What motivates and frustrates four trailblazing women in neurosurgery.
Special care is taken to preserve eloquent regions of the brain during awake craniotomy surgery to ensure the preservation of motor, speech or language function. But while the critical brain regions for these functions have been established, there is less certainty surrounding which critical brain regions are responsible for music production.
For musicians, preservation of their musical ability is critical as well; to lose it would be to potentially lose their main source of income and quality of life. In order to address this issue, recent research has sparked an interest in cortical mapping musical function during awake craniotomy.
Here’s what two studies have found on music and cortical mapping techniques, patient success and feasibility of the procedure:
Can Music Ability Be Preserved During Awake Craniotomy Surgery?
In their 2020 case report, Bass et al. treated a 19-year-old girl with a 3-to-4-year history of musicogenic seizures. These episodes consisted of left-sided numbness, subjective stuttering and an inability to sing, frequently triggered by singing or even just listening to music.
Although she had normal physical health and a negative electroencephalogram, radiographic evaluation revealed a 16-mm calcified, non-enhancing legion on her posterior right temporal lobe that was suspected to be a low-grade glioma.
Acknowledging that the patient wanted to be a professional musician, and noting the relationship of her seizures to music and the location of the tumor, Bass et al. sought to create a novel strategy to not only achieve maximal tumor resection but preserve her musical ability.
During her preoperative evaluation, the patient was given imaginary listening and melody generation tasks to identify the brain regions involved in music production without the contamination of auditory input or motor planning. During these tasks, she was asked to imagine someone else perform a song she was familiar with, as well as imaging herself singing the song. Both of these tasks were found to activate the cortical brain regions surrounding the tumor, with the most prominent activations found in the left hemisphere.
The patient was also evaluated by the hospital’s music therapist, who assessed her baseline rhythm, tone and singing pitch, and agreed that she would sing “Island in the Sun” by Weezer during the tumor resection—chosen for its wide range of notes, challenging rhythm and upbeat melody. Assessment of the patient’s musicality included accuracy of pitch and movement between scales.
During the surgery, the hospital’s neuropsychologist and music therapist were both present to assess the patient’s neurocognitive status and interruptions in her musical performance respectively. Neither expert noted any loss of vocal range, accuracy in pitch, or other musical defects.
After cortical mapping did not show any brain regions that affected her ability to process tone and rhythm, the patient was asked to sing “Island in the Sun” as the tumor was being resected, as guided by preoperative fMRI and intraoperative stimulation. The music therapist did not identify any concern for interruption of her musical ability at any point during the surgery.
At day-1 post-op, the patient was re-evaluated for musical ability. She was able to hear and reproduce all pitch relationships across four different keys, consistent with her preoperative baseline. By post-op day 2, she could accompany herself on guitar.
By nine months post-op her seizures had completely resolved, and neuropsychological testing revealed that her intelligence and verbal memory remained far above average. She performed within the normal range of the Seashore Tonal Memory Test and Seashore Rhythm test, and the musical therapist noted that her post-op performance was unchanged compared to preoperative baseline.
The study authors conclude that this case report represents a novel paradigm for cortical mapping of music production that can be used to safely resect a tumor, summarizing the following takeaways from their experience:
- Singing should be disrupted during surgery so that the exact contribution of intraoperative cortical mapping to clinical success can be determined.
- Stimulation of adjacent tissue did not cause any impairments in music production, and this could be attributed to the fact that the patient’s early musical training may have promoted lateralization of her music centers toward her dominant hemisphere.
- This also could be attributed to the tumor-related epilepsy, which could have caused the function of musical production to be remapped to the contralateral side.
- Similar future operations could target additional sites based on the fMRI studies but slightly further from the resection cavity, which could help substantiate the fMRI data and further demonstrate the feasibility of intraoperative cortical mapping of music.
Music Cortical Mapping During Awake Craniotomy: A Review
But is music cortical mapping during awake craniotomy worthwhile as a standard surgical practice?
In 2021, researchers in the Netherlands conducted an extensive search in four electronic databases to determine the feasibility and value of music mapping in patients undergoing awake craniotomy, as a clear overview of the specific intraoperative mapping methods could serve as a guideline for clinicians and future studies.
Kappen et al. included 10 studies and 14 patients in their final analysis, which included a mix of singers and instrumentalists, and awake craniotomies for tumor section, epilepsy and cerebral cavernous malformation.
Here are some key takeaways from their review:
- They found music mapping to be successful in 13 out of 14 cases. The one remaining case could not be mapped due to a stimulation-induced general seizure.
- 38% of the music mapped patients experienced isolated disruption of musical function
- 31% experienced music disruption combined with speech and language disruption
- 15% experienced music disruption combined with motor disruption
- 15% experienced no music disruption during awake craniotomy
While Kappen et al.’s research indicated that music mapping is feasible given that it was successful in 93% of patients, they warn that their results should be handled with caution since negative results are not often published, and bias cannot be ruled out.
Additionally, they note that limitations of their study including small size, lack of a control group, and limited available information concerning post-operative musical function, make it difficult to draw solid conclusions on the true value of mapping music for preserving musicality.
However, their findings that isolated music disruption occurred in both hemispheres with preservation of musicality in all patients demonstrates the value of this mapping technique for both hemispheres.
They make the following recommendations for future studies in order to reach standardized protocols:
- Unsuccessful case reports should be published to gain further insight into the feasibility of musical performance during awake craniotomy surgery.
- Disruption of music should always be compared with speech/language and/or motor tasks to uncover the origin of the deficit.
- Musicality should be evaluated with a standardized objective scoring form before and after surgery in order to establish a baseline for comparison among several studies.
- Pre-operative fMRI with musicality related tasks should occur in order to improve knowledge on the localization of music to specific brain regions in neurosurgical patients and allow for better interpretation of intraoperative data.