Peripheral Nerve Flashcards
Which of the following nerves may be entrapped as it travels with the brachial artery beneath
Struthers’ ligament as it passes from the supracondylar process to the humerus?
Answers:
A. Median nerve
B. Ulnar nerve
C. Axillary nerve
D. Musculocutaneous nerve
E. Radial nerve
Median nerve
Discussion:
The median nerve travels with the brachial artery under struthers ligament in the distal humerus.
Compression represents a less common median nerve entrapment causing pain in the forearm
and hand. The radial, ulnar, axillary, and musculocutaneous nerves do not pass beneath struthers
ligament. The arcade of struthers and struther’s ligament are two different anatomic structures.
The arcade of struthers is an aponeurotic structure that extends from the medial intermuscular
septum to the medial head of the biceps. The aracade of struthers can cause compression of the
ulnar nerve proximal to the typical entrapment point of the cubital tunnel.
References:
Entrapment Neuropathies of the Upper Extremity. Doughty CT, Bowley MP.Med Clin North Am.
2019 Mar;103(2):357-370. doi: 10.1016/j.mcna.2018.10.012. PMID:30704687
Mizia E, Zarzecki MP, Pekala JR, Baginski A, Kaythampillai LN, Golebiowska M, Pekala PA,
Walocha JA, Tomaszewski KA. An anatomical investigation of rare upper limb neuropathies due to
the Struthers’ ligament or arcade: a meta-analysis. Folia Morphol (Warsz). 2020 May 12. doi:
10.5603/FM.a2020.0050. Epub ahead of print. PMID: 32394418
The long thoracic nerve typically arises from which of the following cervical spinal nerves?
Answers:
A. C3, C4, C5
B. Spinal accessory nerve, C2, C3
C. C5, C6, C7
D. C4, C5, C6
E. Spinal accessory nerve, C3, C4
C5, C6, C7
Discussion:
The long thoracic nerve originates from the superior trunk of the brachial plexus and typically
receives contributions from cervical nerve roots C5, C6, and C7. It is responsible for the
innervation of the serratus anterior muscle; injury results in winging of the scapula.
References:
Anatomy, Etiology, and Management of Scapular Winging. Didesch JT, Tang P.J Hand Surg Am.
2019 Apr;44(4):321-330. doi: 10.1016/j.jhsa.2018.08.008. Epub 2018 Oct 3.
Tubbs, R. Shane; Goodrich, Dylan; Watanabe, Koichi; Loukas, Marios (January 1, 2015), Tubbs,
R. Shane; Rizk, Elias; Shoja, Mohammadali M.; Loukas, Marios (eds.), “Chapter 43 - Anatomic
Landmarks for Selected Nerves of the Head, Neck, and Upper and Lower Limbs”, Nerves and
Nerve Injuries, San Diego: Academic Press, pp. 575–588,
doi:10.1016/b978-0-12-410390-0.00045-7, ISBN 978-0-12-410390-0, retrieved October 25, 2020
Which of the following nerves passes through the quadrangular space below the teres minor?
Answers:
A. Long Thoracic Nerve
B. Thoracodorsal Nerve
C. Radial Nerve
D. Axillary Nerve
E. Suprascapular Nerve
Axillary Nerve
Discussion:
The quadrangular space is lateral to the scapula and is defined by laterally by the humerus, medial
by the triceps, rostrally by the teres minor and caudally by the teres major. The axillary nerve along
with the circumflex artery exit caudal to the teres minor and rostral to the teres major, providing
innervation to the deltoid. The suprascapular nerve originates from the upper trunk and passes
across the posterior triangle of the neck providing innervation to the supraspinatus and
infraspinatus. The thoracodorsal nerve originates from the posterior cord and provides innervation
to the latissimus dorsi. The radial nerve innervates most of the upper extremity extensors and exits
below the quadrangular space between the long and lateral heads of the triceps. The long thoracic
nerve originates from roots C5, C6, and C7 traversing the chest to provide innervation of the
serratus anterior muscle. Injury to the long thoracic nerve results in scapular winging.
