The so-called "Kawase approach" is a technically challenging surgical approach to the brainstem region that requires manual dexterity and the ability to visualize in three dimensions. Any neurosurgeon who has ever used this approach may wonder how this technique was originally developed historically. In this article, we describe the life of Takeshi Kawase, the man who introduced this approach, highlighting his unique background, talents, and life struggles that have shaped his career.

Kawase’s Love for Art and Nature

Takeshi Kawase was born in 1944, during WWII, as the second-born child in his family, in an evacuation town near Tokyo, when the food supply was scarce. Kawase grew up watching his father, originally born in Taiwan, work all day as a medical doctor for patients in his clinic in downtown Tokyo. Kawase’s mother, a cultured Japanese woman who was excellent at playing the traditional Japanese guitar shamisen, enrolled Kawase in violin school at an early age. Kawase’s unique upbringing cultivated in him a deep passion for the arts and sciences (T. Kawase, personal communication, July 28, 2022).

Kawase attended the Keio school system in Tokyo from junior high school to medical school. His junior high school teacher, who was also the head of the Keio Mountaineering Club, affected young Kawase immensely.1 Kawase was inspired by his mentor’s wisdom and ability to visualize, predict, and efficiently manage dangerous situations in the natural world. Consequently, this special encounter caused Kawase’s lifestyle to dramatically shift from indoors to outdoors (T. Kawase, personal communication, July 28, 2022). In medical school, Kawase belonged to two sports clubs, the Keio Wander Vogel (KWV) Club and the Keio Medical Rowing Club, where he made many friends. The intense physical training under harsh circumstances equipped Kawase with resilience and strong survival and team-building skills, which later influenced Kawase’s career.

Near-Fatal Expedition to the Swiss Alps

After graduating from medical school, Kawase embarked on a grand expedition to Monte Rosa, the highest peak in the Swiss Alps, with a close friend from his mountaineering club. The year was 1968—an era in which overseas travel was not popular among the Japanese. The two were young and fearless, and for Kawase it was his first travel abroad. Since the two were poor, they planned the most economical route to Europe. They departed Yokohama harbor by ship to go to Nakhodka, Russia. Upon landing, they crossed Siberia by train and took a local flight to Moscow. After 5 days, they finally reached Vienna, Austria, by the Trans-European Express train. With a strict daily expenditure limit of 4 dollars that barely covered meal fees, they could only afford to stay in youth hostels and could not hire a tour guide. Although neither of them could communicate in English at that time, they managed to find bakeries and bus stops on their own, and even hitchhiked along the way (T. Kawase, personal communication, July 28, 2022).

Unsurprisingly, this economical travel came with a price, especially by naively attempting to tackle the highest mountain in the Swiss Alps without a rope or tour guide. Kawase and his friend left Monte Rosa cottage at 2 am and walked along the glacier using only a flashlight. The hike started out pleasant and upbeat, and the two men were surprised to find a beautiful morning glory on the way. As the hike progressed, they were awed by the glorious, panoramic view of the pyramid of the Matterhorn stained in gold and the vast snow-capped mountains changing colors from purple to rose pink.

By the time they had climbed more than 4000 m in elevation, however, things began to look grim. The pair became fatigued, starved, and started developing severe headaches due to the low oxygen levels. The icy, rocky ridges were steep and too risky to cross without a rope, and if they slipped, they would immediately fall into a crevasse. The two were already at the point of no return. Halfway into the perilous endeavor, they confessed to each other, "I am so very sorry, but if there is an accident, I am not able to rescue you" (T. Kawase, personal communication, July 28, 2022).

After 9 hours of grueling climbing on the knifelike ridge, Kawase and his partner finally reached the 4634-m summit without a rope or tour guide. Upon returning to Zermatt, they were called "kamikaze" climbers. This dramatic experience taught Kawase two important life lessons: 1) exposure to foreign cultures and languages during youth is critical for personal growth, and 2) faith and perseverance are necessary to get through adverse conditions to achieve victory. After this outdoor mission, he married the beautiful love of his life, Mieko, who belonged to his mountaineering club.1

Political Unrest During Residency: The University Restroom as a Safe Haven

After graduating from Keio Medical School in 1970, Kawase decided to pursue neurosurgery at Keio University. His reasoning was simple—the field was still underdeveloped in the 1970s. At that time, diagnostic imaging tools such as CT and MRI were not widely available, and neurosurgeons relied heavily on angiography and pneumography.

