Toshio Hyogo

How did you find your way into neurosurgery, and then, interventional neuroradiology?

My graduation from medical school overlapped with the early stages of computed tomography. I felt that this technique had huge potential, the ramifications of which we were only just beginning to fathom. Then, I encountered the Tracker catheter (microcatheter) in 1988 which led me on to interventional neuroradiology because navigating intracranial vessels with a therapeutic intent attracted me and I felt that this was a future full of possibilities.

Which innovations in interventional neuroradiology/endovascular neurosurgery have shaped your career?

The Guglielmi Detachable Coil was a revolutionary innovation for endovascular treatment and I found this to be true in my career as well. This coil was the first device for safe and reliable aneurysm treatment, and it has been used for over 20 years. I am sure that the present belief in endovascular treatment and new devices owe much to this coil and related technology.

Who were your mentors in the field and what do you still remember of their wisdom?

My particular mentors were two Japanese physicians. The first, Dr Junichi Nakamura, the previous chief and owner of our hospital led me to neurosurgery and taught me the importance of patient care and always remaining in contact with the patient. He was quick to grasp potential future of endovascular treatment and supported me to get into interventional neuroradiology. Akira Takahashi, a professor at Tohoku University, taught me the first steps and primary techniques in endovascular treatment.

I also have two mentors outside Japan. Michel Mawad, a professor at Baylor College of Medicine, Houston Texas, USA, became a mentor when I was in Houston in 1996. This was just before the introduction of the Guglielmi Detachable Coil to Japan and I had gone abroad to study aneurysm coil embolization. He taught me extensively about endovascular treatment and I appreciated his kindness in my first uneasy experience of life abroad. Luc Picard, a professor from the Department of Neuroradiology, Nancy University, France, was a mentor when I was in Nancy in 1997. We had many cases of aneurysm coil embolization and cerebral arteriovenous malformation glue embolization at Nancy, and Luc taught me not only the clinical aspect but also a part of the spirit and essence of neuroradiology which originated and developed in France.

Could you describe an early moment in your career in interventional radiology where you were amazed by what the specialty could achieve?

I was amazed by what interventional neuroradiology could achieve when I saw a patient recover dramatically from symptoms on the angiography suit table during my first stroke treatment. The patient had a right hemiparesis and speech disturbance and was diagnosed with a left middle cerebral artery occlusion. I then navigating the microcatheter to the occlusion site and infused urokinase. During the infusion, she suddenly spoke and intended to remove her oxygen mask with her with right hand. Angiography revealed a complete re-opening of the occluded vessel.

Can you describe a memorable case and how interventional neuroradiology came to the rescue?

A 17-year-old high school girl suffering subarachnoid haemorrhage was transferred to our hospital. The diagnosis was pial arteriovenous fistula (an arteriovenous malformation). I treated her by endovascular embolization using glue with a flow control balloon catheter.

Using two catheters in one branch of the middle cerebral artery was a brand-new, revolutionary technique for me at that time, and her fistula was treated completely. I was so very glad that she made an impressive recovery and went to nursing college and then to become a midwife.

Another case when interventional neuroradiology came to the rescue was in the case of a pituitary tumour. During an operation to remove the tumour by trans-sphenoidal approach, one side of the carotid artery was injured and the neurosurgeon could not control the haemorrhage. We carried out a rescue treatment with endovascular technique by coil embolization of the injured carotid artery, and the haemorrhage stopped.

What is the research you have done that has been most rewarding?

My hospital is the Stroke Centre of Sapporo city, so I have treated stroke patients ever since the microcatheter was first introduced. I have got good results by including cerebral blood flow factor measurement to the indication criteria. My work was also instrumental in organising and performing a Japanese randomised controlled trial for endovascular stroke treatment, the Melt-Japan study. Evidence from the study contributed to the introduction of rtPA in Japan and I am very proud of the success of Melt-Japan.

How does the practice of interventional neuroradiology in Japan differ from Europe and North America?

Traditionally, cerebral angiography has been performed by neurosurgeons in Japan and this has continued on into endovascular treatment. The Japanese Society of NeuroEndovascular Therapy (JSNET) has about three thousand members and over 90% of the members are neurosurgeons. This is a big difference from the West. Recently, the number of neurosurgeons who are devoted to endovascular treatment is increasing in the USA. I think it is very important that endovascular treatments should be performed by doctors who have experience of watching cerebral aneurysm from the outside or who know how the plaque is fragile at carotid endarterectomy.

Another difference is in the integration of the cases. In Japan, neuroendovascular treatment is performed in many different kinds of hospitals—university hospitals, municipal hospital and even small private hospitals. In the smaller institutes, experience with endovascular treatment is usually very limited. So we had to meet the challenge of how to ensure a standard level of endovascular treatment for the patient. This became a very important problem in Japan. One of the answers was to create a JSNET specialist qualification system, which was established in 2000. I wrote the paper in Interventional Neuroradiology. I am very proud of this system, a specialist examination system which is constant and fair. With the expansion of interventional neuroradiology, the same problem will be apparent in many countries. We hope our specialist qualification system will be a model case to help solve this problem.