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:

see also bulbar palsy

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

Am. Family Physician - 1998

Table of Contents

Neuropathies

Mononeuropathies:

definition:

aetiology:

common nerves involved:

Polyneuropathies:

introduction:

aetiology:

predominantly motor peripheral neuropathy:

predominantly sensory peripheral neuropathy

painful peripheral neuropathy:

extensor plantar response with absent ankle jerks:

rapid onset neuropathies (within days)

subacute onset (weeks to months)

insidious onset with chronic course

relapsing/remitting course

investigations:

treatment:

Multiple cranial nerve palsies:

aetiology:

References