Recognition and treatment of rabbit syndrome, an uncommon complication of neuroleptic therapies

A Systematic Review of Oral Vertical Dyskinesia ("Rabbit" Syndrome)

Background and Objectives: Vertical rhythmic dyskinetic movements that are primarily drug-induced and affect solely the jaw, mouth, and lips without involving the tongue have been historically described as "rabbit" syndrome (RS). Evidence on the unique features and implications of this disorder remains limited. This literature review aims to evaluate the clinical-epidemiological profile, pathological mechanisms, and management of this movement disorder. Materials and Methods: Two reviewers identified and assessed relevant reports in six databases without language restriction published between 1972 and 2024. Results: A total of 85 articles containing 146 cases of RS were found. The mean frequency of RS among adults in psychiatric hospitals was 1.2% (range 0-4.4%). The mean age of affected patients was 49.2 (SD: 17.5), and 63.6% were females. Schizophrenia was the most frequent comorbidity found in 47.6%, followed by bipolar disorder (17.8%), major depressive disorder (10.3%), and obsessive-compulsive disorder (3.7%). Five cases were idiopathic. The most common medications associated with RS were haloperidol (17%), risperidone (14%), aripiprazole (7%), trifluoperazine (5%), and sulpiride (5%). The mean duration of pharmacotherapy before RS was 21.4 weeks (SD: 20.6). RS occurred in association with drug-induced parkinsonism (DIP) in 27.4% and with tardive dyskinesia (TD) in 8.2% of cases. Antipsychotic modification and/or anticholinergic drugs resulted in full or partial recovery in nearly all reported cases in which they were prescribed. Conclusions: RS occurs as a distinct drug-induced syndrome associated primarily but not exclusively with antipsychotics. Distinguishing RS from TD is important because the treatment options for the two disorders are quite different. By contrast, RS may be part of a spectrum of symptoms of DIP with similar course, treatment outcomes, and pathophysiology.

Newer antipsychotics and the rabbit syndrome

BACKGROUND

Rabbit syndrome is a movement disorder that is associated with long-term exposure to neuroleptic medications. Of particular interest and importance is the risk of rabbit syndrome with exposure to the newer atypical antipsychotics. Our recent experience with such a case brought to light the importance of exploring this risk.

METHODS

MEDLINE and PubMed (1972-2006) databases were searched for English language articles using the keywords rabbit syndrome, tardive dyskinesia, antipsychotic, extrapyramidal symptoms and side effects. A recent case study is used to expand upon the literature available on newer antipsychotics and rabbit syndrome.

RESULTS

We reviewed papers that addressed the following aspects of rabbit syndrome 1) the clinical manifestations 2) prevalence and risk factors, 3) etiopathogenesis 4) older antipsychotics and rabbit syndrome 5) newer antipsychotics, 6) treatment options. Moreover, we report a case of RS in a 50 year old white female, diagnosed with bipolar I disorder, that, after the discontinuation of risperidone, developed involuntary movements of the mouth that were fine, rhythmic and rapid, along the vertical axis, and without involvement of the tongue. After the re-introduction of risperidone, the symptoms decreased in a few hours and disappeared after 3 days.

CONCLUSION

Eleven cases of rabbit syndrome have been documented since the implementation of newer antipsychotics. Future research is needed to better understand the etiopathogenesis of rabbit syndrome in psychiatric populations treated with the atypical antipsychotics. Understanding the differences and similarities of rabbit syndrome and tardive dyskinesia is crucial to the creation of a successful treatment paradigm.

Botulinum toxin a may be efficacious as treatment for jaw tremor in Parkinson's disease

Jaw tremor in Parkinson's disease (PD) may not respond well to conventional treatment. It causes embarrassment and social handicap. We piloted the use of botulinum toxin (BTX) injections in three patients with PD jaw tremor. BTX A (Dysport; mean, 53 U; range, 30-100 U) was given into each masseter muscle. Outcome was assessed by subjective and clinical improvement and by video recording before and 4 to 9 weeks after injections. There was an excellent response in all without side effects. BTX injections into the masseter may effectively improve jaw tremor and be useful in PD and other conditions.

Dystonic Rabbit Syndrome From Citalopram

OBJECTIVE

Two cases are described of dystonic rabbit syndrome induced by citalopram. This syndrome is a movement disorder with a 5-Hz rhythmic vertical motion of the mouth and lips without involvement of the tongue.

METHOD

The patients were interviewed and examined, and additional history was taken from the medical records. The Naranjo adverse drug reaction rating scale was applied. Relevant literature was reviewed.

