Unusual Nerve Entrapment Unusual Nerve Entrapment Syndromes Syndromes Rajiv Midha, MD, MSc, FRCS(C) Hotchkiss Brain Institute & Department of Clinical Neurosciences, Professor and Chief, Division of Neurosurgery, University of Calgary
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