Brain and CNS

Question 1

Brain

Answer 1

Acute 2Gy:
Encephalitis (hypothalamus) (inflammation of the brain) causes swelling of the head, nausea, vomiting, and headaches
Treatments: paracetamol, ibuprofen, and dexamethasone (for swelling), nausea treated with strong antiemetics such as ondansetron, fatigue light exercise

Chronic: memory impairment, somnolence (drowsiness), headache, seizures, cognitive problems

QUANTEC: A maximum radiation dose of less than 60Gy within the brain creates a less than 3% chance of symptomatic necrosis (occurs months to years post-treatment), for which there is no cure.
Symptoms include headaches, fatigue, nausea, imbalance, extremity weakness, seizures, and speech deficits

Endpoint: Necrosis and infarction (obstruction of blood supply to tissue) occurs months to years post-treatment, for which there is no treatment

Question 2

Brain Stem

Answer 2

QUANTEC: a maximum radiation dose of less than 54Gy within the whole organ creates a less than 5% chance of endpoint reaction occurring.

Endpoint: neuropathy or necrosis can occur months to years post-treatment, for which there is no cure

Question 3

Optic Nerve

Answer 3

QUANTEC: A maximum radiation dose of less than 55Gy within the organ creates a less than 3% chance of the endpoint reaction.

Endpoint: Optic neuropathy leading to blindness in associated eye months to year post-treatment, for which there is no cure

Question 4

Optic Chiasm

Answer 4

QUANTEC: a maximum radiation dose of less than 55Gy within the whole organs creates a less than 3% chance of endpoint reaction occurring

Endpoint: optic neuropathy leading to blindness in both eyes occurring months to years post-treatment, for which there is no cure

Question 5

Pituitary

Answer 5

46Gy to the whole structure, normal function becomes suppressed, hormone replacement therapy

Question 6

Spinal Cord

Answer 6

Acute/Chronic: Lhermitte’s syndrome, an electrical sensation running down back to limbs, occurs at 35Gy, usually seen post-treatment

QUANTEC: A maximum radiation dose of 50Gy to the partial organs creates a less than 0.2% chance of the endpoint reaction

Endpoint: radiation-induced myelitis necrosis leading to paralysis, incontinence, and possibly death (c-spine), for which there is no treatment

Question 7

Larynx

Answer 7

Acute:
Laryngitis (swelling)
Dysphagia (breathing) and dysphonia (speaking)
45Gy causes laryngeal oedema (inflammation) and changes in voice quality, which can become permanent at 60Gy

Treatments: Gargle aspirin, lignocaine viscous gel, soft foods, Ensure Plus for weight loss, nasogastric tube, peg tube

QUANTEC: a dose of less than 66Gy within the organ causes a less than 20% chance of vocal dysfunction months post-treatment

Endpoint: chronic laryngitis and necrosis at 70Gy causes cartilage necrosis months to years post-treatment due to vascular damage

Treatments: pain medication, surgical intervention, speech therapy

Question 8

Parotid Gland

Answer 8

Acute: temporary xerostomia (dryness) and increases risk of tooth decay and gum disease 10-20Gy

QUANTEC: for uni/bilateral parotid glands: a whole/both parotid glands receiving a mean dose of less than 20/25Gy creates a less than 20% chance of long term reduced salivary function by 25%

Question 9

Mucosa (lips, mouth, and pharynx)

Answer 9

Acute:
mucositis and stomatitis 20Gy: gargle aspirin and avoid drinking, smoking, and spicy foods
yeast infection and ulceration 30Gy: nystatin

Chronic: mucosal atrophy, ulceration, and telangiectasia

Endpoint: fibrosis (excess fibrous tissue) and necrosis from 60Gy years post-treatment

Question 10

Thyroid Gland

Answer 10

30Gy: side effects of functional problems, hormone replacement therapy

Question 11

Mandible

Answer 11

40-50Gy: radiation-induced osteoradionecrosis resulting in pathological fracture due to impaired vascularization and trauma, years to decades post-treatment. Bone graft.

Question 12

Eye lens

Answer 12

4Gy: cataracts (years post-treatment), surgical removal

Question 13

Retina

Answer 13

45Gy: endpoint: retinopathy leading to blindness weeks to months post-treatment for which there is no treatment

Question 14

Facial Muscles (Pterygoid muscle)

Answer 14

TD 5/5 60Gy
Endpoint: trismus (muscle spasms)
Treatment: muscle relaxant

Question 15

Lacrimal Gland

Answer 15

30Gy
Endpoint: loss of tears leading to dry eyes and ulceration, occurring weeks to months post-treatment
Treatment: lubricating eye-drops

Question 16

External and Middle Ear

Answer 16

Acute 30Gy : acute serous otitis (fluid build-up in the middle ear) and tinnitus (ringing)
Treatment: anti-inflammatory ear drops and pain relief

Endpoint: 45Gy chronic serous otitis and tinnitus months to years post-treatment
Treatment: anti-inflammatory ear drops and pain relief