Surgery Intraventricular Approaches
Intraventricular approaches provide access to the craniopharyngioma via the ventricles, which are predominantly accessed through the transcallosal–transventricular approach and the transcortical– transventricular approach.
The transcallosal–transventricular approach permits access through the lateral ventricle and the foramen of Monroe through an incision in the corpus callosum. In cases where the foramen of Monroe is dilated by a tumour projecting into the lateral ventricle, this approach permits a corridor through which portions of tumour in the third ventricle can be removed.7
Retraction of the frontal lobe
risks retraction injury, and care must also be taken to avoid damage to the pericallosal arteries, the fornix, the anterior commissure, the choroid plexus, the choroidal arteries and the veins of the wall and floor of the third ventricle.11
The transcortical–transventricular approach provides an alternative approach for access to the third ventricle, especially in patients with enlarged lateral ventricles. It lowers the risk to the essential draining vein of the sagittal sinus and to the pericallosal arteries, but also risks injury to the fornix, thalamus and deep venous structures. The transcortical–transventricular approach also increases the risk of post-operative seizures by exposing the cortex to potential injury. This approach has been reserved for cases with large ventricles and tumour extending to the dorsal surface of the frontal lobe.6,13
Translamina Terminalis
The translamina terminalis approach provides another option to access the third ventricle. It entails opening the lamina terminalis, which is a soft, thin white-matter structure located in the anterior ventricular wall and bound by the optic tracts medially, by the posterior edge of the optic chiasm anteriorly, and by the anterior commissure posteriorly. A pterional or a subfrontal approach can be used to access the lamina terminalis; however, a pterional approach may be more appropriate as the tumour may force the chiasm toward the tuberculum sellae, effectively making it pre-fixed and less amenable to a subfrontal approach.27
Combined Approaches
In some cases, a combination of the above approaches may be employed. The subtemporal–transpetrosal approach can be used for primarily retrochiasmatic unilateral tumours that extend to the posterior fossa along the clivus.26
The pterional–transcallosal
approach can aid removal of adherent and calcified tumour within the third ventricle. The trans-sphenoidal and transcallosal approaches have also been combined with the pterional approach to allow resection of large craniopharyngiomas. When the transcallosal approach is combined with the pterional approach, intraventricular portions of the tumour should be removed first, with the pterional approach only being performed if basal portions of the tumour remain inaccessible.7
The subfrontal–pterional
approach has been utilised to remove lateral parts of tumour within the Sylvian fissure.6
Endoscopy
Approaches to the skull base have traditionally been performed via transfacial, transcranial or combined open cranial approaches. Recently, endoscopic approaches to the skull base have been
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developed and offer a less invasive alternative to open procedures. Whereas traditional microscope-based techniques are used in the transphenoidal approach, endoscopic approaches use rigid and angled endoscopes that allow for up to 360º visualisation of the skull base without the need for magnification. Furthermore, endoscopic techniques reduce the need for significant brain retraction and the cosmetic deficit associated with open techniques. Depending on the anatomy, different endoscopic approaches have been described utilising various endoscopic corridors (e.g. transnasal, trans-sphenoidal, transethmoidal and transmaxillary).28,29
When applied appropriately, endoscopic
techniques can achieve high rates of GTR in skull base tumours. Schwartz et al. described a gross total resection rate of 84% in patients with pituitary tumours for whom GTR was the surgical goal. With regard to patients with craniopharyngiomas, this group reported a GTR rate of 100%.28
Careful patient selection is an essential component of skull base endoscopy. Not all tumours and locations are amenable to this therapeutic strategy. Some general guidelines are that this approach is not appropriate when the lateral extent of the tumour passes more than 1cm beyond the lateral limits of the exposure or when the epicentre of the tumour does not lie within the midline.
Furthermore, surgeons must be aware of and realistic about their surgical abilities; for example, although tumour encasing blood vessels is not an absolute contraindication to the endonasal endoscopic approach, pistol grip rather than bayoneted instruments and lack of stereoscopic vision increase the difficulty of dissecting small arteries from the tumour as opposed to the more traditional microscope-guided trans-sphenoidal approach. However, when utilised by a skilled surgeon, endonasal endoscopic approaches have tremendous utility in craniopharyngioma resection, particularly when STR is preferred to GTR and in cases of grade I and II craniopharyngiomas.
Radiation Therapy
Several alternative therapies can be considered when GTR is not a possibility. Adjuvant radiotherapy may follow STR and be administered via conventional RT, intracavitary radiation or fractionated radiotherapy and as stereotactic radiosurgery.30
Although radiotherapy is generally performed as an adjuvant treatment for craniopharyngiomas, there are examples of it being used as a primary treatment modality. Gopalan et al.31
performed a
The mean morbidity rate after GKS was 4%, with a mortality rate of 5% seen in only one study (0.05% overall mortality rate across all studies reviewed). Favourable quality of life outcome was associated with tumours that decreased in size following GKS, while poor outcomes were associated with tumour progression.
meta-analysis of 10 studies to examine the utility, morbidity and mortality of gamma knife surgery (GKS) in craniopharyngioma treatment. Overall tumour control rates were excellent, with single- type tumours demonstrating better control rates than mixed-type tumours.32
GKS involves the delivery of a single high-dose fraction of radiation to a precise target determined by stereotactic neuroimaging-based planning. The precision of targeting and the steep dose fall-off allows for relative sparing of surrounding structures such as the hypothalamus and the visual pathways. A limitation to the use
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