This appeared only once, in Question 24.5 from the first paper of 2009. As such, it is a of little importance. However, while looking to expand on the college answer, I was disturbed to find that nowhere is there a list of differentials for this.

Thus, for completeness, here is one such list, within a familiar VINDICATE template.

Vascular:

  • Dural sinus thrombosis
  • Subarachnoid hemorrhage

Infectious:

  • Epidural abscess
  • Neck abscess
  • Meningitis/encephalitis
  • Tetanus

Neoplastic:

  • C-spine vertebral metastasis or primary

Drug-related:

  • Dystonic reaction
  • Withdrawal

Idiopathic/inflammatory:

  • Osteoarthritis
  • Cervical spondylitis
  • Torticollis

Autoimmune:

  • Rheumatoid arthritis
  • Ankylosing spondylitis

Traumatic

  • Whiplash
  • C-spine dislocation, subluxation or fracture
  • Prolonged neck hyperextension during surgery (eg. tracheostomy)

Endocrine:

  • Hypocalcemia

 

References

Oh's Intensive Care manual: Chapter 49   (pp. 549) Disorders  of  consciousness  by Balasubramanian  Venkatesh

Plum, Fred, and Jerome B. Posner. The diagnosis of stupor and coma. Vol. 19. Oxford University Press, 1982. - warning! This link takes you to a download of the whole 9.0Mb file, which represents the entire volume of the 1980 second edition.

Maramattom, Boby Varkey, and Eelco FM Wijdicks. "Uncal herniation."Archives of neurology 62.12 (2005): 1932-1935.

Skrzat, J., et al. "The clinical significance of the petroclinoid ligament." Folia morphologica 66.1 (2007): 39-43.

Conomy, John P., and Michael Swash. "Reversible decerebrate and decorticate postures in hepatic coma." New England Journal of Medicine 278.16 (1968): 876-879.

Bateman, David E. "Neurological assessment of coma." Journal of Neurology, Neurosurgery & Psychiatry 71.suppl 1 (2001): i13-i17.

Feldman, Martin H., and Shirley Sahrmann. "The Decerebrate State in the Primate: II. Studies in Man." Archives of neurology 25.6 (1971): 517-525.

Teasdale, Graham, and Bryan Jennett. "Assessment of coma and impaired consciousness: a practical scale." The Lancet 304.7872 (1974): 81-84.

Dowell, Anthony R., et al. "Cheyne-Stokes respiration: a review of clinical manifestations and critique of physiological mechanisms." Archives of internal medicine 127.4 (1971): 712.

Andreas, Stefan, et al. "Cheyne-Stokes respiration and prognosis in congestive heart failure." The American journal of cardiology 78.11 (1996): 1260-1264.

Douglas, C. Gordon, and J. S. Haldane. "The causes of periodic or Cheyne-Stokes breathing." The Journal of physiology 38.5 (1909): 401-419.

Tomlinson, B. E. "Brain-stem lesions after head injury." Journal of Clinical Pathology. Supplement (Royal College of Pathologists). 4 (1970): 154.

Perman, Sarah M., et al. "Timing of neuroprognostication in postcardiac arrest therapeutic hypothermia." Critical care medicine 40.3 (2012): 719.

Towne, A. R., et al. "Prevalence of nonconvulsive status epilepticus in comatose patients." Neurology 54.2 (2000): 340-340.

TEASDALE, GRAHAM, and BRYAN JENNETT. "Assessment of coma and severity of brain damage." Anesthesiology 49.3 (1978): 225.

Green, Steven M. "Cheerio, laddie! Bidding farewell to the Glasgow Coma Scale." Annals of emergency medicine 58.5 (2011): 427-430.

Gill, Michelle R., David G. Reiley, and Steven M. Green. "Interrater reliability of Glasgow Coma Scale scores in the emergency department." Annals of emergency medicine 43.2 (2004): 215-223.

Riechers, Ronald G., et al. "Physician knowledge of the glasgow coma scale."Journal of neurotrauma 22.11 (2005): 1327-1334.