A 40-year-old man comes to the office due to coughing while drinking. Over the past 2 months, the patient has been coughing when he drinks water because it "goes down the wrong pipe." On occasion, water will come out of his nose when drinking. Also, his speech sounds slurred and nasal. The patient has no medical conditions and takes no medications. On examination, there are no mucosal lesions in the oral cavity or oropharynx. Palate elevation is sluggish on the right side. The tongue appears thin and there are fasciculations. When the physician taps on the chin while the mouth is slightly open, the jaw jerks forward briskly. Which of the following is the most appropriate next step to establish a diagnosis in this patient?
Amyotrophic lateral sclerosis | |
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EMG = electromyography; NIPPV = noninvasive positive pressure ventilation; PEG = percutaneous endoscopic gastrostomy. | |
This patient has amyotrophic lateral sclerosis (ALS), a neurodegenerative disease that can affect upper and lower motor neurons anywhere in the body. Twenty percent of ALS patients have an initial onset in the bulbar muscles, which may result in:
Dysphagia: Tongue and pharyngeal muscle weakness lead to poor control of liquids. Palatal weakness leads to fluid refluxing into the nasopharynx and out the nose.
Dysarthria: Lip and tongue weakness lead to slurred speech; palate weakness leads to hypernasal speech.
Jaw jerk reflex: A pathologic reflex mediated by the trigeminal nerve (CN V) that is present in patients with bilateral upper motor neuron lesions.
Tongue atrophy and fasciculations: Lower motor neuron signs are due to denervation of tongue musculature.
Sensation is classically preserved. Laboratory testing may be performed to rule out other potential causes of muscle weakness (eg, thyroid studies, autoantibodies, vitamin B12). Nerve conduction studies, electromyography, and neuroimaging (eg, MRI) are typically also obtained to exclude alternate diagnoses.
(Choice A) Acetylcholine receptor antibody tests are used in the diagnosis of myasthenia gravis, which can present with bulbar muscle weakness. However, because it is due to antibodies at the neuromuscular junction, upper motor neuron signs (eg, jaw jerk reflex) would not be present.
(Choice B) Bulbar symptoms are primarily mediated by cranial nerves, suggesting pathology above the level of the cervical spine, so a cervical spine x-ray would be unlikely to reveal this patient's diagnosis.
(Choices D and E) Muscle biopsies and serum creatine kinase levels are used to diagnose inflammatory myopathies, which typically cause symmetric muscle weakness. However, because they are due to inflammatory infiltrates of the muscles, upper motor neuron signs (eg, jaw jerk reflex) would not be present.
(Choice F) A serum toxin assay is sometimes used in the diagnosis of botulism, which can present with bulbar muscle weakness (ie, descending paralysis) but usually presents acutely (ie, days not months). In addition, because botulinum toxin acts at the neuromuscular junction, upper motor neuron signs (eg, jaw jerk reflex) would be absent.
Educational objective:
Amyotrophic lateral sclerosis can present with bulbar symptoms (eg, dysphagia, dysarthria) with examination revealing both upper motor neuron signs (eg, pathologic jaw jerk reflex) and lower motor neuron signs (eg, tongue fasciculations and atrophy).