Page 344 - Medicine and Surgery
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                   340 Chapter 7: Nervous system


                     dependsonthelengthofnerveneededtoregrowdown  Guillain–Barr´ e syndrome
                     the nerve sheath. Excessive fibrosis (scarring) hinders
                                                                Definition
                     growth.
                                                                An acute inflammatory poly-radiculo-neuropathy char-
                     Neurotmesis is division of a nerve, following which

                                                                acterised by progressive muscle weakness and areflexia.
                     there is distal Wallerian degeneration. The nerve bun-
                     dleis interrupted, in-growth of fibrous tissue pre-
                     vents re-innervation, so that surgical repair is needed  Incidence
                     if function is to be restored. Ideally, immediate repair  Although rare (∼1–2 per 100,000 population per an-
                     with end to end suture is undertaken with a reason-  num), it is the commonest cause of acute flaccid paral-
                     able prognosis. However if there is contamination the  ysis in healthy people. It affects all ages and both sexes
                     nerve ends are marked with non-absorbable sutures  equally.
                     and after 2–3 weeks the nerve is surgically repaired –
                     good recovery of function is rare.         Aetiology/pathophysiology
                   Any cause of mononeuritis multiplex may also present  Immune mediated demyelination of peripheral nerves
                   initially as a mononeuropathy.               typically 2–4 weeks after a mild respiratory or gastroin-
                   Mononeuritis multiplex: An uncommon form of neu-  testinal illness. It is thought that antibodies to the infect-
                   ropathy where two or more peripheral nerves are af-  ing organism cross-react with components of myelin.
                   fected either together or sequentially. If symmetrical  In particular, recent infection with Campylobacter jejuni
                   nerves are affected it may mimic a polyneuropathy. The  is associated with a worse prognosis. Remyelination oc-
                   main causes are diabetes mellitus, malignancy, amy-  curs over a period of 3–4 months and is associated with
                   loidosis, polyarteritis nodosa, connective tissue disor-  recovery in most cases.
                   ders, HIV infection and leprosy (commonest cause
                   worldwide).                                  Clinical features
                   Peripheral neuropathy: Asymmetrical disorder of pe-  Patients complain of distal paraesthesiae and numbness
                   ripheral nerves, usually distal more than proximal.  followedbyweaknessofdistallimbmuscles.Thisascends
                   It excludes cranial nerve palsies, mononeuropathies,  over hours or days (up to 4 weeks) causing weakness,
                   mononeuritis multiplex and bilateral single nerve le-  areflexia and sensory loss in the legs and arms, cranial
                   sions. The commonest causes are              nerve involvement with difficulty swallowing and respi-
                     Diabetes mellitus.
                                                                ratory muscle weakness in 20%. There may be backache
                     Malignancy (e.g. lung, leukaemia, lymphoma, mye-
                                                                or shooting pains down the back of the leg early in the
                     loma).                                     course. Over the following weeks to months, the condi-
                     Vitamin B deficiency (Thiamine (B 1 )deficiency in al-
                                                                tion slowly improves.
                     coholics, Vitamin B 12 deficiency).           Miller–Fischer syndrome, a clinical variant of
                     Drugs (e.g. isoniazid, phenytoin, nitrofurantoin, vin-
                                                                Guillain–Barr´ e syndrome, causes ophthalmoplegia, fa-
                     cristine, cisplatin).                      cial weakness, ataxia and areflexia.
                   Other rare causes include uraemia; hypothyroidism; sys-
                   temic diseases and vasculitis, e.g. sarcoid, systemic lupus  Microscopy
                   erythematosus, amyloidosis, polyarteritis nodosa; toxins  Nerves show infiltration by lymphoid cells with phago-
                   such as lead (motor), arsenic & thallium (initially sen-  cytosis of myelin by macrophages.
                   sory); infections such as leprosy, diphtheria; Guillain–
                   Barr´ e syndrome (acute inflammatory or postinfective  Complications
                   polyneuropathy).                             Respiratory insufficiency or aspiration risk (due to swal-
                   Radiculopathy: Damage to one or more nerve roots or  lowing difficulties) may necessitate intubation and pos-
                   anerve plexus. The most important causes are trauma,  itive pressure ventilation. Autonomic involvement may
                   compression (e.g. prolpased intervertebral disc, cervi-  occur at any stage, causing sweating, bladder dysfunc-
                   cal or lumbar spondylosis or neurofibroma), malignant  tion, hypo- or hypertension, arrhythmias and even sud-
                   infiltration and herpes zoster.               den death by asystole.
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