Table 1

Clinical overlap of CRPS and FND

Complex regional pain syndromeFunctional neurological disorderPathologically defined disease
TriggerPhysical injury or surgeryPhysical injury or surgery in 37%–80%e1 Dependent on disorder
SensoryLoss or hyperalgesiae2
Non-dermatomal, densee 3, may be whole limbe4 or hemisensorye4
Common response to placeboe5
Loss or hyperalgesiae6
Non-dermatomal, dense, may be whole limb or hemisensorye6 e 7 e 8
Common response to placeboe7
In keeping with expected lesion location
Lesser response to placeboe5
Movement disordersCombination of movement disorders common (dystonia, tremor, myoclonus) e9 Combination of movement disorders or other FNDs commone15 Unusual to have several different movement disorders
DystoniaRapid onset, often fixed, dystonia of hand or foote 10 e11
Can spread to other limbse12
May seek limb amputatione 13
Rapid onset, often fixed, dystonia of hand or foote 15–e 17
Can spread to other limbse16
May seek limb amputatione 13 e15
Gradual onset over months/years of mobile dystoniae 19
Unlikely to seek amputatione13
TremorEntrainment of tremor possible and diminished by distractione11 e 9 e14 Entrainment of tremor possible and diminished or stopped by distractione 18 Entrainment rare in patients with tremore 20
WeaknessGive-waye3 e21
Distribution and Hoovers sign not studied.
Give-waye22
Global pattern of weakness with signs of internal inconsistency (eg, Hoovers sign)
Follows expected patterns based on lesion location
Description from patient‘My mind tells my hand/foot to move, but it won’t work’e 23 e12
‘My painful limb feels as though it is not part of my body’e 24
Symptoms described as neglect-like but actually involving increased attention and dissociation)
‘His left leg would sometimes drag behind him, accompanied by an odd sense that it did not belong to him.’ e25
Common for patients to describe feelings of disconnection or lack of ownership of limbs. Usually interpreted as dissociative.
Feeling of limb dissociation can be seen in some conditions such as parietal dysfunction.
Neglect of limb involves absence of interest/awareness of limb. e26
Comorbid functionaldisordersSome evidence of excess comorbidity of functional disorders such a fibromyalgia although poorly studiede27 e28 Comorbid functional disorders including other FND greatly in excess of populatione29 e 30 Functional disorders common in population, including those with disease e 31 e32
  • CRPS, complex regional pain syndrome; FND, functional neurological disorder.