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Ultrasound of Peripheral Nerves
Levon N. Nazarian, M.D.
Professor of Radiology
Thomas Jefferson University Hospital
Disclosures
• None relevant to this presentation
Educational Objectives
• Following the presentation, participant should be able to:
–Discuss normal and pathologic anatomy of peripheral nerves
–Describe the clinical scenarios where US provides helpful information
Different Scenarios in Nerve US Imaging
• Clinical assessment and US both positive
–US confirms clinical diagnosis
–US can show the anatomy (nerve injury, mass, entrapment, etc.) to help guide further treatment
• Clinical assessment positive, US negative
–US may alter management decision, for example, show that a nerve release or exploration is unlikely to help
Different Scenarios in Nerve US Imaging
• Clinical assessment equivocal, US positive
–US helps clarify pathology
• Clinical assessment equivocal, US negative
–US may increase confidence in ruling out pathology
• US sees an incidental finding
–Contralateral subclinical disease
–Finding unrelated to the referral
Musculoskeletal Ultrasound Technique
• High frequency linear transducers
• At least 12 MHz
–Higher frequency, better resolution but less penetration
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Musculoskeletal Ultrasound Technique
• Contralateral side for comparison
–Helps differentiate normal from abnormal
–Beware of bilateral pathology, especially where one side is asymptomatic
Peripheral Nerves
Peripheral Nerves: Short Axis Peripheral Nerves: Long Axis
Clinical Scenario:Signs and Symptoms of
Median Neuropathy
Normal Carpal Tunnel
essr.org
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Bifid Median NerveBifid Median Nerve with Median
Artery
Carpal Tunnel Syndrome US Criteria
• Cross-sectional area of median nerve at distal wrist crease
–Up to 0.09 sq cm is normal
–Greater than 0.12 sq cm is abnormal
–0.09 to 0.12 sq cm: “gray zone”
• Other signs
–Thickening of flexor retinaculum
–Flattening of median nerve within tunnel
Klauser Carpal Tunnel Criteria
• 100 wrists in 68 patients
• Clinical and EMG “gold standard”
• Measure median nerve at proximal third of pronator quadratus (CSAP)
• Measure median nerve at carpal tunnel (CSAC)
• CSAC minus CSAP > 0.02 sq cm
–99% sensitive
–100% specific
Radiology 2008; 250: 171-177
Normal Median Nerve Measurement
Carpal Tunnel Syndrome
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Severe Carpal Tunnel Syndrome
0.35 sq cm
Secondary Carpal Tunnel Syndrome
Median Neuropathy, History of CMT Median Neuropathy, History of CMT
Median Neuropathy, History of CMT Severed Median Nerve: Shot in Iraq
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Median Neuropathy, History of Neurofibromatosis
Median Neuropathy, History of Neurofibromatosis
Pronator Syndrome
PT
PT
Motor branch that arises just after the median nerve emerges from the pronator teres muscle
It lies deeply on the anterior interosseous membrane and supplies the flexor digitorum profundus (II-III), the flexor pollicis longus, and the pronator quadratus
FDS
FDPFPL
FCR
Anterior Interosseous Nerve
MN
BA
Br
BB
FDS
PrT
PrT
Median Nerve
Anterior Interosseous Nerve
Median Nerve
Anterior Interosseous Nerve
Anterior Interosseous Nerve Entrapment
• Difficult to visualize directly
• Muscle atrophy in classic pattern
–Pronator quadratus
–Flexor digitorum profundus
–Flexor pollicis longus
Anterior Interosseous Nerve Entrapment
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Anterior Interosseous Nerve Entrapment
Anterior Interosseous Nerve Entrapment
Anterior Interosseous Nerve Entrapment
RU
R
U
Anterior Interosseous Nerve Entrapment
61-Year-Old Woman Who Cannot Actively Flex Her First and Second DIP Joints After
Wrist Surgery
“Localize site of FDP and FPL Rupture”
Flexor Tendons Intact
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US of Forearm Muscles
FPL FDP
FPLFDP
Right Left
70-Year-Old Woman with Severe Pain After Blood Draw
VN
Lateral Antebrachial Cutaneous Nerve Perineural Injection
Clinical Scenario:Signs and Symptoms of
Ulnar Neuropathy UN
Condylar Groove
At the distal humerus, the ulnar nerve passes in an osteofibrous ring formed by the medial epicondyle and the medial collateral ligament and bridged by the cubital tunnel retinaculum (Osborne ligament)
O
ME
T
Ulnar Nerve – elbow
Ulnar Nerve
Osborne lig
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O
MELE
UNTT
T
FCU
Distal to the condylar groove, the ulnar nerve enters in a tunnel formed between the ulnar and humeral heads of the flexor carpi ulnaris muscle, which are connected by the arcuate ligament
