Lack of trigemino-cervical reflexes in progressive supranuclear palsy.

Trigemino-cervical reflexes (TCRs) are multisynaptic neck muscle withdrawal responses that are clearly identifiable in humans. Mediated by neural circuits at brainstem level, these reflex responses have been found to be significantly impaired in patients with Parkinson's disease (PD), and it has been hypothesized that a degeneration of brainstem neural structures could play a role in these abnormalities. Because extensive neuronal degeneration at brainstem level has been demonstrated in progressive supranuclear palsy (PSP), in this pilot study we evaluated the TCR responses in 12 subjects with PSP, and in 16 healthy controls. The TCRs were absent in 11 out of the 12 PSP patients while clear responses were evoked in all the healthy subjects. These findings indicate that PSP patients are unable to react to the painful stimuli to the face, suggesting a generalized impairment of the brainstem circuits mediating TCRs.