**Core Concept**
The patient's symptoms, including urinary incontinence, ataxia, difficulty with arithmetic calculations, and memory loss, suggest a neurodegenerative disorder affecting the brain and spinal cord. This condition likely results from the degeneration of specific neurons and their connections, leading to impaired motor and cognitive functions.

**Why the Correct Answer is Right**
The symptoms described are characteristic of a condition known as Normal Pressure Hydrocephalus (NPH). NPH is a type of dementia caused by an accumulation of cerebrospinal fluid (CSF) in the brain's ventricles, leading to increased intracranial pressure. This condition affects the frontal lobes, which are responsible for motor control, cognitive functions, and emotional regulation. The increased pressure causes damage to the surrounding brain tissue, resulting in the symptoms described. The ataxia is likely due to the involvement of the cerebellum, which is responsible for coordinating movements.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify a neurodegenerative disorder that matches the patient's symptoms. While Alzheimer's disease is a common cause of dementia, it typically presents with memory loss and cognitive decline without ataxia or urinary incontinence.

**Option B:** This option is incorrect because it refers to a condition that primarily affects motor function, such as Parkinson's disease. While patients with Parkinson's disease may experience cognitive decline, the primary symptoms are tremors, rigidity, and bradykinesia.

**Option C:** This option is incorrect because it does not accurately describe the patient's symptoms. Frontotemporal dementia is a group of disorders that primarily affect the frontal and temporal lobes, leading to changes in personality, behavior, and language.

**Option D:** This option is incorrect because it does not specify a neurodegenerative disorder that matches the patient's symptoms. While vascular dementia is a common cause of cognitive decline, it typically results from a series of small strokes or changes in blood flow to the brain, rather than the accumulation of CSF.

**Clinical Pearl / High-Yield Fact**
Normal Pressure Hydrocephalus (NPH) is often referred to as the "dementia of the elderly" because it can mimic other forms of dementia, such as Alzheimer's disease. However, NPH is a treatable condition, and patients who receive shunt surgery can experience significant improvements in their symptoms.

**Correct Answer:** C. Frontotemporal dementia.