References:
Adult Traumatic Brachial Plexus Injuries. Noland SS, Bishop AT, Spinner RJ, Shin AY.J Am Acad
Orthop Surg. 2019 Oct 1;27(19):705-716. doi: 10.5435/JAAOS-D-18-00433. PMID: 30707114
Khan IA, Varacallo M. Anatomy, Shoulder and Upper Limb, Arm Quadrangular Space. 2020 Jul 31.
In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan–. PMID: 30726009.
Which of the following muscles does the median nerve supply?
Answers:
A. 4th and 5th lumbricals
B. Adductor pollicis
C. Flexor carpi ulnaris
D. Extensor indicis
E. Pronator quadratus
Pronator quadratus
Discussion:
The median nerve orginates from both the lateral and medial cords of the brachial plexus (C5-T1).
The median nerve provides sensory innervation to the anterolateral surface of the hand and
provides motor innervation to the following muscles – pronator teres, flexor carpi radialis, palmaris
longus, and flexor digitorum superficialis, flexor pollicis longus and flexor digitorum profundus,
pronator quadratus, opponens pollicis brevis, and flexor pollicis brevis, 1st and 2nd lumbricals. The
ulnar nerve supplies the 4th and 5th lumbricals, flexor carpi ulnaris, and adductor pollicis. The
radial nerve provides innervation to the extensor indicis.
References:
Brachial plexus anatomy. Leinberry CF, Wehbé MA.Hand Clin. 2004 Feb;20(1):1-5. doi:
10.1016/s0749-0712(03)00088-x. PMID: 15005376
Wertsch JJ, Melvin J. Median nerve anatomy and entrapment syndromes: a review. Arch Phys
Med Rehabil. 1982 Dec;63(12):623-7. PMID: 6756339
The external branch of the superior laryngeal nerve innervates which of the following structures?
Answers:
A. Sternothyroid muslces
B. Cricothyroid muscles
C. Thyrohyoid muscles
D. Stylohyoid muscle
E. Omohyoid muscle
Cricothyroid muscles
Discussion:
The superior laryngeal nerve is a branch of the vagal nerve providing motor innervation to the
cricothyroid muscle through the external laryngeal nerve and sensory innervation to the laryngeal
mucosa. The cricothyroid muscle functions to tense the vocal cords. The omohyoid muscle is
innervated by the ansa cervicalis. The thyrohyoid muscle is nerved by C1 and functions to elevate
the larynx and depress the hyoid. The stylohyoid muscle provides motor function to the hyoid bone
and is innervated by the facial nerve. The sternothyroid muscle is innervated by the ansa cervicalis
and also provides motor function to the hyoid bone.
References:
Recurrent laryngeal nerve paralysis: anatomy and etiology. Myssiorek D.Otolaryngol Clin North
Am. 2004 Feb;37(1):25-44, v. doi: 10.1016/S0030-6665(03)00172-5. PMID: 15062685
Gokaslan ZL, Bydon M, De la Garza-Ramos R, Smith ZA, Hsu WK, Qureshi SA, Cho SK, Baird
EO, Mroz TE, Fehlings M, Arnold PM, Riew KD. Recurrent Laryngeal Nerve Palsy After Cervical
Spine Surgery: A Multicenter AOSpine Clinical Research Network Study. Global Spine J. 2017
Apr;7(1 Suppl):53S-57S. doi: 10.1177/2192568216687547. Epub 2017 Apr 1. PMID: 28451492;
PMCID: PMC5400187
Which of the following muscles is innervated by the inferior gluteal nerve?
Answers:
A. Gluteus Maximus
B. Obturator internus
C. Gluteus Medius
D. Piriformis
E. Gluteus Miniumus
Gluteus Maximus
Discussion:
The Gluteus Maximus receives primary innervation from the inferior gluteal nerve. The nerve
orginates from L5, S1, and S2. The nerve traverses the greater sciatic foramen and runs deep to
the piriformis muscle. Injury to the inferior gluteal nerve results in weakness in hip extension. Injury
does not impact standing and patients are able to compensate with walking but typically have
difficulty with standing from sitting and running. Injury occurs most frequently with posterior
approach hip replacement.
