Short Notes in Plastic Surgery

April 20, 2019

Chapter 72.  Injuries Of The lower brachial Plexus C8 T1

Filed under: Chapter 72,Uncategorized — ravinthatte @ 6:39 am

Chapter 72.  Injuries of the Lower brachial Plexus C8 T1

The chapters included in this blog so far for the treatment of injuries to the brachial plexus have covered (1) the general principles including the treatment of injuries to the nerves and their classification chapter 69; (2) treatment of injuries to the plexus of a global nature (when all the roots are avulsed or ruptured) chapter 70 and (3) the treatment of injuries to the plexus at the level of the C5 C6 roots and the their nerves chapter 71. This chapter deals with injuries to lower brachial plexus involving it’s C8 T1 roots.

The compiler of this blog is indebted to Dr. P.S. Bhandari a leading plastic surgeon specialising in the treatment of injuries and other pathologies of the brachial plexus as well as peripheral nerves and who works at the Brij Lal Super-speciality hospital and research centre in Haldwani, Nainital in the Uttarakhand state of India for helping in the writing of this chapter on the injuries to the lower brachial plexus (C8 T1). Dr. Mukund Thatte plastic, hand and brachial plexus surgeon from the Bombay hospital Mumbai India has as in the previous chapters been of equal help in this chapter as well. In addition, because of the intricate nature of the nerve supply of the muscles of the fore arm Professor Maksud of the department of plastic surgery at the Lokmanya Tilak hospital of Mumbai India as well as his two younger colleagues, Drs. Saumil Shah and Sanket Ekhande were a great help in ‘brain storming’ and the anatomical cadaveric dissections of the relevant nerves as well as for the photographs and drawings included in this chapter.

The compiler of these short notes is aware that such an anatomical division as narrated in the first para for the treatment of these injuries is not ideal because in reality not infrequently the nature of injuries is not clearly defined in terms of the location of the injury and is of a mixed nature across the roots. However, this arrangement was followed with the thought that it would be easier for a post-graduate to grasp the subject if it was divided in separate parts. It was also the impression of this compiler that the available texts are somewhat jumbled up with the assumption that the readers would be able to sort out the information which they needed. The compiler of these short notes differed from this assumption when he approached these texts as a postgraduate would do.

The other caveat that was followed was also somewhat different in that procedures which involved re-innervation from extra or intra plexal sources were mostly included in the previous chapters. This too does not conform to all the protocols. For example, in the chapter on global palsy one surgeon who was invited to contribute includes a free muscle transfer with micro neural as well as micro vascular repair as a primary treatment. But that was only an exception. Free muscle transfers as well as local muscle transfers to overcome deficiencies will be covered in a later chapter. This is not to mean that these procedures are meant only for salvage after the original re-innervation did not yield satisfactory results and therefore that option of a primary free muscle transfer will also be covered at that time.

The treatment of lower brachial plexus lesions in one respect differs from those of the upper part of the plexus in the distances involved in the process of re -neurotization. As examples (1) the transfer of the spinal accessory nerve to the suprascapular nerve supplying the supra-Spinatus muscle that is proposed to be re-innervated or (2) the re-innervation of the biceps muscle by borrowing from the adjacent ulnar nerve to the branch of the musculocutaneous nerve that supplies the biceps muscle near its hilum do not involve more than a distance of few centimetres for the reinnervation to succeed. This is not true of the injuries to the lower brachial plexus as explained below.

The nerves affected in the paralysis of the C8 T1 roots, either avulsions or rupture of the nerves that emerge from these roots, leads to mixed results in the ulnar median and radial nerve motor territories because of the way these nerves form. The radial nerve for example is formed by all the roots (C5 to T1) while the median nerve draws its fascicles from C5C6 and C8T1. The ulnar nerve is however an exception in that it is wholly formed by theC8 T1 roots. The ulnar motor supply therefore is completely lost but the effects on the other nerves are more variable because the root values of the branches of these nerves might be from outside the supply from the roots C8, T1. To explain this intricacy a chart is given below of individual supply of muscles and the root values of nerves that supply them. Those which are definitely paralysed are shown in red, those that may be spared are shown in blue and the muscles that are definitely spared are shown in green. The chart begins with the ulnar nerve which is the most affected.

This chart draws its information from a recent edition of Gray’s Anatomy but is not always accurate when the muscles are tested in patients who suffer from injuries to the C8 T1 roots. In fact if one was to consult other standard texts such as by Last or Lister some variation is quite apparent. In the chart below Dr P.S. Bhandari who has a vast experience in the field of these injuries has pointed out this discrepancy by noting the nerve supply that he thinks is correct from what he has seen in his clinical practice. Those observations and highlighted in yellow in the case of pronator quadratus, flexor digitorum superficialis, flexor pollicis longus and palmaris longus muscles.

