Complications of cranial radiation therapy are fairly common, particularly in long-term survivors, and especially in paediatric patients.

Cranial radiation therapy is used for a variety of brain tumours, either in isolation or in combination with concurrent chemotherapy. Complications from irradiation are various and differ in their aetiology and time at which they become apparent. They can best be divided according to when they occur into acute, early-delayed and late ⁴. 

Acute

Acute toxicity from cranial irradiation occurs within days or at most first few weeks of therapy. Although they are relatively common, particularly seen in whole brain irradiation, they are usually relatively well-controlled or self-limiting. Symptoms and signs include ⁴: 

• fatigue

• nausea and vomiting

• loss of appetite

• cerebral oedema

Radiation-induced alopecia and dermatitis are also sometimes encountered ⁴. 

In the earlier days of cranial radiation therapy, where doses were poorly fractionated (e.g. individual doses of 10 Gy of gamma radiation) acute radiation-induced toxicity was frequent, occurring within mere hours of treatment, and resulting in fulminant symptoms and not infrequent death ⁴. 

Early-delayed

Early-delayed toxicity, also sometimes referred to as 'subacute', occurs within weeks to 3 months of treatment. Many of the symptoms are similar to acute toxicity with headaches, fatigue, irritability, anorexia, nausea, and vomiting most frequently encountered. Somnolence may be particularly prominent, especially in children ⁴. 

It is during this early-delayed phase that pseudoprogression typically is encountered (although it can present later than this, even within 6-9 months) and represents florid treatment effect, oedema and contrast enhancement. 

Late

Late toxicity occurs any time after 90 days of commencement of radiation therapy. It has a far greater variety of complications, and many of them are irreversible and severe. 

Cognitive dysfunction has been extensively studied and recognised to be very prevalent in patients receiving whole brain radiation therapy. It can be seen fairly early in the late phase (within 4-6 months) but is sometimes not encountered until decades later ⁴. 

Other late sequelae can be divided into a number of groups: 

• white matter

  • treatment-induced leukoencephalopathy

  • coagulative necrotic leukoencephalopathy

• radiation induced vasculopathy

  • radiation-induced microhaemorrhages

  • radiation-induced moyamoya pattern

  • mineralising microangiopathy

  • radiation-induced cavernous malformations (cavernomas)

  • radiation-induced capillary telangiectasias

• radiation-induced intracranial neoplasms

  • radiation-induced meningioma 

  • radiation-induced glioma

  • radiation-induced sarcomas