Neurosurgical Management of Complex Malignant Skull Base Lesions

Fellow: Adel Helmy MA MB BChir FRCS (SN), PhD

Queensland Skull Base Unit,
Princess Alexandra Hospital, Brisbane, Australia
University of Queensland, Brisbane, Australia

Supervisor: Professor Benedict Panizza

The Queensland Skull Base Unit provide a supra-regional, state-wide service for complex skull base lesions. The team of clinicians includes representatives from neurosurgery, head and neck surgery, radiation oncology, radiology and an active research theme. The work of the unit is channelled through a 4 weekly Multi-Disciplinary Team meeting for which I was responsible for during my time as a surgical fellow. This involved triaging referrals, reviewing patients and their imaging in clinic and preparing and presenting the MDT list.

I was exposed to a wide range of surgical techniques related to all aspects of skull base surgery, including transpetrous approaches to cerebellopontine angle lesions such as vestibular schwannomas, deep posterior fossa lesions, endoscopic endonasal approaches to midline tumours including pituitary lesions and anterior skull base pathology. This experience has allowed me to develop my own technique and approach to these diverse skull base pathologies and provided me with a great deal of confidence in my surgical approach to the patient.

The most important technical aspect of the work I carried out was the treatment of advanced head and neck malignancies with perineural spread into the cranial cavity. Queensland is the sunshine state in Australia, and with a large Caucasion population, it also the skin cancer state of Australia. With a large incidence of skin malignancies, there is also a large incidence of spread of these superficial malignancies through the cranial nerves to the head and neck into the cranial cavity. The Queensland Skull Base Unit has the largest case series of these complex lesions, of anywhere in the world. The surgical techniques to these patients are complex and varied, requiring input from neurosurgery, head and neck surgery, as well as plastic and reconstructive surgery. As these are malignant lesions, they require complete removal, ideally en bloc, with histologically clear surgical margins in order to maximise the potential benefit to life expectancy. This requires a detailed knowledge of the skull base both intra-cranially, as well as the boundary zone with the head and neck through the upper nasal cavity, orbit, infratemporal fossa and parapharyngeal spaces. This is anatomy which is rarely encountered in neurosurgical training in the UK and provides a finishing school for specialist skull base surgeons.

The specific techniques required for this surgery require a combination of endoscopic endonasal experience, the use of the high speed drill over the skull base in close proximity to critical neurovascular structures, and the careful dissection of involved cranial nerves back towards the brainstem. I also gained experience in orbital surgery and learned techniques for opening surgical corridors from the posterior orbit back towards the cavernous sinus. In the middle cranial fossa, I was taught the extradural dural splitting approach (Dolenc’s approach) to the cavernous sinus. This was originally described for meningiomata of the cavernous sinus and is now only rarely required. However in perineural spread of malignancy, this approach is required to follow the various branches of the trigeminal nerve back through the middle fossa skull base and into the cavernous sinus in order to section the involved nerves at the trigeminal ganglion. I gained more experience of this approach in one year, than I could have gained in any UK unit over a decade.

There is a concern in all surgical training in the UK that trainees are exposed to a fewer number of complex cases due to cuts in training time, but also the high degree of scrutiny that surgeons are under. This means that it is very difficult to gain the necessary exposure to complex pathology during the final years of training and the first years of consultant practice. This fellowship has provided me with a ‘finishing school’ of surgical techniques that allow me to go into a consultant job with the necessary skill to provide high quality care in the UK environment straight away. Partly based on the strength of the fellowship I completed, I have been appointed as a University Lecturer in Neurosurgery and Honorary Consultant Neurosurgeon in Addenbrooke’s Hospital, Cambridge. The skills I have brought back will also allow me to educate the next generation of trainees in the management, both clinical and surgical, of complex skull base lesions. I am a course organiser for the British Neurosurgical Trainee Course, a national trainee course, and will use my new found knowledge to further educate and disseminate the knowledge I have acquired.

Patients with complex skull base lesions are often faced with very difficult decisions about undergoing high risk surgery which inevitably carries some morbidity. The surgeon’s role is to provide the best treatment that is carefully tailored to the pathology, the patient’s wishes and the specific surgical goals. This high-level approach requires a thorough knowledge and wide experience that can only be gleaned from training in a high volume specialised unit.

Summary

The Queensland Skull Base Unit provide a supra-regional, state-wide service for complex skull base lesions. The team of clinicians includes representatives from neurosurgery, head and neck surgery, radiation oncology, radiology and an active research theme.

I was exposed to a wide range of surgical techniques related to all aspects of skull base surgery, including transpetrous approaches to cerebellopontine angle lesions such as vestibular schwannomas, deep posterior fossa lesions, endoscopic endonasal approaches to midline tumours including pituitary lesions and anterior skull base pathology. This experience has allowed me to develop my own technique and approach to these diverse skull base pathologies and provided me with a great deal of confidence in my surgical approach to the patient.

The most important technical aspect of the work I carried out was the treatment of advanced head and neck malignancies with perineural spread into the cranial cavity. Queensland is the sunshine state in Australia, and with a large Caucasion population, it also the skin cancer state of Australia. With a large incidence of skin malignancies, there is also a large incidence of spread of these superficial malignancies through the cranial nerves to the head and neck into the cranial cavity. The Queensland Skull Base Unit has the largest case series of these complex lesions, of anywhere in the world.

The specific techniques required for this surgery require a combination of endoscopic endonasal experience, the use of the high speed drill over the skull base in close proximity to critical neurovascular structures, and the careful dissection of involved cranial nerves back towards the brainstem. I also gained experience in orbital surgery and learned techniques for opening surgical corridors from the posterior orbit back towards the cavernous sinus. In the middle cranial fossa, I was taught the extradural dural splitting approach (Dolenc’s approach) to the cavernous sinus.

Patients with complex skull base lesions are often faced with very difficult decisions about undergoing high risk surgery which inevitably carries some morbidity. The surgeon’s role is to provide the best treatment that is carefully tailored to the pathology, the patient’s wishes and the specific surgical goals. This high-level approach requires a thorough knowledge and wide experience that can only be gleaned from training in a high volume specialised unit.