FIGURE 1. (A, B) Fluid-attenuated inversion recovery (FLAIR) and T2 magnetic resonance images (MRIs) show confluent hyperintensities in bilateral parieto-occipital subcortical white matter. (C, D) FLAIR and T2 MR images show hyperintensities in the splenium of the corpus callosum. (E, F) Diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) images show acute diffusion restriction corresponding to the areas of hyperintensities shown in (A) and (B), respectively. (G, H) DWI and ADC images show acute diffusion restriction in areas that correspond to the changes seen in (C) and (D), respectively. The hyperintensities and diffusion restriction resolved on follow-up brain MRI 3 months after presentation (not shown). 9. Basu A, Horvath R, Esisi B, Birchall D, Chinnery PF. Recurrent stroke like episodes in X-linked Charcot-Marie-Tooth disease Neurology 2011;77:1205–1206. 10. U-King-Im JM, Yiu E, Donner EJ, Shroff M. MRI findings in X-linked Charcot-Marie-Tooth disease associated with a novel connexin 32 mutations. Clin Radiol 2011;66:471–474. 11. Paulson H, Garbeern J, Hoban T, Krajewski KM, Lewis RA, Fischbeck KH, et al. Transient central nervous system white matter abnormality in X-linked Charcot-Marie-Tooth disease. Ann Neurol 2002;52:429– 434. 12. Rahman S, Evans WH. Topography of connexin32 in rat liver gap junctions. Evidence for an intramolecular disulphide linkage connecting the two extracellular peptide loops. J Cell Sci 1991;100:567– 578. 13. Fairweather N, Bell C, Cochrane S, Chelly J, Wang S, Mostacciuolo ML, et al. Mutations in the Connexin 32 gene in X-linked dominant Charcot-Marie-Tooth disease (CMTX1) Hum Mol Genet 1994;3:29– 34. Erratum in: Hum Mol Genet 199431034
Published online 18 July 2014 in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/mus.24343
--------------------------------------------------------IATROGENIC INJURY TO POSTERIOR ANTEBRACHIAL CUTANEOUS NERVE A 46-year-old woman presented with persistent numbness of the dorsal aspect of the left forearm along with intermittent sharp pain. She related the onset of symptoms to a surgical procedure of the elbow 10 months previously. Prior to the surgery she had been suffering from severe pain over the lateral aspect of elbow for several years. Lateral humeral epicondylitis was diagnosed, and treatment included activity modification, occupational therapy, oral non-steroidal anti-inflammatory agents, and local corticosteroid injections. Persistence of symptoms led to a surgical procedure consisting of debridement of 1024
Letters to the Editor
extensor muscle origins at the lateral humeral epicondyle (LHE) under anesthetic block and tourniquet. She noticed significant improvement of the epicondylar pain but was left with the sensory symptoms noted above. Examination revealed loss of pain and light touch sensations over the dorsal forearm and a positive Tinel sign over the surgical scar. A radial nerve study showed normal motor conduction across the elbow and in the posterior interosseous nerve. Superficial radial sensory studies showed normal sensory nerve action potentials (SNAPs). Sensory conduction in the posterior antebrachial cutaneous nerve (PACN) was studied using a previously described technique.1,2 An 11.3-lV SNAP with an onset latency of 2.5 ms and peak latency of 3.7 ms was recorded on the right with the recording electrode at 15 cm (Fig. 2); no SNAP could be recorded on the left side, indicating axonal injury to the PACN. Lateral humeral epicondylitis, or tennis elbow, is among the many causes of chronic elbow pain and is often attributed to degenerative changes at the origin of the extensor carpi radialis brevis muscle from the lateral epicondyle. When conservative treatment measures fail, surgery is considered; this may include open or arthroscopic debridement.3 Surgical denervation of the lateral epicondyle by sectioning the posterior branches of PACN is considered an effective alternative.4 The PACN is in close proximity to the LHE and is at risk for injury during any of these surgical procedures. One recent report5 described painful neuroma of the PACN in 9 patients with persistent pain after surgery for lateral epicondylitis, but nerve conduction study data were lacking. Surgical procedures that may potentially injure the PACN include arthroscopy of the elbow, surgery for lateral humeral epicondylitis, surgical repair of distal MUSCLE & NERVE
December 2014
FIGURE 2. SNAP with amplitude of 11.3 lV, onset latency of 2.5 ms, and peak latency of 3.7 ms was recorded on stimulation of the right PACN at 2 cm proximal to the lateral epicondyle with the recording electrode at 15 cm distally. No SNAP could be recorded on the left side.
