Although not as aggressive as some specialists,
neurosurgeons have been actively engaged in the development of endoscopic applications for the central nervous system. L2 Espinasse first described use of endoscope in the central nervous system. Dandy reported performing endoscopic choroid plexotomy for hydrocephalus using cystoscope in 1932. Gradually since then the scope of neuroendoscopy increased to include many indications. Fukushima reported using flexible endoscope to biopsy tumours in 1978.1 Many surgeons reported excision of colloid cysts, cystic craniopharyngiomas and fenestration of cysts in the next few years. Although the use of endoscope to diagnose and treat various central nervous system conditions has been well recognized for years, the story of modern neuroendoscopy is just beginning.
The equipment for neuroendoscopy includes rigid and/or flexible endoscopes, light sources, cameras, video monitors, special instruments, cautery and lasers. The advances in optics and instrumentation have increased the scope and reach of neuroendoscopy. Neuroendoscopic accessories have been developed as follows: a biopsy-grasping forceps to perform biopsy for histological diagnosis, needle to punch and aspirate without contamination, various balloon catheter for opening of the membrane and/or enlargement of a stoma, the contact Nd:YAG laser endoprobe for coagulation and vapourization, and CUSA for endoscope and for aspiration of the tumour and blood clot. All these instruments are sterilized in ethylene oxide gas at a temperature of 50°C for 12 hours.
The indications of neuroendoscopy can be divided into intraventricular surgery and neuro-oncology.
- Endoscopy in Hydrocephalus: Currently, the most common use of endoscopes in neurosurgery is for the treatment of certain forms of hydrocephalus. Hydrocephalus is caused by either a blockage in the normal pathway of cerebrospinal fluid or by an inability to absorb the fluid. Either case results in increased pressure on the brain and can lead to neurological impairment and death. Most cases of hydrocephalus are treated by shunt procedures but in selected cases endoscopic third ventriclulostomy is a good alternative. Aqueductal stenoses, both congenital and acquired are good indications for endoscopic third ventriclulostomy (Fig. 1).
Endoscopy may also be useful in treating complex cases of hydrocephalus which require multiple shunts. Infection and bleeding may cause scarring in the ventricular system which can form small compartments of CSF which are not in communication. It is conventionally treated by placing a separate shunt in each compartment. However, this increases the risk of infection and malfunction of the shunt. Alternatively, endoscopic procedures can be used to communicate the different compartments so that only one shunt is needed.
- Biopsy and/or excision of intraventricular lesions such as colloid cysts, ependymomas, cysticercosis etc.
Fig. 1 : Schematic diagram of the effect of performing an endoscopic third ventriculostomy on the circuit diagram of cerebrospinal fluid flow.
Endoscopy in Neuro-Oncology
Cranial surgery is a constant struggle against poor visualisation. Any tool that improves visualization, thereby offering patients a better surgical outcome, should be embraced by the neurosurgeon. Endoscopy enhances the view of the surgeon by increasing illumination and magnification. Small tumour remnants can be resected and a more complete resection can be achieved. Often a smaller exposure may suffice, in keeping with the concept of minimally invasive yet maximally effective surgery.
- Ventriculoscopy – The prognosis of some intracranial tumours is dependent on the presence or absence of ependymal spread. Ventriculoscopy can be more sensitive than MRI with a little added morbidity.
- Management of secondary hydrocephalus – Endoscopic third ventriclulostomy can be used for CSF diversion before the tumour causing hydrocephalus is tackled. The patient can be assessed properly and proper CSF dynamics established before attempting tumour removal.
- Endoscopic tumour biopsy – Tumours in the ventricle or presenting to the ventricular surface can be endoscopically biopsied. These include colloid cysts, subependymal giant cell astrocytomas, tectal gliomas, central neurocytomas and choroids plexus tumours.
- Endoscopic intraventricular tumour resection – Tumours with moderate to low vascularity, small size, soft consistency may be amenable to endoscopic resection. Colloid cysts are most appropriate for this technique.
- Endoscope-assisted microsurgery – With endoscopy previously inaccessible areas located in the skull base or within narrow cavities can be seen well. These techniques are particularly applicable to a wide range of sellar tumours, clival chordomas, brainstem related tumours etc.2
Endoscopic Spinal Surgery – Through a minimally invasive approach, lumbar and cervical discectomy can be done as day care surgery with good results, minimal morbidity and early return to work.
Postoperative course after neuroendoscopy
Intracranial pressure remains elevated for 24 to 48 hours after endoscopic third ventriculostomy, hence adequate monitoring of neurological status is essential. A good watch for occasional complications like ventriculitis, CSF leak and subdural collections should be kept. The monitoring is like in any conventional neurosurgical procedure.
Neuro-endoscopy versus other alternative procedures
As we all know shunt surgery for CSF diversion is fraught with many complications like shunt infection, shunt blockage, shunt dependence, under-drainage, over-drainage etc. These may necessitate many unwanted investigations and interventions. The morbidity and mortality associated with shunt revisions is a high price to pay for the treatment of hydrocephalus. The added cost to healthcare is another argument against shunt procedures. It will be foolhardy to think that all hydrocephalus can be managed by endoscopic third ventriculostomy but with the right choice of patients it can be the answer for many. With right selection of patients 60-70 % of adult hydrocephalus patients could be shunt-free. The avoidance of a permanent foreign body is in itself a good indication to use endoscopic third ventriculostomy. At the initial diagnosis of hydrocephalus, the patient and his family should be informed of this potential alternative to shunting. Every shunted patient with shunt failure should also be considered potential candidates for endoscopic third ventriculostomy.
Neuro-oncological use of endoscopy has changed quite a few things in neurosurgery. Improved visualisation of deep skull base tumours has led to more complete excisions and better outcomes. Prognosis is related to degree of resection in most intracranial lesions, therefore neuroendoscopy is the next logical step for surpassing the limitations of traditional microsurgery. Critical neural and vascular structures are safeguarded with more ease and patient’s quality of life can be protected.
As experience with endoscopy grows, it will be performed by increasing number of neurosurgeons. Appropriate training and experience are important for the success of the procedure and for complication avoidance. In the last two years we have carried out over 30 cases of endoscopic third ventriculostomy. In addition we have resected intraventricular lesions and treated compartmental hydrocephalus. It is an extremely rewarding experience to make a patient shunt free and this is achieved in 70 % of adults and 50 % of children. In a developing country like India, the costs of hydrocephalus management can be reduced dramatically with endoscopy.
- Fukushima T. Endoscopic Biopsy of intraventricular tumors with the use of ventriculofiberscope. Neurosurgery 1978; 2 (2) : 110-3.
- Abdullah J, Caemart J. Endoscopic management of craniopharyngioma: A review of 3 cases. Minim Invasive Neurosurg 1995; 38 : 79-84.
- Perneczky A, Tshabitscher M, Resch K: Endoscopic Anatomy for Neurosurgery, xii-xv, Thieme, 1993.