Letter to the Editor |
Focal dystonia associated with pain
Neurology and Neurosurgery, 1040 NW 22nd Avenue, Suite 600, Portland, OR 97210, USA and Neurology, University of Chile, Santiago E-mail: jochoa{at}nervesense.net
Sir,
We applaud the solid article by Schrag et al. on the enigmatic syndrome of focal dystonia associated with pain, one that may follow physical trauma to a limb, in the absence of clinical and neurophysiological evidence of underlying neuropathology. In our experience dystonia or abnormal movements do not occur in comparable post-traumatic chronic pain patients who do harbour demonstrable neurological and neurophysiological equivalents of neuropathology (‘CRPS II’). The positive motor phenomena and pain only occur in patients with medically unexplainable and largely subjective sensory loss or hyperalgesia and weakness of wilful movements of pseudoneurological identity (Verdugo and Ochoa, 2000
; Verdugo et al., 2004). A psychogenic nature for this disorder is now convincingly documented by Schrag et al., based on psychoneurological evidence.
The fact that a number of these patients fit the descriptive term ‘CRPS I’ in no way challenges the psychopathological origin of the present condition, given that, after correcting for neglected differential diagnosis, the non-specific profile of CRPS I can be shown to embrace disparate neuropathologically based disease as well as psychopathologically based entities (Ochoa, 2002). Moreover, according to respected authorities CRPS I can only be understood as a pain syndrome or disease that is actively generated by the brain (Jänig, 2001), a concept which, as noted by Schrag et al., is in keeping with recent evidence contributed by functional brain imaging studies.
References
Jänig W. CRPS-I and CRPS-II: a strategic view. In: Harden RN, Baron R, Jänig W, editors. Complex regional pain syndrome. Progress in pain research and management. Seattle: IASP Press; 2001. p. 3–15.
Ochoa JL. Pathophysiology of chronic neuropathic pains In: Burchiel KJ, editor. Surgical management of pain. New York: Thieme Medical and Scientific; 2002. p. 25–41.
Schrag A, Trimble M, Quinn N, Bhatia K. The syndrome of fixed dystonia: an evaluation of 103 patients. Brain 2004; 127: 2360–72.
Verdugo RJ, Ochoa JL. Abnormal movements in complex regional pain syndrome: assessment of their nature. Muscle Nerve 2000; 23: 198–205.[CrossRef][Web of Science][Medline]
Verdugo RJ, Bell LA, Campero M, Salvat F, Triplett B, Sonnad J, et al. Spectrum of cutaneous hyperalgesias/allodynias in neuropathic pain patients. Acta Neurol Scand 2004; 110(6): 368–76.[CrossRef][Medline]
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