CNS Flashcards
CNS Tumour types
PNET - Primitive neuroectodermal tumours
Pinealoblastoma - rare
Medullablastoma - most common childhood brain tumour
Characteristics of CNS tumours
Highly invasive
Spread rapidly through CSF
60% survival after 5 years
20% have spread to SC before diagnosis
Epidemiology - medullablastoma
20% of childhood brain tumours, more common in males than female
Medullablastoma signs and symptoms
Headache
Vomiting
Irritability
Problems with motor function
Glioblastoma signs and symptoms
Headaches
Seizures
Vomiting
Trouble speaking
Blurred vision
Clinical management of CNS tumours
Dependent of risk/staging
Surgery
Craniospinal irradiation
Adjuvant chemo
Fields
Usually 2-3 fields
Dependent on patient size
2 lateral for brain
1-2 post fields for spine
Junction considerations
The junction for lateral fields and posterior spine field should abut
To ensure this, collimator of lateral field is changed until the junction abutts
Overshoot
Ensure overshoot ant, sup and post
However, inferiorly, 0 jaw can be used by placing iso close to eyes
Spinal field boundaries
From C-spine to 2nd/4th Sacral foraminifera to include sacral nerve roots
Depending on spine length 1 or 2 isocentres may be requires
Spinal beams
2 fields adjoining to cover sup-inf
An anterior arc (1/4 arc) may also be required
Posterior fields are only 3/4 arcs
Brain/skull CNS VMAT technique
Usually 1-2 arcs
An extra arc using floor turn (non-coplanar) to achieve OAR tolerances
Patient positioning considerations
Chin position is crucial
Too tucked in (junction edge)/too extended (causes neck rolls)
Moving junction
Junction between the spinal fields are moved every 4-5 fractions to reduce hot/cold spots and create homogeneity
Can be moved 1cm inf or sup
ISOCENTRE
2-3 ISO
Ant-post and laterally in line
Junctions and gaps
Gaps are created between the two abutting junctions of spinal fields
The fields intersect in spinal cord
Advantages of prone positioning
Access to spine - palpation for setup
Skin marks for junctions
General accuracy
Advantages of supine
Development of new technologies
Paeds consideration - access to GA, feeling comfortable and secure
Prone positioning setup
Torso & legs elevated and supported
Styrofoam Board; and/or Vac Bag; other?
Cushion or bolster under ankles
Head supported with a comfortable face-rest
Prone pillow; mask; two-piece shell?
Arms by sides with shoulders supported and drawn inf
Minimise obscuring vertebrae on lateral films
C-Spine drawn horizontal
Ensure no skin folds on back of the neck
Posterior surface as level as possible with rest of back
Chin not tucked too far
Post spine field should not diverge into the mouth.
Supine positioning setup
Supine, straight and level
Ideally a Vac Bag for support and reproducibility
If no Vac-Bag, bolster under knees, +/- footstocks
Head and shoulders in mask
For reproducibility and field placement marks
Arms by sides with shoulders supported and drawn inf
Minimise obscuring vertebrae on lateral films
C-Spine as horizontal as possible
Try to maintain neck as level as possible with rest of back
Chin raised only to avoid exit from post spine field
Post spine field should not diverge into the mouth.
treatment side effects
Erythema, dry and moist desquamation and
oedema
Hair loss
20GY to 40Gy: Temporary hair loss
> 40Gy: Hair loss may be permanent
Drowsiness & lethargy
Decreased mental status/ cognitive impairment
Worsening of tumour symptoms
Cognitive impairment can include:
Decreased IQ
Decreased visual, spatial, motor, fine motor,
memory, and arithmetic skills
Increases in children < 7 yo
Patient Care
Assess patient well being: esp. emotional stability
Paediatrics
May need more time/ be patient
Prepare a separate area to talk
Patients can be aggressive
Must consider parent’s needs as well
Encourage patients to eat well and rest
Weekly blood tests
