2.6 Thoracic Outlet Syndrome & Peripheral Nerve Entrapment

ABPMR Physical Medicine and Rehabilitation Board Exam Study Guide Exam

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1 Chapter 1: Introduction & Exam Overview

1.1 ABPMR Part I Exam Overview & Format 1.2 Board Review Strategy & Content Blueprint Breakdown

2 Chapter 2: Musculoskeletal Medicine

2.1 Shoulder & Upper Extremity Diagnostics 2.2 Knee, Hip & Lower Extremity Conditions 2.3 Spine Pathology, Radiculopathy & Myelopathy 2.4 Inflammatory Arthritis, Tendinopathies & Concussion 2.5 Bone Health, Osteoporosis & Metabolic Bone Disease 2.6 Thoracic Outlet Syndrome & Peripheral Nerve Entrapment 2.7 Fracture Rehabilitation & Immobilization Complications 2.8 Overuse Tendinopathies & Regenerative Medicine 2.9 Gait Analysis & Abnormal Gait Patterns

3 Chapter 3: Spinal Cord Injury Rehabilitation

3.1 ASIA Examination & Impairment Scale 3.2 Spinal Cord Injury Syndromes 3.3 Autonomic Dysreflexia & Acute Complications 3.4 Neurogenic Bladder, Bowel & Secondary Complications

4 Chapter 4: Stroke & Neuromuscular Rehabilitation

4.1 Stroke Vascular Syndromes & Acute Assessment 4.2 Stroke Motor Recovery & Hemiplegic Complications 4.3 Spasticity Assessment & Multimodal Management 4.4 ALS, GBS, CIDP & Neuromuscular Disease Rehab 4.5 Multiple Sclerosis & Demyelinating Disease Rehabilitation 4.6 Parkinsonism, Movement Disorders & Functional Neurologic Disorder

5 Chapter 5: Electrodiagnostics (EMG/NCS)

5.1 Nerve Conduction Studies Principles & Physics 5.2 Needle Electromyography & MUAP Analysis 5.3 Mononeuropathies & Radiculopathy Patterns 5.4 Neuromuscular Junction Disorders & Myopathies

6 Chapter 6: Traumatic Brain Injury

6.1 TBI Severity Classification, Glasgow Coma Scale, and Pathophysiology 6.2 Rancho Los Amigos Levels of Cognitive Functioning and Disability Rating Scale 6.3 Neurobehavioral Sequelae and Agitation Management 6.4 Concussion Evaluation, Vestibular-Ocular Dysfunction, and Return-to-Play/Work Protocols

7 Chapter 7: Chronic Pain & Interventional Spine

7.1 Fluoroscopic Spine Interventions 7.2 Opioid Stewardship & Controlled Substance Compliance 7.3 Complex Regional Pain Syndrome, Fibromyalgia & Myofascial Pain 7.4 Spinal Cord Stimulation & Intrathecal Therapy

8 Chapter 8: Amputee Rehabilitation & Prosthetics

8.1 Amputation Surgical Levels & Medicare K-Levels 8.2 Socket Designs & Suspension Systems 8.3 Prosthetic Feet & Microprocessor Knee Mechanisms 8.4 Post-Amputation Care, Residual Limb & Phantom Pain

9 Chapter 9: Pediatric Rehabilitation

9.1 Cerebral Palsy Classification & GMFCS 9.2 Spina Bifida & Myelomeningocele Management 9.3 Muscular Dystrophies & Neuromuscular Disease in Children 9.4 Pediatric Brachial Plexopathy & Congenital Disorders

10 Chapter 10: Prosthetics, Orthotics & Assistive Technology

10.1 Lower Limb Orthoses — AFOs & KAFOs 10.2 Spinal & Upper Extremity Orthoses 10.3 Upper Limb Prosthetics — Body-Powered vs Myoelectric 10.4 Wheelchairs, Seating Systems & Pressure Mapping

11 Chapter 11: Medical Rehabilitation & Outcomes

11.1 Dysphagia Assessment & Management 11.2 Neurogenic Bladder & Bowel Management 11.3 Pressure Injuries & Wound Management 11.4 Outcome Measures & Medical Complications 11.5 Cancer Rehabilitation & Oncologic Rehabilitation 11.6 Burns, Endocrine/Metabolic & Medical Complications Rehabilitation

