Which upper extremity synergy pattern—flexor or extensor—has the poorer prognosis?

Upper Extremity Synergy Patterns and Prognosis After Stroke

Flexor synergy of the upper extremity has a significantly poorer prognosis than extensor synergy, with extensor synergy being an independent predictor of better functional outcomes including motor independence, personal care, and mobility. 1

Evidence for Differential Prognosis

Functional Outcomes by Synergy Pattern

Patients with extensor synergy of the upper limb demonstrate superior functional recovery compared to those with flexor synergy. 1 In a cohort of 208 stroke patients undergoing rehabilitation:

• Extensor synergy of the upper limb was an independent predictor of final motor-FIM (Functional Independence Measure) scores, personal care abilities, and mobility 1
• Motor-FIM scores at rehabilitation completion were significantly higher in patients with extensor synergies compared to those with flexor synergy alone 1
• Patients with mixing synergies (both flexor and extensor components) showed intermediate outcomes 1

Recovery Hierarchy

The functional recovery hierarchy from poorest to best prognosis follows this pattern 1:

1. No movements (worst prognosis)
2. Flexor synergy alone (poor prognosis)
3. Extensor synergy (better prognosis)
4. Mixing synergies (intermediate-good prognosis)
5. No dependence on synergies (best prognosis)

Biomechanical and Clinical Distinctions

Upper Extremity Flexion Synergy Characteristics

Flexion synergy in the upper extremity produces stereotyped coupling that severely limits functional hand use. 2 Key features include:

• Strong shoulder abduction elicits obligatory wrist and finger flexion that increases proportionally with shoulder effort 2
• This coupling creates a functional barrier to reaching and grasping activities 2
• The flexion synergy pattern is more rigid and less adaptable for functional tasks 3

Upper Extremity Extension Synergy Characteristics

Extension synergy, while still abnormal, allows for more functional movement patterns. 2 Important distinctions:

• Shoulder adduction produces less obligatory wrist and finger flexion compared to the flexion synergy 2
• Extension synergy patterns show greater variability and potential for functional adaptation 1
• The presence of extensor synergy indicates preserved capacity for antigravity limb positioning 1

Clinical Implications for Rehabilitation

Prognostic Assessment

When evaluating stroke patients, the presence of extensor synergy components should be specifically assessed as a positive prognostic indicator. 1 The Fugl-Meyer Assessment provides validated measures for quantifying synergy patterns 1, 3:

• Higher scores on extensor synergy components predict better functional independence 1
• The relationship between synergy components can guide rehabilitation focus 3
• Moderate to high correlations (r = 0.5 to 0.89) exist between various upper extremity movement components 3

Rehabilitation Strategy

Task-specific training should be prioritized for all patients, with intensity and approach modified based on synergy pattern. 4 For patients with predominant flexor synergy:

• Constraint-induced movement therapy (CIMT) requires baseline ability to control wrist and finger extension, which may be limited in pure flexor synergy 4
• Neuromuscular electrical stimulation (NMES) combined with task-specific training may be beneficial when volitional muscle activation is minimal 4
• Robotic therapy can deliver larger amounts of movement practice for those with severe paresis 4

Common Pitfalls to Avoid

Do not assume equivalent prognosis between flexor and extensor synergy patterns—this distinction has significant implications for realistic goal-setting and resource allocation. 1 Additional considerations:

• Avoid focusing solely on proximal shoulder movements without assessing distal hand function, as flexion synergy creates obligatory coupling that limits functional hand use 2
• Do not overlook the potential for patients with extensor synergy to benefit from intensive rehabilitation interventions 1
• Recognize that the strength of synergy expression varies across joints, with hand and wrist showing more similar responses to both flexion and extension synergies compared to the elbow 2

Time Course Considerations

Inter-limb correlations between upper and lower extremity synergies are strongest in the acute-to-subacute phase (<90 days) but decrease significantly by one year post-stroke. 5 This temporal pattern suggests:

• Early rehabilitation should address whole-body synergy patterns 5
• Chronic phase recovery (>360 days) shows greater independence between upper and lower extremity synergy expressions 5
• The reduction in correlation over time may reflect corticospinal tract recovery or remodeling of alternative neural pathways 5