570222 research-article2015

JHS0010.1177/1753193415570222Journal of Hand Surgery (European Volume)Short report letter

JHS(E)

Short report letter

The Journal of Hand Surgery (European Volume) XXE(X) 1­–3 jhs.sagepub.com

Intraneural microvascular patterns of the median nerve assessed using contrast-enhanced ultrasonography in carpal tunnel syndrome

et al., 2014). The forearm and hand were fixed on an arm stand with the wrist in full supination and without any radial/ulnar deviation or flexion/extension (Figure 1(A)). The scaphoid tubercle, pisiform and hook of hamate were marked on the skin surface by palpation and US. Sagittal views of the median nerve were obtained at the midpoint between the scaphoid tubercle-pisiform line and hook of hamate (Figure 1(B)). B-mode images with a 5.5  MHz frequency linear transducer were obtained initially to confirm optimum visualization of the median nerve and to place an oval region of interest with a size of 2.26 × 1.41 mm in the median nerve proximal to the carpal tunnel (Figure 1 (C) and (F). CEUS provides high reproducibility in evaluation of intraneural blood flow of the median nerve proximal to the carpal tunnel, though it is difficult to evaluate the intraneural blood flow just within, and distal to, the carpal tunnel because of the artefacts and attenuation (Ishizaka et al., 2014). An intravenous catheter was placed in the left arm of each volunteer and in the arm of each patient corresponding to the intact or less severe hand. A microbubble contrast agent (Sonazoid, GE Healthcare, Waukesha, Wisconsin) was injected intravenously at a concentration of 0.015 ml/kg, and was followed by a 10 ml saline

Dear Sir, We carried out an unblinded comparison of intraneural blood flow in the median nerve of 13 patients with a moderate to severe carpal tunnel syndrome (CTS) and 15 unmatched control subjects using contrast enhanced ultrasound (CEUS) imaging. Table 1 shows their demographic data. The diagnosis of CTS was indicated by the following criteria: nocturnal hand pain and paraesthesia of the median nerve-innervated area, a positive Phalen test, and prolonged motor nerve distal latency (>5 ms). Table 2 shows disease severity of the patients. All ultrasound (US) examinations were performed by a certified sonographer in a blinded manner. US images were corrected using an ultrasound unit (AplioTM 500, Toshiba Medical Systems Corp., Tochigi, Japan) with an 8.0 MHz centre frequency linear transducer (PLT-805AT) as previously reported (Ishizaka Table 1.  Demographic data.

Volunteers (n) Female:Male Age (y) Body mass index Area under the curve (AUC)

Control

CTS

p

15 8:7 41 (26–73) 15 (SD 0.8) 37 (SD 7.8)

 13  11:2   61 (49–80)   25 (SD1.4) 108 (SD 22)

– – 0.04 0.04 0.002

CTS: carpal tunnel syndrome.

Table 2.  Disease severity of patients. Patient No. 

Disease Period (month)

SW test

13

19 (SD 22)

3.89 (SD1.08)

SNAP

CMAP

Velocity (m/s)

Distal latency (ms)

38.2 (SD 2.0) 7 detected

7.1 (SD 0.7) 12 detected

Pain VAS

43 (SD 9)

CTSI

DASH

Symptom

Function

 

2.12 (SD 0.18)

1.54 (SD 0.16)

19.0 (SD 3.6)

CMAP: compound motor nerve action potential; CTSI: carpal tunnel syndrome instrument; DASH: disabilities of the arm, shoulder and hand; SNAP: sensory nerve action potential; SW test: Semmes-Weinstein monofilament test; VAS: visual analogue scale.

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The Journal of Hand Surgery (Eur)

Figure 1.  (A) The forearm and hand were fixed on an arm stand with the wrist in full supination and without any radial/ ulnar deviation or flexion/extension. (B) A US transducer was put on longitudinally, perpendicular to the scaphoid tuberclepisiform plane. The flexor retinaculum (yellow square) is drawn based on surface bony landmarks. A sagittal view of the median nerve is obtained at the midpoint between the scaphoid tubercle-pisiform line and hook of hamate. Sub-figures (C), (D) and (E) depict US images of a control subject: in this machine, the region of interest of the CEUS mode moves together with that of the B mode. (C) B-mode sagittal image of the median nerve. (D) A hypovascular pattern was found in the median nerve proximal to the carpal tunnel in the CEUS image. (E) Time-intensity curves show no increase of blood flow. Sub-figures (F), (G) and (H) depict US images of a CTS patient. (F) B-mode sagittal image of the median nerve. (G) A hypervascular pattern can be confirmed in the region of interest in the CEUS image. (Arrows show the borders of the carpal tunnel.) (H) Time-intensity curves clearly show the increase of intraneural blood flow. H: hook of hamate; P: pisiform; S: tubercle of scaphoid; Me: median nerve; T: tendon.

flush. The CEUS images were recorded for 80 seconds after the contrast medium injection (Figure 1 (D) and (G). Time-intensity curves based on continuous raw data (1190 frames) were collected from all subjects

(Figure 1 (E) and (H) and this was divided into two epochs. The first 270 frames were taken to represent a baseline level before the contrast agent reaches the region. The remaining 920 frames record an increase

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Short report letter on the baseline signal believed to result from passage of the contrast medium through the region of interest, and the area under the curve (AUC) for these 920 frames was calculated and expressed as a ratio to the baseline measurement. All data are presented as mean ± standard error of mean. Statistical significance was determined using the unpaired t-test. P