Cubital Tunnel
Ulnar Nerve – elbow
FCU
Ulnar Nerve at Elbow
Ulnar Nerve Area
0.30 sq cm 0.08 sq cm
Cubital Tunnel Syndrome
Severe Cubital Tunnel Syndrome Ulnar Nerve Compression by Hypertrophic Synovium
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Ulnar Nerve: Which Side is Symptomatic?Ulnar Nerve Subluxation
• Seen on elbow flexion
• Occurs in 15% of normals
• Differentiate from snapping triceps syndrome
Ulnar Nerve Subluxation
Epi
Extension Flexion
Ulnar Nerve Subluxation
Snapping Triceps Syndrome
Guyon Tunnel - anatomy
The walls of the Guyon tunnel consist of the pisiform medially and the hook of the hamate laterally
floor flexor retinaculum
roof palmar carpal ligament The Guyon tunnel houses the ulnar nerve and the ulnar artery
a
a
P
H
fcu
Ulnar NerveFlexor retinaculum
Palmar carpal lig
Ulnar Artery
P
H
fcu
motor sensory
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Ulnar Nerve in Guyon’s Canal
PisA
Ulnar Nerve Compression in Guyon’s Canal
Clinical Scenario:Competitive biker, severe APB
atrophy, mild CTS at EMG
Mildly Enlarged Median Nerve at Wrist
Markedly Enlarged Ulnar Nerve at Wrist Ulnar Nerve at Wrist
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Clinical Scenario:Signs and Symptoms of
Radial Neuropathy
Radial Nerve Mass
Intraoperative Guidance: Neurofibroma
Medical intern with wrist drop the day after a flu shot
Transverse Radial Nerve
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Sagittal Radial Nerve Sagittal Radial Nerve
Two Weeks Later: PINPosterior Interosseous Nerve
Entrapment
• Presents with motor weakness in extensors of wrists or fingers
• May have pain and tenderness mimicking lateral epicondylitis
• US has been shown useful in DDx
Ong C, et al. Radiology Case Reports 2007; 2:1-4. radiology.casereports.net
Normal PIN Normal PIN
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PIN at Arcade of Frohse PIN Throughout Supinator
Posterior Interosseous Nerve Entrapment
PIN Entrapment
PIN Post Release PIN Entrapment Arcade of Frohse
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PIN Entrapment Arcade of Frohse
Clinical Scenario:Lateral thigh pain and
numbness
Meralgia Paresthetica
Clinical Scenario:Lateral thigh pain and numbness. History of total hip replacement.
Lateral Femoral Cutaneous Nerve Lateral Femoral Cutaneous Nerve
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Lateral Femoral Cutaneous Nerve Lateral Femoral Cutaneous Nerve
Femoral Neuropathy After THR
Clinical Scenario:Signs and Symptoms of
Sciatic Neuropathy
Plexiform Neurofibroma of Sciatic Nerve
Sciatic Nerve Transection
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Clinical Scenario:Signs and Symptoms of
Peroneal Neuropathy
Normal Peroneal Nerve
Fib
Normal Peroneal Nerve Peroneal Nerve Entrapment
Peroneal Ganglion: MRI Peroneal Ganglion
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Peroneal Neuropathy After MVA Peroneal Neuropathy After MVA
Peroneal Neuropathy After MVA Peroneal Neuropathy After MVA
Peroneal Nerve Laceration
Clinical Scenario:Signs and Symptoms of
Tibial Neuropathy
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Tibial Nerve
M
Tibial Nerve Schwannoma Loss of Plantar flexion After Calf Laceration
Tarsal Tunnel Syndrome From Anomalous Artery Tarsal Tunnel Ganglion
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Tarsal Tunnel Ganglion
N
Neurofibroma of Tibial Nerve at Ankle
Neurofibroma of Tibial Nerve at Ankle
Tarsal Tunnel Syndrome
Tarsal Tunnel: “Inject Nerve Sheath Tumor” Tarsal Tunnel: “Inject Nerve Sheath Tumor”
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Tarsal Tunnel: “Inject Nerve Sheath Tumor” Stump Neuroma of Sural Nerve
* *
Stump Neuroma of Sural NerveMorton’s Neuroma
Technique
• Linear transducer
• 10-12 MHz
• Place transducer at plantar aspect
• Compress with finger dorsally, try to trap neuroma between finger and probe
• Also can try Mulder test
Morton’s Neuroma Morton’s Neuroma
*
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Sagittal Morton’s Compression Sagittal Morton’s Compression
Mulder Maneuver Brachial Plexus Traction Injury
Dynamic Brachial Plexus Imaging Dynamic Brachial Plexus Imaging
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Disadvantage of US
•Shows form not function
Advantages of US vs. MRI
• Well tolerated
• Low cost
• Superior resolution
• Not limited to one body segment
• Contralateral comparison
• Real time dynamic studies
Conclusion
• When combined with the clinical examination, ultrasound is an excellent tool to depict the anatomic cause of peripheral neuropathies
