Tongue fasciculations with denervation pattern in osmotic demyelination syndrome: a case report of diagnostic dilemma

Abstract

Background: The pathogenesis of osmotic demyelination syndrome is not completely understood and usually occurs with severe and prolonged hyponatremia, particularly with rapid correction. It can occur even in normonatremic patients, especially who have risk factors like alcoholism, malnutrition and liver disease. Bilateral tongue fasciculations with denervation pattern in electromyogram is a manifestation of damage to the hypoglossal nucleus or hypoglossal nerves. Tongue fasciculations were reported rarely in some cases of osmotic demyelination syndrome, but the exact mechanism is not explained.

Case presentation: A 32-year-old Sri Lankan male, with a history of daily alcohol consumption and binge drinking, presented with progressive difficulty in walking, dysphagia, dysarthria and drooling of saliva and alteration of consciousness. On examination he was akinetic and rigid resembling Parkinsonism with a positive Babinski sign. Clinical features were diagnostic of osmotic demyelination syndrome and MRI showed abnormal signal intensity within the central pons and basal ganglia. He also had tongue fasciculations. The electromyogram showed denervation pattern in the tongue with normal findings in the limbs. Medulla and bilateral hypoglossal nerves were normal in MRI.

Conclusion: We were unable to explain the exact mechanism for the denervation of the tongue, which resulted in fasciculations in this chronic alcoholic patient who developed osmotic demyelination syndrome. The hypoglossal nuclei are located in the dorsal medulla and radiologically undetected myelinolysis of the medulla is a possibility. Hypoglossal nerve damage caused by methanol or other toxic substances that can contaminate regular ethyl alcohol is another possibility, as it is known to cause neurological and radiological features similar to osmotic demyelination syndrome with long-term exposure. So these toxic substances might play a role in chronic alcoholic patients with central pontine myelinolysis.

Keywords: Central pontine myelinolysis; Hypoglossal nerve denervation; Osmotic demyelination syndrome; Tongue fasciculations.

Fig. 1

MRI, done 2 weeks after the onset of symptoms, showing high signal intensity within the central pons and bilateral basal ganglia in fluid-attenuated inversion recovery

Fig. 2

MRI, done 1 month after the first MRI, showing FLAIR high intensity in the central pons with resolution of the changes in the basal ganglia

Fig. 3

MRI of the brain stem, done 1 month after the first MRI showing signal intensities in FLAIR localized to the pons

Fig. 4

MRI of the brain stem, done 1 month after the first MRI showing normal medulla and hypoglossal nuclei

Fig. 5

MRI of the brain stem, done 1 month after the first MRI coronal views, showing high signal intensities localized to the pons and not extending into the medulla