Kawase’s neurosurgical training coincided with the student-led democratic movement across Japanese universities nationwide. School members were divided into two groups—the revolution and the anti-revolution groups.1 Many medical school officials were reshuffled and lost their positions. Keio University was not spared from this political fallout, and the neurosurgery department lacked a professor for a record 13 years. Kawase trained during political chaos and was forced to complete his entire neurosurgery residency in the absence of a professor.2

Throughout residency, Kawase worked with his coresident "buddy," Hirotoshi Sano. Together, they rotated in radiology, translational research, and electroencephalography. As the faculty were not particularly supportive, they had to rely on each other to progress, and the pair was known as the "power duo" by senior residents (H. Sano, personal communication, August 4, 2023).

In his intern year, Kawase was overworked and was not given a salary or space to study. Kawase’s senior resident took pity on his misery and suggested that he use the dirty, old restroom as his study space. This restroom had a small broken window through which pigeons freely entered. The entire floor was covered with a 10-cm-thick carpet of bird droppings. Kawase was overjoyed at this unexpected opportunity. Kawase invited Sano, and together they cleared the floor with a shovel, scrubbed the tiled floor clean, brought a small study table inside, and occupied the restroom for 1 year as their divine study place until they were inevitably forced to leave by the administration2 (H. Sano, personal communication, August 4, 2023).

Using Artistic Imagination to Visualize the Operative Field

Kawase’s three notable talents—manual dexterity from playing the violin and guitar, the capacity to visualize neuroanatomy in three dimensions from mountaineering, and his ability to draw—all helped him excel in neurosurgery. As a young resident, he routinely made detailed sketches of the imagined operative field before the operation. After surgery, he drew colorful pictures on what was observed intraoperatively, and then compared his drawing to the preoperative imaging to detect discrepancies. While he observed senior surgeons perform microsurgery, he often referred to the anatomically accurate and detailed illustrations in Pernkopf’s textbook of anatomy, a book he purchased as a medical student in 1966. Kawase’s routine of making detailed illustrations of surgery enabled him to excel at surgical image training.

The surgical microscope was introduced during Kawase’s training. In the 1970s, microsurgery was still in its early stages, and as a resident Kawase often noticed his faculty frequently becoming disoriented during microsurgical procedures. At that time, the transpetrosal approach was under development by the neurosurgery and otolaryngology teams at Keio University to treat vestibular schwannoma. One day, Kawase (as chief resident) drilled the petrous bone for a vestibular schwannoma in an operation led by the senior staff. However, Kawase had unknowingly drilled too far anteriorly, and inadvertently created a corridor to the basilar artery (BA) through the middle fossa (H. Sano, personal communication, August 4, 2023). Kawase and Sano were in awe of the BA pulsating on the wonderous human brainstem, or the so-called "no man’s land"6 where human life was entirely controlled. After this experience as chief resident, Kawase had an idea that the transpetrosal approach could potentially be used as a corridor to access the brainstem (T. Kawase, personal communication, July 28, 2022).

Kawase’s Research Mindset During Cerebrovascular Studies at Mihara

After residency at Keio University, Kawase worked as a vascular neurosurgeon at Mihara Memorial Hospital in Gunma prefecture from 1977 to 1981. The 5 years spent at the busy stroke center had a profound effect on Kawase as he was able to develop both research and clinical mindsets. Kawase strongly believed that innovation in research and technology was critical to minimizing surgical complications. At Mihara, Kawase studied the efficacy of multimodal treatment methods for stroke, such as combining endovascular and regenerative therapies. Kawase’s doctoral research topic was identifying the indication for superficial temporal artery (STA) to middle cerebral artery (MCA) bypass surgery for ischemic stroke. For this research, he used 4 measurements: cerebral blood flow using xenon-133, CT scans, electromagnetic flowmeter recordings, and fluorescein microangiography, which he developed by himself as a resident in 1974. He performed xenon-133 cerebral blood flow studies in more than 1000 cases of ischemic stroke and vasospasm following subarachnoid hemorrhage. After painstaking data analysis, he discovered that the indication for the STA-MCA bypass was a reduction of cerebral blood flow by 60%.7 Although Kawase had already produced groundbreaking data early in his career, he did not gain much international recognition because much of his published work was in Japanese. It was only in his later years that he started to publish his work in English.

