**Core Concept**
Medulloblastoma is a malignant brain tumor commonly occurring in children, often presenting with symptoms like increased intracranial pressure, hydrocephalus, and malnourishment. The primary treatment modality involves a combination of surgery, chemotherapy, and radiation therapy.

**Why the Correct Answer is Right**
The correct answer, **D. Radiotherapy 35-40 Gy was given to the whole craniospinal axis**, is incorrect in this context. Radiation therapy to the whole craniospinal axis is typically reserved for patients with medulloblastoma who have evidence of metastatic disease or have a high risk of dissemination. In the case of a 1.5-year-old patient with a localized medulloblastoma, such extensive radiation would be considered excessive and potentially detrimental to the child's development.

**Why Each Wrong Option is Incorrect**
**Option A:** Craniotomy and subtotal excision of the tumor are often the initial surgical steps in treating medulloblastoma, aiming to relieve pressure and remove as much tumor as possible while preserving surrounding neural structures.

**Option B:** Ventriculoperitoneal shunting is a common treatment for obstructive hydrocephalus, which can be caused by the tumor. However, it does not address the underlying tumor or the risk of tumor recurrence.

**Option C:** CCNU (Lomustine) and vincristine are chemotherapeutic agents commonly used in the treatment of medulloblastoma. They can be effective in reducing tumor size and preventing recurrence.

**Clinical Pearl / High-Yield Fact**
In pediatric patients with medulloblastoma, the goal of treatment is to balance tumor control with minimizing long-term side effects, particularly cognitive and endocrine dysfunction. Radiation therapy to the whole craniospinal axis is generally reserved for patients with high-risk features.

**✓ Correct Answer: D. Radiotherapy 35-40 Gy was given to the whole craniospinal axis**