Introduction

Botulinum neurotoxin type A (BoNT-A) injections are established as a standard procedure for the treatment of functional shortening of different muscles in spastic or dystonic children. Preconditions for beneficial effects are:

• a functional problem resulting from dynamic hyperactive muscle shortening without major structural changes

• a focal problem caused by hyperactivity of a few muscles

• application of the BoNT in the target muscle close to the neuromuscular junctions

• a sufficient dose

• no antibodies to BoNT-A.

Muscles that are superficial and palpable are easy to inject. In contrast, exact placement of the needle is more difficult and less controllable in muscles that are not palpable and deeply situated (e.g. iliopsoas) or are small and difficult to selectively identify (such as forearm muscles). Exact needle placement is, however, essential for optimal functional result, avoidance of side effects and evaluation of therapeutic failures.

To localize the target muscle and to control the placement of the injection needle several techniques are available:

• orientation at anatomical landmarks and palpation supported by moving the distal joint to observe the motion of the needle placed in the target muscle (Buchthal technique)

• electromyography

• electrical stimulation

• real-time ultrasound

• CT.

Clinical application of BoNT has been shown to be inaccurate except for the gastrocsoleus complex (Chin et al., 2005). Electromyography is good, but many muscles may be simultaneously active. Control by electrical stimulation is quite uncomfortable and painful and often requires anesthesia. Guidance under CT is not appropriate for routine use because of the exposure to radiation and high costs. By comparison, the advantages of the ultrasound-guided technique are clear:

• real-time observation of the injection

• readily available

• easily applicable after a manageable learning period

• cost effective

• no serious side effects.