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Median Neuropathies Flashcards

1
Q

Define Carpal Tunnel syndrome?

A

Most common compressive neuropathy of median nerve at the wrist

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2
Q

Describe the aetiology of Carpal Tunnel syndrome?

A
  • Pathologic Inflammed Synovium most common cause of idopathic CTS
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3
Q

What is the epidemiology of CTS?

A
  • 0.1-1% general population effected
  • Risk factors
    • Female
    • obesity
    • Pregnancy
    • Hypothyroidism
    • RA
    • advanced age
    • Chronic kidney failure
    • Smoking
    • ETOH excess
    • Repitive motion activities
    • Mucopolysaccharidosis
    • Mucoliposis
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4
Q

Describe the pathophysiology of CTS?

A
  • Mechanism- precipitation to repititive motions and vibrations
    • cyclists, tennis, throwing
  • Compression maybe due to
    • repetitive motions in patients with normal anatomy
    • Space occupying lesions- e.g. gout/ synovial sarcoma/lipma/ganglions
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5
Q

Name associated conditions with CTS?

A
  • Diabetes Mellitis
  • Hypothyroidism
  • RA
  • Pregnancy
  • Amyloidosis
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6
Q

What is the prognosis of CTS?

A

Good prognostic indicatiors are

  • Night symptoms
  • Short incisions
  • relief of symptoms with steriod injections
  • Not improved when incomplete release of transeverse carpal ligament is discovered
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7
Q

What is the anatomy of the carpal tunnel?

A

Defined by

  • Scaphoid tubercle and trapezium radially
  • hook of hamate and pisiform ulnarly
  • Transverse carpal ligament -roof
  • proximal carpal row distally - floor
  • narrowest at Hook of HAMATE

Contains

  • 9 flexor tendons- FDP/FDS/ FPL
  • 1 nerve- Median
  • FPL most radial structure
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8
Q

Name the branches of the median nerve?

A
  • Palmar cutaneous branch of median n- between PL & FCR at wrist flexion crease
  • Recurrent motor branch of median nerve
    • ​50% Extraligamentous w recurrent innervation
    • 30% Subligamentous with recurrent innervation
    • 20% Transligamentous with recurrent innervation
    • Cut transverse ligament far ULNAR to avoid cutting nerve if transligamentous
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9
Q

Can you describe the signs and symtpoms of carpal tunnel?

A

Symptoms

  • Numness and tingling in radial 3 1/2 digits
  • clumsiness
  • Pain and parathesia that awaken pt at night
  • self administered hand digram= 76 % carpal tunnel

O/E

  • Thenar atrophy
  • Durkan’s compression test- most sensitive dx- pressing thumbs over carpal tunnel and pressure hold for 30 seconds- onset of pain & parathesia within 30s= +ve
  • http://www.orthobullets.com/video/view?id=12
  • Phalen’s test- Wrist flexion with elbow extended for 60sec= + symptoms
  • http://www.orthobullets.com/video/view?id=13
  • Tinels test- tapping nerve over volar carpal tunnel
  • Semmes- Weinstein testing- most sensitive sensoy test for detecting ealry carpal tunnel syndrome, measures single nerev fiber innervating a receptor/gr of receptors
  • Innervation density test- statis adn moving 2 point discrimination. Measure mutiple overlapping of diff sensory units and complex cortical integration. Gd at testing functional nerve regeneration after n injury
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10
Q

What investigations are helpful in CTS diagnosis?

A

EMG and NCV

not needed to establish diagnosis as this is clinical

  • NCV
  • Demyelination-> Increase latencies= slowing NCV
    • distal sensory >3.2ms, motor >4.3 ms
    • decrease condition velocities, V<52m/sec abn
  • ​EMG
    • ​Test the electrical activity of individual muscle fibres and motor units
    • Details insertional/ sponataneous activity
    • Increase insertional activity
    • Sharp waves
    • Fibrillations
    • Fasciculations
    • Complex repetitive discharges
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11
Q

What is neve histology characterised by?