12 Chapter 12: Cardiopulmonary Rehabilitation

12.1 Cardiac Rehabilitation Phases & Metabolic Equivalents 12.2 Pulmonary Rehabilitation & COPD Management

13 Chapter 13: Foundational Rehabilitation Concepts

13.1 Kinesiology, Biomechanics & Functional Anatomy 13.2 Rehabilitation Pharmacology & Medication Management 13.3 Research Methodology, Biostatistics & Evidence-Based Practice 13.4 Nutrition, Metabolism & Energy Expenditure in Rehabilitation 13.5 Diagnostic Procedures: Imaging, MSK Ultrasound, Urodynamics & Neuropsych Assessment

2.6 Thoracic Outlet Syndrome & Peripheral Nerve Entrapment

Key Takeaways Explain This Topic AI

Thoracic outlet syndrome (TOS) is categorized into neurogenic (most common, lower trunk/C8-T1), arterial, and venous subtypes; Adson, Wright, and Roos tests are provocative but imperfect and must be interpreted alongside electrodiagnosis and vascular studies.

Conservative therapy (physical therapy, postural correction, nerve gliding) is first-line for neurogenic TOS; surgical decompression (first-rib resection, anterior scalenectomy) is reserved for refractory or vascular TOS.

Pronator syndrome compresses the median nerve at the pronator teres; anterior interosseous nerve syndrome causes pinch weakness without sensory loss, distinguishing it from pronator syndrome.

Suprascapular nerve entrapment at the suprascapular notch denervates both supraspinatus and infraspinatus, producing shoulder abduction/external rotation weakness; spinoglenoid notch lesions affect infraspinatus only.

Last updated: July 2026

Thoracic Outlet Syndrome & Upper-Limb Nerve Entrapment

Upper-limb peripheral nerve entrapments are recurrent Domain D topics. Thoracic outlet syndrome (TOS) and its mimics (pronator syndrome, anterior interosseous nerve syndrome, suprascapular nerve entrapment) test the candidate's ability to localize compression by history, provocative exam, and electrodiagnostic pattern.

Thoracic Outlet Syndrome Subtypes

The thoracic outlet is the space between the clavicle and first rib through which the brachial plexus and subclavian vessels pass. Three subtypes differ in anatomy, presentation, and workup:

Subtype Structure Compressed Presentation Key Diagnostic Test

Neurogenic (~95%) Lower trunk / medial cord (C8-T1) Paresthesias in C8-T1 distribution, thenar atrophy, reproduced by elevation Electrodiagnosis (EMG/NCS) + clinical

Venous Subclavian/axillary vein Upper-extremity swelling, cyanosis, effort thrombosis (Paget-Schroetter) Venous Doppler / venography

Arterial (~1%) Subclavian artery Claudication, pallor, pulse deficit, distal embolization, subclavian aneurysm Arterial Doppler / angiography, cervical rib films

Provocative maneuvers (Adson, Wright hyperabduction, Roos/elevated arm stress test, Tinel at supraclavicular fossa) reproduce symptoms but limited specificity; they are interpreted with electrodiagnosis and vascular imaging rather than used in isolation.

Neurogenic TOS Management

Conservative first-line : physical therapy emphasizing postural correction, scapular stabilization, first-rib decompression maneuvers, and nerve-gliding; activity modification.

Surgical : first-rib resection with anterior scalenectomy reserved for refractory neurogenic cases or for any vascular TOS, which is less amenable to conservative care.

Electrodiagnostic caveat : NCS are often normal early; only advanced cases show ulnar sensory and medial antebrachial cutaneous amplitude reduction with lower-trunk motor changes.

Median Nerve Entrapments Beyond Carpal Tunnel

Pronator syndrome : compression of the median nerve at the pronator teres (or ligament of Struthers / sublimis arch). Symptoms resemble carpal tunnel—palmar thenar numbness—but include proximal forearm pain and a negative Phalen sign , and the thenar muscles and lumbricals are affected (unlike isolated carpal tunnel, which spares the thenar in early disease... actually carpal tunnel affects thenar). Distinguishing features: symptoms provoked by resisted elbow flexion/pronation or resisted middle-finger PIP flexion; preserved thenar strength differentiates from advanced CTS.

