The contribution of trigemino-cervical reflexes in distinguishing progressive supranuclear palsy from multiple system atrophy

Objective: Trigemino-cervical reflexes (TCRs) are electromyographic responses induced by electrical stimulation of the trigeminal nerve and recorded in the neck muscles. Trigemino-cervical reflexes are detectable in Parkinson's disease, whereas they are absent in progressive supranuclear palsy (PSP), an atypical parkinsonism associated with brainstem degeneration. To date, no study has investigated TCRs in multiple system atrophy (MSA), another atypical parkinsonism associated with brainstem involvement, which resembles PSP. Methods: To understand whether TCRs are helpful in differentiating PSP from MSA, we compared the TCRs recorded in 10 PSP patients with those obtained from 10 patients diagnosed as having probable MSA, parkinsonian type (MSA-P). Results: Trigemino-cervical reflexes were not recorded in any of the PSP patients, while they were clearly detectable in all the MSA-P patients. Conclusions: Trigemino-cervical reflex recording is a rapid neurophysiological method, which could assist in the differential diagnosis between PSP and MSA-P. Significance: This study further improves our understanding of the different neuronal functioning of extrapyramidal disorders. TCRs monitoring may be useful to support the diagnosis of atypical parkinsonisms especially when clinical evidence is uncertain.