A rare cause of forearm pain: anterior branch of the medial antebrachial cutaneous nerve injury: a case report

Necmettin Yildiz and Füsun Ardic*
*
Corresponding author: Füsun Ardic [email protected] Author Affiliations
Department of Physical Medicine and Rehabilitation, Faculty of Medicine, Pamukkale University, Denizli, Turkey
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Journal of Brachial Plexus and Peripheral Nerve Injury 2008, 3:10 
doi:10.1186/1749-7221-3-10The electronic version of this article is the complete one and can be found online at: http://www.jbppni.com/content/3/1/10 Received:20 November 2007 Accepted:21 April 2008 Published:21 April 2008 © 2008 Yildiz and Ardic; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
AbstractMedial antebrachial cutaneous nerve (MACN) neuropathy is reported to be caused by
iatrogenic reasons. Although the cases describing the posterior branch of MACN neuropathy
are abundant, only one case caused by lipoma has been found to describe the anterior
branch of MACN neuropathy in the literature. As for the reason for the forearm pain,
we report the only case describing isolated anterior branch of MACN neuropathy which
has developed due to repeated minor trauma.
We report a 37-year-old woman patient with pain in her medial forearm and elbow following
the shaking of a rug. Pain and symptoms of dysestesia in the distribution of the right
MACN were found. Electrophysiological examination confirmed the normality of the main
nerve trunks of the right upper limb and demonstrated abnormalities of the right MACN
when compared with the left side. Sensory action potential (SAP) amplitude on the
right anterior branch of the MACN was detected to be lower in proportion to the left.
In the light of these findings, NSAI drug and physical therapy was performed. Dysestesia
and pain were relieved and no recurrence was observed after a follow-up of 14 months.
MACN neuropathy should be taken into account for the differential diagnosis of the
patients with complaints of pain and dysestesia in medial forearm and anteromedial
aspect of the elbow.
IntroductionThe medial antebrachial cutaneous nerve (MACN) arises from the medial cord (78%) and
the lower trunk (22%) of the brachial plexus. It goes along the course of the median
and ulnar nerves, vena basilica, and arteria brachialis, in the upper arm [1]. In the literature, causes of MACN neuropathy include iatrogenic reasons such as
steroid injection due to medial epicondylitis, routine venipuncture, cubital tunnel
surgery, loose body removal, elbow arthroscopy, open fractures fixation, tumour excision,
and arthrolysis [2-7]. It is also caused more rarely by repeated minor trauma (from tennis) and soft tissue
laceration. It is even more rarely brought about by tuberculoid leprosy neuritis or
subcutaneous lipoma [8-10]. However, MACN neuropathy is thought to be noticed less often due to the fact that
it causes minor discomfort for the patients and does not affect the hand [10]. Although in some cases where MACN neuropathy was diagnosed, it was not specified
which branch of the nerve was affected [3,7,9]. Due to the variety in its anatomic localization, the posterior branch of MACN is
inclined to be more vulnerable to iatrogenic causes such as cubital tunnel surgery
and direct invasive procedures to the medial part of the elbow [2,4-6,11]. Although the cases in the literature describing neuropathy of the posterior branch
of the MACN are abundant [2,4-6] only one case caused by lipoma has been found to describe the anterior branch of
the MACN as the site of neuropathy [10]. As for the reason for forearm pain, we report the only case describing isolated
neuropathy of the anterior branch of the MACN which has developed due to repeated
minor trauma.
Case presentationA 37-year-old woman patient who is a homemaker was accepted to our hospital with the
complaint of a 10-day pain in her right upper limb. She mentioned that the pain first
involved the elbow and then the forearm, particularly the medial part of it. Nearly
10 days before, while she was cleaning and shaking the rug, she developed a discomforting
pain in her right elbow. She explained that the pain in her elbow had become worse
and in 24 hours spread through her whole forearm. She added that, previously, the
pain had been partially responding to NSAI drugs, but subsequently, it continued to
progressively increase.
There was a pain in her medial forearm and elbow. She felt abnormal when she was palpated
on her medial forearm. During her examination, she was able to describe the point
where her pain started in the proximal part of her elbow. On detailed neurological
examination, a region of dysesthesia which extends from the elbow to the medial forearm
was detected (Figure 1). The patient had no history of polyneuropathy, chronic systemic disease, injection
or surgical intervention at the elbow. Range of motion, motor, and reflex examinations
of both upper extremities were normal. Cervical spine examination was normal. Varus-valgus
stress test for the elbow was normal. Medial epicondylitis test and tinel test for
the ulnar nerve were negative.
