Anatomy of median nerve

Anatomy of median nerve by Dr. Bipul Borthakur

1. MEDIAN NERVE By: Dr. Bipul Borthakur , Professor, Dept of Orthopaedics, SMCH

2. A natomy of Median nerve Condensation of lateral and medial cords of brachial plexus Root value : C5,C6,C7,C8,T1 Mixed nerve Also known as Labourers nerve

3. Median nerve in arm Enters a rm from axilla at inferior margin of teres major Passes vertically down on medial side of arm in anterior compartment related to brachial artery throughout its course: Proximaly - lies immediately lateral to brachial artery Distally - crosses the brachial artery -descends on its medial side - passes anterior to elbow joint . No branches in arm

4. Median nerve in forearm Median nerve passes into forearm anterior to elbow joint b/w 2 heads of pronator teres . Supplies FDS , FCR and Palmaris longus ,pronator teres. Its branches innervates most of the muscles in anterior compartment of forearm except flexor carpi ulnaris, medial half of FDP, which are innervated by ulnar nerve . Gives an Ant.Interosseous nerve at around 6-8 cm from medial epicondyle ,supplies FPL,FDP of index and middle fingers and pronator quadratus mules

5. Median nerve in hand Median nerve passes throughout carpal tunnel ,deep to flexor retinaculum the recurrent motor branches supplies – thenar muscles i.e abductor pollicis brevis , opponens pollicis , superficial head of flexor pollicis brevis .

6. Median nerve in hand Digital cutaneous branches provides sensation to volar aspect thumb ,index,middle and radial half of ring fingers. Palmer cutaneous branch of median nerve arises proximal to wrist ,provides sensation to radial palm Short motor branches supplies index and middle finger lumbricals.

7. ANATOMY CARPAL TUNNEL Bounderies : Volarly –transverse carpel ligament Dorsaly -Carpel bones,deep volar carpel ligament and volar interosseous ligaments Laterally -Scaphoid tuberosity and trapezium Medially –Pisiform and hook of hamate Contents: 9 tendons –tendon of flexor pollicis longus, 4 tendons of flexor digitorum profundus , 4 tendon of Flexor digitorium superficialis and median nerve Transverse carpel ligament :Flexor retinaculum : - thick fibrous band from tuberosity of scaphoid & aportion of trapezium to the pisiform and hook of hamate

8. CARPAL TUNNEL SYNDROME Most common entrapment neuropathy Entrapment of median nerve at wrist Most frequent cause of idiopathic CTS : pathologic synovium Idiopathic variety is the most common cause (95 %) Affects 0.1-10% of general population.

9. CARPAL TUNNEL SYNDROME :Clinical presentation Pain : Dull aching pain,awakens patient at night Intermittent course Aggravated by activities that involve flexing or extending the wrist Releived by changes in hand posture shaking the hand Tingling ,numbness of radial 3.5 fingers Paresthesia Weakness

10. Aetiology of carpal tunnel syndrome: a)Idiopathic ( 95%) b)Anatomic c)Systemic d)Exertional (Occupational )

11. Aetiology of carpal tunnel syndrome: Trauma -post traumatic swelling/hemorrhage/scar -Post traumatic arthritis -Carpel dislocation -Distal radius malunion Small carpal canal Basal joint arthritis Anomalous structures muscles – -palmaris profundus -Anomalous slip of flexor pollicis longus - Reversed palmaris longus Vascular - persistent / thrombosed median artery Masses/tumors - ganglion Lipoma Fibroma/lipofibroma Synovial sarcoma Neuroma/neurofibroma/neurilemoma

12. Systemic Disorders affecting fluid balance -Pregnancy -Renal failure -Thyroid disease - Congesative heart failure - Obesity - Myxedema - Acromegaly Neuropathic diabetes thyroid disease vitamin nutritional defeciency vitamin toxicity Alcoholism Medication( Lithium,beta blocker,ergot ) Inflammatory condition Rheumatoid arthritis lupus gout/pseudogout scleroderma dermatomyositis amyloidosis Hemorrhagic disorders leukemia hemophilia anticoagulation Infection Constitutional factors A dvancing age female sex

13. Percussion test ( Tinel sign ) Gentle percussion along course of median nerve from distal to proximal direction Tingling sensation felt by patient in distribution of nerve Importance : whether nerve interrupted In process of regeneration

14. Carpal tunnel compression test ( Durkan test ) Direct compression is applied to median nerve for 30 seconds with the thumbs. Patient with carpel tunnel syndrome usualy have symptoms of numbness,pain,or paresthesia in median nerve distribution

15. Tourniquet test ( Gilliat test ) Arm tourniquet inflated above systolic pressure for 60 seconds. Numbness /tingling in the median nerve distribution

16. Investigation EMG /NCV: distal sensory latencies >3.2 ms or motor latencies >4.2ms considered abnormal MRI not essential in preoperative diagnosis A positive Semmes weinstein monofilament test (most predictive sensory test) and a consistent brigham hand diagram are features.

17. Treatmen t Splinting of wrist in neutral position especially night time and rest ,Nsaids, activity modification must be initial management Corticosteroid injection into the carpal tunnel is indicated when median nerve compression is predicted to be temporary as in pregnancy or when patient activity modified. Indication of surgery : any two of following persistent symptoms, positive physical examination positive electrodiagnostic testing

18. Absolute indication for surgery : constant paraesthesia thenar atrophy markedly delayed median nerve conduction velocity or abnormal EMG Open CTR or Endoscopic carpal tunnel release Recurrence rate after carpal tunnel release - 20% Most common cause of recurrence – incomplete division of retinaculum .

19. THANK YOU “ vāsāṃsi jīrṇāni yathā vihāya navāni gṛhṇāti naro’parāṇi tathā śarīrāṇi vihāya jīrṇā - nyanyāni saṃyāti navāni dehī ” “As a man casts off worn-out garments and puts on others that are new, so does the soul cast off its worn-out bodies and enter into others that are new .”