Deep- seated tumours
- Remain challenging to treat due to their proximity to important vascular structures and location around functional areas.
- Lesions within the insula, cingulate, and thalamus were previously considered inoperable due to the high risk of perioperative complications.
Insular lesions
- Insular tumours are among the most challenging neurosurgical lesions to manage.
- Tumour location and hemisphere of language dominance determines whether a transcortical or trans- Sylvian approach should be considered (Benet et al., 2015).
- Patients are positioned semi- lateral with the head parallel to the floor (Sanai et al., 2010).
- For tumours located predominately above or below the Sylvian fissure the vertex of the head is positioned 15 degrees towards the ceiling or floor (respectively).
- A craniotomy is tailored based on the tumour’s location and involvement of the overlying frontal or temporal opercula.
- Cortical and subcortical sensorimotor and language mapping may be utilized.
- Once functional areas have been identified transcortical windows superior and inferior to the Sylvian fissure are created through non- functional areas between insular arteries (‘cortical windows’).
- Surgical resection then continues as the vessels of the Sylvian fissure are skeletonized.
- The resection continues by working under the Sylvian fissure along the uncinate fasciculus.
- The supra- Sylvian lenticulostriate arteries must be identified and preserved and subcortical motor mapping of the corticospinal tract marks the medial border of the resection.
- Early identification of the long lenticulostriate perforating branches to the internal capsule and corona radiata and avoidance of excessive manipulation, which may induce vasospasm, minimizes ischaemic complications.
- The horizontal fibres of the superior longitudinal fasciculus are adjacent to the superior peri- insular sulcus while the uncinate fasciculus is adjacent to the inferior peri- insular sulcus.
- The IFOF at the level of the external capsule is identified by inducing semantic paraphasia through subcortical stimulations.
Cingulate lesions
- The cingulate gyrus covers the corpus callosum and is positioned immediately below the falx cerebri.
- The cingulate is subdivided into anterior and posterior regions and is covered by the callosomarginal artery, which runs along its medial surface.
- Due to their location deep within the interhemispheric fissure, tumours within the anterior and posterior cingulate gyrus are difficult to access surgically.
- Patients are positioned either supine or in a sitting position, for a unilateral or bilateral craniotomy according to the tumour location, size, vascularity, and pathology.
- Preoperative imaging should be carefully inspected for bridging veins, which may influence the surgical approach.
- The dura should be opened cautiously to avoid injury to the superior sagittal sinus or proximal draining veins.
- The surgical approach begins by creating a surgical corridor followed by tumour devascularization, and identification of the callosomarginal and pericallosal arteries.
- Approaches depends on surrounding functional areas, vascularity, tumour size and location (Talacchi et al., 2010)
- Interhemispheric approach
- Superior frontal gyrus resection
- Superior parietal lobule resection
Thalamic lesions
- Thalamic tumours are relatively rare representing 1– 5% of all brain tumours (Sai Kiran et al., 2013).
- While lesions in this location have historically been treated with stereotactic biopsy and radiotherapy alone, advanced structural imaging and microsurgical techniques have allowed for surgical resection with minimal postoperative morbidity.
- Surgical resection is reserved for contrast enhancing tumours with clear margins on preoperative imaging.
- Non- enhancing tumours with poorly defined margins should be managed with a biopsy.
- Surgical approach is based on
- Tumour location (anterior or posterior within the thalamus)
- If located anteriorly and presenting into the lateral ventricle especially if the ventricle is enlarged, a transcallosal approach is suitable but is limited by the lateral extension of larger lesions. Care is needed to avoid damage to the crus of the fornix overlying the thalamus or the choriodal fissure in cases where there is medial extension to the third ventricle.
- A posterior interhemispheric or infratentorial supracerebellar approach may be used to access those lesions located posteriorly in the pulvinar. Visual tract fibres are at risk as a number of these are closely associated with the pulvinar adjacent to the lateral geniculate body.
- Proximity to the posterior limb of the internal capsule.
- The majority of deep- seated intrinsic tumours cause anterolateral displacement of posterior limb of the internal capsule making the middle temporal gyrus corridor the common approach.
- After a temporal corticectomy the tumour is approached through the lateral ventricle along the posterolateral margin of the tumour. Upon reaching the temporal horn of the lateral ventricle the tumour is approached through the choroidal fissure.
- This approach ensures an entry corridor inferior to the insula and posterior to the internal capsule.
Postoperative surgical management
- In the immediate postoperative period, patients are observed closely in the setting of an intensive care unit, where serial neurological examinations are carried out
- Depending on the tumour location and extent of resection, corticosteroids may be tapered over the days following surgery.
- Anticonvulsants are continued in patients who have a history of seizures and for tumours in areas known to have a propensity to cause seizures.
- The longterm use of seizure medications for prophylaxis remains controversial.
- Post op MRI
- Given the prognostic significance of the extent of resection for glioma patients and the difficulty in detecting residual tumour during surgery, it is becoming standard practice for surgeons to obtain postoperative MRIs with enhancement to look for residual tumour within 24 hours of resection.
Complications
- Supra tentorial
- Neurologic complications
- 10 to 25%
- Deficits in
- Visual field
- Motor
- Sensory
- Cognitive
- Language deficits (Chang et al., 2005).
- Due to
- Injury of the functional cortical and subcortical pathways,
- Cerebral oedema
- Haematoma
- Vascular injury
- Risks increase with
- Older age,
- Deeper tumour location
- Tumour proximity to functional regions
- A low performance score
- Decrease complications via
- Individualizing the surgical approach planned based on anatomic and functional imaging,
- Cortical mapping techniques
- Minimizing excessive brain retraction
- Meticulous haemostasis
- Early identification of major vascular structures.
- Other post op complications
- Rates
- 1– 5%
- Types
- Surgical wound infections 1– 2%
- Bacterial contamination from the skin by Staphylococcus aureus or Staphylococcus epidermidis.
- Pneumocephalus
- CSF leaks
- HCP
- Seizure
- 0.5-5%
- Brain abscess/cerebritis/meningitis
- Pseudomeningocele
- Fq
- More readily in Elderly patients
- Re-operation
- Systemic medical complications 5– 10%
- Such as
- DVT
- 1– 10%
- Early postoperative mobilization, intermittent compression devices, and postoperative anticoagulation with low molecular weight heparin may decrease the incidence of postoperative DVT.
- PE
- Pneumonia
- UTI
- MI
- Sepsis
- Higher risk in
- Older
- Presence of neurological deficits
- Posterior fossa
- Higher rate of
- Pseudomeningocele
- CSF fistula
- HCP
- Wound infections
- Craniotomy for resection of intrinsic brain tumours can be performed safely and most complications can be prevented with careful preoperative planning, meticulous surgical technique, and attentive postoperative care.
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