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n_neuropathies

Neuropathies

see neurology

Mononeuropathies:

definition:

  • lesions of individual nerve bundles

aetiology:

  • trauma, compression
  • causes that may result in more than one nerve affected (ie. mononeuritis multiplex):
    • acute (usually vascular):
      • diabetes mellitus
      • polyarteritis nodosa, SLE, Rh.A
    • chronic:
      • multiple compressive neuropathies, esp. with joint deforming arthritis
      • sarcoid
      • amyloid
      • acromegaly
      • Lyme disease
      • leprosy
      • neoplasia (rare)

common nerves involved:

  • median nerve
  • ulnar nerve
  • radial nerve
  • sciatic nerve
  • lateral popliteal nerve
  • tibial nerve

Polyneuropathies:

introduction:

  • derangements of peripheral nerves which usually begin distally & spread proximally giving rise to 'glove & stocking' anaesthesia (peripheral neuropathy)
  • distal motor weakness may also occur, & reflexes reduced
  • different patterns are discernible with different causes
  • pain & tenderness in affected muscles is notable in neuropathies of diabetes & alcoholics

aetiology:

  • common causes of peripheral neuropathy:
    • Guillain-Barre syndrome
    • metabolic:
      • diabetes mellitus, renal failure, liver failure, alcohol, hypothyroidism, porphyria, hypoglycaemia xanthomatosis
    • CT diseases:
      • polyarteritis nodosa
    • malignancy:
      • incl. polycythaemia rubra vera
    • infections:
      • esp. leprosy, TB, syphilis
    • vitamin deficiencies:
      • B1
      • B6
      • B12 (subacute combined degeneration of the cord):
        • symmetric post. column loss (vibration & position sense) ⇒ ataxic gait
        • symmetric UMN signs in lower limbs with absent ankle jerks
        • knee reflexes may be absent, or, more often, exaggerated
        • peripheral sensory neuropathy (less common & mild)
        • optic atrophy, dementia
    • genetic:
      • Refsum's syndrome
      • Charcot-Marie-Tooth syndrome (HMSN Type I):
        • pes cavus, distal muscle atrophy, absent reflexes, thickened nerves, optic atrophy
    • toxins:
      • lead, metronidazole, phenytoin, vincristine, nitrofurantoin, amiodarone
predominantly motor peripheral neuropathy:
  • Guillain-Barre syndrome
  • Charcot-Marie-Tooth syndrome
  • acute intermittent porphyria
  • lead poisoning
  • diabetes
  • NB. remember MND & NM junction disorders
predominantly sensory peripheral neuropathy
  • unusual & results in sensory ataxia & pseudoathetosis
  • carcinoma eg. lung, ovary, breast
  • paraproteinaemia
  • B6 intoxication
  • Sjogren's syndrome
  • diabetes
  • syphilis
  • B12 deficiency (occas)
painful peripheral neuropathy:
  • diabetes
  • alcohol
  • B12 or B1 deficiency
  • carcinoma
  • porphyria
  • arsenic or thallium poisoning
  • hereditary
  • NB. burning soles of feet may be painful periperal neuropathy, tarsal tunnel syndrome or an S1 lesion
extensor plantar response with absent ankle jerks:
  • B12 deficiency
  • conus medullaris lesion
  • UMN lesion + cauda equina compression or peripheral neuropathy
  • syphilis (tabo-paresis)
  • Friedrich's ataxia
  • diabetes (uncommon)
  • adrenoleukodystrophy or metachromatic leukodystrophy
rapid onset neuropathies (within days)
  • ischaemic
  • pressure - direct pressure on a nerve; compartment syndrome; etc.
  • iatrogenic - injection into nerves
  • penetrating wounds or thermal injury
  • polyarteritis nodosa
  • rheumatoid arthritis
  • diabetic cranial neuropathies
  • diabetic amyotrophy
  • Guillain-Barré syndrome
  • Acute intermittent porphyria
  • Critical illness polyneuropathy
  • Diphtheric neuropathy
  • thallium toxicity
subacute onset (weeks to months)
  • Maintained exposure to toxic agents/medications
  • Persisting nutritional deficiency
  • Abnormal metabolic state
  • Paraneoplastic syndrome
  • chronic inflammatory demyelinating polyradiculoneuropathy (CIDP)
insidious onset with chronic course
  • Hereditary motor sensory neuropathies
  • Dominantly inherited sensory neuropathy
  • chronic inflammatory demyelinating polyradiculoneuropathy
relapsing/remitting course
  • Guillain-Barré syndrome
  • chronic inflammatory demyelinating polyradiculoneuropathy
  • HIV/AIDS
  • toxic
  • porphyria

investigations:

  • FBE, ESR, glucose, U&E, TFT, B12, protein electrophoresis, syphilis serology, ANA, CXR
  • consider: porphyria screen; nerve conduction studies & electromyography

treatment:

  • Rx cause

Multiple cranial nerve palsies:

aetiology:

  • think of malignancy first
  • nasopharyngeal carcinoma
  • chronic meningitis eg. carcinoma, TB, sarcoid
  • Guillain-Barre syndrome (usually spares I, II, & VIII)
  • brainstem lesions:
    • usually due to vascular disease causing crossed sensory or motor paralysis(ie. cranial nerve lesions on one side & contralateral long tract signs)
    • pts with brainstem gliomas may have similar signs & may live for many years
  • Arnold Chiari malformation - protrusion of the cerebellar tonsils through the foramen magnum, with the more severe types (II to IV) which may cause lower cranial nerve palsies, cerebellar limb signs & upper motor neurone signs in legs
  • trauma
  • lesion of base of skull (eg. Paget's disease, metastasis)
  • rarely, mononeuritis multiplex (eg. diabetes)

References

n_neuropathies.txt · Last modified: 2017/10/02 13:13 by gary1