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A Brain Tumor Education Resource*
DERMOID TUMOUR / DERMOID CYST:
Petroclival tumour - a "ruptured dermoid" (above collage): A dermoid is a rare type of tumor, often referred to as a "dermoid cyst". A dermoid is classified as an "inclusion cyst", i.e., from a problem during the development of the central nervous system where certain skin structures get incorporated into the nervous system. It is not cancerous and can be removed (i.e., is a "curable" condition). This young patient presented with new headache and disturbance of sensation along one side of the body. Upper-left panel: MRI shows part of the tumour (red circle). Note the close proximity of the tumour to the upper brainstem around which the tumour wraps (red arrow head). Upper-centre panel: MRI shows some interesting parts of the tumour (red circle). It projects a tongue that wraps around one side of the brainstem (green arrow) and displaces and compresses the brainstem here. Delicate nerves for eye movement (cranial nerves 3 and 4) pass in this compressed corridor, as do critical blood vessels such as the posterior cerebral artery, none of which can be injured during removal of the mass. Upper-right panel: Intraoperative image shows the soft, white cheese-like tumour (blue arrow head) exposed and being aspirated. Surgery was carried out through a "modified pterional transSylvian and medial subtemporal" surgical approach. Lower-left panel is an intraoperative photograph that shows part of the tumour cavity following removal of tumour from around the brainstem. In this region the tiny "whisp-like" perforatong arteries that nourish the brainstem are preserved (blue arrow heads). Lower-centre panel is a postoperative MRI scan showing complete removal of the tumour. The tumour was previously located in the area encompassed by the red dotted circle. The brainstem portion of the tumour (red arrow head) is also no longer present as intended. Lower-right panel is another postoperative MRI scan of this patient showing no residual tumour. Some blood products and haemostatic fabric are present as expected in the cavity of the medial temporal lobe from which an additional knuckle of tumour was also extracted. The man has no neurological impairment and returned to his University studies.
EPIDERMOID TUMOUR / EPIDERMOID CYST:
Posterior fossa tumor - An "epidermoid" (above collage): An epidermoid is a rare type of tumor, often referred to as an "epidermoid cyst". An epidermoid, like a "dermoid", is also classified as an "inclusion cyst", i.e., from a problem during the development of the central nervous system where certain skin structures get incorporated into the nervous system. This type of tumor contains the skin product "keratin", and in this particular location (i.e., along the brainstem) is prone to reaccumulation even after microsurgical evacuation. However, it is not cancerous. This patient presented with dysfunction of swallowing, sensation, and hearing. Upper-left panel: MRI shows part of the tumor (red arrow heads) along the lower part of the brainstem (B). Upper-right panel: The tumor has a thin, pearly-white capsule with a shiny lustre. The capsule in this location is very adherent to the critical small blood vessels and nerves around the brainstem. Lower-left panel: The tumour itself (part of it shown in red dotted circle) has a cheesy consistency. Lower-right panel: The tumour has been debulked from the region by carefully working around the local neurovascular structures. Some cranial nerves (5 - trigeminal; 7 - facial; 8 - vestibulocochlear) can been seen here. It is expected that patients with epidermoids located along the brainstem can re-present in the future with reaccumulation of the "cyst's" keratin content.
