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Week 13 - neurology > Peripheral neurology > Flashcards

Peripheral neurology Flashcards

1
Q

What is the peripheral nervous system?

A

Everything outside of the brain and spinal cord i.e. ganglion, nerve roots, peripheral nerves etc.

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2
Q

What is the function of the peripheral nervous system?

A
  • Sensory input to the CNS
  • Motor output to the muscles
  • Innervation of the viscera
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3
Q

Where does incoming sensory information enter the spinal cord?

A

Via the posterior root

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4
Q

Where does motor innervation exit the spinal cord?

A

The anterior root

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5
Q

Describe the organisation of nerves

A

Multiple collections of axons in endoneurium in peineurinum in epineurium

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6
Q

What are the nerve fibre types?

A
  • Large myelinated fibres
  • Thinly myelinated nerves
  • Small unmyelinated nerves
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7
Q

Which nerves are the large fibres and what are the modalities of large fibres?

A
  • Motor nerves

* Proprioception, vibration and light touch

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8
Q

What are the modalities of thinly myelinated fibres?

A

•Light touch, pain and temperature

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9
Q

Explain what happens at the neuromuscular junction

A
  • Action potential arrives
  • Voltage gated calcium channels open and there is a Ca2+ influx
  • This causes neurotransmitter vesicles to fuse with the membrane
  • ACh is released from the vesicles into the the synaptic cleft where they bind to postsynaptic receptors on the muscle causing ion channels (Na+ and Ca2+) to open
  • the influx of Na+ depolarises the cell
  • Postsynaptic muscle cell depolarises causing the opening of voltage gated Ca2+ channels causing muscle contraction
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10
Q

What is the clinical presentation of a motor neuropathy?

A

Weakness/muscle atrophy

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11
Q

What is the clinical presentation of a sensory neuropathy?

A
  • If large myelinated fibres then sensory ataxia, loss of vibration sense +/- numbness and tingling
  • If small (thinly myelinated or unmyelinated) then impaired pin prick, temperature, painful burning numbness and tingling
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12
Q

What is the clinical presentation of an autonomic neuropathy?

A
  • Postural hypotension
  • Erectile dysfunction
  • GI disturbance
  • Abnormal sweating
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13
Q

What results in the glove and stocking pattern?

A

Length dependent axonal neuropathy

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14
Q

What is length dependent axonal neuropathy?

A
  • Diffuse involvement of the peripheral nerves - (myelin and axon degrade?)
  • Age >50
  • Length dependent so starts in toes/feet
  • Symmetrical
  • Slowly progressive
  • No significiant sensory ataxia
  • Any weakness is distal and mild
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15
Q

What are the causes of length dependent axonal neuropathy?

A
  • Diabetes
  • Alcohol
  • Nutritional - folate, b12, thiamine, B6 deficiency
  • Immune mediated - RA, lupus, vasculitis, polyarteritis nodosa
  • Metabolic/endocrine - renal failure, hypothyroidism
  • Drugs - isoniazid, cisplatin, amiodarone, gold
  • Infectious - HIV, Hep B and C
  • Inherited - Charcot-marie-tooth, hereditary neuropathy
  • Neoplastic - myeloma
  • Paraneoplastic - distant cancer
  • Critical illness - bed bound for a long time
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16
Q

What is Guillain-Barre syndrome?

A
  • Acute inflammatory demyelinating neuropathy
  • Progressive (ascending) weakness over days, flaccid, quadraparesis with areflexia
  • May have respiratory/bulbar/autonomic involvement
17
Q

What is the treatment of Guillain-Barre syndrome?

A

IV immunoglobulin or aphaeresis (removing blood)

18
Q

What is the chronic form of Guillain Barre syndrome?

A

CIDP (chronic inflammatory demyelinating polyneuropathy)

19
Q

What is CIDP responsive to?

A

Steroids and IV immunoglobulin

20
Q

Describe how a nerve conduction study is carried out

A
  • Recording electrodes on thumb and lateral anterior forearm (recording muscle is abductor policies brevis)
  • 1st stimulation site on the wrist
  • 2nd stimulation site is above the elbow on the anterior aspect of the arm and the 3rd is above that
21
Q

Describe the results of a nerve conduction study

A

•Normal - two peaks one shortly followed by a second
•Axonal issue- both peaks are smaller but second peak still follow closely after the first
•Demyelinating issue: 2 presentations:
1. Same height of peak but a conduction delay
2. Conduction block with a smaller second peak, temporal dispersion can occur where the second peak is flattened

22
Q

What is mononeuritis multiplex?

A
  • Sequential or simultaneous development of neuropathy in 2 or more nerves
  • Cluster of conditions, it is not itself a diagnosis
23
Q

Which sites are most commonly effected in mononeuritis multiplex?

A
  • Common perineal
  • Radial
  • Axillary
  • Median
  • sciatic
24
Q

What are the symptoms of a common perineal neuropathy?

A
  • Weak ankle dorsiflexion

* Sensory disturbance lateral aspect of calf and foot

25
Q

What are the symptoms of a radial neuropathy?

A
  • Wrist/finger drop

* Sensory disturbance to the dorsum of the hand

26
Q

What are the symptoms of axillary neuropathy?

A
  • Weakness of shoulder abduction

* “badge” of sensory disturbance inferior deltoid region

27
Q

What are the symptoms of a median neuropathy?

A
  • weakness of hand muscles: lateral two lumbricals, opponens pollicis, abductor pollicis brevis, flexor pollicis brevis
  • Sensory disturbance
28
Q

What are the symptoms of femoral neuropathy?

A
  • Weak hip flexion and knee extension

* Sensory disturbance of lateral calf and dorsum of foot

29
Q

What are the common causes of mononeuritis multiplex?

A
  • Diabetes
  • Vasculitic - Churg Strauss, polyarteritis nodosa
  • Rheumatological - RA, lupus, Sjogren’s syndrome
  • Infective - Hep C, HIV
  • Sarcoidosis
  • Lymphoma
30
Q

What investigations should you carry out in a suspected mononeuritis multiplex?

A
  • Nerve conduction studies
  • EMG
  • consider MRI of plexus with contras
  • If inflammatory causes, consider an LP
31
Q

What are the symptoms of muscle disease?

A
  • Proximal limb weakness - difficulty raising arms above head, arising from seated position
  • Facial weakness - characteristic myopathic facies, drooling
  • Eyes - ptosis, ophthalmoplegia
  • Bulbar - dysarthria, dysphagia
  • Neck and spine - head drop, scoliosis
  • Respiratory - breathlessness (especially on lying flat)
  • Myocardial - exercise intolerance, palpitations
32
Q

What are the causes of muscle disease?

A
  • Muscular dystrophies
  • Metabolic muscle disorders
  • Mitochondrial disorders
  • Myotonic dystrophies
  • Inflammatory muscle disorders
  • Neuromuscular junction disorders
33
Q

What is myasthenia Gravis?

A
  • Immune disorder with antibodies against post synaptic acetylcholine receptor
  • Fatiguable weakness of ocular, bulbar, neck, respiratory and/or limb muscles
34
Q

How is myasthenia gravis managed?

A
  • Pyridostigmine (anti-acetylcholine esterase)

* Immunosuppressive therapies - steroids and immunoglobulin

Week 13 - neurology (12 decks)

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