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High Yield Facts for the Final FRCA > Neurophysiology > Flashcards

Neurophysiology Flashcards

1
Q

Which of the following is true regarding the anatomy of the autonomic nervous system?

  1. Preganglionic fibres in the sympathetic nervous system originate from cell bodies in the white matter of the lateral horn of the spinal cord
  2. The paravertebral sympathetic chain is divided into five parts
  3. Preganglionic fibres are unmyelinated myelinated and post-ganglionic fibres are myelinated
  4. The thoracic paravertebral sympathetic chain consists of ganglia from T1-T7
  5. Cranial parasympathetic fibres arise from the 3rd, 7th, 9th and 10th cranial nerves
A
  1. Cranial parasympathetic fibres arise from the 3rd, 7th, 9th and 10th cranial nerves

Explanation:

The sympathetic nervous system originates from the grey matter of the lateral horn of the spinal cord from T1 to L2/3

The paravertebral sympathetic chain is divided into four parts - cervical, thoracic, lumbar and pelvic plexuses

The thoracic portion consists of ganglia from T1-T5

Preganglionic fibres are myelinated and postganglionic fibres unmyelinated

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2
Q

Guillain-Barre syndrome is a post-infection demyelinating polyneuropathy strongly associated with which bacteria?

A

Campylobacter jejuni

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3
Q

How does Miller Fisher syndrome differ from Guillain-Barre?

A

Usually presents with cranial nerve palsy

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4
Q

What are the three vagus nerve nuclei and what do they do?

A
  • Dorsal nucleus of the vagus - parasympathetics to viscera
  • Nucleus tractus solitarius - sensory information from viscera
  • Nucleus ambiguus - motor to pharynx, palate and larynx, and parasympathetic to heart
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5
Q

What are the anatomical relations to the vagus nerve at the level of C6?

A
  • Right lobe of thryoid (anterior)
  • Anterior scalene muscle (posterior)
  • Common carotid artery (medial)
  • Internal jugular vein (lateral)
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6
Q

What are the anatomical relations of the right vagus nerve at T4?

A
  • Superior vena cava (or azygos vein) (anterior)
    • Right lung and oesophagus (posterior)
    • Trachea (medial)
    • Brachiocephalic vein (lateral)
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7
Q

A myasthenic crisis may be associated with the following - true or false?

Hyperkalaemia
Motor neurone disease
Thyroid disease
Bronchogenic carcinoma
Thymus cancer

A

False
False
True
True
True

Myasthenic crises can be associated with Bronchogenic and Thymus cancers, Thyroid disease and intracranial lesions

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8
Q

What factors contribute to respiratory failure in Guillain-Barré syndrome?

A

Diaphragm weakness
Intercostal muscle weakness
Increased airway resistance
Laryngeal and pharyngeal muscle weakness
Infection

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9
Q

Describe the underlying pathological process in GBS

A

Demyelination of peripheral nerves and spinal roots
Axonal degeneration in more severe cases
Wallerian degeneration
Periaxonal macrophages

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10
Q

What blood tests should be performed for suspected GBS?

A

Full blood count - for signs of infection
Electrolytes and urinary sodium - SIADH is associated with GBS
Urea and creatinine
Liver function tests
Clotting
Calcium
Plasmapheresis requires normal clotting, and may worsen hypocalcaemia
Positive anti-CD3 titre for diagnosis
Specific antibodies to infective organism can also be tested
Inflammatory markers

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11
Q

What are the treatment options for GBS?

A

Supportive care and ventilation
Physiotherapy
Intravenous immunoglobulin (IVIG)
Plasma exchange
Corticosteroids should not be used as a therapy in GBS

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12
Q

What are the indications for intubation in GBS?

A
  • Vital capacity less than 20ml per kilogram or decrease of >30%
  • Maximal inspiratory pressure less than 30cmH2O
  • Maximal expiratory pressure less than 40cmH2O

Autonomic dysfunction, facial and bulbar involvement and rapid progression of weakness make intubation more likely

Generally non invasive ventilation is avoided as it doesn’t help clear secretions, and patients tend rapidly progress to needing intubation anyway.

Patients on the intensive care unit should be regularly re-assessed to ensure their weakness isn’t progressing

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13
Q

What are the anaesthetic considerations for a patient with GBS?

A
  • Early elective intubation if evidence of rapidly worsening ascending muscle weakness
  • Invasive blood pressure monitoring due to autonomic instability
  • Avoid depolarising muscle relaxants
  • Reduced dose of non-depolarising agents may be required
  • Epidural anaesthesia can be useful to reduce opioid use if performing an operation
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14
Q

What autonomic symptoms may be seen in GBS?

A

Labile blood pressure
Tachycardia
Arrhythmias
Sweating
Urinary retention
Constipation

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15
Q

What ECG changes may be seen in GBS?

A

Arrhythmias
ST depression
T wave inversion
Prolonged QT interval

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16
Q

What are the commonest causes of death in patients suffering from GBS?

A

Sepsis
ARDS
Respiratory failure
Pulmonary embolism
Cardiac arrest due to arrhythmia or autonomic dysfunction

17
Q

What are the different subtypes of GBS?

A

Acute inflammatory demyelinating polyradiculopathy (AIDP)
Acute motor axonal neuropathy (AMAN)
Acute motor sensory axonal neuropathy (AMSAN)
Miller Fisher syndrome

18
Q

Which organisms are known to trigger GBS?

