Base of Skull Surgery
Introduction
Base of Skull Surgery (BSS) is the subspeciality in Neurosurgery that is focused on dealing with problems involving the region “at the under surface of the brain” and the skull beneath the brain. Problems here usually involve tumours but sometimes may include access the blood vessels in this region and congenital problems.
The need for a sub-speciality within Neurosurgery to deal with these problems is because of the complex anatomy of this area due to the multiple cranial nerves that exit through the skull to reach the rest of the body, also the various blood vessels that supplies and drains the brain and finally the need to deal with the bones of the base of skull and cerebro-spinal fluid.
Commonly managed pathology in this area include benign tumours like the acoustic neuromas and other neuromas that arise from other cranial nerves, meningiomas, pituitary adenomas and craniopharyngiomas and malignant tumours like squamous cell carcinomas, neuroendocrine tumours and other nasal tumours extending into the skull.
The University of Malaya is the first unit to provide a comprehensive team based approach to tumours of the base of skull. This unit has been in existence since 2001 and was formalized in 2007. This unit presently consist of:
- Prof Vickneswaran Neurosurgeon
- Prof Prepagaran ENT Surgeon
- Assoc Prof Vairavan Neurosurgeon
- Assoc Prof Kalai Arasu Neurosurgeon
- Dr Rushdie ENT Surgeon
- Dr Zulkifly ENT Surgeon
- Dr Elizabeth ENT Surgeon
- The team is supported by neurophysiologist, anaesthetist with plastic surgeons and maxillofacial surgeons being called in when necessary.
The work that is performed in UM include:
- Anterior Skull Base- CSF leak, Mid line meningiomas, Cancers of the sinuses.
- Middle Skull base including pituitary- Pituitary adenomas, Craniopharyngiomas and infections
- Posterior Skull base- Acoustic and other neuromas, meningiomas and other abnormalities like cranio-vertebral abnormalities.
The team specializes in minimally invasive endoscopic techniques for almost all tumours of the anterior and midline middle and posterior skull base. We have pioneered and published on various surgical techniques and operating devices designed and developed in UM.
We are also involved in the training of other specialist in Malaysia and fellows from the around the world.
Pituitary tumours
The pituitary is a gland that is connected to the under surface of the brain and produces a number of hormones responsible for various metabolic functions in the body.
The pituitary gland is commonly afflicted by a benign tumour called a pituitary adenoma. These in turn are classified as functioning ie they tumours produce one of the hormones in excess resulting in metabolic problems (growth hormone secreting- acromegaly, prolactine secreting- prolactinoma and cortisol secreting- Cushing’s disease) but most tumours are non secreting (do not secrete any of the hormones) and become symptomic by their size (pituitary macroadenoma). Macroadenomas have a tendency to grow upwards and compress on the optic chiasm resulting loss of peripheral vision or grow sideways and result in opthalmoplegia (the loss of ability to move the eyes resulting in double vision). Occasionally a tumour may suddenly bleed within itself resulting in a sudden increase in size causing loss of vision, reduced consciousness or loss of hormonal functioning. The vast majority of pituitary adenomas are benign with malignant versions being very rare.
Other than pituitary adenomas, we also not uncommonly encounter craniopharyngiomas and meningiomas in this area.
Pituitary tumours are diagnosed by MRI and CT scans and all patients routinely have a formal eye examination by ophthalmologists and a full endocrine workup including a consultation with an endocrinologist prior to surgery as many patients often have altered hormone secretion that should be corrected for safer surgery.
In this centre all these operations are conducted carried out by the skull base team (consisting of an ENT surgeon and a Neurosurgeon). The aim of performing such an operation is to combine the expertise of an ENT surgeon for the nasal portion of the operation and the Neurosurgeon for the cranial portion. This team presently performs between 40-50 such operations a year.
All operations are performed in a minimally invasive fashion endoscopically. All operations are also performed using image guided surgery occasionally they maybe performed under radiological control to ensure patient safety.
Most operations performed for a pituitary adenoma take approximately 1.5 to 2 hours to complete. Patients are warded between 5 and 7 days.
Meningiomas and craniopharyngiomas
These two tumours are relatively less common in this area. Conventionally performed via a craniotomy however when these tumours occur within the region of the sella and have suitable characteristics as defined in the MRI, these tumours are excised by the skull base team endoscopically. While a more extensive undertaking when compared to an excision of a pituitary adenoma, none the less this is a more minimally invasive procedure without the need for brain retraction thereby reducing risks of brain injury and seizures.
Posterior Skull Base Surgery
The posterior skull base surgery involves surgery confined to the narrow area between the lateral edges of the cerebellum and the lateral and anterior edges of the brain stem with the skull base adjacent to these two structures. This narrow space is occupied by a variety of delicate structures namely the cranial nerves, the important blood vessels that supply these structures and the all important brainstem.
The commonly occurring pathologies in this area requiring surgery include:
- The acoustic neuroma
- Other neuromas ( trigeminal, lower cranial and hypoglossal)
- Meningiomas (petrous and tentorial)
- Craniovertebral junction abnormalities.
Surgery in this area is again performed by the dedicated base of skull team that employ a number of techniques depending on the various pathologies. As this team has been in existence for over 10 years, the team can call upon a the various skill sets belonging to the individual members of the team to perform a variety of challenging procedures that include:
- Standard retrosigmoid approache
- Translab and extended petrous approaches
- Various transtentorial approaches
- Minimally invasive endoscopic approaches
This team performs about 30 operations in this area a year. In addition to surgery members of this team also conduct fellowships, training both locally and abroad and have published their series and pioneering techniques in international peer review journals
In the interest of patient safety all patients undergoing surgery within the posterior fossa are also have their cranial nerves and brain stem functioning monitored using elector physiological techniques. During the excision of an acoustic neuroma all patients will have their 5th, 7th and 8th nerves monitored. For tumours involving the lower cranial nerves and meningiomas other cranial nerves such as the 9th, 10th, 11th and 12th are also monitored.
Image Guidance is also utilised routinely for the excision of these tumour to allow the operation to flow more smoothly and safely.
Beginning 2015 all operations involving the base of skull will be performed within the new state of art brain suites. These allow the operations to be performed in operating rooms directly connected to either MRI or CT scans. This will allow surgeons to confirm the adequacy of surgery and any possible complications early. This will be the first comprehensive facility of its kind in the Malaysia and one of the few facilities worldwide to have such facilities integrated not just for the imaging but also the radiation oncology unit that will allow seamless planning and treatment so that there is no time delay.