Brainstem and spinal reflex studies in patients with primary progressive freezing of gait

• Brainstem and spinal reflexes exhibit different features in PSP and PPFOG.
• BRs were all normal and similar in PSP and PPFOG and control groups.
• Probabilities of TCR, ASR and LLFR were all reduced in the PSP group.
• Probability of ASR was exaggerated in the PPFOG group.

Our aim was to investigate the extent and pattern of involved pathways using brainstem and spinal reflexes by comparing primary progressive freezing of gait (PPFOG) progressive supranuclear palsy (PSP) with FOG. Seven patients with PPFOG and age and sex matched seven PSP patients and 16 healthy subjects were included in the study. All subjects underwent blink reflex (BR), trigemino-cervical reflex (TCR), auditory startle reflex (ASR) and long latency flexor reflex (LLFR) investigations under the same conditions. All three groups had normal BR latencies. ASR probability was lowest in the PSP group and was highest in PPFOG (p = 0.005). The presence rate of TCR was lowest in PSP and it was highest in PPFOG (p = 0.007 for SC and p = 0.023 for SCM). The presence rate and amplitude of LLFR (R II) were decreased in the PSP group (p = 0.010 and p = 0.031, respectively) whereas it was in a continuous pattern in some of PPFOG patients. ASR, TCR and LLFR were all inhibited in PSP and we suggest that suppression of all three reflexes is probably related to degeneration of brainstem reticular formation and basal ganglia connections. However, interestingly, in PPFOG, excitabilities of ASR and TCR circuits are increased suggesting loss of pathways mediating suprasegmental control.