A
  • Oedema
  • Fibrosis
  • Vascular sclerosis
  • Scattered lymphocytes
  • Amyloid deposits shown with special stains in some cases
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12
Q

Describe the Tx of CTS?

A

Non operative

  • Night splints, NSAIDs, Activity modifications
  • night splints gd for nocturnal symptoms, activity modification- neutral position as extension increases carpal tunnel pressure and symptoms
  • Steriod Injection- 80% transient improvement- 22% symptom free at 1 yr. Failure to improve post injection= poor prognostic sign

Operative

  • Carpal Tunnel Release-open vs arthroscopic failed Consx Tx/Acute radius Fracture, temporarily improvement w steriod -pt gd outome with surgey
    • Pinch strength return in 6 weeks
    • Grip strength expected to return to 100% preop levels by 12 weeks
  • ​Revision for CTS for incomplete release
    • ​Failure to improve post primary surgery
    • Incomplete release most common cause
    • Outcomes= only 25% will have complete relief after revision CTR, 50% some relief, 25% no relief
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13
Q

Describe the technique for CTS release?

A
  • Antibiotics not required for elective pts
  • Guyon’s canal doesn’t need release as decompressed by carpal tunnel release
  • Tourniquet
  • Local anaesthetic
  • Incision= inline with 3rd webspace 3-4cm in palm
  • thru skin, fat, down to transverse carpal ligament
  • Be aware of recurrent branch of median nerve may cross TCL
  • Cut TCL under direct vision then see median nerve
  • Put macdonalds uner neath distal to fat - distal palmar artery branch close
  • Release proximal over tendon first then thru tendon
    *
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14
Q

Describe the complications of open CT decompression?

A
  • Incomplete release
  • Damage to recurrent branch of median nerve-> thenar muscle atrophy
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15
Q

what are the advantages of arthropscopic ct release?

A
  • Accelerated rehabiliation
  • Long term results same as Open
  • Incomplete division of transverse carpal ligament
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16
Q

Define AIN compression neuropathy?

A
  • Compressive neuropathy of the AIN that results in
  • Motor Deficit only
  • _No sensory loss _
17
Q

Describe the anatomy course of AIN?

A
  • Terminal branch of median nerve
  • AIN arises from median n approx 4cm distal to medial epicondyle where it passes into the anterior interosseous membrane to sites of innervation

AIN 3 letters supplies 3 muscles ‘OK sign”

  • Supplies
    • FDP to Index and middle finger
    • FPL
    • Pronator quadratus
18
Q

Dsecribe the pathoanatomy of AIN compression?

A

Potential sites of entrapment

  • Tendinous edge of deep head of PRONATOR TERES- most common area
  • FDS arcade
  • Edge of lacertus fibrosus
  • Accessory head of Gantzer’s muscle
19
Q

What are the signs and symptoms of AIN compression?

A

Symptoms

  • Motor deficit only
  • No pain

​Signs

  • Complete palsy of all 4 muscles innervated by AIN
  • Weakness of grip and strength esp at thumb= unable to make an OK sign- test FPL/FDP
  • Pronator quadratus weakness- weak resisted pronation w elbow maximally flexed
  • Distinguigh FPL attritutio rupture (RA) by passively flexing and extending wrist to confirm tenodesis effect in intact tendon
20
Q

What if a patient has incomplete palsies of the muscles supplied by AIN on examination?

A

This is abnormal as normally all 4 effected

so think weird anatomy/ Martin-Gruber anastomies

  • 15% population axons of AIN may cross over to innervate other muscle groups and so present differently
21
Q

Names associated conditions with AIN compression neuropathy?

A
  • Parsonage- Turner Syndrome
    • Bilateral AIN caused by Viral Brachial neuritis
    • be sucipious if motor loss Preceded by INTENSE SHOULDER PAIN/ VIRAL Prodrome
22
Q

What investigations are helpful in diagnosis of AIN compression?

