The spastic hand

Resting posture of the upper limb

Inspecting the limb at rest prior to examination provides much information on spasticity. It usually predominates in the adductor, flexor, and pronator muscles, leading to a typical resting posture in shoulder adduction and internal rotation, elbow flexion, forearm pronation, and wrist flexion ( Figs. 29.1 & 29.2 ). But on occasions some patients display very different positions, such as shoulder abduction and external rotation (most often in quadriparetic children), elbow or wrist hyperextension.

The fingers may assume varied positions. Most frequently they are clenched into a tight fist. Less typically they assume a swan-neck deformity, an “intrinsic plus” deformity with flexion of the metacarpophalangeal (MCP) joints and hyperextension of the interphalangeal (IP) joints ( Fig. 29.3 ), or the opposite “intrinsic minus” deformity, with the MP joints hyperextended and the proximal interphalangeal (PIP) joints flexed. A boutonnière deformity is less common.

The thumb can assume either an adducted or an adducted and flexed posture, often referred to as “thumb-in-palm”, where the thumb is embedded in the palm with full flexion of both MCP and IP joints, preventing any kind of use of the hand ( Fig. 29.4 ).

Evaluation of spasticity

Spasticity is a muscle hypertony, characterized by five classical clinical features:

• 1.

  It is selective, predominantly involving the flexor, adductor, and pronator muscles and responsible for the characteristic “flexion–pronation” deformity of the upper limb.

• 2.

  It is elastic. Attempts at reducing the deformity meet with a resistance, which increases with the strength applied. If the opposing force is maintained long enough, the deformity usually yields, but the limb returns to its initial position as soon as the attempt is stopped.

• 3.

  It is present at rest, and exaggerated with voluntary movement, emotion, fatigue, and pain.

• 4.

  Osteotendinous reflexes are exaggerated, brisk, diffuse and polykinetic.

• 5.

  There may be associated synkineses, described as “the phenomenon whereby paralysed muscles incapable of a certain voluntary movement, execute this movement in a voluntary fashion by accompanying intact muscles”.

The shoulder is usually relatively spared. At the elbow level, spasticity involves predominantly all three flexors, but the triceps can also be spastic.

Spasticity of the wrist flexors and pronators leads to the characteristic hyperflexed and hyperpronated deformity. Finger spasticity is difficult to assess if the wrist is hyperflexed. The finger flexors are frequently involved, and the interossei muscles to a various amount. All thenar muscles may be affected.

Quantitative evaluation of spasticity is challenging. The classical Ashworth and modified Ashworth scales have been recognized as too subjective and should be combined with the more accurate Tardieu scale.

Muscle contracture

Muscle contracture is a result of longstanding, unopposed spasticity of muscles. Unlike spasticity, it is permanent and cannot be overcome, although shortening the involved articular segment can alleviate it. For example, posturing the wrist in flexion relieves contracture of the finger flexors. This is assessed by Volkmann’s angle, which is the degree of wrist flexion required to obtain full passive finger extension. Contracture of the intrinsic muscles of the fingers is assessed by the Finochietto test ( Fig. 29.5A,B ).

Clinical distinction between contracture and spasticity may be difficult to establish. In such cases nerve blocks, or botulinum toxin are useful.

Joint deformity

Passive motion of the involved joints may be difficult to assess because of associated muscle contractures. Sometimes it is not until muscle contractures have been surgically released that the actual range of passive motion can be evaluated.

In spastic children, increased passive extension of some joints may result in joint instability, mostly at the thumb MCP joint, and at the finger PIP joints (leading to a swan-neck deformity) ( Fig. 29.6 ).

Motor assessment

Motor examination of the spastic upper limb is difficult, especially when the deformities are severe. The flexor, adductor, and pronator muscles, mostly spastic, usually retain some voluntary control. Assessing their strength with the classical Medical Research Council (MRC) grading scale may be challenging when severe deformities are present.

The palsy usually predominates distally, and involves the antagonist muscles (extensor and supinator muscles). Rather than actually paralysed, these muscles may be present, but made ineffective by the spastic agonists. Botulinum toxin of the spastic agonists can be helpful: by decreasing their tone, it allows a proper evaluation of the “paralysed” muscles, which may end up demonstrating a satisfactory voluntary control.

Spontaneous involuntary movements are recorded: dystonia, characterized by involuntary intermittent muscle contractions causing repetitive movements and/or abnormal postures, is common in cerebral palsy patients. When predominant, it is a contraindication to surgery.

Some attempts at classification of the spastic upper limb have been made. Aside from Tonkin’s specific thumb classification, we have not found any of them very helpful because of the infinite range of clinical pictures, many of which do not fit into any of the described categories.