We are grateful for the additions to our article (1). FU Beutner highlights again that polyneuropathy is a common cause of spontaneous foot drop—that is our experience as well. In addition, it should be recognized that there is a high coincidence between polyneuropathies and compression syndromes (2): Because of changes in their myelin sheaths that may result from the systemic disease, the nerves are, per se, more sensitive to local pressure. To perform HbA1c testing in patients with foot drop is a valuable suggestion for daily practice which should be added to our algorithm.
Neuromuscular electrical stimulation is briefly touched upon in our article. In animal experiments it was shown that electrical stimulation of denervated muscles can stop the development of muscle atrophy, provided muscle fiber–specific stimulation frequencies, intervals, and stimulus locations are used (3). Its effectiveness in patients remains the subject of controversy. It would miss the point to attribute a direct beneficial effect on foot drop to conventional transcutaneous electrical nerve stimulation (TENS) (4). The efficacy of TENS in the treatment of polyneuropathy-associated pain is supported by a considerable amount of evidence and a beneficial effect of TENS on spasticity in patients after stroke has also be demonstrated (5). Furthermore, we think that the psychological benefit for patients from the perceived sensation of electrical pulses in the affected area of the foot should not be underestimated. However, one should explain to the patients that these devices are unlikely to improve the actual paralysis and thus do not represent a viable alternative to other causal treatments, if any are available in the individual case. Furthermore, TENS is no substitute for active physiotherapy which includes joint mobility and training of compensatory movements. TENS should be distinguished from direct nerve stimulation, the technique mentioned by A. Winkelmann and A. Bitsch. The method exploits the integrity of the peripheral nerve in patients with central foot drop and its beneficial effects have been demonstrated. As mentioned above, currently this treatment is hampered by its prohibitively high costs.
Given the numerous inquiries of readers—many thanks for these—here some additional information about tendon transfer techniques: The most important prerequisite for successful tendon transfer surgery is that the paresis is limited to the area innervated by the common fibular nerve, i.e. that only the tibialis anterior muscle and the peroneal muscles are affected. Patients with polyradicular lesions and advanced polyneuropathies typically do not meet this criterion. In addition, patients should not have severe pes planovalgus deformity, because in these patients the tibialis posterior muscle, which is used for the transfer, is an important stabilizer of the inner arch of the foot. In such cases, tendon transfer surgery can be combined with subtalar arthrodesis. If these factors are taken into account when making the decision to operate, the patients’ quality of life can be significantly improved by the procedure.
Dr. med. Anne Elisabeth Carolus
Klinik für Neurochirurgie
Universitätsklinik Knappschaftskrankenhaus, Bochum, Germany
Conflict of interest statement
The authors of all contributions declare that no conflict of interest exists.
|1.||Carolus AE, Becker M, Cuny J, Smektala R, Schmieder K, Brenke C: The interdisciplinary management of foot drop. Dtsch Arztebl Int 2019; 116: 347–54 VOLLTEXT|
|2.||Rajabally YA, Narasimhan M: Electrophysiological entrapment syndromes in chronic inflammatory demyelinating polyneuropathy. Muscle Nerve 2011; 44: 444–7 CrossRef MEDLINE|
|3.||Tanaka M, Nakanishi R, Murakami S, et al.: Effectiveness of daily eccentric contractions induced via kilohertz frequency transcutaneous electrical stimulation on muscle atrophy. Acta Histochem 2016; 118: 56–62 CrossRef MEDLINE|
|4.||Lin S, Sun Q, Wang H, Xie G: Influence of transcutaneous electrical nerve stimulation on spasticity, balance, and walking speed in stroke patients: A systematic review and meta-analysis. J Rehabil Med 2018; 50: 3–7 CrossRef MEDLINE|
|5.||Poulsen JB, Møller K, Jensen CV, Weisdorf S, Kehlet H, Perner A: Effect of transcutaneous electrical muscle stimulation on muscle volume in patients with septic shock. Crit Care Med 2011; 39: 456–61 CrossRef MEDLINE|