Ultrasound in Med. & Biol., Vol. -, No. -, pp. 1–4, 2014Copyright � 2014 World Federation for Ultrasound in Medicine & Biology

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http://dx.doi.org/10.1016

d Clinical Note

HIGH-RESOLUTION ULTRASONOGRAPHIC EVALUATION OF‘‘HOURGLASS-LIKE FASCICULAR CONSTRICTION’’ IN PERIPHERAL

NERVES: A PRELIMINARY REPORT

YUKO NAKASHIMA, TORU SUNAGAWA, RIKUO SHINOMIYA, and MITSU OCHI

Department of Orthopedic Surgery, Hiroshima University Hospital, Hiroshima, Japan

(Received 18 July 2013; revised 29 November 2013; in final form 6 December 2013)

Aoshima

Cconflic

Abstract—An hourglass-like constriction is a focal fascicular lesion observed in one or a few places in one or a fewfascicles of a peripheral nerve trunk, and usually affects the anterior interosseous (AIN) or posterior interosseous(PIN) nerve. Constrictions have previously been discovered only by surgical exploration, and have been unable tobe recognized on pre-operative imaging. We encountered some cases in which the lesion was able to be diagnosedpre-operatively by high-resolution ultrasonography; these findings were then confirmed intra-operatively. Fiveconsecutive cases were included in this study. In three cases with constrictions revealed on pre-operative ultra-sound, the findings were confirmed intra-operatively. In the remaining two cases in which no constrictions weredetected pre-operatively, no constriction was revealed intra-operatively. High-resolution ultrasonography mayplay a significant role in the diagnosis of hourglass-like constrictions, and may thus lead to significant changesin treatment strategies for AIN and PIN palsy. (E-mail: torusuna@hiroshima-u.ac.jp) � 2014World Federationfor Ultrasound in Medicine & Biology.

Key Words: Diagnosis, High-frequency ultrasonography, Nerve fascicle, Hourglass-like constriction, Peripheralnerve palsy.

INTRODUCTION

An hourglass-like constriction is a focal fascicular lesionobserved at one or a few places in one or a few fasciclesof a peripheral nerve trunk, and usually affects the ante-rior interosseous nerve (AIN) or posterior interosseousnerve (PIN) (Burns and Lister 1984; Comtet andChamboud 1975; Englert 1976; Haussmann 1982;Nagano et al. 1996; Ochi et al. 2011; Pan et al. 2011).These constrictions have always only been discoveredby surgical exploration in cases without spontaneousrecovery within several months of onset.

The development of high-resolution ultrasonogra-phy allows accurate and cost-effective diagnosis of softtissue lesions. Some reports have described quantitativeevaluation of peripheral nerve disorders using thismethod, targeting nerve fascicles as well as nervetrunks (Liu et al. 2012; Tagliafico et al. 2010;Watanabe et al. 2010). Although this method can

ddress correspondence to: Toru Sunagawa, 1-2-3 Kasumi, Hir-734-8551, Japan. E-mail: torusuna@hiroshima-u.ac.jponflicts of Interest: The authors have indicated that they have nots of interest regarding the content of this article.

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detect intrinsic nerve abnormalities in the PIN(Nakamichi and Tachibana 2007; Rossey-Marce et al.2004), whether lesions in the AIN can be identifiedremains unclear. We encountered some cases of AINand PIN palsy in which a pre-operative diagnosiswas able to be reached using high-resolution ultraso-nography; these findings were subsequently confirmedintra-operatively. We therefore report the utility of ul-trasonography for imaging of these constrictions.

METHODS

This study was conducted with the approval of ourinstitutional review board and all participants. Fiveconsecutive male patients who had visited our institutionsince September 2012 and were diagnosed with idio-pathic AIN or PIN palsy based on clinical findings wereexamined (Table 1). Post-traumatic cases were excludedfrom this study. Mean age at the time of diagnosis was36.8 y. The diagnosis was AIN palsy in four cases andPIN palsy in one case. The duration between onset ofsymptoms and ultrasonographic examination rangedfrom 7 d to 8 mo, and the duration between examinationand operation ranged from 3 d to 1 mo.

Table 1. Case summary

Case Age SexClinicaldiagnosis

Time from onsetto US exam

Time from USexam to surgery

1 37 M AIN palsy 21 d 3 d2 40 M PIN palsy 7 d 7 d3 75 M AIN palsy 2 mo 3 wk4 35 M AIN palsy 5 mo 2 wk5 37 M AIN palsy 8 mo 1 mo

AIN 5 anterior interosseous nerve; PIN 5 posterior interosseousnerve; US 5 ultrasound.

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The high-resolution device used was the HI VISIONAvius (Hitachi Aloka Medical, Tokyo, Japan) with a 14-to 6-MHz linear probe. All sonographic studies wereperformed by the same hand surgeon (Y.N.) with 3 y ofexperience in musculoskeletal imaging, especially ofthe hand and elbow. First, we observed nerve fasciclesin the median or radial nerve trunks in a transversefashion around the site of tenderness at the elbow jointlevel and confirmed the presence of changes in fasciclesize. We then conducted observations in longitudinalfashion after confirming fascicular swelling or stenosisand evaluated the presence or absence of fascicularconstriction. A comparison with the opposite side at thesame level was crucial for diagnosis. If there was patho-logic change in the fascicular size, we measured thediameter using the measurement tool equipped basicallyon the ultrasonographic device.

Surgical treatment was performed in all cases by thesame hand surgeon (T.S.) after taking the ultrasono-graphic information into consideration. During surgery,interfascicular neurolysis was performed by removingthe perineurium to divide out nerve fascicles, and theultrasonographic and intra-operative findings werecompared.

