Can CRPS Type 2 Cause Dystonia?
Yes, CRPS type 2 can cause dystonia, though the available evidence predominantly focuses on CRPS type 1, suggesting dystonia occurs across both CRPS subtypes without clear distinction between them in the literature.
Clinical Evidence for Dystonia in CRPS
The relationship between CRPS and dystonia is well-established, though research has not specifically differentiated outcomes between type 1 (without nerve injury) and type 2 (with documented nerve injury):
Dystonia is a common motor manifestation of CRPS, occurring in approximately 25% of all CRPS cases 1, 2. This prevalence figure comes from studies that included both CRPS subtypes, indicating dystonia develops regardless of whether an identifiable nerve injury is present.
In a large retrospective evaluation of 185 CRPS patients, dystonia was the most prevalent movement disorder, occurring in 91% of patients who developed any movement disorder 3. The study did not exclude CRPS type 2 patients, suggesting dystonia affects both subtypes.
The diagnostic distinction between CRPS type 1 and type 2 is based solely on the presence or absence of documented nerve injury 4, 5. Type 2 occurs after a confirmed nerve injury, while type 1 occurs without identifiable nerve lesion 4.
Characteristic Patterns of CRPS-Related Dystonia
The dystonia associated with CRPS (both types) presents with specific patterns:
Upper Extremity
- Dominant pattern involves flexion of fingers (94% of affected arms), wrists (33%), and elbows (31%) 1
Lower Extremity
- Plantar flexion of toes (48% of affected legs), plantar flexion and inversion of ankle (64%), and knee flexion (48%) 1
Temporal Characteristics and Progression
The onset of dystonia shows highly variable latency: 26% develop dystonia within one week of CRPS onset, while 27% develop it after more than one year 3
Patients with dystonia are typically 11 years younger at CRPS onset and more frequently develop CRPS in multiple extremities 3
The hazard of developing dystonia in additional extremities increases with the number of extremities already affected by dystonia 3, suggesting a progressive central nervous system mechanism rather than purely peripheral pathology.
Pathophysiological Mechanism
The mechanism underlying CRPS-related dystonia appears distinct from classic dystonia:
Computational modeling suggests aberrant force feedback regulation from Golgi tendon organs may underpin the typical fixed flexion postures 1. This mechanism would apply regardless of whether the initial CRPS was triggered by identifiable nerve injury (type 2) or not (type 1).
EMG studies demonstrate that CRPS-related abnormal postures are NOT characterized by sustained muscle contractions typical of classic dystonia 6. Instead, agonist and antagonist muscles activate in normal proportions but over a limited range 6.
Patients with CRPS-related dystonia show reduced force feedback weights and disturbed integration of sensory force feedback 2, representing a central sensorimotor integration problem rather than peripheral nerve dysfunction alone.
Clinical Implications
Important Caveats
The delayed onset and variable progression of dystonia (weeks to years after CRPS onset) suggests involvement of maladaptive neuroplasticity 3, which would occur in both CRPS type 1 and type 2.
Since CRPS-related dystonia does not exhibit excessive muscle contraction characteristics of classic dystonia 6, treatments aimed at reducing muscle spasm may be ineffective.
Treatment Considerations
Intrathecal baclofen has demonstrated efficacy for CRPS-related dystonia, with substantial improvement in dystonia severity, pain, disability, and quality of life maintained over 12 months 7
However, intrathecal baclofen carries a high complication rate in CRPS patients, with 89 adverse events in 26 of 36 patients, and pump explantation required in 6 patients during follow-up 7
The absence of literature specifically distinguishing dystonia outcomes between CRPS type 1 versus type 2 strongly suggests that the presence of dystonia is related to the CRPS syndrome itself rather than the specific presence or absence of initial nerve injury. The pathophysiology appears to involve central sensorimotor integration dysfunction that develops secondarily, making dystonia a potential complication of both CRPS subtypes.