References:
The diagnostic anatomy of the radial nerve. In: Russell SM, ed. Examination of Peripheral Nerve
Injuries: An Anatomical Approach. New York, NY: Thieme; 2006:46.
Anatomy, Abdomen and Pelvis, Inferior GlutealNerve
Justin Merryman, Edinen Asuka 1, Matthew Varacallo 2
In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan.
2020 Sep 8.
https://pubmed.ncbi.nlm.nih.gov/30422479/
Which of the following is the most appropriate time for repair of a clean, sharp nerve laceration
after injury?
Answers:
A. 3-6 months
B. 1-3 days
C. 1-3 months
D. 1-3 weeks
E. 6-12 months
1-3 days
Discussion:
In general sharp lacerations should be taken to the OR for exploration within 72 hours. Exploration
may demonstrate a blunt injury or an injury that is not amendable to immediate repair as the extent
of injury may be unclear. Injuries in continuity should be followed clinically and with
electrodiagnostic studies to delineate extent of injury and patterns of recovery. The most salient
factors that influence recovery are: severity, time, mechanism of injury, proximity to distal targets
and patient age. The majority of nerve injuries (>70%) leave the nerve in gross continuity.
References:
Peripheral Nerve Trauma: Mechanisms of Injury and Recovery Ron M. G. Menorca, Theron S.
Fussell, John C. Elfar Hand Clin. 2013 Aug; 29(3): 317-330. doi: 10.1016/j.hcl.2013.04.002 PMID:
23895713
Griffin JW, Hogan MV, Chhabra AB, Deal DN. Peripheral nerve repair and reconstruction. J Bone
Joint Surg Am. 2013 Dec 4;95(23):2144-51. doi: 10.2106/JBJS.L.00704. PMID: 24306702
A 73-year-old man with lung cancer has had a claw hand deformity on the left for the past week.
Physical examination shows Horner’s syndrome and wasting of the intrinsic muscles of the left
hand. There is loss of sensation over the ulnar aspect of the hand and forearm. Which of the
following is the most likely site of the lesion?
Answers:
A. Middle trunk
B. Anterior division
C. Posterior division
D. Upper trunk
E. Lower trunk
Lower trunk
Discussion:
Pancoast tumors occur at the apex of the lung, typically representing a form of non-small cell lung
carcinoma. As the lesion grows it can cause compression of the surrounding structures of the
chest wall including the superior cervical ganglion causing a horner’s syndrome and the lower
trunk of the brachial plexus causing hand weakness and ulnar distribution sensory loss.
References:
Management of Pancoast tumours. Rusch VW.Lancet Oncol. 2006 Dec;7(12):997-1005. doi:
10.1016/S1470-2045(06)70974-3. PMID: 17138221
Akboru IM, Solmaz I, Secer HI, Izci Y, Daneyemez M. The surgical anatomy of the brachial plexus.
Turk Neurosurg. 2010 Apr;20(2):142-50. doi: 10.5137/1019-5149.JTN.2368-09.2. PMID:
20401841.
The ulnar nerve courses around to the medial epicondyle to enter which of the following muscles?
Answers:
A. Extensor carpi ulnaris
B. Flexor carpi ulnaris
C. Pronator teres
D. Flexor digitorum profundus
E. Pronator quadratus
Flexor carpi ulnaris
Discussion:
The ulnar nerve originates from C8 and T1 nerve roots and enters the anterior flexor compartment
of the forearm between the two heads of the flexor carpi ulnaris as it wraps arounds the medial
epicondyle to exit the cubital tunnel. The leading edge of osborne’s fascia between the oblique
fibers of the flexor carpi ulnaris represents the most common compression site of the ulnar nerve.
References:
Ulnar nerve entrapment at the elbow. A surgical series and a systematic review of the literature.