RESULTS

Ultrasonography revealed swollen and constrictedlesions interrupted by hyperechoic bands within fasciclesin three cases pre-operatively (cases 1, 2, 5) (Table 2).The diameter of the constricted lesion ranged from 0.3

Table 2. Ultrasonographic and intra-operative findings

Case

Number of constrictions

Ultrasound findings Intraoperative findings

1 3 in one fascicle and1 in other fascicle

3 in one fascicle and 1 in other fascicle

2 2 in one fascicle 2 in one fascicle3 None None; scar formation around anterior

interosseous nerve4 None None; slight compression on median nerve5 1 in one fascicle 1 in one fascicle

to 0.9 mm, and the diameter of swollen fascicles betweenconstrictions ranged from 1.6 to 2.0 mm. Power Dopplerexamination revealed no hypervascularity around thelesions. All constrictions revealed ultrasonographicallywere confirmed intra-operatively (Figs. 1, 2), and noother constrictions were identified during surgery. In theother two cases in which no constrictions were detectedpre-operatively by ultrasonography (cases 3, 4), no con-strictions were revealed intra-operatively. In one of thesepatients, there was scar formation around the AIN, and inthe other, there were no abnormal findings other than theimpression of the median nerve in the arch of the flexordigitorum superficialis.

DISCUSSION

The cause of AIN or PIN palsy is obscure, but islikely to be multifactorial and is suspected to involveneuralgic amyotrophy (Parsonage and Turner 1948), iso-lated neuritis (Kiloh and Nevin 1952) and entrapmentneuropathy (Fearn and Goodfellow 1965). Althoughentrapment neuropathy is one likely cause of this palsy,its incidence is low, and the most common causes arelikely neuritis and neuralgic amyotrophy (Nagano2003). Theoretically, conservative treatment is recom-mended for isolated neuritis or neuralgic amyotrophy,whereas decompression is advised for entrapment. How-ever, clinical signs, symptoms and examination tools fordifferentiating these conditions are lacking, and deter-mining whether to recommend conservative or operativetreatment has been difficult. In general, the surgical routeis suggested for cases with no sign of recovery by 3 to6 mo after symptom onset (Nagano 2003; Ochi et al.2011; Sood and Burke 1997).

The etiology of hourglass-like constriction remainsunclear; however, local inflammation may play a signifi-cant role in its formation (Lundborg 2003; Nagano 2003).Certain cases of isolated neuritis or neuralgic amyotrophyinclude hourglass-like constrictions in the involvednerve, and may require surgical treatment. The abilityto identify such constriction on imaging would be helpfulin planning treatment.

Recently, ultrasonography has been used in quanti-tative peripheral nerve evaluations such as nerve cross-sectional measurement, nerve density calculation andfascicle size measurement (Liu et al. 2012; Tagliaficoet al. 2010; Watanabe et al. 2010). The present studywas able both to measure the diameter of involvedfascicles and to accurately diagnose hourglass-like con-strictions in AIN and PIN. Confirmation was madeintra-operatively, and neither false-positive nor false-negative cases were encountered.

Mohammadi et al. (2012) reported significant corre-lation between median nerve hypervascularization and

Fig. 1. Case 2, posterior interosseous nerve (PIN) palsy. (a) Axial ultrasonography. One of the fascicles on the affectedside (right arrow) is markedly swollen (2.0 mm in diameter) compared with that on the intact side (left arrow, 1.1 mm indiameter). (b) Longitudinal ultrasonography. Two constrictions (arrows) and diffuse swelling are apparent. The asteriskindicates the trochlea of the humerus. (c) Intra-operative findings were the same as those of ultrasonography. Two con-

strictions (arrows) were identified.

Hourglass-like fascicular constriction in peripheral nerves d Y. NAKASHIMA et al. 3

the severity of carpal tunnel syndrome using colorDoppler sonography technique. However, we could notdetect the hypervascularization around the lesions,similar to the results for radial nerve constriction reportedby Rossey-Marec et al. (2004). The etiology of this lesionmay differ from that of entrapment neuropathy.

As the number of cases in this study was very small,we can only report the possibility of diagnostic ultraso-

Fig. 2. Case 5, anterior interosseous nerve (AIN) palsy. (a)0.3 mm in diameter) and proximal swelling (2.0 mm in diametulum of the humerus. (b) Intra-operative examination reveal

constriction (arrow) and marked proxim

nography. The severity of constriction varies from a slightimpression to a situation in which the nerve is more orless totally tied off. In our series, apparent constrictionswere able to be diagnosed, but the extent to which severelesions can be identified remains uncertain. The durationbetween symptom onset and examination varied in ourcases; therefore, the optimal timing of diagnostic ultraso-nography likewise remains unclear. Further studies are

Longitudinal ultrasonography. One constriction (arrow,er) are clearly apparent. The asterisk indicates the capit-s the same findings identified on ultrasonography. Oneal swelling (asterisk) are evident.

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needed to determine issues such as accuracy, specificityand timing.

The natural course of this pathology when treatedconservatively and the association between clinical his-tory and postoperative course of the constrictions willneed to be observed on ultrasonography. Significantchanges in treatment choice may occur when such issuesare better understood. In case 1, in which the patient wasalready symptom-free by 4 mo after surgery, no constric-tion was detected on ultrasonography.

In conclusion, high-resolution ultrasonography mayplay a significant role in the diagnosis of hourglass-likeconstrictions, and may potentially lead to significantchanges in treatment strategies for AIN and PIN palsy.

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