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LETTER TO EDITOR
Year : 2011  |  Volume : 59  |  Issue : 2  |  Page : 296-297

Combination of ultrasound and nerve conduction studies in the diagnosis of tarsal tunnel syndrome


1 Neurology Diagnostic Laboratory, National University Hospital, Singapore
2 Division of Neurology, National University Hospital, Singapore
3 Department of Orthopaedic Surgery, National University Hospital, Singapore

Date of Submission08-Nov-2010
Date of Decision28-Nov-2010
Date of Acceptance29-Nov-2010
Date of Web Publication7-Apr-2011

Correspondence Address:
A K Therimadasamy
Neurology Diagnostic Laboratory, National University Hospital
Singapore
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0028-3886.79152

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How to cite this article:
Therimadasamy A K, Seet R C, Kagda Y H, Wilder-Smith E P. Combination of ultrasound and nerve conduction studies in the diagnosis of tarsal tunnel syndrome. Neurol India 2011;59:296-7

How to cite this URL:
Therimadasamy A K, Seet R C, Kagda Y H, Wilder-Smith E P. Combination of ultrasound and nerve conduction studies in the diagnosis of tarsal tunnel syndrome. Neurol India [serial online] 2011 [cited 2019 Aug 21];59:296-7. Available from: http://www.neurologyindia.com/text.asp?2011/59/2/296/79152


Sir,

Tarsal tunnel syndrome is a rare compression neuropathy of the posterior tibial nerve as it travels through the fibro-osseous tunnel at the level of medial ankle. [1] Nerve conduction studies are useful in supporting the diagnosis. Combining ultrasound with nerve conduction studies adds a morphological component to functional aspects of nerve damage in entrapment neuropathies. [2] We present a case of tarsal tunnel syndrome where this approach provided comprehensive information regarding etiology and location of tibial nerve compression at the tarsal tunnel.

A 44-year-old female presented with numbness involving the right foot sole of 2 months duration. Neurological examination revealed reduced sensation to light touch over the inferior aspects of the toes and positive Tinel's sign at the tarsal tunnel. There was no intrinsic foot muscle wasting and foot architecture was normal. Nerve conduction studies were performed following standard protocol for diagnosing tarsal tunnel syndrome. [3] The orthodromic medial and lateral plantar sensory nerve action potentials were absent when recorded above the tarsal tunnel. The medial and lateral plantar mixed nerve action potentials were also absent following mid-foot stimulation. Compound muscle action potentials recorded from abductor hallucis (AH) and abductor digiti quinti (ADQ) muscles showed prolonged distal latency (AH 5.55 vs. 3.80 ms and ADQ 6.55 vs. 5.15 ms) and low amplitude (AH 1.0 vs. 7.3 mV and ADQ 0.8 vs. 2.0 mV) compared to the contralateral side. There was no dispersion of the compound muscle action potential. Electrodiagnostic findings were consistent with a mixed axonal and demyelinating pathology of the posterior tibial nerve at or distal to the tarsal tunnel. Ultrasonography of the posterior tibial nerve was performed with a 10 MHz linear array transducer. The posterior tibial nerve was scanned from above the ankle to its terminal branching at the distal tarsal tunnel. The tibial nerve appeared normal above the ankle, but showed marked enlargement at the tarsal tunnel (cross-sectional area of 0.17 cm 2 vs. 0.10 cm 2 unaffected side) [Figure 1] and [Figure 2]. The Intraneural fascicles were unevenly enlarged with inferior fascicles larger and more hypoechoic. A hypoechoic cystic structure (area 0.14 cm 2 ) was observed immediately distal to the nerve enlargement extending from the flexor hallucis longus tendon [Figure 3]. The cyst was in close communication with the nerve, infiltrating inferior tibial nerve aspects.
Figure 1: Transverse images of the posterior tibial nerve at the tarsal tunnel showing uneven enlargement of the nerve fascicles on the symptomatic side compared to the normal side. Short arrows mark the epineural margins of the nerve

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Figure 2: Longitudinal images of posterior tibial nerve across the tarsal tunnel showing enlargement on the symptomatic side compared to the normal side

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Figure 3: Transverse image showing the synovial cyst from flexor hallucis longus tendon communicating with posterior tibial nerve. FHL - Flexor hallucis longus

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Although nerve conduction studies are standard in evaluating entrapment neuropathies, our patient demonstrates the additional value of ultrasonography in eliciting underlying etiology and site of nerve compression in tarsal tunnel syndrome. Nerve conduction studies are limited in localizing the site of tibial nerve compression which can be within the tarsal tunnel or distal to it. [4] Ultrasound provides direct evidence of nerve compression by demonstrating focal nerve enlargement and change in nerve echogenicity. In our patient, ultrasound localized the tibial nerve pathology at the tarsal tunnel due to a synovial cyst attached to flexor hallucis tendon. Our patient serves as an example how conventional nerve conduction testing can be complimented by adding ultrasound evaluation, providing comprehensive information for better treatment planning.

 
 » References Top

1.Finkel JE. Tarsal tunnel syndrome. Magn Reson Imaging Clin N Am 1994;2:67-78.  Back to cited text no. 1
[PUBMED]    
2.Padua L, Aprile I, Pazzaglia C, Frasca G, Caliandro P, Tonali P, et al. Contribution of ultrasound in a neurophysiological lab in diagnosing nerve impairment: A one-year systematic assessment. Clin Neurophysiol 2007;118:1410-6.  Back to cited text no. 2
[PUBMED]  [FULLTEXT]  
3.Patel AT, Gaines K, Malamut R, Park TA, Toro DR, Holland N, et al. Usefulness of electrodiagnostic techniques in the evaluation of suspected tarsal tunnel syndrome: An evidence-based review. Muscle Nerve 2005;32:236-40.  Back to cited text no. 3
    
4.Dellon AL. The four medial ankle tunnels: A critical review of perceptions of tarsal tunnel syndrome and neuropathy. Neurosurg Clin N Am 2008;19:629-48.  Back to cited text no. 4
[PUBMED]  [FULLTEXT]  


    Figures

  [Figure 1], [Figure 2], [Figure 3]

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