Case: 42-year-old Man with Weakness

by Roy Strowd, MD

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    00:01 In this lecture, we're going to learn about Neoplastic or Paraneoplastic causes of neuromuscular junction disorders.

    00:08 We're going to focus on Lambert-Eaton myasthenic syndrome.

    00:12 A really rare but fascinating syndrome that you know it when you see it and say you ought to know it so you can see it.

    00:20 Let's start with a case.

    00:21 This is a 42-year-old man who presents with weakness.

    00:25 This 42-year-old man presents for evaluation of weakness and new right upper lobe lung mass.

    00:32 He reports three months of blurry vision, sometimes double vision, as well as weakness that began in his arms and have progressed to include his legs.

    00:42 He's been unable to ride his motorcycle due to these symptoms.

    00:45 He reports a 20-pound weight loss in the last three months.

    00:49 He has no fatigable weakness but does report dry mouth, that is also new.

    00:54 Examination shows bilateral ptosis, mild dysarthria, proximal upper and lower extremity weakness, normal sensation, and diffuse hyporeflexia.

    01:06 So, what's the diagnosis? Well, let's look at those three main features of a peripheral nervous system disorder.

    01:13 What's the distribution? What are the sensory findings? What's the reflex exam? And are there any important wildcard symptoms present in this case? The distribution here, involves bulbar weakness.

    01:26 We see bilateral ptosis, mild dysarthria, there are bulbar findings, in addition to proximal weakness.

    01:33 That's the distribution that doesn't support a muscle localization.

    01:37 This doesn't sound like peripheral nerve dermatome.

    01:40 This sounds like a neuromuscular junction disorder, proximal weakness with prominent bulbar findings.

    01:47 The sensory exam is normal pointing away from a nerve problem and the reflexes show hyporeflexia.

    01:53 Not a reflexia likely would see with a nerve problem, but diffuse hyporeflexia that is supportive of a junctional disorder.

    02:01 What about wildcard features? Well, here this patient has a right upper lobe lung mass, that's concerning.

    02:07 It needs to be further evaluated and a 20-pound weight loss.

    02:10 We're worrying about cancer and a possible cancer associated condition like a paraneoplastic disorder.

    02:17 Let's look at this patient's chest x-ray.

    02:20 We see that here.

    02:21 We see the normal findings of the lung and the heart, and this opacity in the right lung, that's concerning for a new mass and needs to be further evaluated in this for a possible lung cancer.

    02:35 So what's the diagnosis? Is this myasthenia gravis, organophosphate poisoning, botulism toxicity or Lambert-Eaton myasthenic syndrome? All our neuromuscular junction disorders, all can present with weakness.

    02:48 Which one is present in this case? Well, myasthenia gravis could be the case for this patient.

    02:56 But with a new lung mass, a 20-pound weight loss, we have to be concerned for an alternative etiology.

    03:02 The patient has not ingested organophosphates, and organophosphate poisoning does not sound like, the likely diagnosis for this patient.

    03:09 There's no exposure to botulism toxin to suggest botulism or botulism toxin toxicity.

    03:16 This is a case of Lambert-Eaton myasthenic syndrome.

    03:19 And we see a classic presentation of proximal weakness with prominent bulbar fibers, excuse me, prominent bulbar findings and some other important clinical features that point us in that direction.

    03:30 Lambert-Eaton is associated with certain types of cancer and we're concerned that this patient may have a new diagnosis of lung cancer.

    About the Lecture

    The lecture Case: 42-year-old Man with Weakness by Roy Strowd, MD is from the course Disorders of the Neuromuscular Junctions.

    Included Quiz Questions

    1. Reversal of symptoms with AChE inhibitor administration
    2. Proximal muscle weakness
    3. Autonomic symptoms
    4. Improves with muscle use
    5. Association with small cell lung cancer
    1. Pupillary findings
    2. Ptosis
    3. Mild dysarthria
    4. Proximal upper and lower extremity weakness
    5. Impotence

    Author of lecture Case: 42-year-old Man with Weakness

     Roy Strowd, MD

    Roy Strowd, MD

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