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LETTER TO EDITOR
Year : 2007  |  Volume : 55  |  Issue : 4  |  Page : 422

Variability of the palmar cutaneous branch median nerve sensory nerve action potential with carpal tunnel syndrome


1 Neurology, National University Singapore, 5 Lower Kent Ridge Road, 119074, Singapore
2 Neurology Diagnostic Laboratory, National University Hospital, 5 Lower Kent Ridge Road, 119074, Singapore

Date of Acceptance24-Apr-2007

Correspondence Address:
E P Wilder-Smith
Neurology, National University Singapore, 5 Lower Kent Ridge Road, 119074
Singapore
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0028-3886.37106

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How to cite this article:
Wilder-Smith E P, Kannan AT. Variability of the palmar cutaneous branch median nerve sensory nerve action potential with carpal tunnel syndrome. Neurol India 2007;55:422

How to cite this URL:
Wilder-Smith E P, Kannan AT. Variability of the palmar cutaneous branch median nerve sensory nerve action potential with carpal tunnel syndrome. Neurol India [serial online] 2007 [cited 2020 Jul 5];55:422. Available from: http://www.neurologyindia.com/text.asp?2007/55/4/422/37106


Sir,

The palmar cutaneous median branch (PCBm) sensory nerve action potential (SNAP) can be useful in investigating hand sensory symptoms. [1],[2] The PCBm SNAP when recorded using an antidromic technique yields two negative peaks followed by the motor potential [Figure - 1]a. The first negative peak represents the PCBm SNAP; the second peak a far field potential from transcarpally mediated hand sensory nerve fibers traveling to the thumb. [3] The second peak is a consequence of not being able to selectively stimulate the PCBm. The first and second peak are in close proximity with the first having the appearance of a shoulder sticking out from a hill. It is important to be cognizant of how this shape alters with median nerve entrapment in carpal tunnel syndrome (CTS). [4]

When the transcarpal median sensory fibers are solely affected in CTS, this results in the first and second peaks separating out. With increasing pathology of transcarpal fibers [Figure - 1]b, the degree of separation increases and in severe CTS can result in a lone SNAP from the PCBm [Figure - 1]c.

1 = PCBm sensory onset latency

2 = PCBm sensory peak latency

3 = Median transcarpal digital sensory peak latency

4 = Median motor onset latency

 
  References Top

1.Imai T, Wada T, Matsumoto H. Entrapment neuropathy of the palmar cutaneous branch of the median nerve in carpal tunnel syndrome. Clin Neurophysiol 2004;115:2514-7.  Back to cited text no. 1  [PUBMED]  [FULLTEXT]
2.Ayse TB, Feride G, Sumer G, Isik K, Mustafa G. The role of sensory nerve conduction study of the palmar cutaneous nerve in the diagnosis of carpal tunnel syndrome in patients with polyneuropathy. Neurol India 2007;55:17-21.  Back to cited text no. 2    
3.Bergeron JW, Braddom RL. Palmar cutaneous nerve recording and clarification of median premotor potential generators. Am J Phys Med Rehabil 1998;77:399-406.  Back to cited text no. 3  [PUBMED]  [FULLTEXT]
4.Rathakrishnan R, Therimadasamy AK, Chan YH, Wilder-Smith EP. The median palmar cutaneous nerve in normal subjects and CTS. Clin Neurophysiol 2007;118:776-80.  Back to cited text no. 4  [PUBMED]  [FULLTEXT]


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Online since 20th March '04
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