Casi Clinici
Chirurgia della Mano - Vol. 51 (2) 2014
SCHWANNOMA OF THE ANTERIOR INTEROSSEOUS NERVE:
A CASE REPORT
Roberto Adani*, Luigi Tarallo**, Stefano Colopi***, Raffaele Mugnai*
* Department of Hand Surgery and Microsurgery, University Hospital of Verona, Verona, Italy
** Department of Orthopedics, University Hospital of Modena, University of Modena and Reggio Emilia,
Modena, Italy
*** Department of Radiology, University Hospital of Modena, University of Modena and Reggio Emilia,
Modena
Referente
Roberto Adani Piazzale La Scuro, 10 Verona - E-mail: roberto.adani@ospedaleuniverona.it
SCHWANNOMA OF THE ANTERIOR INTEROSSEOUS NERVE: A CASE REPORT
SINTESI
Gli Schwannomi sono i tumori più frequenti dei nervi periferici. Il coinvolgimento del nervo interosseo
anteriore (AIN) è piuttosto insolito, a differenza del nervo mediano che è uno dei più interessati. Per
la loro bassa incidenza in questo distretto, i segni clinici ed i sintomi di questi tumori possono portare
talvolta a diagnosi erronee (i.e. altri tumori dei tessuti molli, in particolare gangli o tenosinoviti). Presentiamo il caso di un atleta di 27 anni, praticante judo a livello agonistico, e giunto all’ osservazione per
la comparsa di un dolore presente al momento in cui veniva afferrato al polso durante l’attività sportiva.
La RMN con contrasto ha mostrato la presenza di una massa ovalare (12x10x9mm) a livello del fascio
vascolo-nervoso anteriore ed in contiguità con il muscolo pronatore quadrato. L’esame istopatologico ha
confermato la diagnosi di Schwannoma. Un mese dopo l’asportazione chirurgica del tumore il paziente
ha ripreso l’attività sportiva agonistica. In conclusione la diagnosi di Schwannoma dell’AIN può risultare
non semplice, per questo motivo è necessario un attento esame clinico per ricercare i segni clinici tipici
dello Schwannoma, in particolare il segno di Tinel.
Parole chiave: Schwannoma, neurilemmoma, nervo interosseo anteriore
SUMMARY
Schwannomas are the most common tumours of the peripheral nerves. While the median nerve is one of
the most affected, the involvement of the anterior interosseous nerve (AIN) is rather unusual. Because of
this low incidence, the clinical signs and symptoms are often misunderstood, and somehow associated
to other soft tissue tumors such as gangliomas, or to a tenosynovitis. We describe a case of a 27-year-old
man that practised judo at competitive level and reported pain when his forearm was grasped distally
during sport activity. MRI with contrast showed an oval mass (12x10x9 mm) in correspondence of the
neurovascular anterior interosseous bundle. Histopathologic examination revealed it to be a schwannoma. One month after surgery, the patient returned to normal sport activity. Diagnosis of AIN schwannoma
is not simple: specific clinical signs only appear when the tumour is located proximally. For these reasons
a meticulous clinical examination should search for typical signs of schwannomas such as a positive
Tinel sign.
Keywords: neurilemmoma, schwannoma, anterior interosseous nerve
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Roberto Adani, Luigi Tarallo, Stefano Colopi, Raffaele Mugnai
Chirurgia della Mano - Vol. 51 (2) 2014
INTRODUCTION
Schwannoma is a benign tumor developing from
Schwann cells. In 95% of cases those tumors present
as an isolated mass [1], and they are characterized
by a slow and non infiltrating pattern of growth. The
tumor is often associated to a “tingling sensation”,
which is not constant at clinical evaluation. The incidence of Schwannoma in eastern countries is 5%
in adults and 2% in children [2]. Because of this low
incidence, the clinical signs and symptoms are often misunderstood, and somehow associated to other
soft tissue tumors such as gangliomas, or to a tenosynovitis [3]. Hems et al. reviewed a series of 104
peripheral-nerve benign tumors, and demonstrated
that in only 7 cases the preoperative diagnosis was
accurate [4].
CASE REPORT
The patient gave informed consent to participate and
was informed that data concerning the case would be
submitted for publication. This report was performed
in accordance with the Ethical standards of the 1964
Declaration of Helsinki as revised in 2000.
A 27-year-old right handed man was observed for
persistent discomfort (six months) in the volar region
of the left wrist following external pressure. The patient practised judo at competitive level and reported
pain when his forearm was grasped distally during
sport activity. On examination there was no visible
external swelling, but on deep palpation a firm and
slightly tender mass could be felt in the soft tissues
over the palmar region of the distal third of the left
forearm. The Tinel sign was partially positive. There was no muscle weakness and no sensory deficit.
High-resolution sonography identified a well-defined
hypoechoic mass along the anterior interosseous nerve (AIN) at the distal forearm (Fig. 1). MRI was performed to better define the origin of the mass and to
show its relation to surrounding structures.
Casi Clinici
MRI with gadolinium contrast showed at the distal
third of the forearm an oval mass (12x10x9 mm)
in correspondence of the neurovascular anterior interosseous bundle and in contact with the pronator
quadratus muscle. The mass was isointense on T1weighted images, hyperintense on T2-weighted images and characterized by significant contrastographic
impregnation (Fig. 1). Surgery was performed under
loupe magnification employing the Henry volar approach. The pronator quadratus muscle was incised
on the radial border revealing a yellowish, smooth,
oval mass connected to the AIN (Fig. 2). The mass
presented two small pedicles both originating from
the AIN. Resection of the tumour was completed without the need to reconstruct the small nerve fascicle
involved. Histopathologic examination revealed it to
be a schwannoma. One month after surgery, the patient returned to normal sport activity. At 12 months
follow up there was no evidence of recurrence and
the patient was free of symptoms.
DISCUSSION
Schwannomas are the most common tumours of
the peripheral nerves. Neurilemmomas are slowgrowing, soft in consistency, mobile in nature, and
sometimes painless. They are often misdiagnosed as
lipomas, fibromas, ganglion, or xanthoma [6]. Schwannomas are usually localized on the volar surface
of the limb due to the higher concentration of nerve
fibres. While the median nerve is one of the most
affected [7], the involvement of the AIN is rather
unusual [8,9]. Diagnosis of AIN schwannoma is not
simple: specific clinical signs only appear when the
tumour is located proximally. For these reasons a
meticulous clinical examination should search for
typical signs of schwannomas such as a positive Tinel sign and peripheral paresthesias.
US examination may be very helpful although it
cannot always reveal the connection of the tumour
*
*
Figure 1. Axial view
of the Ultrasound and
MRI (SE T2 weighed)
showing the schwannoma (*) under the
pronator
quadratus
muscle (°).
Schwannoma of the Anterior Interosseous Nerve: a Case Report
71
Casi Clinici
Figure 2. Intraoperative view of the schwannoma
under the pronator quadratus muscle connected to
the AIN (*).
with the nerve. MRI is considered the gold standard
to identify the dimension of the tumour, to define
its origin, and to show the neurovascular structures
involved [5]. However with MRI it’s not possible
to distinguish between schwannomas and neurofibromas in all cases. Resection of the schwannoma
should be performed carefully in order to preserve
as much nerve as possible. When approaching a
palpable mass in the upper limbs, the presence of a
peripheral nerve tumour should also be considered.
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Roberto Adani, Luigi Tarallo, Stefano Colopi, Raffaele Mugnai
Chirurgia della Mano - Vol. 51 (2) 2014
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