Abnormal head nociceptive withdrawal reaction to facial nociceptive stimuli in Parkinsonʹs disease

Introduction Trigemino-cervical-spinal reflexes (TCSRs) are complex brainstem stereotyped nociceptive responses involved in a defensive withdrawal reaction of the head from facial nociceptive stimuli. Objective The present study was undertaken to collect data on possible TCSR abnormalities in idiopathic Parkinsonʹs disease (PD) and investigate any correlation with motor signs and L-DOPA administration. Methods TCSRs were registered from the semispinalis capitis and biceps brachii muscles after electrical stimulation of the supraorbital nerve in 18 patients with PD and 24 controls. The latency (L) and area (A), as well as the sensory (ST), painful (PT) and reflex (RT) thresholds were measured during the ‘off’ and ‘on’ state, and possible correlations with the UPDRS III total score, selected subscores (tremor, neck rigidity, upper limb rigidity, akinesia, rising from a chair, posture and posture instability) and duration of illness were investigated. Results Significant changes between controls and PD patients were found in the L, A, PT and RT of TCSRs. These results were not significantly influenced by L-DOPA treatment. A significant correlation was found between neck rigidity, postural instability scores and duration of illness and the TCSR L and A values in PD patients in the ‘off’ state. Conclusions TCSRs abnormalities, combined with dopamine resistance, are consistent with a primary loss of brainstem neurons mediating a complex sensory-motor integration including neck muscle tone and postural control as well as the head withdrawal reaction to the nociceptive stimuli. Significance TCSRs may represent a useful tool for the assessment of brainstem sensory-motor function in PD as well as other movement and degenerative disorders.