RESULTS

Two patients developed dystonic rabbit syndrome soon after starting escitalopram 10 mg/day or citalopram 5 mg/day. Neither patient had any past or current exposure to a dopamine-blocking drug or any history of movement disorder. [Es]citalopram discontinuation led to disappearance of the movement disorder. The Naranjo scale indicates high probability of dystonic rabbit syndrome from citalopram.

CONCLUSION

Citalopram can rapidly induce dystonic rabbit syndrome. This effect suggests that for some patients citalopram has neuropsychiatric effects similar to those of a dopamine-blocking antipsychotic drug. This might be of concern with patients who cannot communicate well (eg, young children; patients with dementia, developmental disabilities, or aphasia).

Antipsychotic-induced rabbit syndrome: epidemiology, management and pathophysiology

Rabbit syndrome is an antipsychotic-induced rhythmic motion of the mouth/lips, resembling the chewing movements of a rabbit. The movement consists of a vertical-only motion, at about 5Hz, with no involvement of the tongue. Usually, the involuntary movements associated with rabbit syndrome appear after a long period (in most cases months or years) of antipsychotic treatment; however, a few patients with the syndrome have had treatment histories with no antipsychotic involvement. The reported prevalence of rabbit syndrome ranges from 2.3 to 4.4% of patients treated with typical antipsychotics. There have been isolated reports of rabbit syndrome in patients treated with the atypical agents risperidone and clozapine. Patients with rabbit syndrome are most often misdiagnosed as having oral tardive dyskinesia. In such cases the key for correct diagnosis is the involvement of tardive tongue movements, which does not occur in rabbit syndrome. The treatment of rabbit syndrome is empirical, reflecting poor understanding of its neuropathology. The first step is to reduce the amount of antipsychotic treatment as much as possible. However, since, in most cases, full withdrawal of antipsychotic treatment is impossible, the syndrome cannot be completely abolished without additional measures. The next stage of treatment involves specific drugs that aim to control the syndrome. Anticholinergic drugs are the best known treatment. Rabbit syndrome does not respond to treatment with levodopa or dopamine agonists. The most striking aspect of this syndrome is its specificity. Rabbit syndrome affects only the buccal region, and within this area it involves a highly stereotyped involuntary movement. This immediately focuses attention on the basal ganglia, in particular the substantia nigra pars reticulata, which is also implicated in oral dyskinesia. Continuing neurophysiological and pharmacological research of the basal ganglia holds the key to better understanding and treatment of this syndrome in the coming years.

Rabbit syndrome secondary to risperidone

After taking risperidone for 4 months, a 38-year-old man with a major depressive disorder experienced rabbit syndrome. This uncommon extrapyramidal side effect is characterized by rhythmic movements of the mouth and may be caused by typical antipsychotics and risperidone secondary to blockade of dopamine D2 receptors. The syndrome, whose exact mechanism is unknown, responded to anticholinergic treatment in this patient. A literature review indicated that most recent cases have occurred as reactions to the atypical antipsychotic risperidone. Changing treatment to an atypical antipsychotic other than risperidone, such as olanzapine 10 mg/day, may lead to suppression or elimination of the syndrome.

Risperidone-induced rabbit syndrome: an unusual movement disorder caused by an atypical antipsychotic

Rabbit syndrome is a rare side effect of chronic neuroleptic administration characterized by rapid, fine, rhythmic movements of the mouth along a vertical axis. It gains its name from an unusual resemblance to the chewing and puckering motions of the rabbit. It is generally thought to be an extra-pyramidal side effect, in part due to its rapid response to anti-cholinergic medication. This is the first case report of risperidone, an atypical antipsychotic, inducing the syndrome. The theoretical implications for the classification of the syndrome along the spectrum of neuroleptic-induced movement disorders are discussed.

Rabbit syndrome--a rare complication of long-term neuroleptic medication

A case of rabbit syndrome, a complication of long-term neuroleptic medication, is reported. It is important to differentiate it from tardive dyskinesia and continuous therapy with an antiparkinsonian agent may be required for control of symptoms of rabbit syndrome.

Recognition and differential diagnosis of tardive dyskinesia

Tardive dyskinesia (TD) is a consequence of chronic neuroleptic therapy. It is an irregular stereotyped movement disorder that is usually choreic in appearance, and is subject to temporary volitional control. Dystonia, akathisia, and tics are uncommon variants of the classic tardive syndrome. Characteristic clinical features including amelioration by action, augementation by distraction, partial volitional suppressibility, and lack of subjective distress help differentiate TD from other movement disorders such as resting tremor, Huntington's disease, spontaneous dyskinesias, and abnormal movements accompanying psychiatric illnesses.