Unusual Nerve EntrapmentUnusual Nerve EntrapmentSyndromesSyndromes

Rajiv Midha, MD, MSc, FRCS(C)

Hotchkiss Brain Institute & Department ofClinical Neurosciences, Professor and

Chief, Division of Neurosurgery,University of Calgary

Objectives

• Integrate the knowledge of nerve anatomy andphysiology, with the pathophysiology of nerveentrapment

• Learn diagnostic features of some of the unusualnerve entrapment syndromes affecting nerves ofthe upper and lower extremity

• List management options and surgical indicationsfor nerve entrapment syndromes

Nerve Entrapment

Nerve passes through a narrow tunnelNerve passes through a narrow tunnelcomposed of fibrous or bony elementscomposed of fibrous or bony elements

Static compression in constricted tunnelStatic compression in constricted tunnel

Dynamic, repetitive movement within a tightDynamic, repetitive movement within a tightspacespace

Pathophysiology of EntrapmentNeuropathy

• Anatomical compartment:bone, ligament orfibrotendinous covering

• Nerve compression• Static vs. repetitive

compression; nervetraction

• Secondary vascular factorsand oedema

• Nerve ischemia andswelling

Nerve

BoneLigament

Anatomical compartment

• Ulnar nerve at elbow (cubital tunnel)• Static and dynamic considerations

Blood- nerve Barrier

BNB Breakdown

Histopathology:(Chronic) Nerve Compression

Oedema, IC infiltrate,Fibroblast proliferation

SymptomsChronic Nerve Compression

Clinical FindingChronic Nerve Compression

Axonal Remyelination

Electrophysiology of nerveentrapment

• Segmentaldemyelination ->increased latency ordecreased nerveconduction velocity,even conduction blockon inching studies

• Axonal loss ->decreased amplitudeof waveform

EMGs in nerve entrapment• Usually negative

• Unless muscledenervated (atrophy):– Fibrillation potentials– Positive sharp waves– Decreased MUPs

Unusual Nerve Entrapments:Upper Extremity

• Suprascapular nerve• Thoracic outlet syndrome• Median nerve/Pronator syndrome/AIN • Posterior interosseous nerve (PIN)• Radial sensory nerve• Ulnar nerve at the wrist (Guyon’s canal)

Unusual Nerve entrapments:Lower Extremity

• Lateral Femoral Cutaneous Nerve (Meralgiaparesthetica)

• Peroneal Nerve Entrapment• Tarsal Tunnel Syndrome

Upper Extremity Nerve Anatomy

Suprascapular Nerve Entrapment

• Posterior shoulder pain• Weakness + atrophy of supraspinatus and/or

infraspinatus• 2 potential entrapment sites:

– suprascapular notch (superior transverse scapular ligament)

– spinoglenoid notch (inferior transverse scapular ligament) - only infraspinatus affected

Suprascapular Nerve Entrapment

• Overhead work or athletic activity• No sensory loss• Tenderness over suprascapular or

spinoglenoid notch

Suprascapular Entrapment Neuropathy:Clinical

Suprascapular Nerve Entrapment

• DDx: rotator cuff injury, bursitis, cervical DJD, ganglion cyst

• MRI shoulder for ganglion cyst or rotator cuff tear; MRI neck for disc, osteophyte

• EMG/NCV study to confirm dx and to localize the site of entrapment (may be normal)

• Local injection may be diagnostic & therapeutic

Suprascapular Nerve Entrapment

• Operative treatment– General anesthesia– Prone or supine with a shoulder roll– Transverse incision above & parallel to

scapular spine– Blunt dissection through trapezius &

supraspinatus

Suprascapular Nerve Entrapment

• Operative tx (cont’d)– Palpate along the scapular spine for the

suprascapular notch– Operating microscope is helpful– Identify SSN visually & by stimulation– Suprascapular artery usually superficial to the

superior transverse scapular ligament– Divide the ligament

Release of Suprascapularentrapment

Splenoglenoid Region Ganglion Cyst

Suprascapular Nerve Entrapment

• Outcome of surgery– Pain responds very well– Atrophy does not– External rotation may be normal due to

compensation by teres minor

What is your diagnosis?