humeral fractures, and procurement of a myocutaneous flap using the triceps muscle. However, when compared with other cutaneous nerves in the forearm, the PACN appears to be least vulnerable to injury. A recent review of iatrogenic nerve injuries by Zhang et al.6 reported injuries to the lateral and medial antebrachial cutaneous nerves, as well as the superficial radial nerve, but no example of PACN injury is mentioned. PACN neuropathy confirmed by nerve conduction study has been reported in only 4 published studies.2,7–9 Among the 8 patents reported, 3 had definite and 1 had probable iatrogenic injury. PACN should be identified in the surgical field and, when in doubt, intraoperative stimulation and recording of nerve action potential should be done. If sensory symptoms occur postoperatively, electrodiagnostic evaluation should include study of the PACN. Vasudeva G. Iyer, MD, DM Department of Neurology, University of Louisville, Louisville, Kentucky, USA 1. Ma DM, Liveson JA. Nerve conduction handbook. Philadelphia: F.A. Davis; 1981. p 79–81. 2. Souayah N, Bhatt M, Sander HW. Posterior antebrachial cutaneous nerve conduction study technique. Neurol Neurophysiol Neurosci 2007;5:1–5. 3. Calfee RP, Patel A, DaSilva MF, Akelman E. Management of lateral epicondylitis: current concepts. J Am Acad Orthop Surg 2008;16:19–29. 4. Rose NE, Forman SK, Dellon AL. Denervation of the lateral humeral epicondyle for treatment of chronic lateral epicondylitis. J Hand Surg Am 2013;38:344–349. 5. Dellon AL, Kim J, Ducic I. Painful neuroma of the posterior cutaneous nerve of the forearm after surgery for lateral humeral epicondylitis. J Hand Surg Am 2004;29:387–390.
Letters to the Editor
6. Zhang J, Moore AE, Stringer MD. Iatrogenic upper limb nerve injuries: a systematic review. ANZ J Surg 2011;81:227–238. 7. Chang CW, Cho HK, Oh SJ. Posterior antebrachial cutaneous neuropathy. Case report. Electromyogr Clin Neurophysiol 1989;29:109–111. 8. Chang CW, Oh SJ. Posterior antebrachial cutaneous neuropathy. Case report. Electromyogr Clin Neurophysiol 1990;30:3–5. 9. Doyle JJ, David WS. Posterior antebrachial cutaneous neuropathy associated with lateral elbow pain. Muscle Nerve 1993;16:1417–1418.
Published online 24 July 2014 in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/mus.24347
--------------------------------------------------------IS NERVE CROSS-SECTIONAL AREA RELATED TO HEIGHT-SQUARED? We read with interest the recent excellent article by Walhout-van Burg et al. in which they explored normal values for median nerve cross-sectional area (CSA) at the level of the wrist and a number of anthropometric variables between samples of Indian and Dutch populations.1 They concluded that normal values for median nerve CSA were different in the populations examined even after correction for age, height, and weight. This finding reinforces the idea that laboratories worldwide should obtain their own normative data. We strongly agree, especially in light of the fact that normal median nerve CSA for the Dutch population (8.3 6 1.9 mm) overlapped significantly with the 8.5–10-mm range considered abnormal in a recently reviewed series of class I studies.2 MUSCLE & NERVE
December 2014
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Published online 18 July 2014 in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/mus.24343
--------------------------------------------------------IATROGENIC INJURY TO POSTERIOR ANTEBRACHIAL CUTANEOUS NERVE A 46-year-old woman presented with persistent numbness of the dorsal aspect of the left forearm along with intermittent sharp pain. She related the onset of symptoms to a surgical procedure of the elbow 10 months previously. Prior to the surgery she had been suffering from severe pain over the lateral aspect of elbow for several years. Lateral humeral epicondylitis was diagnosed, and treatment included activity modification, occupational therapy, oral non-steroidal anti-inflammatory agents, and local corticosteroid injections. Persistence of symptoms led to a surgical procedure consisting of debridement of 1024
Letters to the Editor
extensor muscle origins at the lateral humeral epicondyle (LHE) under anesthetic block and tourniquet. She noticed significant improvement of the epicondylar pain but was left with the sensory symptoms noted above. Examination revealed loss of pain and light touch sensations over the dorsal forearm and a positive Tinel sign over the surgical scar. A radial nerve study showed normal motor conduction across the elbow and in the posterior interosseous nerve. Superficial radial sensory studies showed normal sensory nerve action potentials (SNAPs). Sensory conduction in the posterior antebrachial cutaneous nerve (PACN) was studied using a previously described technique.1,2 An 11.3-lV SNAP with an onset latency of 2.5 ms and peak latency of 3.7 ms was recorded on the right with the recording electrode at 15 cm (Fig. 2); no SNAP could be recorded on the left side, indicating axonal injury to the PACN. Lateral humeral epicondylitis, or tennis elbow, is among the many causes of chronic elbow pain and is often attributed to degenerative changes at the origin of the extensor carpi radialis brevis muscle from the lateral epicondyle. When conservative treatment measures fail, surgery is considered; this may include open or arthroscopic debridement.3 Surgical denervation of the lateral epicondyle by sectioning the posterior branches of PACN is considered an effective alternative.4 The PACN is in close proximity to the LHE and is at risk for injury during any of these surgical procedures. One recent report5 described painful neuroma of the PACN in 9 patients with persistent pain after surgery for lateral epicondylitis, but nerve conduction study data were lacking. Surgical procedures that may potentially injure the PACN include arthroscopy of the elbow, surgery for lateral humeral epicondylitis, surgical repair of distal MUSCLE & NERVE
December 2014
FIGURE 2. SNAP with amplitude of 11.3 lV, onset latency of 2.5 ms, and peak latency of 3.7 ms was recorded on stimulation of the right PACN at 2 cm proximal to the lateral epicondyle with the recording electrode at 15 cm distally. No SNAP could be recorded on the left side.