Figure 1. The view of dysesthesic region.
X-ray views of the elbow, including oblique views, appeared normal. Electromyography
showed normal findings in the right biceps, triceps, flexor digitorum sublimis, pronator
quadratus, interosseous and abductor pollicis brevis muscles, and nerve conduction
studies in both upper limbs except for the right MACN were found normal. The MACN
is stimulated antidromically at the lateral border of the biceps brachii tendon in
the cubital fossa. An active surface recording electrode is placed on the anteromedial
surface of the forearm 14 cm from the active stimulating electrode. Sensory action
potential (SAP) amplitude of the right anterior branch of the MACN was detected to
be lower in proportion to the left. The sensory conduction velocity (SCV) was normal.
On both right and left sides, the posterior branch of the MACN was normal and symmetrical
for amplitude and velocity (Table 1). On magnetic resonance imaging of the elbow, no lesion was detected which may cause
MACN neuropathy.
Table 1. The nerve conduction data of the case.
As well as NSAI drug treatment, physical therapy of 15 days (TENS, ultrasound, ROM
exercises) was applied to the patient. The complaint of pain was totally relieved.
Two months later, the dysesthesia disappeared. No recurrence occured after a follow-up
of 14 months.
ConclusionAlthough isolated MACN neuropathy may be caused by various iatrogenic reasons, it
is described rarely by the reasons of repeated minor trauma or soft tissue laceration
[6,8]. In the study by Stahl and Rosenberg, 12 patients with MACN neuropathy were described.
In two patients, the reason for neuropathy was stated to be soft tissue laceration
but the shape and the cause of the injury was not described [6]. Chang and Ho reported that MACN neuropathy described in one of their cases was not
isolated, but was assosiated with lesion of the median nerve, and that the reason
for a second case with isolated MACN neuropathy was repeated minor trauma [8]. In the literature, the reason for the only case stating that the anterior branch
of the MACN was damaged was lipoma [10]. Our case, however, is the only case describing isolated neuropathy of the anterior
branch of the MACN which was developed by repeated minor trauma. Shaking a rug is
a specific method of cleaning the rug in which the elbows and wrist will be used in
repetitive flexion and extension. This activity requires forceful sustained contraction
of the shoulder girdle, upper arm, and forearm muscles to hold the rug against the
force of the weight of the rug and gravity. Because of the superficial location of
the nerve adjacent to the biceps tendon, full extension of the elbow and repetetive
forceful contracture of the flexor musculature may place this nerve under stretch,
effectively bowstringing it across the elbow.
Both because it does not cause any limitation in the elbow and it can not be detected
by the radiologic MR imaging, the neuroma is marginalized. Seror stated that the lesions
of MACN are rarely seen because we do not notice them for several reasons such as
isolated lesions of MACN not affecting the hands, their causing only minor discomfort,
and the electrophysiological studies of MACNs not being part of routine upper extremity
electrodiagnostic examinations [10]. Izzo et al. noted that in addition to the median nerve sensory studies, the forearm
sensory nerve examinations can also be used to detect the situations of peripheral
neuropathy, brachial plexopathy and local neuropathy [12]. MACN conduction studies were performed by Seror in 70 control subjects to determine
normal values and define the lower limits of normality. The mean SAP amplitude was
17.5 μV, and the SCV was 61 m/s. In the same study no SAP amplitude was lower than
6 μV [13]. With reference to the reported normal conduction values and the studies by Chang
and Ho, and by Seror, our case was diagnosed with right MACN neuropathy due to the
detections of normal SCV and lower SAP amplitude of the right MACN [8,10,12,13] (Table 1).
Any surgical intervention, injection, trauma or forcing activity of the elbow should
be questioned and nerve neuropathies should be considered, though they are rare, for
the complaints of forearm pain.
In conclusion, especially for the patients with complaints of pain and dysesthesia
in the medial forearm and anteromedial aspect of the elbow, MACN neuropathy should
be taken into account for the differential diagnosis and, therefore, electrophysiologic
examination should be performed.
Competing interestsThe authors declare that they have no competing interests.Authors’ contributionsNY and FA contributed equally to this case report. All authors read and approved the
final manuscript
ConsentWritten informed consent was obtained from the patient for publication of this case
report and any accompanying images.
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