• Young man• Lifting weights in gym• Night, severe shoulder and

arm pain• Over days, noted pain

somewhat improving, butshoulder movementsimpaired and weak

• No sensory complaints

Acute Brachial Neuritis• Sudden onset• Spontaneous or minimal

“trauma”• Associated with severe pain

then weakness and atrophy• Long thoracic nerve

involvement frequent• Also C5, C6 and UT

distributions, branches• EMG helpful in looking for

sub-clinical and bilateralinvolvement

Brachial neuritis (plexits):management

• Make the diagnosis (clinical, aided byelectrical studies)

• Rule out other causes (imaging of spine, SCand BP as needed)

• Do NOT offer surgery• Most patients improve: pain resolves,

weakness better in majority residual deficitsin some

Thoracic Outlet Syndrome

• Definition: set ofsymptoms due tocompression of thebrachial plexus (BP) and /or subclavian vessels inthe cervical region.

• First description by Galenand Vesalius (2nd centuryAD)

• Incidence ?• Under/over diagnosed

TOS: history and terminology• * Confusing terminology:• - Scalenus anticus syndrome

• (Adson and Coffey, 1927)• - Cervical rib syndrome• - Costo-clavicular syndrome

• (Falconer and Weddel, 1943)• - Hyperabduction syndrome

• (Wright, 1948)• - « Thoracic outlet syndrome »

• (Peet et al, 1956)• Clinicians Anatomists• = scalene = inferior thoracic

triangle aperture• - Cervico-axillary syndrome

Anatomy of Thoracic Outlet andAnomalies

• Anatomical anomalies / variants:• osseous: - cervical rib (1%)• - long transverse C7• process• myofascial: - accessory scalene m.• - falciform median• scalene muscle• - fibrous band• ( 9 types described• by Roos)• ⇒ compression of lower BP and / or

subclavian artery

Thoracic Outlet Syndrome

VascularArterialVenous

NeurogenicPain Syndrome – common or disputedTOSPlexus Compression – Classic TOS

TOS symptoms• Vasogenic syndrome (< 10 %)• Numbness entire UE• Coldness hand• Swelling / cyanosis• Acute art. Insufficiency

• Neurogenic syndrome (> 90 %)• Pain / paresthesia UE• Pain neck, chest, headache• Aggravation of pain with use of UE, especially on

elevation• Atrophy hand m.

Common (Disputed) TOS

• History of trauma in at least 50%• Supraclacicular tenderness• Pain and /or paresthesias may be reproduced by a

variety of provocative maneuvers, such as Adson’s• Neurolgical exam normal• Electrophysiologic tests (EMG,NCV,SSEP) usually

normal• Cervical rib (1% of general population) or abnormal

C7 transverse process seen but rare

909000 abduction & external abduction & externalrotation, or spear-throwingrotation, or spear-throwing

positionposition

Disputed TOS- provocative tests• Decreased radial pulse on various manouevers• Hands up test• Modified Roos test• Sensitive, frequently +ve, but poor reliability and

specificity

Classical Neurogenic TOS:Clinical Features

• Chronic unilateral arm pain followed byhand intrinsic atrophy

• Women > men (4:1)• Seldom seen in childhood• Occupational factors• Postural factors:

– Asthenic, long necked– Droopy shoulders

Classic Neurologic Syndrome• Pain and paresthesias rare; dull ache in

medial forearm• Sensory loss in 4th and 5th fingers• Tinel’s sign or tenderness over

supraclavicular plexus• Weakness and wasting in hand intrinsics

(lower trunk plexopathy)• Characteristic findings on EMG and NCV• Cervical rib or elongated C7 transverse

process nearly always present

Classic TOS:Atrophy often selective - lateral thenar (APB)

Gilliat-Summner hand

True Neurogenic TOS:Electrodiagnostic Studies

• Most affected = amplitude of CMAP tomedian nerve stimulation (median motorpotential)

• Reduced ulnar sensory potential• Ulnar motor potential mildly reduced or nl• Median sensory potential normal (upper

trunk)• EMG shows denervation in abductor

pollicis brevis, lesser chronic neurogenicchanges in other hand muscles

Classic TOS Imaging

C7 Tranversomegaly Cervical ribs

MR NeurographyMR Neurography

Zhou et al, Zhou et al, Muscle NerveMuscle Nerve 30;305-309, 2004 30;305-309, 2004

MR NeurographyMR Neurographyin Neurogenic TOSin Neurogenic TOS

TOS- Conservative Treatment

• Initially for all with Disputed TOS• Modify predisposing factors

– Obesity, breast hypertrophy– Optimisation of ergonomic conditions

• Medication: NSAIDs, analgesics, myorelaxants,antidepressants,...

