How doctors think – and treat with botulinum toxin A Sebastian Schroeder 1 , Inga Koerte 2 , Steffen Berweck 3 , Birgit Ertl-Wagner 2 , Florian Heinen 1 1 Department of Paediatric Neurology and Developmental Medicine, Dr von Hauner's Children's Hospital, Ludwig-Maximilians-University of Munich, Munich, Germany. 2 Institute of Clinical Radiology, Ludwig-Maximilians-University of Munich, Munich, Germany. 3 Specialist Centre for Paediatric Neurology, Epilepsy Centre for Children and Adolescents, Vogtareuth, Germany. Correspondence to: sebastian.schroeder@med.uni-muenchen.de doi: 10.1111/j.1469-8749.2010.03692.x SIR–A recent bestseller in popular medicine is How Doctors Think by Jerome Groopman. 1 This book narrates true stories that illustrate how some doctors went spectacularly wrong because they were trapped in their established ways of think- ing unable to adjust to newly emerging evidence. Even in the face of new compelling data doctors tend to stay with their old concepts. Here we add a note about botulinum toxin type A (BoNT-A), a substance used worldwide in applications ranging from (child) neurology to aesthetics, contributing to significantly improved medical care in one field and generating big business in the other. BoNT-A injections are performed thousands of times every day worldwide. Based on the evidence accumulated in over 10 000 publications (PubMed search under ‘botulinum toxin’) there is general consensus that the clinical effect of BoNT-A lasts for about 3–6 months. Therefore, in keeping with clinical observations and seemingly supported by data from animal experiments, 2 BoNT-A is usually reinjected at 3- to 6-month intervals. Recent data on the duration of neurogenic atrophy after injection into healthy human muscle have had little impact on clinical practice so far 3,4 and data on spastic muscle are missing. Using three Tesla magnetic resonance imaging (MRI) with water sensitive T2-weighted short tau inversion recovery sequences we report a 1-year follow-up examination in a male with cerebral palsy after a single injection of BoNT-A into the lower leg according to published recommendations. 5 The treated muscle shows the same high signal intensity pattern (Fig. 1) as previously reported for healthy volun- teers, 4 indicating that focal neurogenic atrophy at the site of injection is still present 6 months (and to some extent 1 year) after BoNT-A injection. Since its introduction in the 1980s, and encouraged by posi- tive clinical effects, BoNT-A has been used ahead of a com- prehensive fundamental knowledge about its biological effects in humans. The data on spastic muscle presented here are con- sistent with earlier observations in healthy muscle 4 indicating that focal neurogenic atrophy following BoNT-A persists longer than expected. The discrepancy between the observed ‘focal long-term structural alterations’ and the clinically reported ‘short-term functional efficacy’ remains unclear. This should induce further investigations and provoke reconsidera- tion of the established regimes of BoNT-A treatment. 6wks 6mo 12mo * HSIP a b * * Figure 1: T2 short tau inversion recovery (STIR-) MR sequence, time course of BoNT-A in the lower leg. Male (9y) with unilateral spastic CP of the right body side (Gross Motor Function Classification System (GMFCS) level I). Injection of BoNT type A (preparation Botox â ) into two sites of the right soleus at the mid- dle of the lower leg: medial site 50 Units, lateral site 50 Units. The high signal intensity pattern (HSIP) in short tau inversion recovery (STIR) MR sequence of the lateral injection site of soleus muscle can be seen in the encircled area. (*) indicates the HSIP in the medial injection site. (a) Coronal view of the lower legs 6 months after injection. (b) Axial view of the same patient over course of 12 months. ª The Authors. Journal compilation ª Mac Keith Press 2010 875 DEVELOPMENTAL MEDICINE & CHILD NEUROLOGY LETTER TO THE EDITOR