Question 11

You are asked to assess a 54 year old man scheduled for an urgent laparotomy for a suspected perforated duodenal  ulcer.  He has recently developed symptoms of double vision, ptosis, dysarthria and generalised muscle weakness.  He was due to be reviewed by a neurologist next week.  The anaesthetist asks for a post-op bed in ICU.  The patient has a 25-pack year history of smoking but ceased smoking 3 months ago.

11.1     What are your differential diagnoses for his weakness?

11.2     The  above  patient  is admitted to  ICU  post-op.  A perforated DU was oversewn  in theatre.

a)  What are the essential pieces of information you would expect from the anaesthetist at handover upon the patient’s  admission to ICU?

11.3     What investigations could help you establish the diagnosis for his weakness?

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College Answer

11.1     What are your differential diagnoses for his weakness?

  • Gullian-Barre syndrome
  • Myasthenia gravis
  • Motor neurone disease
  • Paraneoplastic syndrome – Eaton Lambert
  • (Myotonic dystrophy)
  • Periodic paralysis
  • Botulism
  • (Endocrine & metabolic myopathies)
  • (Drug induced myopathies)

11.2     The  above  patient  is admitted to  ICU  post-op.  A perforated DU was  oversewn  in theatre.

a)          What are the essential pieces of information you would expect from the anaesthetist at handover upon the patient’s  admission to ICU?

Specific:
GA drugs used – esp muscle relaxants; muscle relaxation in response to sux (if used)

Findings on nerve stimulator NMJ monitoring
Reasons extubation could not be attempted

General:
Operative findings

Haemodynamic stability

Antibiotics used

11.3     What investigations could help you establish the diagnosis for his weakness?

  • Edrophonium or neostigmine test (with atropine cover)
  • ACh receptor Abs
  • EMG NCS – Muscle biopsy
  • LP – CSF protein
  • Neurological review

Discussion

The fist part of the question is a straightforward differential-generating exercise. What are the causes of subacute-onset weakness in a smoker? Guillain-Barre, myasthenia gravis and motor neuron disease are reasonable guesses which apply everywhere. Particularly, diplopia would make one think of myasthenia gravis. The Lambert-Eaton (or Eaton-Lambert) Myasthenic Syndrome is a special one, which relates partiocularly to people with neoplasms (it is a paraneoplastic syndrome of autoantibody secretion, resulting in the destruction of voltage-gated calcium channels). Botulism is thrown in for some reason. Periodic paralysis is also mentioned, even though it is an insanely rate genetic disorder. Drug-induced myopathies are more common, but are mentioned last.

What would you want to know from the anaesthetist?

Well; for one, you would like to know whether they used any muscle relaxant, and if yes- then how much, what kind, and when. One would also be interested in the nerve stimulator test. The administration of gentamicin may potentiate NMJ disturbances and it would be good to know whether one should expect something like this.

As for investigations... A panel of standard tests would include the following:

  • Electrolyte levels
  • CK level
  • B12 level
  • Acetylcholine receptor antibodies (for myasthenia gravis)
  • CXR looking for malignancy (as support for a diagnosis of Eaton-Lambert syndrome)
  • Inflammatory markers
  • Lumbar puncture
  • Nerve conduction studies
  • Electromyography
  • MRI of the brainstem and spine
  • Muscle biopsy if no satisfactory explanation is found.

It is worth noting that the college is not too proud to seek a neurology consult when confronted by this sort of problem.

Approach to the ICU patient with generalised weakness is discussed elsewhere.

 

References

Oh's Intensive Care manual: Chapter   51   (pp. 568)  Acute  cerebrovascular  complications by Bernard  Riley  and  Thearina  de  Beer

Chapter   57   (pp. 617)  Neuromuscular  diseases  in  intensive  care by George  Skowronski  and  Manoj  K  Saxena

Yuki, Nobuhiro, and Hans-Peter Hartung. "Guillain–Barré syndrome." New England Journal of Medicine 366.24 (2012): 2294-2304.

Jani, Charu. "Critical Illness Neuropathy." Medicine (2011): 237.

Young, G. Bryan, and Robert R. Hammond. "A stronger approach to weakness in the intensive care unit." Critical care 8.6 (2004): 416.

Mareska, Michael, and Laurie Gutmann. "Lambert-Eaton myasthenic syndrome." Seminars in neurology. Vol. 24. No. 2. [New York]: Thieme-Stratton Inc.,[c1981-, 2004.

Engel, Andrew G., ed. Myasthenia gravis and myasthenic disorders. Oxford University Press, 2012.