Ipsilateral and contralateral auditory brainstem response reorganization in hemispherectomized patients

Area of Science:

• Neuroscience
• Auditory Neuroscience
• Neuroplasticity

Background:

• Cortical hemispherectomy can lead to long-term degeneration of ipsilateral subcortical structures.
• This degeneration suggests potential reorganization of the brainstem auditory pathway.

Purpose of the Study:

• To assess brainstem auditory pathway reorganization in long-term hemispherectomized patients.
• To measure auditory brainstem response (ABR) to evaluate auditory pathway function post-surgery.

Main Methods:

• Bilateral monaural stimulation and bilateral ABR measurements were performed in 8 hemispherectomized patients and 10 controls.
• Magnetic resonance imaging (MRI) was used to assess structural degeneration in patients.

Main Results:

• Patients showed degenerated ipsilateral brainstem structures via MRI.
• Nonsurgical-side stimulation resulted in significantly longer ABR wave V latencies compared to surgical-side stimulation.
• Hemispherectomized patients exhibited longer ABR waves III and V latencies with nonsurgical-side stimulation compared to controls.

Conclusions:

• Differences in ABR latency indicate bilateral brainstem auditory pathway activity, not just brainstem volume changes.
• ABR Waves III and V primarily originate in the contralateral brainstem.
• Subcortical auditory pathways demonstrate reorganization in the long term following hemispherectomy.