• Individually tailored physical therapy program– Postural correction– Stretching exercises (upper trapezius, levator scapulae,

pectoral,…)– Strengthening exercises (lower scapula stabilizers)

TOS- Physical Therapy Program

• Nowak et al. J Hand Surg, 1995.• « Outcome following conservative management of

TOS »• 42 patients mean age: 38• Physical therapy at least 6 months• 25 symptom improvement• 10 no change• 7 worse

TOS Surgery:TOS Surgery:A Randomized TrialA Randomized Trial

55 patients with primarily pain55 patients with primarily painSNBP (25) vs. TFRR (24, 2 pts SNBP (25) vs. TFRR (24, 2 pts bilatbilat.).)Mean F/U 37 mos.Mean F/U 37 mos.TFRR better by all measuresTFRR better by all measures75% TFRR vs. 48% SNBP good or excellent75% TFRR vs. 48% SNBP good or excellentoutcomesoutcomes

ShethSheth & Campbell, & Campbell, J Neurosurg SpineJ Neurosurg Spine 2005;3:355 2005;3:355

TOS Surgical Indications

• Vascular TOS• Neurogenic classical TOS with muscle

weakness and positive electrical studies• Some cases of common TOS

– Poor response to well attempted conservativetherapy and physical therapy program

– Well motivated (no secondary gain issues)

Thoracic Outlet Syndrome:Operative Approaches

• Anterior supraclavicular - allows neurolysisat root and trunk level, cervical rib resection

• Transaxillary - allows 1st rib resection, lysisof congenital bands

• Posterior subscapular - avoids scar in re-docases

35 y.o. F with classic neurogenic TOS

Lower trunk compression:Musculotend bands > bone

*

UT MT

C8

C8

Thoracic Outlet Decompression:Technical Issues

Full exposure of all 3 trunks Requires division of anterior scalene- identify and protect

the phrenic nerve Exposure and protection of long thoracic nerve, posterior

and lateral to upper trunk, within medial scalene TOS is a soft tissue disease, C8/T1 being compressed by

fibro-muscular anomalies Surgery should concentrate on the anomalies and not on the

1st rib Resect all compressive soft tissue pathology +/- bony

elements

Thoracic Outlet Syndrome:Surgical Series of 1st Rib

Resection• Most suffer from observer bias• Most are retrospective• Indications for surgery differ• No uniform rating scales for preop

condition or postop outcome• Different surgical techniques

Thoracic Outlet Syndrome

• Conclusions:– Classic TOS is rare– Think - soft tissue compression– Think - close to the spine– We must improve our diagnostic techniques

(MR neurography?)– We must improve conservative management– Never trust a surgeon

Median Nerve at Elbow

Median Nerve and AIN

Pronatar teres is KEY muscle

Median Nerve Compression inthe Forearm: Symptoms

• Aching, heaviness in the forearm• Clumsiness, weakness of the hand• Numbness in the hand - usually more vague

than CTS• Worse after repetitive motions• Night sx’s not prominent, unlike CTS• Changes in wrist position do not provoke

sx’s, unlike CTS

FDP

Anterior Interosseous Nerve (AIN)Entrapment

• Weakness of FPL & FDP• Pinch posture (OK sign)• Weak pronation w/ elbow flexed• No sensory loss – pure motor nerve• Site of entrapment controversial• Trauma more common than entrapment• Idiopathic cases may be brachial neuritis

Median Nerve:Potential Points of Compression

• Forearm– Lacertus fibrosus

(bicipitalaponeurosis)