A

EMG

  • may rule out more proximal lesions
  • May reveal abnormalities to FPL,FDP index and middle finger and pronator quadratus
23
Q

Describe the TX of AIN compression?

A

Non operative

  • Observation, rest , splinting in elbow 90o flexion 8-12 wks
    • Majority imporve with Consx

Operative

  • Surgical decompression of AIN - if non op fails
  • 75% success rate with surgery
24
Q

Define pronator syndrome?

A

Compressive neurology of median nerve at elbow

25
What is the epidemiology of pronator syndrome?
* More common in **women** * more common **5th decade** * ssociated with well developed forearm muscles= **weight lifters **
26
Describe the pathoanatomy of pronator syndrome?
5 potential sites of compression= **SLAP F** * **Supracondylar process**- residual osseous structure on distal humerus = 1% * **Ligament of Struthers** * travels tip of supracondylar process to medial epicondyle * can-\> ulnar/median nerve neuropathies * **Bicipital aponeurosis** ( Lacertus fibrosis) * Between ulnar/radial heads **Pronator teres** * **FDS aponeurotic arch**
27
Name any associated conditions with pronator syndrome?
* **Medial Epicondylitis**
28
What are the signs and symptoms of pronator syndrome?
Symptoms- motor and sensory! * **parathesia to thumb, index and middle finger & radial 1/2 ring** * _Acting pain over proximal forearm_ * **_Sensory distrubance over distribution of PALMAR Cutaneous branch of median nerve ( palm of hand)_** which arises 4-5 cm proximal to carpal tunnel * _NO_ of night pain O/E Provocations tests specific for sites of compression * Positive **Tinels in PROXIMAL forearm**, but _NO tinels sign at WRIST/ symptoms with wrist flexion_ * Resisted _elbow flexion w supination_ forearm= BICIPITAL APONEUROSIS compression * Resisted _forearm pronation w elbow extended=_ 2 heads of PT compression * resisted _contraction of FDS to middle finger_= FDS fibrous arch * coexisting medial epicondylitis
29
What investigations are useful in Pronator syndrome?
Elbow films mandatory- ? supracondylar process
30
Describe the tx of Pronator syndrome?
_Non operative_ * **Rest, splinting and nsaids for 3-6 months** * mild/moderate pain * splint should avoid forearm rotation _Operative_ * **Surgical Decompression of median nerve** * When consx fails after 3-6months * Decompression of nerve at 5 possible sites * outcomes variable **80% relief of symptoms**
31
Describe the course of the median nerve?
* Origin- medial and lateral cords of brachial plexus C5-T1 roots * Anterior compartment of arm * Anteromedial to humerus * runs with BRACHIAL arrtery ( lat on upper arm/medial at elbow) * No branches in arm * Forearm * enters foerarm between pronator teres & biceps tendon * Travels between FDS and FDP * Emerges between FDS & FPL * Hand * Enters via Carpal tunnel along with FDS/FDP & FPL * terminal Branches * **Anterior interosseous nerve**- Pronataor quadratus, FDP and FDS middle/index and FPL * **Palmar cutaneous branch**- sensation lat palm * **Recurrent motor branch**-thenar muscles * **Digital cutaneous branch** - senstation palmar radial 3 1/2 digits, index, long and ring dorsally
32
what does the median nerve innervate?
_Superficial volar_ * Pronator teres * Flexor carpi radialis * Palmaris longus _Intermediate_ * Flexor digitorium superficialis- AIN _Deep _ * Flexor digitorium profundus ( lateral)- AIN * Flexor pollicis longus- AIN * Pronator quadratus-AIN Hand- recurrent branch * 1st and 2nd lumbricals * Opponens pollicis * Abductor pollicis brevis * Flexor pollicis brevis
33

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