humeral fractures, and procurement of a myocutaneous flap using the triceps muscle. However, when compared with other cutaneous nerves in the forearm, the PACN appears to be least vulnerable to injury. A recent review of iatrogenic nerve injuries by Zhang et al.6 reported injuries to the lateral and medial antebrachial cutaneous nerves, as well as the superficial radial nerve, but no example of PACN injury is mentioned. PACN neuropathy confirmed by nerve conduction study has been reported in only 4 published studies.2,7–9 Among the 8 patents reported, 3 had definite and 1 had probable iatrogenic injury. PACN should be identified in the surgical field and, when in doubt, intraoperative stimulation and recording of nerve action potential should be done. If sensory symptoms occur postoperatively, electrodiagnostic evaluation should include study of the PACN. Vasudeva G. Iyer, MD, DM Department of Neurology, University of Louisville, Louisville, Kentucky, USA 1. Ma DM, Liveson JA. Nerve conduction handbook. Philadelphia: F.A. Davis; 1981. p 79–81. 2. Souayah N, Bhatt M, Sander HW. Posterior antebrachial cutaneous nerve conduction study technique. Neurol Neurophysiol Neurosci 2007;5:1–5. 3. Calfee RP, Patel A, DaSilva MF, Akelman E. Management of lateral epicondylitis: current concepts. J Am Acad Orthop Surg 2008;16:19–29. 4. Rose NE, Forman SK, Dellon AL. Denervation of the lateral humeral epicondyle for treatment of chronic lateral epicondylitis. J Hand Surg Am 2013;38:344–349. 5. Dellon AL, Kim J, Ducic I. Painful neuroma of the posterior cutaneous nerve of the forearm after surgery for lateral humeral epicondylitis. J Hand Surg Am 2004;29:387–390.
Letters to the Editor
6. Zhang J, Moore AE, Stringer MD. Iatrogenic upper limb nerve injuries: a systematic review. ANZ J Surg 2011;81:227–238. 7. Chang CW, Cho HK, Oh SJ. Posterior antebrachial cutaneous neuropathy. Case report. Electromyogr Clin Neurophysiol 1989;29:109–111. 8. Chang CW, Oh SJ. Posterior antebrachial cutaneous neuropathy. Case report. Electromyogr Clin Neurophysiol 1990;30:3–5. 9. Doyle JJ, David WS. Posterior antebrachial cutaneous neuropathy associated with lateral elbow pain. Muscle Nerve 1993;16:1417–1418.
Published online 24 July 2014 in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/mus.24347
--------------------------------------------------------IS NERVE CROSS-SECTIONAL AREA RELATED TO HEIGHT-SQUARED? We read with interest the recent excellent article by Walhout-van Burg et al. in which they explored normal values for median nerve cross-sectional area (CSA) at the level of the wrist and a number of anthropometric variables between samples of Indian and Dutch populations.1 They concluded that normal values for median nerve CSA were different in the populations examined even after correction for age, height, and weight. This finding reinforces the idea that laboratories worldwide should obtain their own normative data. We strongly agree, especially in light of the fact that normal median nerve CSA for the Dutch population (8.3 6 1.9 mm) overlapped significantly with the 8.5–10-mm range considered abnormal in a recently reviewed series of class I studies.2 MUSCLE & NERVE
December 2014
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