Lingual Dystonia Following Thalamic Infarction in a Patient on Methotrexate Therapy for Hidradenitis Suppurativa.

Lingual dystonia is a rare form of focal dystonia involving involuntary, repetitive, and often painful muscle contractions of the tongue, which can lead to abnormal tongue posturing or protrusion, dysarthria, and/or dysphagia. Lingual dysotnia can be primary or secondary to various conditions. The thalamus is a key relay center between the motor cortex and basal ganglia, and damage here can disrupt motor signaling pathways, possibly leading to focal dystonia, like lingual dystonia. Methotrexate (MTX) can cause acute to subacute neurological complications, which are linked with high doses of MTX, while chronic MTX neurotoxicity develops more slowly, resulting in persistent focal neurological deficits. We present a 56-year-old male patient on MTX therapy who developed an isolated lingual dystonia as a chronic presentation of a small infarction in the posterolateral thalamus. The finding of thalamic infarction on brain CT and the lack of clinical improvement in dystonia symptoms after prolonged MTX withdrawal from therapy indicate that lingual dystonia could be directly causally related to thalamic insult, while it is less likely that lingual dystonia is a side effect of MTX therapy. This case provides us with new knowledge in determining the etiology of lingual dystonia in the light of thalamic infarction and MTX neurotoxicity.