Abstract
BackgroundTaste disorder is a common symptom in the general population. Several studies have shown that patients with neurological disorders, such as amyotrophic lateral sclerosis and Parkinson’s disease, develop taste disturbance. Facial onset sensory and motor neuronopathy (FOSMN) is a rare disease characterized by sensory disturbance and weakness spreading from the face to the limbs caudally. We describe a patient with FOSMN who showed taste disorder as the sole initial symptom.Case presentationA 49-year-old man who smoked cigarettes developed taste disturbance. Despite using zinc supplements, an herbal medication, and an ointment, his taste disorder worsened. 4 years later, a tingling feeling emerged at the tip of his tongue and gradually spread to his entire lips. At 55 years of age, he showed difficulty in swallowing, followed by facial paresthesia, muscle atrophy, and weakness in the face and upper limbs without apparent upper motor neuron sign. Cessation of smoking did not improve his taste disturbance, and he was unable to discriminate different tastes on the entire tongue. In an electrogustometric study, electrical stimulation did not induce any type of taste sensation. Blink reflex showed delayed or diminished R2 responses. Needle electromyography revealed severe chronic neurogenic changes in the tongue and masseter muscles. Mild chronic neurogenic changes were also observed in the limbs. In the thoracic paraspinal muscles, active neurogenic changes were detected. Findings of hematological and cerebrospinal fluid analyses, and magnetic resonance images of the brain and spinal cord were unremarkable. One cycle of intravenous immunoglobulin therapy did not improve his symptoms. We diagnosed him as having FOSMN with the sole initial symptom of taste disorder. Nine years after the onset of taste disorder, he developed impaired sensation of touch in the right upper limb and required tube feeding and ventilator support.ConclusionTaste disorder can be the initial manifestation of FOSMN and might involve the solitary nucleus.
Highlights
Taste disorder is a common symptom in the general population
Facial onset sensory and motor neuronopathy (FOSMN) is a rare disease characterized by sensory disturbance and weakness of the face followed by muscle weakness in the limbs [10,11,12]
FOSMN might be a variant of amyotrophic lateral sclerosis (ALS) resulting from an irreversible disease progression with a lack of response to immunotherapies as well as deposition of TAR DNA-binding protein 43 (TDP-43) in the nervous systems [13,14,15]
Summary
Taste disorder is among the common symptoms encountered in routine medical practice. previous studies have reported that 0.6–20% of the general population suffer from taste dysfunction [1,2,3,4,5]. Case presentation The patient was a Japanese man without a significant family history He was a smoker and had noticed impairment of his sense of smell following a sinusitis surgery at the age of 20 years. He stopped smoking, but it did not improve his taste disturbance He developed speech difficulties and muscle wasting of the neck and upper limbs and was referred to our hospital. He presented with mild impairment of the smell sensation. One session of intravenous immunoglobulin (IVIG) therapy (2 g/kg body weight over 5 days) did not improve any of his symptoms and signs Based on these results, we diagnosed him as having FOSMN with the sole initial symptom of taste disorder.
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