Cervical Dystonia (CD), or Spasmodic Torticollis, is characterized by abnormal movement or positioning of the head and neck muscles. These sustained muscle contractions result in abnormal head postures which vary depending on the muscles that are affected. CD is the most common form of focal dystonia (it affects one area of the body) and is found in twice as many women as men (Sims, Stack, & Demerjian, 2012). Symptoms of CD include rotational twisting (laterocollis), backward rotation (retrocollis), or frontal rotation (anterocollis), of the head / neck and/or a combination of these. Pain or head tremor is often associated with those that have sustained contractions and there is often associated dystonia in the upper muscles of the same side (segmental dystonia) (Sims & Demerjian, 2012).
Symptoms of cervical dystonia can present itself between childhood and old age, but its underlying cause has yet to be conclusively determined. Research studies have suggested links between trauma or overuse of the affected area and focal dystonia; however, it does not sufficiently explain the development of the disorder in most patients. Some researchers also argue that there is a genetic component to dystonia that is prompted by trauma, which then triggers the onset of the disorder (Sims et al., 2012).
Current treatments for CD include botulinum toxin (Botox) injections to various muscles affected by the disorder, denervation neck surgery, which cuts the nerves to the muscles and allows for possible corrections of the torticollis, and deep brain stimulation surgery (DBS), which implants electrodes into the brain to control the movement disorder. Botox injections require multiple applications and it is often the case that the body becomes immune to the toxin and loses efficiency. Denervation neck surgery is irreversible and may develop complications, such as numbness in the back of the head or difficulty swallowing, that outweigh its benefits. DBS is used for general dystonias and for those who do not respond to other treatments; however it is only 50% effective and is also irreversible. It requires a secondary surgery to implant a neurostimulator and its effectiveness varies from patient to patient with continued medication intake after surgery. An alternative treatment option is the use of an oral orthotic that increases the vertical dimension and decrease the neuropathy within the temporomandibular joint (TMJ) (Sims et al., 2012).
Research studies have shown that motor activity in specific muscles of the neck is present when the TMJ is stimulated. This stimulus travels to an area of the brainstem called the reticular formation which are nerves that, when stimulated, cause the head and neck muscles to turn toward the same side as the stimulation (Demerjian, Sims, & Stack, 2011). It may be the case that cervical dystonia is a result of chronic activation of the reticular formation due to overstimulation of the nerves within the TMJ (Sims & Demerjian, 2012). When the stimulus is relieved in the TMJ, the stimulus in the reticular formation is also relieved, which then relieves the turning of the head to that side (Sims & Stack, 2009). When the compression is relieved by an oral orthotic, there is a gradual reduction of CD, and the muscles of the head and neck begin to return to normal with a decrease in pain (Sims et al., 2012).