Seizures

Definition

Sudden paroxysmal episodes of involuntary muscle contractions (movements) with changes in consciousness, behavior, sensation and autonomic functioning.

Clinical Signs

May see any of the following:

Rising up on hind legs, sniffing hard
Appears to bat at air with “hands”

Note: the above clinical signs may be similar to an aura (peculiar sensory disturbances) that humans sometimes experience prior to actual seizure activity.

Muscle stiffening (e.g., limbs or entire body)
Clenched teeth
Falling over
Eyes glazing over
Flailing violently
Uncontrolled jerking or spasms
Tongue protruding from mouth
Loss of consciousness
Sudden cessation of activity along with appearing to stare absently

May see any of the following post seizure (post-ictal):

Remains awake, or awakens and resumes normal activity.
Limp, lethargic, or shows slight confused state.
An increased thirst post seizure.

*Note: for information on recognizing various signs of pain or discomfort refer to: Signs of Pain In Rats.

Etiology

Seizures are not specifically a disease, but rather constitute clinical signs that may manifest any number of underlying central nervous system disorders that result in the over-stimulation of nerve cells in the brain.

Under normal circumstances the nerve cells of the brain discharge electrical impulses in an organized, coordinated manner, allowing the brain to communicate with nerve cells in other areas of the body (e.g., spinal cord, muscle). When these electrical impulses discharge in a disorganized fashion, or when they don’t discharge normally, seizures can occur. Seizures also occur in the normal brain when enough of a stimulus is present (e.g., low blood sugar, decreased oxygen in the brain).

Seizures can often come on suddenly and may be transient or repeated (as in epilepsy).
They may also (depending on type) be preceded by a premonitory awareness that can include peculiar sensations of auditory, visual, olfactory, or taste disturbances; described in humans as an aura.

A seizure may be described in phases:

Pre-ictal (Aura), meaning the phase occurring just before the seizure itself. Changes in behavior or posture may not be noticed, or may be very subtle, such as restlessness, increased sniffing at air, or stance. This phase may only last a few seconds before onset of seizure.
Ictus (or ictal), the actual seizure. Muscle contractions and/or muscle stiffening may be observed depending on the type and extent of the seizure.
Post-ictal, meaning the phase which follows the actual seizure, may see the rat appearing as dazed, in a slightly confused state, or lethargic/sleepy. This may last for a short period of time depending on the extent of the seizure.

The causes of seizure activity are varied. They may be idiopathic (of unknown cause or identity) such as those arising from genetic or congenital disorders (e.g., hydrocephalus), or they may be acquired due to metabolic disturbances (e.g., crucial changes in blood sugar, calcium, and oxygen delivery to the brain), a stroke or space occupying lesions (e.g., tumors, brain abscess, hematomas), head trauma (injury), infection (e.g., encephalitis), or toxic substances (e.g., ingestion of poisonous plants or certain medications).

The following are types of seizures that may be seen:

Simple partial: often do not involve the entire brain but only a certain area. Involuntary muscle contractions or spasms occur in one area and then spread to involve entire limb or half of body. This is sometimes called a focal or Jacksonian seizure.
Complex partial: seizures of this type are often triggered in the structures of the temporal lobes of the brain. Often preceded by an aura; activity may appear restless, confused, licking of lips, raising up and sniffing hard at the air. Lethargy may follow the seizure.
Generalized: seizures of this type begin locally and immediately spread bilaterally. This category includes the following:
- Absence or Petit mal: an unaware staring, or a sudden cessation of activity. A transient loss of consciousness, and just as quickly as it began it leaves and normal activity resumes.
- Myoclonic: a rapid rhythmic jerking type movements that occur over the entire body (rat in danger of falling if not on one level).
- Tonic-clonic (also referred to as grand mal): muscle rigidity and spasms, jerking, loss of consciousness, followed by limpness, lethargy, confused state; may urinate or defecate as becomes relaxed.

While seizures can be alarming to the rat owner most seizures themselves are often brief lasting just seconds or up to a couple of minutes in rats. And while the rat may appear somewhat lethargic or weak after the seizure this is often a transient state.

What is of concern is that, unless the cause can be identified and corrected, it is highly likely that the frequency and duration of the seizures will increase over time.

Complications that may result from seizure activity are: injury due to falling from cage shelves or ladders, or airway occlusion and aspiration.

