Comparison of Intramuscular Distribution of Different Injection Volumes Via Diffusion Tensor Imaging (DTI)

Background:

Intramuscular application of Botulinum toxin is used as a successful therapy of many conditions (e.g. spasticity, movement disorders, hypersecretory disorders, ophthalmic disorders, painful conditions, pelvic floor and gastrointestinal disorders, cosmetic applications) Clinical practice shows that even with the use of special guidance techniques (electromyography (EMG), ultrasound, electrical stimulation) to increase accuracy of targeting, botulinum toxin may spread to adjacent sites by diffusion. Different therapy goals request variable diffusion of the toxin, depending on the number of muscles involved and loss of function in the affected area, respectively. There is some evidence that larger injection volume lead to greater distribution and a larger affected area. Thus, animal model showed increased efficacy and decreased systemic side effects of botulinum toxin A in the injected muscle after active or passive manipulation of muscle.

Magnetic resonance imaging (MRI) has the potential to noninvasively probe the amount and motion of intracellular and extracellular water using different sequences. T2-weighted and diffusion tensor sequences are especially useful in the quantification and characterization of the chemical behaviour of water in different (animal) tissue types. To our knowledge there has been no systematically performed in vivo MR study using these imaging techniques in the visualization of intramuscular dilution of fluid in human subjects. However, the in vivo effect on tissue distribution of different injection volumes and active muscle movement in humans via DTI has never been observed.

Hypothesis:

Intramuscular distribution of common saline solutions can be non-invasively quantified by DTI in human subjects. DTI can be used to elucidate if:

• Intramuscular distribution is favoured by larger injection volumes and
• Intramuscular distribution is facilitated by active muscle activity.

Rationale:

The effect of large injection volumes and active muscle activity after injection on intramuscular toxin distribution and uptake remains unclear. Physiological sodium is the carrier material of all preparations of Botulinum toxin, suggesting that physiological sodium or natriumchlorid (NaCl) distribution is representative for toxin primary distribution. Dynamic T2-weighted sequences may monitor the inflow and regional distribution of the infused saline solution.

DTI can non-invasively quantify the amount and directionality of motion of protons in human skeletal muscle and may therefore indirectly allow assumptions on the extra- and intracellular distribution of the infused solution/substance.

Methods:

In this exploratory, investigator blinded pilot study, 10 healthy subjects will be investigated by DTI of the musculi biceps brachii after randomised intramuscular injection of two different injection volumes of NaCl and randomisation to active flexion and extension in the elbow joints versus no active flexion and extension. During each injection dynamic T2 weighted magnetic resonance tomographic sequences will be performed. Subsequently diffusion tensor sequences will be carried out at defined time points.