Citalopram is a selective serotonin reuptake inhibitor (SSRI) and one of the most widely used antidepressants in the world.^{Reference Sharbaf Shoar, Fariba and Padhy1} Off-label uses include alcohol use disorder, coronary arteriosclerosis, obsessive-compulsive disorder, panic disorder, postmenopausal flushing and premenstrual dysphoric disorder. It exerts its antidepressant action by potentiating serotonergic activity in the central nervous system with no effects on norepinephrine and dopamine neuronal reuptake.^{Reference Sharbaf Shoar, Fariba and Padhy1} Citalopram could rarely be associated with a range of movement disorders including parkinsonism, akathisia or tardive dyskinesia.^{Reference Leo2} Very seldom citalopram may be also associated with the subacute onset of isolated involuntary movements of the tongue.^{Reference Gaanderse, Kliffen and Linssen3}

We report a 75-year-old male patient who came to our attention for abnormal tongue movements and dysarthria. His family history and his previous clinical history were unremarkable. In the preceding months, the patient had developed symptoms of a mixed anxiety–depressive disorder that led to the introduction of low doses of citalopram (20 mg/day). After 15 days of treatment, he complained of difficulties in speech production and abnormal tongue movements with a sensation of tongue stiffness. Neurological evaluation revealed the presence of dysarthric speech associated with slow, writhing involuntary tongue movements. The involuntary tongue movements were present both at rest with mouth closed and during speech and sustained phonation, with a sensation of tongue stiffness (Video). Maneuvers like chewing or the presence/absence of sensory tricks did not influence the tongue movements as well as distraction maneuvers. In addition, no premonitory urge was reported by the patient. 1.5 T brain MRI did not show any acute alterations (Figure 1A). A perceptual and acoustic analysis of speech using PRAAT software® showed articulatory distortions (Figure 1B). The Oromandibular Dystonia Rating Scale was also administered showing a total severity score of 4 points with a disability scale of 3 points and a pain scale of 0 point.^{Reference Yoshida4} Citalopram was discontinued briefly together with the introduction of low doses of clonazepam (1 mg/daily), leading to a progressive resolution of symptoms over the course of a couple of weeks.

Figure 1.

(A) Brain MRI showed a moderate chronic vasculopathy, no sign of acute or subacute ischemic or hemorrhagic damage and no alterations in the basal ganglia. (B) Acoustic analysis of spontaneous speech performed with PRAAT software, together with perceptual assessment performed by Annalisa Gessani showed the presence of articulatory distortions. The upper window represents the waveform diagram: the horizontal scale represents time, while the vertical scale represents sound amplitude. The lower window represents the signal spectrogram: the vertical direction represents frequency, while the horizontal direction represents time. The yellow line shows the variation of signal intensity; the blue line indicates pitch variations.

Taking into account the time course (i.e., subacute onset after the start of citalopram treatment; resolution after citalopram interruption), we consider the involuntary tongue movements to be a side effect of citalopram intake.

This hypothesis was also supported by the score on the Naranjo scale (n = 6, probable), a measure of assessing the probability of abnormal movements being a medication-related adverse effect.^{Reference Naranjo, Busto and Sellers5} As in a previously reported case,^{Reference Gaanderse, Kliffen and Linssen3} the involuntary tongue movements appeared 2 weeks after the start of the treatment with citalopram, which is in line with the onset of serotoninergic action for depression, about 1–4 weeks.^{Reference Sharbaf Shoar, Fariba and Padhy1}

The differential diagnoses of tongue movements are quite complex and include, among others, lingual dystonia, in which the involuntary lingual movements vary among repetitive or episodic tongue protrusion or curling and are induced when speaking or eating,^{Reference Yoshida6} tardive dyskinesia, functional movement disorders, tics and orolingual tremor.^{Reference Ghadery, Kalia and Connolly7}

In our case, the phenomenology of the tongue’s involuntary movements, which were slow, repetitive and irregular, together with the presence at rest and the lack of sensory tricks, may support the diagnosis of tongue dyskinesia as opposed to tongue dystonia or tremor.^{Reference Ghadery, Kalia and Connolly7} Moreover, a functional movement disorder and tics were excluded, keeping in mind the lack of voluntary suppression, the persistence during distraction maneuvers and the involvement during speech.^{Reference Ghadery, Kalia and Connolly7} The most prevalent etiology of orofacial dyskinesia is tardive dyskinesia, which is linked to chronic antipsychotic use and more rarely to some SSRIs including fluoxetine, paroxetine, sertraline, and fluvoxamine, but not citalopram.^{Reference Ghadery, Kalia and Connolly7} Based on this and the patient’s history (which was negative for antipsychotic use), we excluded the possible diagnosis of tardive dyskinesia. From a pathophysiological point of view, SSRI may rarely lead to dyskinetic movements through an indirect D2 blockade mechanism due to increased tonic inhibition by serotonin on dopaminergic neurons, mimicking the D2 blockade observed with dopamine receptor blocking agents, such as in first-generation antipsychotics.^{Reference Jean and Poulose8} Regarding the treatment, the first step is the discontinuation of citalopram intake, which has led to the resolution of tongue involuntary movements in reported cases,^{Reference Gaanderse, Kliffen and Linssen3,Reference Jean and Poulose8} including our patient.