PITUITARY TUMOUR / PITUITARY ADENOMA:
Pituitary macroadenoma (above collage): The pituitary gland is the brain's master hormone-secreting gland and it is located just under the "optic apparatus", i.e., the nerves for vision. Pituitary tumors can present with with hormonal changes (e.g., gigantism or progressively thickening soft tissues - acromegaly - from excess growth hormone secretion; or premature milk expression and irregular periods from excessive prolactin secretion; or Cushing's disease from excess cortisol secretion) and/or impaired vision (tunnel vision or "bitemporal hemianopia"). When pituitary tumours become very large, they can outgrow their blood supply and bleed into themselves. This is referred to as pituitary apoplexy and is often associated with sudden severe headache and loss of visual field (sudden tunnel vision). Top left image: This patient presented with visual field loss over a few months. The tumor appears as the hour-glass shaped white mass in this MRI coronal image. It has bled (the blood pocket is the grey hat between the yellow arrow heads). The optic nerves (yellow arrow heads) are displaced to the sides by the tumour mass. The internal carotid arteries are seen as shadows here (red arrow heads). Top right image: This is another patient's pituitary tumour which is bowing the optic nerves/optic chiasm upwards (yellow arrow heads) resulting in diminished visual field. The carotid artery on each side is shown by the red arrow head. The approach to such tumours is through the nostril (transnasal) and into the air space (sphenoid air sinus; purple arrow) that lies under where the pituitary gland is housed. This is a trans-sphenoidal approach. Note how the space is located close to the internal carotid arteries (red arrow heads). Neuronavigation (GPS for the brain) can be used to map out a precise trajectory to the tumour target, thereby avoiding surrounding critical structures. These operations can be carried out in conjunction with an ENT surgeon. Bottom left image: The pituitary tumour (red circle) is now on view through a speculum carefully inserted along the patient's nostril and magnified by the operating microscope. A suction (grey-white arrow) and a loop-curette (blue arrow) are used to gradually remove the tumour. Bottom right image: After the removal of the tumour, the optic apparatus (yellow arrow heads) is now well decompressed and clearly visible again. The internal carotid arteries (red arrow heads) are not disturbed and the pituitary gland's stalk is now seen (blue arrow) and intact as expected. Some of the patient's own fat can be left in the sphenoid air space as a packing if needed. Patients with recent visual field impairment before surgery typically experience a recovery in this function within hours to days after surgery.
CHOROID PLEXUS PAPILLOMA:
Fourth ventricular tumour - a "choroid plexus papilloma" (above collage). The tumor arises from "choroidal epithelial cells" which make up the "choroid plexus". The choroid plexus, located in the central cavities of the brain called ventricles, is a structure responsible for making the cerebrospinal fluid (CSF) circulating in and around the brain and spinal cord. A CPP is not cancerous but can send secondary "seeds" throughout the CSF to multiple locations in the central nervous system. This young patient presented with long-standing nausea and vomiting, gradually worsening vision, new-onset uncontrolled hiccups, and impaired ability to walk. Upper-left panel: MRI shows a large solid tumour (red circle) located in the fourth ventricle (a fluid cavity of the brain). Upper-centre panel: MRI shows part of the tumour (white ovoid structure to the right of the arrow). It appears to be firmly adherent to and compressing the floor of the fourth ventricle (green arrow; where critical nerve structures lie - including those subserving facial expression, eye and tongue movement, nausea/vomiting, hearing and balance, and cardiorespiratory control). The dark area to the right of the tumour is a fluid cyst. Upper-right panel: Intraoperative image shows the exposed solid tumour being debulked using a "precision-tip" ultrasonic aspirator (blue arrow head). Lower-left panel is an intraoperative photograph that shows the tumour very adherent to the floor of the fourth ventricle in the region of the human nausea/vomiting centre (obex/area postrema), requiring meticulous dissection using a very fine pair of "microscissors" in order to preserve the local brainstem critical fiber tracts and nuclei. Lower-centre panel is a postoperative MRI scan showing complete removal of the tumor (previously in the area marked by the red circle). Lower-right panel is another postoperative MRI scan of this patient showing that the previously compressed and displaced brainstem region now lies preserved and free of any tumour. The fluid cyst to the right of the tumour is now collapsed as desired. The patient made an excellent postoperative recovery and was independent and ambulating well within 72 hours of surgery.
