Cortical hyperexcitability in corticobasal syndrome as revealed by giant somatosensory evoked potentials.

OBJECTIVE

Corticobasal syndrome (CBS) is characterized by asymmetric symptoms, including myoclonus. Few studies have reported the observation of giant somatosensory evoked potentials (SEPs) in CBS patients. We aimed to clarify the origin and characteristics of myoclonus by examining the relationships among clinical symptoms and electrophysiological and brain imaging findings.

METHODS

We conducted a cross-sectional study of 23 patients with CBS who underwent SEPs at Kyoto University Hospital from 2008 to 2022. We compared SEPs, cortical reflex (C-reflex), and cerebral perfusion in the precentral and postcentral gyri and thalamus between the symptom-dominant and non-dominant hemispheres.

RESULTS

Giant SEPs were observed in 17 of 23 (74 %) patients, and C-reflexes were present in 3 of 13 (23 %) patients. Cerebral perfusion decreased significantly on the symptom dominant contralateral hemisphere.

CONCLUSIONS

The high frequency of giant SEPs than previously reported in CBS demonstrated that at least part of their myoclonus has a cortical origin, warranting further investigation into the underlying mechanisms.

SIGNIFICANCE: The high prevalence of giant SEPs in CBS suggests a cortical contribution to their myoclonus, providing electrophysiological evidence to help better understanding and clinical assessment of the disorder.