The hypothesis is that the structural documentation and analysis of the data of demographics, neuroimaging, IONM and clinical outcomes can help to further standardize the use of such equipment for detecting the integrity of the corticospinal tracts.

We want to confirm that the retrospectively data analysis of neuroimaging, IONM and clinical outcomes does help to understand these methods better in the surgical management of brainstem lesions, and therefore, improve the safety of brainstem surgery.

This will be a prospective data collection and retrospective data analysis study to investigate the effect of pre- and post-neuroimaging, intraoperative monitoring, and clinical outcome during the surgical management of brainstem lesions in our neurosurgical center. The data of demographics, neuroimaging, IONM and patients' outcomes will be acquired based on the medical records and follow-up visits. All data is stored in the personal file of the clinical information system for each patient. The expected duration of each subject's participation is confined to the surgery itself and the routine visits during the follow-up. The overall study duration is expected to collect all the brainstem surgery in next five years.

Inclusion Criteria:

• Patients age 18 - 80 years' old
• With lesions in or near the brainstem
• Patients who are suitable for brainstem surgery
• Patients who accept the surgery
• Patients who signed the informed consent

Exclusion Criteria:

• Patients age < 18 years
• Patients who are not suitable for brainstem surgery (for example patients in coma, very small lesion, pregnancy)
• Patients unlikely to attend the follow-up 12 months after surgery

The study population is patients with lesions in or near brainstem who accept surgical resection as the optimal treatment. Estimation of 50 participants in the intra-axial brainstem surgical group, and 150 in the extra-axial brainstem surgical group. There is no other patient collective that could be used as substitute for the study population.