Anterior interosseous nerve (AIN) syndrome : pure motor branch of median; presents with pinch weakness (inability to flex the DIP of index and IP of thumb, producing the "OK sign" deficit) and no sensory loss .

Suprascapular Nerve Entrapment

The suprascapular nerve (C5-C6, upper trunk) innervates supraspinatus and infraspinatus. Compression location dictates the pattern: Suprascapular Notch ──► Supraspinatus + Infraspinatus Weakness (abduction & external rotation)

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Spinoglenoid Notch ──► Infraspinatus Weakness Only (external rotation; supraspinatus spared)

A ganglion cyst at the spinoglenoid notch (posterior shoulder, common in overhead athletes) selectively compresses the nerve after the supraspinatus branch, causing isolated infraspinatus atrophy and weak external rotation with preserved abduction.

Electrodiagnostic Differentiation

Localization rests on NCS and needle EMG: TOS affects the ulnar sensory and lower-trunk-derived muscles; pronator syndrome shows median sensory involvement with proximal forearm pain; AIN syndrome shows median motor branch involvement with normal sensory studies; suprascapular entrapment shows suprascapular nerve motor changes with preserved deltoid and rhomboid (ruling out C5 radiculopathy).

Ulnar Nerve & Cubital Tunnel Syndrome

The ulnar nerve (C8-T1, medial cord) is vulnerable at the cubital tunnel (most common) and Guyon canal at the wrist. Cubital tunnel syndrome produces paresthesias in the little finger and ulnar half of the ring finger, intrinsic weakness (grip, pinch), and Wartenberg sign (small finger abduction). Provocative testing includes elbow flexion with ulnar nerve compression and Tinel at the cubital tunnel. Management begins conservative: night splinting in extension, avoiding prolonged elbow flexion, ergonomic modification; surgical decompression/transposition for refractory cases.

Radial Nerve Entrapment

Posterior interosseous nerve (PIN) syndrome—a pure motor branch of the radial nerve—causes finger and thumb extension weakness with preserved wrist extension (the ECRL is supplied proximal to the PIN branch), and no sensory loss. Radial tunnel syndrome refers to pain (often at the mobile wad / extensor origin) without motor loss, a controversial clinical entity that must be distinguished from lateral epicondylitis (which is tender at the ECRB origin and provoked by resisted wrist extension).

Nerve Site Sensory Motor
Ulnar Cubital tunnel Medial 1.5 digits Intrinsic atrophy, clawing
Ulnar Guyon canal Variable (spares dorsal cutaneous) Intrinsic (depending on zone)
Radial/PIN Radial tunnel None (motor) Finger/thumb extension; wrist extension preserved
Suprascapular Suprascapular notch None Supraspinatus + infraspinatus
Suprascapular Spinoglenoid notch None Infraspinatus only
Differentiating TOS From Cervical Radiculopathy & Pancoast

Lower-trunk TOS resembles C8-T1 radiculopathy, but radiculopathy produces dermatomal pain extending proximally into the neck/shoulder, reproduces with cervical Spurling maneuvers, and shows denervation in a myotomal (not peripheral-nerve) pattern on EMG. A Pancoast tumor (apical lung) invades the lower trunk and sympathetic chain, producing TOS-like pain plus Horner syndrome (ptosis, miosis, anhidrosis)—an apical-lung mass on imaging excludes simple TOS and demands oncologic workup. This is a high-yield trap: any suspected neurogenic TOS warrants imaging to exclude an apical mass before attributing symptoms to a cervical rib or fibrous band.

Electrodiagnostic & Imaging Workup

NCS in neurogenic TOS may show reduced ulnar sensory and medial antebrachial cutaneous amplitudes; EMG may show chronic neurogenic changes in C8-T1-innervated muscles. Cervical spine imaging excludes radiculopathy; chest/apical imaging excludes Pancoast tumor. Arterial/venous studies are obtained for the corresponding vascular TOS subtypes. The physiatrist synthesizes these to localize and stage treatment.