Flexor carpi ulnaris                                               Ulnar nerve root value C8 T1

Flexor digitorum profundus (ulnar side)          Ulnar nerve root value C8 T1

All palmar and dorsal interossei, C8 T1

Adductor pollicis   C8 T1

Flexor pollicis brevis deep head   C8 T1

The ulnar lumbricals via the deep or other branches of the ulnar nerve C8 T1

The branches of the ulnar nerve which supply the small muscles of the little finger also have the same root value C8 T1

The median nerve

Flexor carpi radialis, median nerve, root value C6 C7

Pronator Quadratus, median nerve, root value C6 C7                          (C8 T1)

Palmaris longus, median nerve, root value C7 C8                                   (C8)

Flexor digitorum superficialis, median nerve root, value C8 T1         (C7 C8 T1)

Flexor digitorum profundus, radial two, Anterior interosseus (AIN) root value C8 T1

Flexor pollicis longus, AIN, root value C7 C8                                             (C8 T1)  

Flexor pollicis brevis, Abductor pollicis brevis, Opponens pollicis and radial lumbricals all by branch of median nerve root value C8 T1

The radial nerve

Extensor carpii radialis longus, Radial, root value C6 C7

Extensor carpii radialis brevis,     P.I.N., root value C7 C8 PIN: Posterior interosseus nerve

Extensor  digitorum                        P.I.N., root value C7 C8

Extensor carpii ulnaris                   P.I.N. root value C7 C8

Extensor indices                               P.I.N. root value C7 C8

Abductor pollicis longus                P.I.N. root value C7 C8

Extensor pollicis longus                 P.I.N. root value C7 C8

Extensor pollicis brevis                  P.I.N. root value C7 C8

Supinator                                           P.I.N. root value C6 C7 (Via separate fascicles?)

Brachioradialis                                 Radial root value C5 C6

(THE BRACHIALIS MUSCLE IN THE ARM IS ALSO MENTIONED HERE BECAUSE ITS NERVE A BRANCH OF THE MUSCULLOCUTANEOS NERVE WITH IT’S ROOT VALUE C5 C6 IS FREQUENTLY USED TO REINNERVATE THE ANTERIOR INTEROSSEUS NERVE ROOT  VALUE C8 T1).

What emerges therefore is the fact that while dealing with these injuries a thorough clinical examination is of great importance and must include examination of muscles which are paralysed and those that are not and to decide if nerves can be borrowed from non- paralysed muscles without causing gross loss of function in the upper arm.

Be that as it may, common clinical experience in injuries to the C8 T1 roots usually reveals that all flexors and extensors of the fingers (including the thumb) all intrinsic muscles of the palm and all small muscles of the thumb and little finger are paralysed. The long radial extensor of the wrist as well as the radial flexor of the wrist are spared which means that the wrist is not normal but functional but the fingers are limp. Of these the small muscles (the crucial intrinsic muscles ) waste rapidly and in most cases are extremely difficult to salvage except in fresh cases involving children or young adults in whom the opposite C7 root might be used to re-innervate the ulnar nerve by way of a nerve graft. These cases are few by far and therefore the surgeon needs to accept the fact that the hand will have to be partially rehabilitated by achieving a pinch action between the index and the middle finger against the thumb.

The anterior interosseus nerve (A.I.N.) also called the million dollar nerve as the name suggests is crucial here because it supplies the long flexors of the thumb as well as the long flexor of the index and the middle fingers (Flexor Digitorum Profundus) and therefore it’s reinnervation if successful will allow a pinch to be formed with the wrist in a position of function (in slight extension) Four prospective nerve donors are available. (1) Nerve to brachialis a branch of the musculocutaneous nerve (root value C5 C6), (2) the nerve to brachioradialis branch of radial nerve (root value C5 C6), (3) and the nerve to extensor carpii radialis brevis if the muscle is not paralysed. The nerve to the intact extensor carpii radialis longus the slightly weaker of the two extensors can also be used if the ECRB is working well.

As to the extensors of the fingers which are supplied by the posterior interosseus nerve the nerve that is commonly used is the nerve to the supinator root value C6 C7 a branch of the radial nerve which leaves the radial nerve carrying separate fascicles as compared the posterior interosseus nerve (P.I.N.) with a root value of C7 C8.

Any treatment therefore will require testing individual muscles confirming that they are not affected and borrowing nerves supplying those muscle without causing too much loss of function. Reproduced below are figures to show how the intact muscles whose nerves might be borrowed without affecting the function of the hand are tested.

Slide1

Slide2

Slide3

Please find below photographs of dissections in the lower arm and forearm showing the nerves and their course which are affected in the lower brachial palsy as well as nerves that escape the effects of the palsy.

Slide4

Slide5

These figures are self-explanatory with incorporated labels.

Below is reproduced a line drawing of the possible procedures for reinnervation.

Slide6

Slide7

The fascicles of the median nerve on top (Red) The posterior fascicles divided and joined to the nerve to brachialis (Blue) and the flow of the nerve impulse in green in the lower diagram.

Please find below intra-operative and clinical examples kindly supplied by Dr. P.S. Bhandari. They mainly show reinnervation of the anterior-interosseous nerve (AIN), also called the Million Dollar Nerve.

Slide8

Slide9

Slide10

Slide11

Slide12

Slide13

Slide14

Slide15

Create a free website or blog at WordPress.com.