A

Campylobacter jejuni
Influenza
Epstein Barr
Mycoplasma
Cytomegalovirus
HIV

19
Q

What factors predict worse prognosis in GBS?

A

Campylobacter infection
Increasing age
Presence of anti-GMI antibodies
Absent CMAP (compound muscle action potential) on nerve conduction studies
Neurone specific enolase and S-100 proteins in CSF
Need for intubation and ventilation
Upper limb paralysis

20
Q

What are the features of post operative ‘pseudo’ seizures?

A

Associated with psychiatric or psychosomatic history
Generalised shaking
Generally last more than ninety seconds
Head shaking
Resistance to eye opening
Maintained pupil reflexes
No post-ictal phase
You can measure prolactin levels if you’re keen - they’ll be raised after a genuine seizure but not a pseudoseizure.

21
Q

What surgical options are available for patients with intractable epilepsy?

A

Cortical speech mapping
Focus resection
Electrode placement
Cortical resection
Hemispherectomy

22
Q

How should antiepilpetic medication be managed in the perioperative period?

A

Continue anti-epileptic agents until as close to surgery as possible
Restart agents as soon as possible afterwards
Consider IV or parenteral alternatives if prolonged fasting time
Talk to neurology if multiple agents required or poorly controlled
Only Keppra (levetiracetam), valproate and phenytoin are available as IV preparations. Carbamazepine can be given PR.

23
Q

What are your anaesthetic concerns for a patient with epilepsy undergoing elective surgery?

A

Avoiding triggering seizures with anaesthetic drugs
Interactions between anti-epileptics and anaesthetic drugs
Avoiding seizures in the perioperative period
Managing other medical comorbidities

24
Q

Which types of epilepsy are only seen in children?

A

Petit mal epilepsy
Infantile spasms
Myoclonic epilepsy
Benign partial epilepsy
Benign childhood epilepsy

25
Q

How would you manage status epilepticus?

A

The aim is to terminate the seizures, reduce cerebral oxygen demand and treat the underlying cause.

  • ABCDE approach
  • IV or IO access
  • Identify and treat electrolyte and glucose derangement that may be causative
  • Keep patient warm
  • If known toxin with antidote then give as soon as possible

First line anticonvulsants

  • Lorazepam IV 0.1mg/kg or
  • Midazolam IV/IM/Buccal 0.1 mg/kg or
  • Diazepam IV/PR 5mg

Second line anticonvulsants

  • Phenytoin IV 15-20 mg/kg
  • Keppra IV 60 mg/kg up to 4.5g

Third line

  • Magnesium
  • General anaesthesia
  • Barbiturate infusion
  • Midazolam infusion
  • Ketamine infusion
  • Isoflurane
26
Q

What are the indications for ECT?

A
  • Acute catatonia (where IM benzos have failed)
  • Life threatening depression (suicide or starvation risk)
  • Drug resistant depression (or previously successful ECT)
  • Mania not responding to first line treatment

ECT isn’t usually employed for schizophrenia unless there’s a significant depressive or manic element that would benefit from treatment.

27
Q

What are the CNS effects of ECT?

A

CNS effects

Increased intracranial and intraocular pressure
Increased regional blood flow
Increased oxygen consumption
Increased glucose consumption
Leaky blood brain barrier
Headache
Confusion
Memory loss

28
Q

What are the cardiovascular effects of ECT?

A

Parasympathetic surge - up to 15 seconds - bradycardia, hypotension, asystole all possible
Sympathetic surger - several minutes - hypertension and tachycardia
Increased myocardial O2 consumption
Arrhythmias
Myocardial ischaemia
Cardiac rupture (very rare but has happened)

29
Q

What induction agents can be used for ECT?

A

Propofol - 0.75-2 mg/kg
Thiopentone - 1.5-2.5 mg/kg
Ketamine - 0.7-2.8 mg/kg
Etomidate - 0.15-0.3mg/kg

30
Q

What muscle relaxants can be used for ECT?

A

You don’t need complete paralysis, as you’re hopefully not intubating, you’re just trying to avoid injury.

Suxamethonium - 0.5-1.5 mg/kg
Rocuronium - 0.3-0.6 mg/kg
Atracurium - 0.3-0.5 mg/kg

The exam answer is that suxamethonium is the agent of choice as it has rapid onset and offset, with fasciculations to tell you when it’s safe to deliver the shock.

31
Q

Describe how you would perform anaesthesia for ECT

A

Consent and fasting status check
IV access
Full anaesthetic monitoring
Preoxygenation
Induction and muscle relaxation
Brief ventilatory support*
Bite block insertion
EEG and ECT electrodes applied
Shock delivered
Support ventilation during clonic phase until breathing adequately
Remove bite block after seizure activity stops
Ensure airway adequately supported
Transfer to recovery

*Hyperventilation immediately prior to shock delivery reduces the seizure threshold and prolongs duration of the seizure.

32
Q

What are the contraindications to ECT?

A

There aren’t any absolute contraindications, partly because the old reliable ‘patient refusal’ answer doesn’t really apply here.

Relative contraindications

MI or CVA within 3 months
Unstable angina
Raised ICP
Cerebral aneurysm (untreated)
Unstable fracture
C spine injury
Phaeochromocytoma
Severe valve disease or heart failure
DVT
Brain implant/cochlear implant - discuss with neurology first
Severe osteoporosis
Glaucoma and retinal detachment

33
Q
A

High Yield Facts for the Final FRCA (22 decks)

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