Predominant extrinsic flexor spasticity
This is by far the most common type.The fingers are flexed, the wrist cannot extend fully due to the spasticity of finger and wrist flexors.
There are several degrees of severity, assessed by examining finger and wrist extension (Zancolli classification):
- Stage 1: active finger extension possible with straight wrist.Surgery is not necessary.
- Level 2: active finger extension is possible only by flexing wrist
- Level 2a: wrist can be extended with fingers flexed.Stretching is not necessary and hyponeurotization surgery indication is confirmed by the effectiveness of botulinum injections on finger flexors.
- Level 2b: Wrist extension is not possible even with fingers flexed. Transitory anaesthesia of median and ulnar nerve confirms finger flexor shrinkage and justifies muscle lengthening surgery. Truncular anaesthesia also makes it possible to test the strength of wrist and finger extensors and if necessary to perform an additional opening tendon transfer procedure.
- Level 3: active finger extension is no longer possible even with the wrist fully extended but passive finger extension remains possible.
- Level 3a: passive finger extension possible with straight wrist. Transitory nerve anaesthesia will make it possible to confirm wrist flexor spasticity over shrinkage, the diagnosis can be further confirmed by the effectiveness of botulinum toxin injections in wrist flexors.
- Level 3b: passive finger extension possible only with wrist strongly flexed. At this stage the results show strong finger and wrist flexor shrinkage.
- Level 4: passive finger extension impossible. At this stage hygiene issues arise with a hand that cannot be washed properly.The objective here is no longer to improve function but to facilitate hand hygiene.
Predominant intrinsic muscle spasticity
Much less common, the hand has an intrinsic hypertonia deformity.