Influence of sympathetic nervous system on sensorimotor function: whiplash associated disorders (WAD) as a model

The Quebec task force suggested for whiplash the term whiplash-associated disorders that includes a wide range of symptoms in one clinical syndrome, and classified with a grading system from 0 to IV (Spitzer et al. 1995). Grade 0 designates no symptoms; grade I neck pain, stiffness and tenderness, with no objective physical signs; grade II neck complaints and musculoskeletal signs (point tenderness, decreased range of movements); grade III: neck pain or stiffness associated with neurological signs (weakness, paresthesias into the arm, reflexes decreased or absent due, e.g., to nerve root compression by a disk protrusion); grade IV: neck pain or stiffness associated with cervical fracture and/or dislocation. All the other numerous physical and psychological problems of a diffuse nature listed below in this introduction may be present in all grades. Patients included in grades I and II represent more than 90% of “whiplash injury claims” (Holm et al. 1999; Hartling et al. 2001; Ferrari et al. 2005). As compared to grades III and IV in which the cause of the injury is more obvious, grade I and II are the most controversial cases, in terms of pathophysiology, diagnosis and prognosis, and therefore also for the insurance compensation system, because of the absence of clearly detectable anatomic injuries and of specific and generally accepted pathological signs. For these reasons most of the studies presented in the literature, and quoted in the present article, refer to this group of patients, some of them also include grade III. Grade IV patients (neck problems due to fracture or dislocations) are excluded.

Besides vasoconstrictor sympathetic supply to blood vessels, which is largely predominant, sympathetic cholinergic fibres producing vasodilatation have been reported in experimental animals. However the existence of neurogenic dilatation is still doubtful in human skeletal muscles since morphological and functional data were unable to prove its presence (for review and refs see Joyner and Halliwill 2000; Joiner and Dietz 2003; Passatore and Roatta 2003). Therefore we are not dealing with neurogenic vasodilatation in this article.

The term complex regional pain syndrome, subdivided in Type I and II (CRPS I, CPRS II) was recommended by the taxonomic Committee of the International Association for the Study of Pain (Mersky and Bogduk 1994). In CRPS I minor injuries precede onset of symptoms while CRPS II develops after major peripheral nerve injury (for rev and ref, and diagnostic criteria, see Mersky and Bogduk 1994; Blair 2003). Sympathetically maintained pain (SMP) is a pain that is maintained by sympathetic afferent innervation or by circulating catecholamines; it may occur in several conditions and is not limited to CRPS I or II (see, for review and refs, Mersky and Bogduk 1994; Blair 2003, see also Fig. 5a).