This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Head and neck, Subject name: Surgery
Long term effect of craniospinal irradiation for medulloblastoma is : 
Select and explain. 
A. Secondary malignancy, B. Neuro endocrine abnormalities, C. Neurocognitive effects, D. Hearing loss
C: Neurocognitive effects
Answer: C: Neurocognitive effects 
Explanation: Craniospinal Irradiation Hypothyroidism: One of the earliest late side effects of CSI and 2nd MC (after GH disturbance) Prevelence of hypothyroidism is 40-80% after CSI Significantly increased risk of development of benign thyroid nodules and papillary carcinoma of the thyroid many years later Ref: www.ncbi.nlm.gov/pubmed/9121399