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Neuro > Peripheral neuropathy > Flashcards

Peripheral neuropathy Flashcards

1
Q

Functions of the PNS

A
  • sensory input to the CNS
  • Motor output to muscles
  • innervation of viscera
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2
Q

Incoming sensory information enters via

A

Posterior root

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3
Q

Motor information exists via

A

Anterior root

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4
Q

Collection of nerve cell bodies is known as

A

ganglia

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5
Q

Layers in a peripheral nerve

A
  • epineurium
  • perienurium
  • endoneurium
  • axons

The vasa nervorium provides the blood supply.

Peripheral nerve trunks contain myelinated and unmyelinated fibres

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6
Q

Three different types of fibres

A
  • Large myelinated fibres - motor nerves- proprioception, vibration and light touch
  • Small myelinated fibres - light touch, pain and temperature
  • Small unmyelinated fibres - light touch, pain and temperature
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7
Q

Pathogenesis of peripheral nerve degerenation

A
  1. Wallerian degeneration- this describes fibre degeneration when the fibre is cut or crushed. Both the axon and the myelin sheath will degenerate over several weeks after the incident
  2. Demyelination - Caused by inflammation( Guillain-Barre syndrome, post-diphtheric neuropathy, hereditary sensory-motor neuropathies) or by entrapment neuropathies - usually occurs as a result of schwann cell damage
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8
Q

Neuropathy

A

A pathological process that affects a peripheral nerve or nerves and may involve axonal degereation (wallerian) or demyelination

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9
Q

Mononeuropathy

A

Focal involvement of a single nerve

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10
Q

Polyneuropathy

A

Affects both sensory and motor neves (depending on the length). Diffuse disease affecting many nerves that is usually distal and symmetrical

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11
Q

Mononeuritis multiplex

A

Simulatenous or sequential development of nerves of 2 or more nerves

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12
Q

Radiculopathy

A

Affects nerve root

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13
Q

Plexoapthy

A

lesion within lumbar or cervical plexus

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14
Q

Sensory symptoms and signs

Negative (loss of sensation)

A

Large myelinated fibres - Loss of touch, vibration and joint position

  • difficulty discriminating textures
  • feet and hands feeling like cotton wool
  • gait unstead

Small myelinated fibres - loss of pain, temerature appreciation

  • painless burns and trauma
  • damage to joints (charcots foot) resulting in painless deformity
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15
Q

Sensory symptoms and signs

positive symptoms

A

Large myelinated fibres - Causes parasthesia (pins and needles)

Small unmyelinated fibre disease - Painful positive symptoms

  • burning sensation
  • dysaesthesia: pain on gentle touch
  • hyperalgesia: lowered threshold to pain
  • Hyperpathia: pain threshold is elevared, but pain is excessively felt
  • lightening pains: sudden, very severe, shooting pains
  • allodynia: when a non painful stimuli becomes painful
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16
Q

Sensory examination

A

Large myelinated fibres:

  • light touch
  • two point discrimination
  • vibration sense
  • joint position sense

small unmyeinated fibres:

  • temperature perception
  • pain perception

When joint position is lost - rombergs test is positive (loss of joint-poisiton is compensated by vision, theregore, when eyes are closed, the stance becomes unsteady)

Sensory examination - neuropathic burns, trauma, ulcers, trophic changes due to loss of sensory and autonomic fibres

17
Q

Autonomic symptoms

A

postural hypotension, erectile dysfunction, GI disturbance abnormal sweating

18
Q

Clinical signs and symptoms of motor neuropathy

A

weakness, fasciculations, cramps and muscle wasting

19
Q

Investigations

A

Neuropathy screen (bloods)

  • -Fasting glucose (OGTT)
  • -FBC
  • -Urea and electrolytes
    • Liver functions tests
  • -Thyroid function tests
  • -B12/folate
  • -protein electrophoresis

Nerve conduction studies - differentiate axonal degeneration(reduced amplitude of electrical impulse) from demyelination (redeuced conduction veolcity) and can characterize whether motor or sensory fibres are involved

EMG: use of a fine needle inserted into a muscle can discern whether complete or partial denervation

Lumbar puncture:
-useful in inflammatory/paraneoplastic neuropathies (gullian-barre syndrome)

20
Q

Nerves can be damaged by

A
  1. acute compression - by a tourniquet or tight fitting cast (tends to affect nerves that lie superficially to the skin)
  2. chronic compression - entrapment neuropathies
21
Q

Mononeuropathy: Median nerve

A

Carpal tunnel syndrome
entrapment within carpal tunnel at wrist

Presenting symptoms :

  • history of intermittent nocturnal pain, numbness and tingling- often relieved by shaking hand grip
  • patient may complain of “weak grip”
  • positive tinels sign

motor weakness:

  • LOAF muscles (lumbricals, opponens pollicis, abuctor pollicis brevis, flexor pollicis brevis)
  • weakness of thumb opposition, abduction, flexion

Sensory loss:

  • palm and lateral three-and-a-half digitis

associations:
- pregnancy
- obesity
- hypothyroidism
- acromegaly

Treatment

  • steroid injection to flexor retinaculum
  • suurgical deecompression
22
Q

Mononeuropathy: Ulnar nerve

A

-entrapment at ulnar groove (medial epicondyle of humerus)

Presenting symptoms

  • history of trauma at elbow
  • sensory disturbance and weakness “weak grip”
  • usually painless

Motor weakness

  • finger/pinkie/thumb abduction
  • wrist flexion

Sensory loss:

  • tingling or numbness affecting little finger, part of the ring finger and ulnar side of the hand distal to the wrist
  • may extend to medial side of forearm
23
Q

Mononeuropathy: Radial nerve compression

A

Saturday night palsy entrapment at spiral groove where the radial nerve is compressed against the humerus

Supploes the BEST (brachioradialis, extensors, supinator, wrist and tricepts

Presenting symptoms

  • wrist and finger drop
  • usually painless

Sensory

  • region of anatomical snuffbox on the dorsum of the hand over the base and shafts of first two metcarpals

Treatment

  • recovery is spontanoeus
24
Q

Mononeuropathy: Common pereneal nerve

A

entrapment at fibular head

presenting symptoms:

  • may be history of trauma, surgery or external compression
  • acute onset foot drop + sensory disturbance on outside of calf
  • usually painless

Motor weakness:
- ankle dorsiflexion, great toe extension

Causes:

  • compression at the neck of the fibular head
  • diabetes
  • lepros
25
Q
A

Neuro (16 decks)

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