Okay, let's tackle this question. The question is about the internal carotid artery occlusion and what it doesn't cause. First, I need to recall the territories supplied by the internal carotid artery. The internal carotid artery branches into several vessels, including the anterior cerebral artery (ACA) and middle cerebral artery (MCA), which supply the anterior and lateral parts of the brain. The posterior circulation is from the vertebral arteries and basilar artery, so that's the posterior cerebral artery (PCA) territory.

So, if the internal carotid is occluded, the ACA and MCA territories would be affected. Classic symptoms would include contralateral hemiparesis (MCA), homonymous hemianopia (MCA), and possibly aphasia if the dominant hemisphere is involved. But what about the posterior parts? The PCA is part of the posterior circulation, so occlusion of the internal carotid wouldn't affect that. Therefore, any symptoms related to PCA territory, like visual field defects in the opposite eye, wouldn't be caused by internal carotid occlusion.

Wait, the options aren't given here, but the correct answer is the one that's an exception. So the wrong options might be symptoms of ACA or MCA, and the correct answer would be a PCA-related symptom. For example, if an option says "ipsilateral CN III palsy," that's from the ophthalmic artery, which is a branch of the internal carotid. But wait, CN III is a cranial nerve, not directly supplied by the internal carotid. The CN III is supplied by the posterior cerebral artery. So if the internal carotid is blocked, the PCA isn't affected. Therefore, a CN III palsy would be due to a different cause.

Wait, the internal carotid artery gives off the ophthalmic artery. If there's occlusion, the eye might be affected, but CN III is from the PCA. So if the question's options include a CN III palsy, that's an exception. Let me check. Suppose the options are:

A. Contralateral hemiparesis (MCA)
B. Homonymous hemianopia (MCA)
C. Ipsilateral CN III palsy (PCA)
D. Aphasia (dominant MCA)

Then the correct answer would be C, because CN III is supplied by PCA, which is part of the posterior circulation. The internal carotid occlusion wouldn't affect the PCA. So the exception is C. Let me structure the explanation accordingly.

**Core Concept**
The internal carotid artery supplies the anterior and middle cerebral arteries, perfusing the lateral and medial frontal, parietal, and temporal lobes. Its occlusion leads to infarcts in these territories, excluding posterior cerebral artery (PCA)-dominant regions.

**Why the Correct Answer is Right**
Ipsilateral cranial nerve III (oculomotor) palsy is caused by PCA territory infarction, as the CN III nucleus and fibers are supplied by the posterior cerebral artery. The internal carotid artery does not supply the PCA, making CN III palsy an exception to its occlusion effects.

**Why Each Wrong Option is Incorrect**
**Option A:** Contralateral hemiparesis (middle cerebral artery territory) occurs due to motor cortex infarction.

✓ Correct Answer: A. Ataxia