Kawase’s cerebrovascular research at Mihara Memorial Hospital in the 1970s. A: Kawase at his desk. © Takeshi Kawase, published with permission. B: Kawase’s self-designed notebook, which reflects his life motto of self-sufficiency. © Takeshi Kawase, published with permission. C: A schematic drawn by Kawase shows the STA-MCA bypass operation and the techniques used to measure STA flow after anastomosis and MCA pressure by temporary clipping of the STA. EM = electromagnetic. © Takeshi Kawase, published with permission. D: Fluorescein microangiography, a technique developed by Kawase, was used to visualize the distribution of bypass flow. This was the topic for Kawase’s doctoral thesis. Figure is available in color online only.

At Mihara, Kawase was a busy clinician, and he continued to explore potential applications of the transpetrosal approach he had experienced at Keio to treat cerebrovascular diseases for the first time ever. Historically, aneurysms arising from the vertebrobasilar junction had been explored by Walter Dandy via the suboccipital route in the 1940s and by the subtemporal-transtentorial approach by Charles Drake in the 1960s. However, these approaches were not ideal, as the exposure was limited, and the operations were fraught with complications such as cranial nerve injuries and venous infarction resulting from injury to the vein of Labbé.

On February 8, 1980, Kawase treated a patient who presented with a ruptured vertebrobasilar junction aneurysm. He clipped the aneurysm via the transpetrosal approach using a Zeiss II microscope equipped with a dark halogen lamp. The patient survived but suffered a prolonged postoperative course consisting of hearing loss, facial palsy, and CSF rhinorrhea, caused by the removal of the organic part of the pyramid of the temporal bone. Seeking to avoid such devastating complications, Kawase turned to his old Pernkopf anatomy textbook for insight. The illustrations indicated that the petrous apex contained no organic structure, while the middle portion of the temporal bone contained the auditory apparatus and the facial nerve. This was the moment of epiphany for Kawase, as he realized that selectively removing the part of the pyramid containing no organic structure could prevent debilitating complications. As cadaver dissection training was not available until 1982 at Keio University, Kawase had to practice drilling the temporal bone using dried human skulls to improve his surgical skills.

The development of Kawase’s approach. A and B: Original photographs of Kawase practicing drilling on the petrous bone using a dry skull. Kawase performed his first successful anterior petrosal approach for the first time on a patient in 1981, after having practiced bone drilling on skulls, as cadaver training was not yet available. IAM = internal auditory meatus; V = cranial nerve V (trigeminal nerve); VII = cranial nerve VII (facial nerve). C: Kawase’s original drawing of the anterior petrosal approach, published in black and white in the Journal of Neurosurgery in 1985. © Takeshi Kawase, published with permission. D: Kawase’s sketch of the anatomy exposed using the right anterior transpetrosal approach. Kawase was gifted with an exceptional skill of conveying difficult concepts elegantly through art. F. ovale = foramen ovale; ICA = internal carotid artery; III = oculomotor nerve; IPS = inferior petrosal sinus; IV = trochlear nerve; MPG = major petrosal groove; PCA = posterior cerebral artery; Pcom = posterior communicating artery; Post. = posterior; SCA = superior cerebellar artery, SPS = superior petrosal sinus, VA = vertebral artery; VII = facial nerve. © Takeshi Kawase, published with permission. Figure is available in color online only.

