The neurosurgical standard of care for treating a patient with a tumor invading hand primary motor cortex (M1) includes performing a craniotomy with intraoperative direct electrical stimulation (DES) mapping and to resect as much tumor as possible without a resultant permanent neurological deficit. However, the subjective nature of current intraoperative hand motor assessments do not offer a comprehensive understanding of how hand strength and function may be impacted by resection. Additionally, there is a paucity of data to inform how altering DES parameters may effect motor mapping. Here, the investigators seek to demonstrate a feasible, standardized protocol to quantitatively assess hand strength and function and systematically assess several stimulation parameters to improve intraoperative measurements and better understand how cortical stimulation interacts with underlying neural function.

AWAKE CRANIOTOMY COHORT

Inclusion Criteria:

1. Age 18 - 75
2. Ability to understand a written informed consent document, and the willingness to sign it
3. Radiographic evidence of tumor on MRI (i.e. non-enhancing) invading primary motor cortex in the non-dominant hemisphere.
4. Karnofsky performance status (KPS) ≥ 70
5. Normal or near normal motor strength (i.e., at least 3/5 in relevant areas)
6. Normal or near normal speech (Can consistently name at least 4/5 cards)
7. Free of other illness, in the judgment of the investigator, that may shorten life expectancy
8. Willing and able to participate in all aspects of the study

Exclusion Criteria:

1. Presence of other malignancy not in remission
2. Evidence of bi-hemispheric or widespread tumor involvement
3. Medically high-risk surgical candidate
4. History of recent scalp or systemic infection
5. Presence of other implants or foreign bodies in the head
6. Inability to receive an MRI for any reason
7. Inability to receive cortical stimulation for any reason
8. Presence of implanted cardiac device (such as a pacemaker or defibrillator)