A 32-year-old woman comes to the emergency department for double vision that started several hours ago. Objects appear blurry, which she has never experienced before. Four weeks ago, the patient had a sore throat with enlarged, tender glands and was treated with azithromycin. She ate home-canned fish yesterday at a friend's house. The patient does not use tobacco, alcohol, or illicit drugs. Her family history is insignificant. Temperature is 36.6 C (98 F), blood pressure is 132/73 mm Hg, and heart rate is 59/min. Oral mucosa is dry. She has mild bilateral ptosis and facial muscle weakness, but no sensory loss or muscle weakness of the extremities. Pupils are dilated with sluggish reactivity to light, and mild dysarthria is seen. Which of the following is the most likely diagnosis?

Question

A 32-year-old woman comes to the emergency department for double vision that started several hours ago.  Objects appear blurry, which she has never experienced before.  Four weeks ago, the patient had a sore throat with enlarged, tender glands and was treated with azithromycin.  She ate home-canned fish yesterday at a friend's house.  The patient does not use tobacco, alcohol, or illicit drugs.  Her family history is insignificant.  Temperature is 36.6 C (98 F), blood pressure is 132/73 mm Hg, and heart rate is 59/min.  Oral mucosa is dry.  She has mild bilateral ptosis and facial muscle weakness, but no sensory loss or muscle weakness of the extremities.  Pupils are dilated with sluggish reactivity to light, and mild dysarthria is seen.  Which of the following is the most likely diagnosis?

Quizplus · Accepted Answer

Explanation: 11ec2b69_c198_0a96_8f63_cb7961213ac9_MD0005_00 This patient, with bulbar weakness, impaired pupillary response, and preserved sensory function after eating home-canned food, has clinical features of acute botulism. Botulism is a serious presynaptic neuromuscular junction disorder caused by botulinum toxin produced by Clostridium botulinum. This is a widespread, anaerobic organism found frequently in improperly canned and preserved foods. Botulinum toxin acts at peripheral nerve endings to inhibit release of acetylcholine into the synaptic cleft. This leads to the inability to achieve a threshold end-plate postsynaptic potential (action potential). Botulinum toxicity leads ultimately to neuromuscular junction failure and subsequent weakness (limb and/or bulbar). It also leads to autonomic dysfunction (eg, blurry vision due to accommodation failure and impaired pupillary responses). Other botulism syndromes include infant botulism due to intestinal colonization, adult enteric botulism, and botulism associated with contaminated wounds. Diagnosis of botulism depends on early awareness and recognition of possibly contaminated food sources. On examination, sensory function is normal, multiple cranial nerve distributions may become weak, and reflexes are usually diminished or absent. Electromyography results may also suggest the diagnosis, which is confirmed by assay of the serum for botulinum toxin. (Choice B) Brainstem stroke can cause oculomotor dysfunction with associated dysarthria/dysphagia and pupillary abnormalities (eg, Weber syndrome/Benedikt syndrome). Additional deficits that may be diagnosed include contralateral hemiparesis/plegia and sensory dysfunction. The presence of bilateral deficits in this patient, absence of vascular risk factors, and young age make a brainstem stroke less likely. (Choice C) Guillain-Barré syndrome is an acute, autoimmune, demyelinating polyradiculoneuropathy that is usually preceded by a respiratory or gastrointestinal illness (eg, Campylobacter jejuni). It typically presents as ascending weakness and mild sensory symptoms (acral numbness/paresthesia) with later bulbar/diaphragmatic involvement and autonomic disturbances. (Choice D) Infectious mononucleosis is caused most commonly by the Epstein-Barr virus. Symptoms are generalized fatigue, headache, fever, sore throat, and swollen lymph nodes. Focal neurological deficits/bulbar symptoms are not found. (Choice E) Myasthenia gravis (MG) is an autoimmune, postsynaptic, neuromuscular junction disorder caused by antibodies against the acetylcholine receptor. It clinically presents with fatigable, fluctuating weakness (arms > legs), ptosis, diplopia, dysarthria, and dysphagia. Patients can develop purely bulbar variants of MG; however, autonomic dysfunction is rare and reflexes as well as sensory functions are usually normal. Educational objective: Botulism is an acute, presynaptic, neuromuscular junction disorder caused by infection with Clostridium botulinum. Botulinum toxin inhibits release of acetylcholine into the synaptic cleft in both the autonomic and somatic nervous systems. Clinically, patients develop acute bulbar and descending limb weakness with absent reflexes and autonomic dysfunction but preserved sensation. References: Neuromuscular junction disorders. (http://www.ncbi.nlm.nih.gov/pubmed/23524069) Botulism, where are we now? (http://www.ncbi.nlm.nih.gov/pubmed/21171845)

A 32-Year-Old Woman Comes to the Emergency Department for Double