The First Successful "Kawase Approach" at Ashikaga Red Cross Hospital

On March 9, 1981, Kawase was invited by Toru Mine, Chief of Neurosurgery at Ashikaga Red Cross Hospital in Tochigi prefecture, to clip a ruptured anterior inferior cerebellar artery aneurysm facing the brainstem. Remembering his patient from Mihara who suffered complications from the transpetrosal approach, this time Kawase conducted only a focal resection of the pyramidal apex to clip the aneurysm. This was the first time Kawase performed the refined anterior petrosal approach on a living patient rather than on a skull (T. Kawase, personal communication, July 28, 2022). As a result of this technique, the patient suffered no postoperative surgical complications and the aneurysm was completely obliterated, as confirmed by angiography. Kawase named this approach the anterior transpetrosal approach. This was the first successful case of the anterior transpetrosal approach, and it was reported in the Journal of Neurosurgery in 1985. Notably, Yoko Kato, a visiting neurosurgery resident from Fujita Health University at the time, was also present at this historical surgery.

After this surgical success, Kawase started applying the anterior transpetrosal approach to treat skull base tumors. He reported two successful resections of petroclival meningioma using this approach at the first Cavernous Sinus Symposium in Ljubljana, Yugoslavia, organized by Vinko Dolenc in 1986. He reported on 10 petroclival meningiomas invading the cavernous sinus operated by this approach in 1991. Since then, Dolenc and Albert Rhoton started referring to the anterior transpetrosal approach as Kawase’s approach, and subsequently his new skull base technique spread quickly around the world. A picture of Kawase’s approach first appeared on the cover of the journal Neurosurgery in 1999. Kawase himself had never referred to this approach as his own, and the international recognition took him by surprise.

Breaking Down Barriers, Building Bridges Across the World

In 1982, Kawase returned to Keio University, when the institution finally became democratic. The neurosurgery department was still lacking a professor, and Kawase returned to help support the staff. It had been a while since Kawase returned to his alma mater. In his heart, he remembered the words of a former faculty member while he was a resident: "Try reconstructing the department by yourself!" At the time, little did he know that this would later become a reality (T. Kawase, personal communication, July 28, 2022).

In 1984, after 13 years without a professor, Keio University finally appointed Shigeo Toya as the new professor of neurosurgery. Under Dr. Toya’s leadership, the department collaborated extensively with the otolaryngology, ophthalmology, and plastic surgery departments under the unifying concept of skull base surgery . This multidisciplinary team at Keio founded the Japanese Society for Skull Base Surgery (JSBS) in 1989, which was the world’s first skull base society established at the national level. Kawase supported the secretary offices of the national skull base society and the Asian-Oceanian Skull Base Society (AOSBS), founded by Kintomo Takakura in 1991, for more than 20 years.

Kawase respected Dr. Toya’s vision to promote interdepartmental and multidisciplinary collaboration, which was difficult to achieve for many years. In 1994, Kawase visited the University of Cincinnati, under the chairmanship of John McLellan Tew, to conduct an anatomical study of the cavernous sinus in John Keller’s laboratory. The group explored new surgical methods to preserve the meningeal layers during cavernous sinus surgery to avoid injuries to the brain and cranial nerves. The team developed the epidural-intradural approach, a less invasive method to approach the cavernous sinus, which could be used for treating trigeminal schwannoma and chordoma. Kawase’s landmark paper, "Meningeal architecture of the cavernous sinus: clinical and surgical implications," was published in Neurosurgery in 1996. After Dr. Toya’s retirement, Kawase was appointed the new professor and chairman of neurosurgery in 1996.

Kawase believed in the Keio doctrine, which states that all individuals are equal and valuable, and he treated everyone with the utmost respect and kindness. Having experienced hardships firsthand, Kawase was a strong advocate for recruiting international fellows and minorities. He welcomed many visitors to Keio University for advanced training and encouraged young Japanese neurosurgeons to study overseas, at a time when international medical exchange was still uncommon in Japan. He prioritized cadaver training for residents early on in residency, and collaborated with the university’s anatomy department to implement major renovations in the cadaver laboratory. Kawase was driven to make these changes because access to cadaver training was limited in Kawase’s early career and he deemed it absolutely necessary to minimize surgical complications (T. Kawase, personal communication, July 28, 2022). The international visitors whom Kawase trained eventually became academic leaders in their respective countries. Notably, Helmut Bertalanffy, a long-time friend and "neurosurgical brother" of Kawase from the early years of skull base surgery, visited Keio as a young research fellow from Germany to collaborate on the transcondylar approach. Bertalanffy assumed professorship in Germany in 1997.

