Somatosensory evoked potentials in progressive supranuclear palsy

Area of Science:

• Neuroscience
• Neurology
• Clinical Neurophysiology

Background:

• Progressive supranuclear palsy (PSP) is characterized by subcortical neurofibrillary degeneration.
• Cortical dysfunction, though uncommon clinically, is increasingly recognized in PSP.
• The neurophysiological underpinnings of cortical changes in PSP remain unclear.

Purpose of the Study:

• To investigate neurophysiological abnormalities in patients with probable PSP.
• To assess somatosensory evoked potentials (SEPs), transcortical reflexes, motor evoked potentials, and auditory startle responses in PSP.
• To explore the relationship between neurophysiological findings and potential cortical pathology in PSP.

Main Methods:

• Median and digital nerve SEPs were recorded in 14 probable PSP patients.
• Transcortical long-loop reflexes, motor evoked potentials, and auditory startle responses were also assessed.
• Analysis focused on identifying enlarged cortical responses and other neurophysiological alterations.

Main Results:

• Enlarged cortical SEPs were observed in most median (14/14) and digital (13/14) nerve studies.
• Auditory startle responses were reduced or absent in 11 out of 14 patients.
• Long-loop reflexes and motor evoked potentials showed limited abnormalities.

Conclusions:

• The observed enlarged cortical SEPs in PSP may indicate cortical hyperexcitability.
• These findings differ from other conditions with giant SEPs, like progressive myoclonus epilepsy.
• Cortical neurofibrillary pathology might cause subclinical intracortical disinhibition, explaining enlarged SEPs in PSP.