Excess accumulation of cerebrospinal fluid within the brain. 

• A. Hydrodurosis 
• B. Hypohydroencephalitis 
• C. Hypopoliohydro 
• D. Hydrocephalus 

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the key terms in the problem. The phrase 'excess accumulation of cerebrospinal fluid within the brain' describes a medical condition involving fluid buildup in the brain's ventricles.
2. Step 2: Break down the word components related to cerebrospinal fluid and brain conditions. 'Hydro-' means water or fluid, 'cephalus' relates to the head or brain, and '-us' is a common noun ending in medical terminology.
3. Step 3: Analyze the given options by their word roots and suffixes: 'Hydrodurosis' suggests fluid flow or dilation, 'Hypohydroencephalitis' implies inflammation with less fluid, 'Hypopoliohydro' is a complex term but does not directly relate to fluid accumulation in the brain.
4. Step 4: Recognize that 'Hydrocephalus' combines 'hydro-' (fluid) and 'cephalus' (head), which literally means 'water on the brain,' matching the definition of excess cerebrospinal fluid accumulation.
5. Step 5: Conclude that the correct medical term for excess cerebrospinal fluid in the brain is 'Hydrocephalus' based on the breakdown of word parts and medical definitions.