Endoscopic SkullBase Surgery
Endoscopic SkullBase Surgery
Endoscopic skull base surgery
Endoscopic Skull Base Surgery is a form of minimally invasive surgery to correct different conditions affecting the skull base (the region between the brain and roof & back of the nose)
Fig.1.
Where is the skull base?
The skull base (Fig.1) is the bony surface under the brain.
There are number of structures lie below the skull base viz. nose & sinuses, eyes, ears etc. Major blood vessels taking blood to and from brain, nerves of the eye, ear and those controlling facial movement, swallowing & speech and spinal cord passes through number of natural foramina in the skull base. The central segment of skull base is related to nose, sinuses and nasopharynx.Which Types of Diseases Are Treated in Endoscopic Skull Base Surgery?
The skull base tumours or tumour-like conditions may arise from the skull base bone itself. Or it may arise from the brain, covering of the brain (dura) or from the nerves. Sometimes these may arise from extra cranial structures like nose & sinuses or eye and encroach on the skull base.
A variety of congenital, inflammatory lesions and tumours occur at the central skull base and these can be managed endoscopically.
Fig.2. Various tumour or tumour-like conditions arise in central skull base
- CSF leaks (rhinorrhoea)
- Meningoencephalocoele (herniation of brain inside nose & sinuses)
- Benign & malignant tumours of ethmoid
- Juvenile nasopharyngeal angiofibroma
- Pituitary adenoma
- Craniopharyngioma
- Meningioma
- Esthesioneuroblastoma
- Clival chordoma
- Petrous apex lesions
- Osteomyelitis of skull base
- Recurrent nasopharyngeal carcinoma
What type of symptoms do patients with the Central skull base tumours have?
The skull base tumours are rare and usually cause few symptoms until they grow to a size where they begin to affect neurologic function. These symptoms may manifest as loss of smell & sight, double vision, nose bleeds, facial pain, hearing loss, or hormonal disturbances.
How is a skull base tumour diagnosed?
These symptoms most often come on gradually and are diagnosed by an ENT specialist and/or neurosurgeon using a CT scan and MRI. Specialized tests such as hearing tests, visual field testing, or arterial studies may also be performed. For very vascular tumours, an angiogram with embolization may be performed prior to surgical resection in order to plug the arteries that feed the tumour. This reduces blood loss during surgery.
What are the disadvantages of Traditional Open Skull Base Surgery?
Tumours of the skull base are underneath the brain and it can be difficult to reach the tumour during surgery. In traditional techniques, neurosurgeon does a craniotomy (open the skull) at a suitable site and significant force is used to retract the patient’s brain out of the way. This may lead to unwanted injury to otherwise normal brain tissue. This neurovascular injury can lead to loss of consciousness and seizure. Tumour is accessed from below by making facial skin incisions (cuts) (Fig.3).
Fig.4 Endoscopic Skull Base Surgery
What is Endoscopic Skull Base Surgery?
Endoscopes have revolutionized sinus surgery. Better illumination and magnification has helped in improving sinus surgery results. It is only a natural progression of science to go beyond the sinuses to treat the conditions at the skull base by working with the neurosurgeons. It is accurate to call these approaches as maximally invasive with minimal access, because the ultimate goal is to perform a resection as aggressively as with an open approach.
Visualization provided by the rigid straight and angled endoscopes can illuminate areas of the skull base that were previously unreachable with standard microscope-based transsphenoidal or transoral approaches. The panoramic view allows visualization, even around corners.
In endoscopic skull base surgery, the skull base bone, the only structure that is present between the sinus and the tumour is removed. It is nothing but a craniotomy through the nose. Then the tumour is removed without touching the adjacent brain. After removal of the tumour, the defect in the skull base is reconstructed using vascularized pedicled mucosal flap.
Sphenoid sinus is the epicenter of the endoscopic skull base surgery. The anterior cranium can be accessed through removal of the cribriform plate – this is called the transcribriform approach. The middle fossa can be approached through either the transplanum or transsellar routes. The posterior fossa through the transclival method. Lateral recess of sphenoid and infratemporal fossa can be accessed through transpterygoid approach. The same approach is used for nasopharyngectomy also.
What are the advantages of Endoscopic Skull Base Surgery?
- The surgery is done through the nostrils without making any skin incision and therefore facial scar is avoided.
- It does not cut through facial bones and therefore it does not affect the facial growth in children.
- The telescope coupled with high definition digital camera gives a clear and magnified view of the operation site.
- Brain is not retracted to expose the area of tumour and this avoids the problems associated with brain retraction in open skull base surgery.
- Malignant tumours of ethmoid sinus and nasopharynx, in early stages, can be resected endoscopically through the nose without opening the skull VIDEO.
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Fig 5 .Neuronavigation
What Technologies Are Used During Skull Base Surgery to make it safer?
The skull base is a complex anatomical region packed with very important nerves and blood vessels. There are normal landmarks surgeon use to identify these structures. But the normal anatomy of the skull base region is distorted by the tumour. In this scenario, it is very difficult for the surgeon to know the location of these neurovascular structures during the surgery.
Since these structures are at risk of injury, the surgeon becomes less aggressive and may leave behind some of the tumour. Similar to a car or mobile Global Positioning System (GPS), the computer assisted surgical navigation system uses cameras or electromagnetic fields to give the surgeon (based on the patient’s CT & MRI) a three dimensional perception as to where he is operating with respect to the tumour as well as to the adjacent neurovascular structures. Using a probe referenced to the patient on the operating table, the surgeon can pinpoint the location of the tumour and verify exactly where each vital structure is in relation to the tumour (Fig.3)These devices allow the surgeon more accuracy and safety in removing disease. This not only improves tumour clearance but also helps to reduce the morbidity.
Other equipment used is endoscopic Doppler to know the position of the internal carotid artery.