Which diagnostic technique would be least helpful in confirming the presence and location of arteriovenous malformations?

Electromyography (EMG) is primarily used to assess the electrical activity of muscles and the nerves that control them. It is effective in diagnosing neuromuscular disorders or issues with peripheral nerves but does not provide information about vascular malformations such as arteriovenous malformations (AVMs).

In contrast, cerebral arteriography offers a detailed view of the blood vessels in the brain and can directly visualize the presence of AVMs, making it a key tool for diagnosis in such cases. Similarly, a CT scan can also be useful for evaluating AVMs, as it can show changes in blood flow and anatomy in the affected area.

While EEG is used to monitor electrical activity in the brain and can help in assessing functional aspects of brain activity, it does not provide direct anatomical detail about vascular structures and is therefore less relevant for confirming AVMs.

Given these distinctions, EMG stands out as the technique that is least helpful in confirming the presence and location of arteriovenous malformations.