– Pronator teres– Flexor digitorum

superficialis(sublimis) arch

– Anomalous muscles– Ulnar collateral or

radial artery branches

Median nerve decompressed

Lacertus fibrosus

AIN Syndrome: Signal change (denervation)on MRI in FDP and FPL

AIN Entrapment: Diagnosis andManagement

• Clinical: lack of sensory features andabnormal pinch posture

• EMGs, hallmark is denervation of pronatorquadratus in addition to FDP (III and IV)and FPL

• Patients worsening or not improving aftersome period (months) are candidates fordecompression

AIN Decompression: all aspects, lacertus, 2 heads of pronatorand flexor sublimis arch

AIN Decompression: Outcome

• No large series• Very anecdotal• My experience (~10 cases) is that the

majority improve with distal thumb FDPflexion restored to MRC 4

Radial Nerve and PIN

Supinator muscle is KEY

Radial Nerve EntrapmentSyndromes

Posterior Interosseous Nerve (PIN)Radial Sensory Nerve (RSN)

Posterior Interosseous Nerve(PIN) Entrapment

• PIN Compression Syndrome– Motor– Classical– Well accepted

• Radial Tunnel Syndrome– Pain– Controversial

PIN (Motor) Compression Syndrome

• PIN palsy:– Finger drop,

partial orcomplete

– Spares ECRL– Allows wrist

extension inradialdirection

Radial Tunnel Syndrome:Clinical Features

• Repetitive activity (bowlers)• Pain over lateral elbow, may radiate• Deep ache, cramp, charley horse (motor

nerve)• Pain worse w/ activity, better w/ rest• Night pain is common• DDx: lateral epicondylitis (tennis elbow)

Radial Tunnel Syndrome:Clinical Features

• No motor deficit• No sensory deficit• No EMG abnormality• Pain precisely located – proximal supinator• Pain provoked by palpation (direct) or by

middle finger test & resisted supination(indirect)

PIN Entrapment: Management

• Confirm clinical diagnosis (electricalstudies)

• Conservative if improving• Indications for decompression:

– Worsening motor syndrome– Persistent motor impairment– Some patients with intractable pain, despite rest

and activity modification

PIN Compression Syndrome:Operative Approaches

• Approaches are relative to MOBILE WAD(BR, ECRB, ECRL)

• Anterior• Transmuscular (BR)• BR - ECRL interval• Posterior

PIN Compression Syndrome:Surgical Pointers

• Goals: Divide superficial supinator, ECRB leading edge,vascular leash of Henry

• Beware of veins• ECRB leading edge may be mistaken for Arcade of Frohse

(superficial supinator free edge)

PIN Decompression through the Supinator Heads

PIN Decompression: Outcomes

• Worthwhile procedures• Progression of motor loss almost always

halted• Most patients with motor deficits improve

over weeks to months• Pain responds in approximately 2/3, in well

selected cases

Radial Sensory Nerve (RSN)

Superficial Sensory RadialNerve (SSRN)

Radial Sensory Nerve (SSRN)Entrapment

• Burning pain, paresthesias of dorsal radialhand. + Tinel’s sign

• No motor loss• Variable sensory loss, small autonomous

zone (anatomic snuffbox)• DDx: cervical radiculopathy, DeQuervain’s

tenosynovitis• Neuroma (tight wrist watches, handcuffs)

SSRN Entrapment: dynamicconsiderations on Exam

Radial Sensory Nerve:Operative Technique

• Regional or general anesthesia• Incision 3-4 cm over volar radial forearm• Beware of lat. antebrachial cutaneous n.• Open fascia between BR & ECRL tendons• Resect neuromas (recurrence rate high)

SSR Decompression

Ulnar Nerve

Ulnar Nerve Anatomy at theWrist: Guyon’s Canal

Guyon’s canal: Anatomy• An oblique fibro-osseous tunnel that lies within proximal

part of hypothenar eminence• Roof: palmar fascia (volar carpal ligament) and palmaris

brevis muscle• Floor: flexor retinaculum and pisohamate ligament• Walls:

– Terminal tendon of FCU and pisiform bone formsmedial wall

– Curved ulnar surface of hook of hamate forms lateralwall distally

• Contains ulnar artery (medial) and ulnar nerve in loosefibrofatty tissue

• Deep motor branch and ulnar artery turn laterally and passunder pisohamate hiatus

