = 16), and healthy age-matched controls (n = 16). All were examined by transcranial sonography in the axial and coronal plane. Tremor frequencies were quantified by an M-mode tremor frequency determination examination protocol. A clinical assessment was conducted in all participants.

Results: The utilization of a coronal examination plane improved the diagnostic strength in discriminating of Parkinson's disease from essential tremor and healthy controls. In combination with the determination of tremor frequency, best discriminative results were achieved (sensitivity, 90.3%; specificity, 96.9%). In the Parkinson's disease group, we found a significant positive correlation between hyposmia and coronal hyperechogenicity.

Conclusion: The combined usage of coronal transcranial sonography and M-mode tremor frequency determination should be considered to improve diagnostic strength of sonographic techniques for the diagnosis of Parkinson's disease.