Median Neuropathies Flashcards
1
Q
Define Carpal Tunnel syndrome?
A
Most common compressive neuropathy of median nerve at the wrist
2
Q
Describe the aetiology of Carpal Tunnel syndrome?
A
- Pathologic Inflammed Synovium most common cause of idopathic CTS
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
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
5
Q
Name associated conditions with CTS?
A
- Diabetes Mellitis
- Hypothyroidism
- RA
- Pregnancy
- Amyloidosis
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
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
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
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
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
11
Q
What is neve histology characterised by?
A
- Oedema
- Fibrosis
- Vascular sclerosis
- Scattered lymphocytes
- Amyloid deposits shown with special stains in some cases
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
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
*
14
Q
Describe the complications of open CT decompression?
A
- Incomplete release
- Damage to recurrent branch of median nerve-> thenar muscle atrophy
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
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
26
Q
Describe the pathoanatomy of pronator syndrome?
A
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
29
Q
What investigations are useful in Pronator syndrome?
A
Elbow films mandatory- ? supracondylar process
31
Q
Describe the course of the median nerve?
A
- 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