Kawase’s friendly personality, fun-loving free spirit, generous hospitality, and magnetic charm granted him many friends and fans, both domestically and internationally. He served as the president of the Japan Neurosurgical Society (JNS) from 2004 to 2006. He recruited over 50 world experts to the Society, for which he was awarded the JNS International Prize in 2007. He was the president of the JSBS from 2005 to 2011, and was the secretary for the JSBS and the AOSBS for more than 20 years. With the support of Ossama Al-Mefty, Robert F. Spetzler, and Shigeaki Kobayashi, he organized the first World Academy of Neurosurgery (WANS) meeting in 2015. Kawase chaired the skull base committee for the World Federation of Neurosurgical Societies (WFNS) for 8 years and organized cadaver courses in developing countries, supporting his own airfare. He was appointed vice president of the WFNS in 2009. He was the alternate president at the World Congress in Seoul in 2013, and honorary president of the WFNS. He was presented the Dandy medal in 2013, and the WANS Golden Neuron Award in 2020 for his lifetime achievements in neurosurgery.

Kawase’s Legacy

Despite his countless accolades, Kawase remained a humble man who never sought fame or leadership roles himself, but instead accepted offers as they came. Notably, the connections that he established with world leaders in organized neurosurgery all originated from many years of friendship and collaboration, long before Kawase rose to prominence. Kawase never sought attention for himself, but always put the spotlight on his patients, saying, "Never forget to feel the pain of our patients." He conducted rounds on his patients every day, and strongly believed that close observation provides important hints to unanswered clinical questions.

Even since his retirement in 2010, Kawase has continued to lecture in microsurgery and cadaver courses worldwide, with this beautiful wife by his side. He has offered courses in micro- and endoscopic surgery in Taiwan, India, Indonesia, Hong Kong, China, Kyrgyzstan, Egypt, Turkey, and Venezuela, among others. To date, Kawase has trained many surgeons in person. His philosophy on what a neurosurgeon must have is as follows: "Not only is the technique important; not only is the science important; but also the heart is important" (T. Kawase, personal communication, July 28, 2022).

Kawase’s contribution to cadaver dissection courses around the world. A and B: Kawase teaches at a hands-on course for neurosurgery residents and fellows in Surabaya (A) and Bandung (B), Indonesia, respectively. © Indonesian Neurosurgical Society, published with permission. C: Kawase supported the AOSBS for 20 years. The photograph shows Kawase with his co-chair, Albino Bricolo, at the AOSBS Congress in Mumbai, India. © Takeshi Kawase, published with permission. D: After serving as instructors at the international Keio cadaver course in 2009, Kawase and Dolenc enjoy a foot bath together. © Takeshi Kawase, published with permission. Figure is available in color online only.

Conclusions

Despite having faced struggles in his early years as a neurosurgeon, Takeshi Kawase used his talent, creativity, and passion to explore and successfully develop a safe surgical trajectory to the most unforgiving area of the human brain—the brainstem. He continues to inspire young neurosurgeons across the world by sharing his surgical skills through his neurosurgical missions. His life story is a testament to all that friendship and collaboration are necessary to overcome divisions and advance our field.

Acknowledgments

We would like to personally thank Professor Takeshi Kawase for providing the authors photographs of his original artwork, as well as pictures from his historical collection. We also thank Professor Hirotoshi Sano for sharing personal stories from Kawase’s earlier years.

Disclosures

The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

Author Contributions

Conception and design: both authors. Acquisition of data: both authors. Analysis and interpretation of data: both authors. Drafting the article: Ganaha. Critically revising the article: both authors. Reviewed submitted version of manuscript: both authors. Approved the final version of the manuscript on behalf of both authors: Shibao. Administrative/technical/material support: Ganaha. Study supervision: Shibao.