The main innervation to these muscles is from cranial nerve XI (the accessory nerve) but the second, third and fourth cervical nerves are also involved. Pathologies in these blood and nerve supplies can lead to torticollis. Diagnosis
Evaluation of a child with torticollis begins with history taking to determine circumstances surrounding birth and any possibility of trauma or associated symptoms. Physical examination reveals decreased rotation and bending to the side opposite from the affected muscle. Some say that congenital cases more often involve the right side, but there is not complete agreement about this in published studies. Evaluation should include a thorough neurologic examination, and the possibility of associated conditions such as developmental dysplasia of the hip and clubfoot should be examined. Radiographs of the cervical spine should be obtained to rule out obvious bony abnormality, and MRI should be considered if there is concern about structural problems or other conditions. Ultrasonography can be used to visualize muscle tissue, with a colour histogram generated to determine cross-sectional area and thickness of the muscle.Evaluation by an optometrist or an ophthalmologist should be considered in children to ensure that the torticollis is not caused by vision problems (IV cranial nerve palsy, nystagmus-associated "null position," etc.). Differential diagnosis for torticollis includes
Cranial nerve IV palsy
Spasmus nutans
Sandifer syndrome
Myasthenia gravis
Cerebrospinal fluid leakCervical dystonia appearing in adulthood has been believed to be idiopathic in nature, as specific imaging techniques most often find no specific cause.
Known causes for head tilt in domestic animals include:

Encephalitozoon cuniculi (or E. cuniculi) infection in rabbits
parasitic infestation by the nematode (roundworm) Baylisascaris procyonis in rabbits
Inner ear infection
Hypothyroidism in dogs
Disease of the VIIIth cranial nerve the N. Vestibulocochlearis through trauma, infection, inflammation or neoplasia
Disease of the brain stem through either stroke, trauma or neoplasia
Damage to the vestibular organ due to toxicity, inflammation or impaired blood supply
Geriatric vestibular syndrome in dogs

Notes
References
External links
Head Tilt: Causes and Treatment