Figures

Case Histories of Seizure Activity

Fig 1: Seizures of idiopathic or unknown origin in male rat (Motely)
Fig 4: Refer to the case history found in figure 4 of hydrocephalus

Important Information For Rat Owners

Before going to your veterinarian, make notes about the seizure so that you can give the vet details. You will want to note the time of day the seizures(s) happened, the duration of each seizure, and if the seizures come on suddenly or slowly and progress. Was there any loss of consciousness and how long before your rat regained consciousness and resumed its normal activity? Remember to include what was happening in your rat’s environment prior to the seizure (any triggering events).

Diagnostics

Obtain history from pet owner or breeder, which includes: familial or sibling history or genetic background, precipitating factors, characteristics (appearance) and the pattern of onset of seizures.

Small animals CT or head x-ray may indicate if there is bony erosion, or evidence of fractures.

Serum draw for electrolytes (to determine imbalance), blood glucose, and BUN (blood urea nitrogen) and creatinine to check for metabolic disturbances or imbalance.

Urine screen: may determine toxic levels of ingested substances.

Treatment

Recommendations for treating seizure activity:

Try to reduce the frequency, duration, and severity of seizures.

The following medications may be prescribed for seizure activity depending on the type and presentation of the seizures, and severity. Where seizures are refractory to initial treatment it may become necessary to adjust medication, dosage given, or to combine with another anticonvulsant as appropriate:

Diazepam
Phenobarbitol
*Note: phenobarbitol may be combined with potassium bromide(KBr) and / or gabapentin, or levetiracetam where seizures are refractory to phenobarbital treatment alone; or where the reduction of phenobarbital is desired due to side effects.

Information on the use of these drugs can be found in the Rat Medication Guide.

Do not judge the efficacy of the medication immediately. It could take from a week to two months in order to achieve sufficient levels, or to reach a steady state, with some anticonvulsants.

Do not discontinue the medication suddenly as status epilepticus may follow.

In the majority of cases with pet rats, the frequency and duration of seizure activity will increase unless the cause can be determined and corrected. Adjustment to drug dosage, medication schedule, or combination of both will be required throughout the remainder of the rat’s life.

Provide oxygen as needed.

Give SQ fluids if dehydrated or if there is danger of aspiration.

Treat any underlying conditions.

Initiate broad-spectrum antimicrobial if infection is believed to be a cause (refer to Rat Medication Guide).

Initiate a corticosteroid (see: Rat Medication Guide) if inflammation is believed to be a factor.

Discuss euthanasia if the quality of the rat’s life is impaired.

Nursing Care

Give medications as prescribed, and do not skip dosages.
Ensure the rat’s environment is as free from stress as possible.
Prevent loud noises.
Prevent sudden changes in environmental temperature.
Approach the rat slowly, speaking softly so as not to alarm.
Allow the rat to stay with cagemates unless they are causing undue stress.
Provide a safe environment with a one-level cage that includes soft bedding/litter.
Maintain a healthy diet free from sugar or sugar additives.
Consult your veterinarian if there are changes in frequency, duration, or type of seizure activity despite medication regimen.

Outcome

During and following seizure activity: airway free of obstruction, and breathing returns to normal.
Safety is maintained. Free from injury during and following seizure.
Comfort owner if euthanasia of pet rat is required.

Prevention

It is difficult to predict and prevent seizures in a pet rat. What is important is to ensure their safety at all times, and seek treatment early in an illness or injury.

Prevent falls and injuries that could lead to seizures, and maintain an environment that is both healthy and safe should your rat develop seizures.
If your rat should develop a seizure, try to observe what the rat was doing just prior to the seizure or what was taking place in the rat’s environment. This will not only be helpful for the vet to know, but will also help you reduce or prevent those environmental causes that may induce a seizure to occur.
Do not attempt to interfere if the rat is in the midst of a seizure (unless there is a danger of your rat falling from a height). Your rat (unaware) may cause an unintentional bite during the seizure due to loss of muscular control.

References

Li, X., Ouyang, G., Yao, X., & Guan, X. (2004). Dynamical characteristics of pre-epileptic seizures in rats with recurrence quantification analysis. Physics Letters A, 33(1-2), 164-171 . Retrieved December 22, 2008, from http://www.cs.bham.ac.uk/~xin/papers/PhysLettA2004EEG.pdf.