This patient has recurrent forceful contraction of the sternocleidomastoid muscle, resulting in head rotation.  This is consistent with cervical dystonia (ie, torticollis), a form of focal dystonia.

Dystonia is a neurologic movement disorder characterized by sustained, involuntary muscle contractions, which force certain parts of the body into abnormal, sometimes painful movements or postures.  Focal dystonias affect a single muscle or group of related muscles, the most common of which include cervical dystonia, blepharospasm, and brachial dystonia (ie, writer's cramp).

The presence of a sensory trick is a common feature of focal dystonias, in which symptoms can sometimes be temporarily relieved with sensory input (eg, placing a hand on the chin).

(Choice A)  Bradykinesia is slow movement.  It is commonly seen in Parkinson disease.

(Choice B)  Chorea is involuntary muscle activity that flows from one muscle group to another.  Movements may appear fragmented or jerky, and the patient may display a dance-like gait.  Chorea is a prominent feature of Huntington disease.

(Choice C)  Cogwheel rigidity refers to the intermittent ratchet-like resistance to movement that can be felt on passive extension/flexion of a parkinsonian limb.

(Choice E)  Hemiballism refers to flinging of the limbs (arm and/or leg) on one side of the body.  Hemiballism occurs due to contralateral injury in or near the subthalamic nucleus.

(Choice F)  Myoclonus is a sudden, brief, sometimes severe (shock-like) muscle contraction.  Examples of physiologic myoclonus are hiccups and hypnic jerks (occur when falling asleep).  Pathologic myoclonus is seen in epilepsy and Creutzfeldt-Jakob disease.

Educational objective:
Dystonia is a neurologic movement disorder characterized by sustained, involuntary muscle contractions that often result in abnormal, sometimes painful posturing.  Many patients can have temporary relief with the use of a sensory trick (eg, touching the face).