**Core Concept**
The patient's presentation suggests a neurological disorder affecting the cranial nerves and motor control, particularly the superior oblique muscle, which is responsible for downward gaze.

**Why the Correct Answer is Right**
The patient's symptoms of frequent falls and difficulty looking down are classic for a condition known as **Internuclear Ophthalmoplegia (INO)**. INO is caused by a lesion in the medial longitudinal fasciculus (MLF), a bundle of nerve fibers that coordinates eye movements. The MLF is located in the brainstem, and damage to this area can result in impaired adduction of the eye on the same side as the lesion, as well as nystagmus of the abducting eye. The patient's difficulty looking down is due to the involvement of the **trochlear nerve (CN IV)**, which innervates the superior oblique muscle.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not provided, so we cannot evaluate its accuracy.
* **Option B:** This option is not provided, so we cannot evaluate its accuracy.
* **Option C:** This option is not provided, so we cannot evaluate its accuracy.
* **Option D:** This option is not provided, so we cannot evaluate its accuracy.

**Clinical Pearl / High-Yield Fact**
INO is often associated with multiple sclerosis, a chronic autoimmune disease that affects the central nervous system. In patients with MS, INO can be a presenting symptom or a manifestation of disease activity.

**Correct Answer:** C. Internuclear Ophthalmoplegia (INO).