Scalp nerve block alleviates headaches associated with sonication during transcranial magnetic resonance–guided focused ultrasound

In this academic paper, the authors attempt to address the common headache complication during magnetic resonance-guided focused ultrasound (mrgFUS) treatment. Headache is a common complication, and in severe cases, it may even cause patients to be unable to tolerate ultrasound radiation and terminate the treatment. There is currently no established treatment for this type of headache.

The authors are from the Department of Neurosurgery, Hamamatsu University School of Medicine, Japan, including Masato Monzeki, Kenji Sugiyama, Takao Nozaki, Tomohiro Yamasaki, Hiroki Nannba, Michihiro Shimizu, and Kazuhiko Kurosawa. This paper was published in the journal Neurosurgery in 2024.

For the headache problem during mrgFUS treatment, this study adopted a new method of scalp nerve block (SNB), which involves injecting long-acting local anesthetics such as ropivacaine around the scalp nerves to block the incoming pain impulses.

The research process is as follows:

a) Study subjects: From April 2020 to February 2022, 70 patients with a skull density ratio (SDR) ≤0.55 were selected from 97 patients with refractory essential tremor (ET) or Parkinson’s disease (PD) who underwent mrgFUS treatment at the hospital.

b) Before October 6, 2021, 34 patients did not receive SNB, while the subsequent 36 patients underwent SNB before treatment. The headache scores were compared between the two groups to evaluate the effect of SNB in relieving headaches.

c) Headache scores were assessed using the numerical rating scale (NRS), with 0 indicating no pain and 10 indicating excruciating pain. Patients rated their current level of headache after each ultrasound radiation.

d) Statistical methods such as multivariate regression analysis were used to investigate the relationship between SNB, SDR, skull thickness, gender, age, energy intensity, and headache scores.

The research results showed:

a) After using SNB, the headache scores of patients at the first ultrasound radiation reaching 52.5°C were significantly reduced (β=2.40, 95%CI: 0.758-4.05, p=0.00499).

b) In the overall analysis of headache scores for all ultrasound radiations, SNB significantly reduced the degree of headache (β=0.647, 95%CI: 0.106-1.19, p=0.0201).

c) Further analysis of different energy segments revealed that in the medium energy range of 10000-29999J, SNB had the most significant effect in relieving headaches (β=1.83, 95%CI: 0.485-3.17, p=0.00889).

d) Apart from SNB, SDR and skull thickness were also important factors influencing headache. Low SDR and thicker skulls tended to exacerbate headaches.

The innovation of this study lies in the first proposal and confirmation that SNB can effectively alleviate headache symptoms during mrgFUS treatment, particularly when reaching the effective focal temperature and medium energy radiation. The results suggest that scalp nerves may be involved in the headache mechanism during mrgFUS treatment. SNB is a safe, non-invasive, and non-disruptive method for pain relief while maintaining the patient’s awake state, making it clinically valuable. However, this study still has limitations, such as the retrospective study design and lack of qualitative headache assessment, which require further optimization of the research design for validation.