Objective: Here we report a case of focal LLD successfully treated with combined botulinum neurotoxin type A (BoNTA) and Nerve block (NB).

Background: Among focal dystonias, lower limb dystonia (LLD) is rather uncommon (1). The most effective treatment is botulinum neurotoxin type A (BoNTA) but evidence for LLD is less solid (2). Nerve block (NB) is a chemodenervation technique successfully used in spasticity (3) but the evidence regarding dystonia is very scarce (4).

Method: A 50-years-old man, former long-distance runner, developed an abnormal posture of right foot and toe in 2014 that initially only appeared while running and not elicited by other exercises, but over time also affected normal walking and remained at rest. Physical examination showed inversion, plantarflexion and internal rotation of the right foot, and hyperextension of the toe at rest, worsening while walking. No other neurological symptoms were found. Instrumental investigations were normal and other causes of LLD were excluded. Patient underwent therapy with Abobotulinumtoxin-A with an initial improvement but a decreased response after 4 years, despite the dosing increase. Patient had also tried oral medications and physiotherapy with no significant improvement. Ultrasonographic evaluation showed an alteration of right leg muscle echogenic pattern.

Results: To test the hypothesis of a structural alteration of muscle influencing BoNTA effectiveness (5), in 2021, diagnostic NB of tibial nerve was performed with 2.5% Lidocaine injection. After the procedure, internal foot rotation and plantarflexion improved and a therapeutic NB with 5% phenol was performed. Hyperextension of EHL was successfully treated with Abobotulinumtoxin-A. Combined treatment led to a marked improvement of symptoms with a lasting response that remained consistent with treatment repetition.

Conclusion: The case presented here suggests that NB could be a useful instrument in patients with focal LLD refractory to BoNTA treatment to evaluate residual response to chemodenervation and to help achieving an effective control of symptoms before considering more invasive strategies.

References: 1. Jinnah HA, Berardelli A, Comella C, DeFazio G, DeLong MR, Factor S, et al. The focal dystonias: Current views and challenges for future research: Unanswered Questions in Focal Dystonias. Movement Disorders. 2013 Jun 15;28(7):926–43.
2. Dressler D, Altavista MC, Altenmueller E, Bhidayasiri R, Bohlega S, Chana P, et al. Consensus guidelines for botulinum toxin therapy: general algorithms and dosing tables for dystonia and spasticity. J Neural Transm (Vienna). 2021 Mar;128(3):321–35.
3. Kirazli Y, On AY, Kismali B, Aksit R. Comparison of phenol block and botulinus toxin type A in the treatment of spastic foot after stroke: a randomized, double-blind trial. Am J Phys Med Rehabil. 1998;77(6):510–5.
4. Kim JS, Lee KS, Ko YJ, Ko SB, Chung SW. Idiopathic foot dystonia treated with intramuscular phenol injection. Parkinsonism Relat Disord. 2003 Aug;9(6):355–9.
5. Picelli A, Bonetti P, Fontana C, Barausse M, Dambruoso F, Gajofatto F, et al. Is spastic muscle echo intensity related to the response to botulinum toxin type A in patients with stroke? A cohort study. Arch Phys Med Rehabil. 2012 Jul;93(7):1253–8.

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