**Core Concept**
During a block dissection of the neck, various structures are at risk of injury, including nerves and vessels. The movement of the head is primarily controlled by the cervical spine and the nerves that innervate the muscles of the neck. The inability to move the head upward and to the side suggests involvement of a specific nerve or group of nerves.

**Why the Correct Answer is Right**
The primary nerves responsible for controlling head movement are the spinal accessory nerve (cranial nerve XI) and the cervical plexus nerves (C3-C4). The spinal accessory nerve primarily innervates the sternocleidomastoid and trapezius muscles, which are responsible for shoulder and neck movement. Damage to this nerve can lead to weakness or paralysis of these muscles, resulting in the inability to move the head upward and to the side. The cervical plexus nerves (C3-C4) primarily innervate the infrahyoid muscles, which are not primarily responsible for this movement.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not specified, but assuming it's another nerve or structure, it's unlikely to be responsible for the described movement deficit.
**Option B:** This option is also not specified, but it's unlikely to be the correct answer given the description of the movement deficit.

**Clinical Pearl / High-Yield Fact**
Damage to the spinal accessory nerve can lead to a characteristic "winged scapula" deformity, where the scapula protrudes from the back due to weakness of the trapezius muscle.

**Correct Answer:** C. Cervical plexus nerves (C3-C4)