Assessment of Rigidity in Patients with Bradykinesia
To assess rigidity in a patient with bradykinesia, passively move the patient's limbs while instructing them to relax, and assess resistance to movement throughout the range of motion, noting any cogwheel phenomenon that may occur when rigidity is combined with tremor. 1
Proper Technique for Assessing Rigidity
- Rigidity is one of the cardinal motor signs of Parkinson's disease, alongside bradykinesia and resting tremor 1, 2
- To properly assess rigidity:
- Have the patient relax completely while you passively move their limbs 1
- Test both upper and lower extremities, comparing sides for asymmetry 1, 2
- Move the joint through its full range of motion at varying speeds 1
- Note any resistance to passive movement that remains constant throughout the range (lead-pipe rigidity) 1, 2
- Look for "cogwheel" phenomenon - a ratchet-like, jerky resistance that occurs when rigidity is combined with tremor 1, 2
Enhanced Testing Methods
- To enhance detection of subtle rigidity, ask the patient to perform an activation maneuver with the contralateral limb (e.g., opening and closing the opposite hand) while you test for rigidity 1, 2
- This activation maneuver often brings out rigidity that might otherwise be difficult to detect 1
- Pay special attention to asymmetric rigidity, which may suggest corticobasal syndrome, especially when accompanied by alien hand phenomenon 1
Scoring Rigidity
- Rigidity can be scored using standardized scales such as the motor section (Part III) of the Unified Parkinson's Disease Rating Scale (UPDRS) 3
- The UPDRS rates rigidity on a scale from 0-4:
- 0 = Absent
- 1 = Slight or detectable only with activation maneuvers
- 2 = Mild to moderate
- 3 = Marked, but full range of motion easily achieved
- 4 = Severe, range of motion achieved with difficulty 3
Distinguishing Features from Other Parkinsonian Syndromes
- Asymmetric rigidity with alien hand phenomenon suggests Corticobasal Syndrome rather than idiopathic Parkinson's disease 1, 2
- The presence of vertical gaze palsy (especially downward) alongside rigidity suggests Progressive Supranuclear Palsy 1, 2
- Rigidity that affects the axial muscles more than limbs may suggest Multiple System Atrophy 1, 4
Common Pitfalls to Avoid
- Failure to have the patient completely relax during testing can lead to false positives due to voluntary muscle contraction 1
- Not using activation maneuvers may cause you to miss subtle rigidity 1, 2
- Confusing spasticity (velocity-dependent resistance that increases with faster stretching) with rigidity (constant resistance throughout movement) 1
- Overlooking cogwheel rigidity, which is an important diagnostic sign when present 2
Remember that rigidity assessment is just one component of evaluating a patient with bradykinesia, and findings should be considered alongside other motor and non-motor symptoms for proper diagnosis and treatment planning 1, 2.