Guyan’s canal entrapment

• Sensory changesconfined to ulnardistribution distally,with sparing ofpalmar and dorsalulnar cutaneous nervebranch distributions

• FCU and FDP to D4and D5 spared

Distal Ulnar Neuropathy(Guyon’s Canal Entrapment)

• Ulnar intrinsic muscle weakness– Hypothenar mass may be spared (along

with sensation) in variant where deepbranch compressed at pisohamate hiatus

• Clawing of D5 (D4) may be pronounced• Tinel’s sign over ulnar nerve overlying

wrist

Surgical approach: Ulnar nerve at wrist

Lower extremity nerves

LFCN

LFCN Entrapment: MeralgiaParaesthetica

• Dysesthethic pain inlateral thigh distribution

• Contributing factors:– Trucal obesity– Tight

• Diagnosis is clincal• R/O upper lumbar

radiclopathy, and lumbarplexus lesion

Management• Modify risk factors• Medical treatment

– Amitrptylline– Gabapentin

• Local anesthetic blockof LFCN diagontic andtherapeutic (up to 80%)

• 1 of 10 may requiresurgical procedure

• Decompression vs.Neuroectomy

Meralgia Paraesthetica: SurgicalAnatomy

Entrapment of lateralfemoral cutaneous nerveof the thigh at theinguinal ligament

Nerve passes throughligament just medial tothe anterior superior iliacspine

Key to finding the nerveis the sartorius; nerve justdeep to fascia overlyingthis

ASIS

LFCNDecompression

Ing Lgt

Nerves in popliteal fossa

Peroneal Entrapment Neuropathy

• Painless (usually) development ofpartial/complete foot drop andsensory loss in peronealdistribution

• Distinguish from L5radiculopathy: no back pain, nosciatica, SLR normal

• findings confined to peronealnerve distribution and Tinel’sbehind fibular head into lateralcompartment

Peroneal Compression• Usually idiopathic• prolonged crouching

position– Strawberry Picker’s Palsy– Roofer’s Palsy

• Habitual crossing of legsthin people

• Focal demyelination atlevel of fibular head

Peroneal Entrapment Neuropathy• Etiology:

– spontaneous– external compression (habitual crossing legs;

postoperative)– metabolic (diabetes)– post-traumatic– lesions (ganglion cyst)– tumors

Peroneal Nerve Entrapment

• Verify diagnosis with electrodiagnostic studies• Conduction delay or block at fibular head/neck

level. Denervational changes.• Eliminate extrinsic compression (avoid leg

crossing)• AFO foot drop brace• Surgery: decompression• Results variable: patients with partial deficits do

better. Complete foot drop often does not reverse.Consider tendon transfers

Peroneal Nerve Entrapment:Surgical Anatomy

Peroneal nerve entrapped byfascia overlying and sharpfibrous band of the peroneuslongus muscle

Nerve crosses fibular neckobliquely, just below head offibula

Can be palpated just below headof fibula

Just beneath fascia – can bedifficult to distinguish fromsurrounding fat

Find nerve just posterior tobiceps femoris tendon, followdistally to decompress

Peroneal Nerve Decompression

Tibial Nerve Anatomy

Tarsal Tunnel Syndrome

• Entrapment of posterior tibial nerve posterior to medialmalleolus (flexor retinaculum) and fibrous septa in foot

• VERY much rarer than CTS• history of previous ankle trauma in 50%• burning pain and paraesthesias along plantar aspect of foot

– medial or lateral plantar or both; heel may be spared(calcaneal branch variable in origin and entrapment)

– pain may radiate to calf– worse with activity (walking), relieved by rest

• sensory findings, foot intrinsic atrophy and Tinel’s

Tarsal Tunnel Syndrome:Diagnosis

• Electrical tests are key to making diagnosis(distinguish many causes of foot pain from themuch rarer tarsal tunnel syndrome)

• normal conduction in leg PT nerve• prolonged distal motor latencies to abductor

hallucis (medial plantar) or abductor digiti quinti(lateral plantar)

• decreased distal sensory nerve CV• denervation of foot intrinsics on EMGs

Surgery: Tarsal Tunnel

• Incision• Undertake thorough

decompression ofmain nerve and distaldivisions at fibrousseptum compartments

• Results of surgeryvariable