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

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 what this phenomenon consists of, what is the substance that causes it and what are the neurological bases for it to happen.

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What is rabbit syndrome?

Rabbit syndrome, known by the medical term periodal tremor, consists of a series of involuntary movements that are repetitive, vertical, and rapid (frequency estimated to be 5 cycles per second, or 5 Hz) in the mouth area, resembling the characteristic movement performed by rabbits, which is why this pathology takes its name from that action.

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

rabbit syndrome is within the so-called extrapyramidal symptoms

, or extrapyramidal side effects (since they are generated as an unwanted effect by 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, such as this case.

Symptoms

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

However, they would not be affecting the muscles of the tongue, as other similar disorders do, such as tardive dyskinesia, so, in that In this sense, it would not be an obstacle for the subject who suffers from it when swallowing food, although it would be to carry out other actions, such as the fact of chew them.

prevalence

Regarding the prevalence of this peculiar disorder, it would be between 2.3% and 4.4% of all those patients who have been treated with antipsychotics, although there are some cases (very few, yes), in which those affected by the rabbit syndrome had not consumed neuroleptics previously, so there would be other causes that would be giving rise to this pathology.

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Causes

By affecting such specific muscle areas (all that involve jaw action and movement of the lips, but not the tongue, as we have already seen), the 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 black.

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

The causes for the appearance of the rabbit syndrome, as already mentioned, come from the consumption of certain types of drugs, which we can divide into two groups, depending on 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 find such symptom.

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

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

There would be a last category, where the drugs that can cause rabbit syndrome as a side effect would enter, even consuming small doses of said medication. This is the case of risperidone, yet another antipsychotic, in this case aimed at treating pathologies such as autism, schizophrenia or Bipolar disorder.

Anticholinergic treatment

We have already seen what are the chemical complexes that can cause the so-called rabbit syndrome, but what would be the way to reverse this process to ensure that the patient stops experiencing those annoying involuntary movements of his mouth? For this, it would be necessary to resort to other types of drugs. These are anticholinergics.

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

The problem is that anticholinergics, in turn, also They can trigger different types of side effects, the most frequent being known as antisialogogue., which refers to the fact that the segregation of saliva in the patient decreases, which is why they may constantly have the sensation of having a dry mouth. Likewise, they can have a small sedative effect, which is why it is a substance widely used in operations, since both effects are useful in said procedures.

But they are not the only side effects that anticholinergics can cause. They can also generate coordination problems at the motor level, increase heart rate, dry out the mucous membranes of the nose, prevent sweating, generate some vision problems such as focus problems or double vision, difficulty holding urine while sleeping, reduced bowel movement, and others.

Regarding the transient affectation of the central nervous system, anticholinergics can make themselves felt, causing a state of disorientation and confusion, feelings of agitation, swinging back and forth between dysphoria and euphoria, difficulty concentrating, memory disturbances or shortness of breath, among others.

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

Apart from the effects seen before, you 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 to this effect, a eat. It is important, therefore, to bear in mind that all these substances are very dangerous if they are 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 periodal tremor or rabbit syndrome as its own disorder, some manuals prefer to include it as a specific type within the so-called tardive dyskinesia. Dyskinesia encompasses all those pathologies characterized by the suffering of involuntary movements.

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

Certain types of tics may also occur, more or less severe, and can also manifest in various areas of the subject's musculature. Likewise, involuntary contractions of various muscle groups are included in dyskinesias, such as dystonia or myoclonus.

And, within the dyskinesias, the tardive type, which is the one that concerns us, to include the rabbit syndrome, would make reference to those caused by the consumption of neuroleptic drugs, that is, antipsychotics, as we have in detail before.

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.; Hochermann, S. (2004). Antipsychotic-induced rabbit syndrome. CNS drugs. Springer.
• Villeneuve A. (1972). The Rabbit Syndrome a Peculiar Extrapyramidal Reaction. Canadian Psychiatric Association Journal.
• Yasa, R.; Lal, S. (1986). Prevalence of the rabbit syndrome. The American journal of psychiatry.