COLLOID CYST:
Colloid cyst (above collage): Patients with colloid cysts can present with progressive headaches (obstructive hydrocephalus), blackout spells (intermittent mechanical obstruction or "ball-valve" effect), or sudden death (in 5-10%). Top left image: The MRI coronal image shows a 10 mm colloid cyst (red circle) causing obstruction of the flow of cerebrospinal fluid (CSF) in the fluid-filled inner chambers of the brain called "ventricles". This is hydrocephalus, as seen by the asymmetrical expansion of one of these fluid chambers (green arrows; lateral ventricle). Top right image: An interhemispheric transcallosal approach or a transfrontocortical approach can be used to microsurgically access the ventricle and visualise the colloid cyst (green arrows). A key anatomical structure known as the "fornix" serving the functions of memory and learning is seen here (yellow arrow heads), as are veins of this region (red arrow heads). Such structures are vital and should not be disturbed during this very delicate operation. Bottom right image: The patient's one-cm colloid cyst (green arrows) has been removed without any neurological impairment.
TRIGEMINAL NEURALGIA & HEMIFACIAL SPASM / MICROVASCULAR DECOMPRESSION (MVD):
Microvascular decompression of the fifth cranial nerve (above collage): Such patients present with severe, frequent sharp-lancinating pain (trigeminal neuralgia) often for several months or years. They have typically tried a variety of oral medications and/or other more invasive interventions with little or no relief. The trigeminal (fifth) nerve can be compressed and irritated by blood vessels (an isolated/single vessel loop of the superior cerebellar artery, or tangles of vessels from a nearby arteriovenous malformation/AVM) and by local tumors. Top left image: The axial MRI scan shows the origin or "root entry zone (REZ)" of the trigeminal nerve (green arrow) being compressed by a blood vessel (red arrow head). P=brainstem "pons" region. Top right image: The compressive blood vessel (red arrow head), in this case from a local AVM, has now been microsurgically dissected and physically separated from the trigeminal nerve origin (yellow arrow head), creating a space between these two structures. By creating this physical separation, the pulsatile/pounding effect of the blood vessel on the trigeminal nerve's origin is significantly diminished, thereby helping to decrease the abnormal "ephaptic" transmission associated with the pain of trigeminal neuralgia ("tic delaroux"). Bottom left image: The ephaptic transmission can be further diminished by gently massaging the relevant nerve root (red circle) in the tips of the bipolar forceps. Bottom right image: At the conclusion of the operation, a tuft of Teflon microfibres (green arrow) has been placed between the offending blood vessel (red arrow head) and the nerve root (yellow arrow head) to keep this space physically "buffered". This patient's symptoms completely resolved after this procedure. A similar technique can be used for patients with hemifacial spasm (persistent facial muscle spasms; microvascular decompression of the seventh cranial nerve) and glossopharyngeal neuralgia (bouts of lancinating pain on swallowing; microvascular decompression of the ninth cranial nerve).
CRANIOPLASTY / SKULL RECONSTRUCTION:
Cranioplasty (above collage) or surgical reconstruction of the skull: Some patients present with skull trauma (physical assault, motor vehicle accident, sporting injury) or with tumours or infections involving skull bones. Such patients may need reconstruction of the skull, and this can be effectively carried out with titanium or a polymer "bone cement" such as methylmethacrylate. Excellent structural and cosmetic results can be achieved with both of these. Top left image: A titanium microplate (blue arrow) has been affixed to a defect in this patient's skull bone via small titanium screws (yellow arrow heads). Top right image: In another patient, a robust acrylic polymer (methyl methacrylate), also referred to as "bone cement", has been carefully moulded to the patient's skull contour and used to replace a larger defect in the patient's skull. Bottom left image: For another patient, a strong titanium plate has been constructed using special computer-CAT scan mapping to exactly fit the patient's skull defect. Bottom right image: The plate has now been screwed into the surrounding skull bone of the patient, and the scalp is then closed over this new strong, cosmetically sound area.
FOR MODULES 1 & 2 (via the Brain Tumor Resource Index): Click here
Modules 1 & 2 include a clinical overview of brain tumors, and specific tumor categories such as glioma (e.g., astrocytoma, GBM/glioblastoma, ependymoma, oligodendroglioma), meningioma, metastasis and Schwannoma
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