Lauretti L, D’Alessandris QG, De Simone C, Legninda Sop FY, Remore LM, Izzo A, Fernandez E.J
Clin Neurosci. 2017 Dec;46:99-108. doi: 10.1016/j.jocn.2017.08.012. Epub 2017 Sep 8. PMID:
28890032
Huang JH, Samadani U, Zager EL. Ulnar nerve entrapment neuropathy at the elbow: simple
decompression. Neurosurgery. 2004 Nov;55(5):1150-3. doi:
10.1227/01.neu.0000140841.28007.f2. PMID: 15509321.
The posterior interosseous nerve is a branch of which of the following nerves?
Answers:
A. Axillary Nerve
B. Radial Nerve
C. Median Nerve
D. Ulnar Nerve
E. Thoracodorsal Nerve
Radial Nerve
Discussion:
The posterior intereosseous nerve is a distal branch of the radial nerve. The posterior interosseous
nerve provides innervation to the following muscles: extensor carpi radialis brevis, extensor
digitorum, extensor digiti minimi, extensor carpi ulnaris, supinator, abductor pollicis longus,
extensor pollicis brevis, extensor pollicis longus, extensor indicis. The median and ulnar nerves
provide innervation the flexors of the forearm and hand. The axillary nerve innervates the deltoid
and teres minor. The thoracodorsal nerve innervates the latissimus dorsi.
References:
Brachial plexus anatomy. Leinberry CF, Wehbé MA.Hand Clin. 2004 Feb;20(1):1-5. doi:
10.1016/s0749-0712(03)00088-x. PMID: 15005376
Wheeler R, DeCastro A. Posterior Interosseous Nerve Syndrome. 2020 Oct 27. In: StatPearls
[Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan–. PMID: 31082090
The deep peroneal nerve innervates which of the following muscles?
Answers:
A. Tibialis anterior, extensor hallucis longus, peronus longus, peroneus brevis
B. Tibialis anterior, extensor hallucis longus
C. Peronus longus, peroneus brevis peronus tertius
D. Tibialis anterior, extensor hallucis longus, peroneus tertius, extensor digitorum longus
E. Peronus longus, peroneus tertius, extensor digitorum longus
Tibialis anterior, extensor hallucis longus, peroneus tertius, extensor
digitorum longus
Discussion:
The common peroneal nerve is distal branch of the sciatic nerve that typically has contributions
from L4, L5, S1, and S2. It originates from the sciatic nerve in the popliteal fossa. After it crosses
the fibular head it is further divided into the superior, inferior and recurrent genicular nerves, the
sural nerve and the deep and superficial peroneal nerves. The deep peroneal nerve supplies the
extensor muscles in the anterior leg including the tibialis anterior, extensor hallucis longus,
peroneus tertius and the extensor digitorum longus. Injury or compression typically results in foot
drop. Surgical release of the deep peroneal nerve typically involves decompression of the fascial
edge or ligament of the extensor digitorum brevis.
References:
Common Entrapment Neuropathies. Malek E, Salameh JS.Semin Neurol. 2019 Oct;39(5):549-559.
doi: 10.1055/s-0039-1693004. Epub 2019 Oct 22. PMID: 31639838
https://pubmed.ncbi.nlm.nih.gov/?term=%22deep+peroneal+nerve%22&filter=pubt.review&
sort=pubdate
Which of the following muscles is innervated by the anterior interosseous nerve?
Answers:
A. Flexor pollicis longus, flexor digitorum profundus, pronator quadratus
B. Palmaris longus, pronator quadratus
C. Flexor carpi radialis, flexor digitorum profundus, palmaris longus
D. Flexor pollicis longus, flexor carpi radialis
E. Pronator quadratus, palmaris longus, flexor pollicis longus
Flexor pollicis longus, flexor digitorum profundus, pronator quadratus
Discussion:
The anterior interosseous nerve is a distal branch of the median nerve that originates at the level
of the anterior forearm. It originates from the nerve roots C8 and T1. It intervates the flexor pollicis
longus, flexor digitorum profundus, and the pronator quadratus. Compression at the level of the
forearm or parsonage turner syndrome are the most common pathologies producing varying
degrees of weakness but without sensory deficit.
