**Core Concept**
Graves ophthalmopathy is a condition characterized by autoimmune inflammation of the tissues around the eye, including the extraocular muscles. The condition leads to muscle enlargement, which can cause a range of symptoms, including proptosis, diplopia, and eyelid retraction. In the context of CT scanning, identifying specific patterns of muscle enlargement can help diagnose and differentiate Graves ophthalmopathy from other conditions.

**Why the Correct Answer is Right**
Fusiform muscle enlargement with sparing of tendons is a classic sign of Graves ophthalmopathy on CT scanning. This pattern of muscle enlargement is due to the autoimmune inflammation, which causes the muscles to swell in a uniform, spindle-shaped manner. The sparing of tendons is a key distinguishing feature, as other conditions may cause muscle enlargement that involves the tendons as well. The fusiform pattern is thought to result from the diffuse inflammation of the muscle fibers, which leads to a uniform expansion of the muscle belly.

**Why Each Wrong Option is Incorrect**
**Option A:** Nodular muscle enlargement is not a characteristic feature of Graves ophthalmopathy on CT scanning. This pattern is more commonly associated with other conditions, such as orbital tumors or infections.
**Option B:** Solitary muscle enlargement is not typical of Graves ophthalmopathy, as the condition usually involves multiple muscles. This option is also more consistent with other conditions, such as a localized tumor or infection.
**Option D:** Kinking of extraocular muscles can occur in Graves ophthalmopathy, but it is not a classic sign on CT scanning. Kinking can be seen in other conditions as well, and is not a reliable distinguishing feature of Graves ophthalmopathy.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that Graves ophthalmopathy can cause a range of orbital symptoms, including proptosis, diplopia, and eyelid retraction. The condition is often associated with hyperthyroidism, and treatment may involve both medical management of the thyroid disease and orbital surgery.

**✓ Correct Answer:** C. Fusiform muscle enlargement with sparing of tendons