Rabbit syndrome: what it consists of, symptoms, causes and treatment.

Rabbit syndrome is a set of involuntary movements caused by psychotropic drugs.

Many drugs, especially those in their early stages of development, can cause various side effects.

One of the strangest in rabbit syndrome. Next we will discover in what consists this phenomenon, which is the substance that causes it and which are the neurological bases for that it happens.

What is rabbit syndrome?

Rabbit syndrome, known by the medical term period tremor, consists of a series of involuntary movements that are repetitive. involuntary movements that are repetitive, vertical and fast (its frequency is estimated to be 5 cycles per second, or 5 Hz) in the area of the mouthThis pathology takes its name from the characteristic movement of rabbits.

It is caused as a side effect of some pharmacological compounds (later we will explore in depth which ones it is), and its appearance usually occurs after a long time. (later we will explore in depth which ones it is), and its appearance is usually given after a long time having taken the treatment, being able to be as much months as years the temporary triggering factor of this disorder.

The rabbit syndrome is one of the so-called extrapyramidal symptoms, or extrapyramidal side effects.Extrapyramidal symptoms, or extrapyramidal side effects (since they are generated as an undesired effect of the consumption of a neuroleptic or antipsychotic pharmacological compound), which are those disorders that affect the movement of a part of the body, either by reducing the ability to move a certain part of the musculature, or because involuntary movements are generated, as in this case.

Symptoms

The movements caused by rabbit syndrome involve the entire labial musculature and masticatory apparatus.

However, they do not affect the muscles of the tongue, as do other similar disorders, such as tardive dyskinesia, so, in that sense, it would not be a hindrance for the subject suffering from it when swallowing food, although it would be a hindrance to perform other actions, such as chewing.

Prevalence

As for the prevalence of this peculiar disorder, it would be of between 2.3% and 4.4% of all patients who have been medicated with antipsychotics, although there are some cases (very few) of this disorder.Although there are some cases (very few, of course), in which those affected by rabbit syndrome had not taken neuroleptics before, so that other causes could be giving rise to this pathology.

Causes

By affecting such specific muscle areas (all that involves the jaw action and the movement of the lips, but not the tongue, as we have already seen), studies indicate that the dysfunction of these movements would come from the brain area of the basal ganglia, specifically from the structure that makes up the pars reticulata within the substantia nigra.

This part of our nervous system is responsible for connecting and sending information from the basal ganglia to another structure called superior colliculus (also known in the manuals as tectum or optic roof), which is located within the midbrain.

The causes for the appearance of rabbit syndrome, as already mentioned, come from the consumption of certain types of drugs, which we can divide into two groups, according to those that have a high probability of triggering this side effect and those that can also cause it but to a lesser extent, so it is less likely to encounter this symptom.

The first group of drugs are called high potency drugs.. In this category we could highlight three different ones, which would be haloperidol (commercially known as Haldol), pimozide (sold as Orap) and fluphenazine (whose name in pharmacies would be Prolixin). All of them are different types of neuroleptics or antipsychotics, used in very diverse pathologies ranging from schizophrenia to bipolar disorder or Tourette's syndrome.

The other types of medical compounds that, to a lesser extent, could also trigger rabbit syndrome would be aripiprazole, olanzapine, thioridazine and clozapine. Also, these are various types of antipsychotic or neuroleptic drugs, designed for disorders such as those seen above.designed for disorders such as those seen above (Tourette's, schizophrenia or bipolar disorder), as well as others, such as schizoaffective disorder, psychosis, some types of tics, autism, major depressive disorder, etc.

There would be a last category, which would include drugs that can cause rabbit syndrome as a side effect even when small doses of such medication are consumed. This is the case of risperidone, another antipsychotic, in this case oriented to the treatment of pathologies such as autism, schizophrenia or bipolar disorder.

Treatment with anticholinergics

We have already seen which are the chemical complexes that can cause the so-called rabbit syndrome, but what would be the way to reverse this process in order for the patient to stop experiencing those annoying involuntary mouth movements? the way to reverse this process so that the patient stops experiencing these annoying involuntary movements of his mouth? To do so, it would be necessary to resort to a different type of drug. We are talking about anticholinergics.

Anticholinergics are used to prevent the release of a very specific type of neurotransmitter: acetylcholine.They are responsible for communicating from the neurons to the muscles, which must initiate movement. By preventing their dispersion, in this case, involuntary movements, such as those involved in rabbit syndrome, would be prevented.

The problem is that anticholinergic drugs, in turn, can also trigger different types of can also trigger different types of side effects, the most frequent being the one known as antisialogogue.which refers to the fact that it decreases the secretion of saliva in the patient, so that he/she may constantly have the sensation of having a dry mouth. Likewise, they can have a small sedation effect, which is why it is a substance widely used in operations, since both effects are useful in such procedures.

But these are not the only side effects that anticholinergics can cause. They can also generate coordination problems at motor level, increase the Heart rate, dry the mucous membranes of the nose, prevent sweating, generate some vision problems such as focusing problems or double vision, difficulties in retaining urine when sleeping, reduction of bowel movement, and others.

As for the transient involvement of the central nervous system, anticholinergics can make themselves felt by causing a state of disorientation and confusion, feelings of agitation, a back-and-forth between dysphoria and euphoria, difficulty concentrating, memory disturbances or difficulty breathing, among others.

Despite this long list of possible adverse effects, anticholinergics are not only used to treat rabbit syndrome and other disorders, but some people use this substance as a drug, and generate the so-called acute anticholinergic syndrome. It can occur voluntarily, seeking an experimentation, or by mistake, when taking a higher dose than prescribed.

Apart from the effects seen before, one can suffer hallucinations, severe psychomotor agitation and even in extreme cases, when the dose has been very high or the patient has conditions that predispose him/her to such effect, a coma. It is important, therefore, to keep in mind that all these substances are very dangerous if not taken under strict medical criteria, so you should never experiment on your own or take more than the amount prescribed by the professional.

Tardive dyskinesia

Although we generally find period tremor or rabbit syndrome as a disorder of its own, some manuals prefer to include it as a specific type within the so-called tardive dyskinesia. Dyskinesia encompasses all those pathologies characterized by involuntary movements..

Dyskinesia, or dyskinesia, can manifest itself in many different ways. For example, with tremors that can range from very specific areas of the body (at the labial and mandibular level, as in the case of rabbit syndrome) or other areas, and even globally. But also the chorea can occur, the uncoordinated and constant movement of the extremities, in what is known popularly as the Dance of San Vito.

Certain types of tics, more or less severe, andThey can also occur, more or less severe, and equally they can be manifested in diverse zones of the musculature of the subject. Also included in the dyskinesias are involuntary contractions of various muscle groups, such as dystonia or myoclonus.

And, within the dyskinesias, those of the late type, which is the one that concerns us, because it includes the rabbit syndrome, would refer to those caused by the consumption of neuroleptic drugs, i.e., antipsychotics, as we have detailed above.

Bibliographic references:

• Rebello, P.; Rao, P.P.; Nayak, P.; Mascarenhas, J.J.; Mathai, P.J. (2018). Risperidone induced rabbit syndrome. Neurology India. Publication of the Neurological Society of India.
• Schwartz, M.; Hocherman, S. (2004). Antipsychotic-induced rabbit syndrome. CNS drugs. Springer.
• Villeneuve, A. (1972). The Rabbit Syndrome a Peculiar Extrapyramidal Reaction. Canadian Psychiatric Association Journal.
• Yassa, R.; Lal, S. (1986). Prevalence of the rabbit syndrome. The American journal of psychiatry.