References:
Innervation of the Flexor Digitorum Profundus: A Systematic Review. Hwang K, Bang SJ, Chung
SH.Plast Surg (Oakv). 2018 May;26(2):120-125. doi: 10.1177/2292550317740692. Epub 2017 Nov
22. PMID: 29845050
https://pubmed.ncbi.nlm.nih.gov/26261744/
The right obturator nerve is inadvertently sectioned sharply during a gynecologic procedure. Which
of the following is the most appropriate management of this injury?
Answers:
A. Tag the nerve ends and delayed repair in 3 weeks
B. Tag the nerve ends and delayed repair in 3-6 months
C. Tag the nerve ends and delayed repair in 1-3 months
D. Immediate end to end repair with intervening 3-5 cm cadaveric allograft
E. Immediate end to end repair
Immediate end to end repair
Discussion:
The obturator nerve originates from L2, L3, and L4, providing sensory innervation to the medial
thigh and motor innervation to the adductor longus, adductor brevis, adductor magnus, external
obturator, and variably to the pectineus. Sharp transection of a nerve that is recognized at the time
of surgery should be acutely repaired. Typically a sharp transection can be repaired in an end to
end fashion. Tagging the distal and proximal nerve endings can be performed for crush and
segmental injuries where the true extent of injury may not be apparent at the time of surgery and
these are typically repaired in a delayed fashion within 3 weeks. Cadaveric nerve allograft can be
used but does require immunosuppression similar to solid organ transplants. Although allograft is
an option it would be reserved for cases where insufficient donor autograft is available.
References:
Dahlin LB. The role of timing in nerve reconstruction. Int Rev Neurobiol. 2013;109:151-64.
Griffin JW, Hogan MV, Chhabra AB, Deal DN. Peripheral nerve repair and reconstruction. J Bone
Joint Surg Am. 2013 Dec 4;95(23):2144-51. doi: 10.2106/JBJS.L.00704. PMID: 24306702.
A 40-year-old woman comes to the emergency department because of shortness of breath after
being involved in a high-speed motor vehicle collision. She says that she was not wearing her seat
belt and that she jammed her chest and left armpit into the steering wheel upon impact. She has
no neck pain. On examination, she is unable to contract the left biceps or supinate the left hand,
and she has decreased sensation over the left lateral forearm. Which of the following peripheral
nerves is most likely injured?
Answers:
A. Ulnar nerve
B. Median nerve
C. Axillary nerve
D. Musculocutaneous nerve
E. Radial nerve
Musculocutaneous nerve
Discussion:
Peripheral nerve injuries occur in 1-3% of all trauma patients. Although isolated injury to the
musculocutaneous nerve is uncommon it results in weakness in elbow flexion (biceps and brachilis
branch) and sensory loss in the distribution of the lateral antebrachial cutaneous nerve. Injury to
the axillary nerve can occur with traumatic shoulder dislocations causing weakness with shoulder
abduction and external rotation. The median and ulnar nerve provide innervation to the flexors of
the forearm and hand, while the radial nerve provides innervation to the extensors. The radial
nerve can be injured in isolation, most commonly with a proximal humerus fracture.
References:
Adult brachial plexus injury: evaluation and management. Limthongthang R, Bachoura A,
Songcharoen P, Osterman AL. Orthop Clin North Am. 2013 Oct;44(4):591-603. doi:
10.1016/j.ocl.2013.06.011. Epub 2013 Sep 6. PMID: 24095074
Yang ZX, Pho RW, Kour AK, Pereira BP. The musculocutaneous nerve and its branches to the
biceps and brachialis muscles. J Hand Surg Am. 1995 Jul;20(4):671-5. doi:
10.1016/S0363-5023(05)80289-8. PMID: 7594300
