This document summarizes a presentation on feline seizures given by Dr. Laurent Garosi. It discusses the peculiarities of seizures in cats, including that they commonly experience partial seizures and high seizure frequency. It also provides information on evaluating cats with seizures, generating a list of potential causes, and choosing an appropriate diagnostic workup. Common structural and metabolic causes of seizures in cats are highlighted.

1. The 7th Annual Vet Education International Online
Veterinary Conference
“Feline Seizures”
With Dr. Laurent Garosi
Specialist in Veterinary Neurology
July 2016
Vet Education is proudly supported by Hill’s Pet Nutrition (Australia) and Lyppard Australia Pty Ltd

2. © Dr L Garosi 2016: Distributed with Permission
PECULIARITIES OF SEIZURES IN CATS
Dr Laurent Garosi DVM, Dip ECVN, MRCVS
RCVS & European Specialist in Veterinary Neurology
President European College of Veterinary Neurology
Head of neurology/neurosurgery
Davies Veterinary Specialists, England
lsg@vetspecialists.co.uk
RECOGNITION OF AN EPILEPTIC SEIZURE
An epileptic seizure is the physical manifestation of an excessive and/or hypersynchronous abnormal
neuronal activity within the cerebral cortex. It is important to recognise that an epileptic seizure is not a
disease entity in itself but a clinical sign generally indicative of a forebrain disorder. Similarly, the term
epilepsy is not a specific disease but the term use to define recurrent epileptic seizures.
Seizure types can be classified into two major categories: partial and generalised. Compared to dogs, cats
commonly exhibit partial seizures. The focal nature of this seizure type is associated with a higher incidence
of focal intracranial pathologic change in cats. These can be focal (partial motor or more often partial complex
seizure) seizures: unaltered consciousness with asymmetric localised motor signs such as eyelid or facial
twitching, clonus of muscle groups of one limb – or psychomotor (complex partial) seizures: behavioural
seizures pattern involving the limbic system which may be seen as growling, vocalization, rage, aggression
without provocation, running in circles, floor licking, tail chasing… Compared to dogs, cats tend to experience
high seizure frequency whatever the underlying cause.
The recognition of an epileptic seizure is essentially based on the owners’ description of the event. Apart for
the unequivocal description of a generalised tonico-clonic seizure, the recognition of a partial or psychomotor
seizure can be a real challenge for the clinician. Video footage obtained by the owner can be for that
particular reason of precious help. An epileptic seizure can be suspected based on the peracute and
unexpected (except cases of “reflex seizures” where seizures are observed in response to specific stimuli
such as auditory reflex seizures which we are currently investigating) onset and offset, stereotypical pattern
(i.e. each seizures are fairly similar in following the same pattern), presence of involuntary motor activity
and/or abnormal mentation and behaviour and/or autonomic signs (salivation, urination and/or defecation),
and elimination of other paroxystic events (syncope, acute vestibular attack, myasthenia gravis).
CLINICAL EVALUATION OF A CAT WITH SEIZURES
An epileptic seizure is not a disease entity in itself but a clinical sign generally indicative of a forebrain
disorder. Neurological examination should therefore focus on detecting forebrain signs (evaluation of mental
status, presence of circling gait, postural reaction testing, assessment of menace response and response to
nasal stimulation). Causes of seizures can be classified as being intracranial or extracranial in origin.
Intracranial causes are further subdivided into those where a structural lesion is identified (vascular,
inflammatory/infectious, traumatic, anomalous, neoplastic disease) and those where no such lesion is present
that is primary (functional or idiopathic) epilepsy.

3. © Dr L Garosi 2016: Distributed with Permission
The detection of forebrain signs on neurological evaluation in the inter-ictal period rules-out as a general rule
the hypothesis of primary epilepsy. The only exceptions to this rule are ischaemic necrotic brain lesions
secondary to violent seizures (excitotoxicity phenomenon). Such lesions are particularly found in cats in the
NMDA receptor-rich brain region such as the hippocampus. Inter-ictal neurological deficits frequently
observed include mainly behavioural changes (aggression, fear, hyperexcitability, uncontrolled biting,
chasing…).
GENERATING A LIST OF DIFFERENTIALS
Seizures refer to a forebrain disorder. Their causes may originate outside (extra-cranial) or inside (intra-
cranial) the brain.
Causes of seizures found outside the brain (extra-cranial) may be found outside the body (toxic disorder) or
inside the body (metabolic disorder). In both instances, the cat may have normal or abnormal neurological
examination in the interictal period. If neurological signs are seen, they are typically symmetrical and non-
localising in term of anatomic diagnosis. Common metabolic causes include hepatic encephalopathy (either
due to portosystemic shunt or to cirrhosis), renal encephalopathy, ionic imbalance (hypocalcemia,
hyponatremia, hypernatremia, hypomagnesemia or hyperkaliemia), hypoglycaemia, polycythemia, and
hyperthyroidism. Common toxic or nutritional disorder seen in cats include lead, ethylene glycol,
organophosphate and methaldehyde poisoning and thiamine deficiency.
Intracranial causes of epileptic seizures can further be divided into functional and structural forebrain disorder.
Most cats with structural forebrain disorder show neurological signs in the interictal period. These signs are
often asymmetric and can localise the lesion. They can refer to a forebrain disorder (ipsilateral circling,
contralateral postural reaction deficit, contralateral menace response loss with normal pupillary light reflex,
contralateral abnormal response to stimulation of the nostril, abnormal behaviour) or to a multifocal disorder
(cranial nerve or spinal cord involvement). The exception to this is a structural lesion in a “silent area” of the
brain (region of the brain which causes only seizures with no other localising signs such as the olfactory lobe
or prefrontal lobes) or in the early stage of an enlarging (and eventually slowly growing) mass. Structural
brain diseases include: cerebrovascular accident (common known causes in cats include cardiomyopathy,
glomerulopathy, hyperthyroidism, intoxication by anti-coagulant and parasitism), infectious encephalitis (Feline
Infectious Peritonitis, FIV, FeLV-associated CNS lymphoma, Toxoplasmosis, Borna disease and bacterial
meningo-
encephalitis), immune-mediated encephalitis, post-head trauma, primary and metastatic brain tumour, and
anomalous (hydrocephalus). A syndrome of complex partial seizures with orofacial automatism (FEPSO) has
been described in cats who will display signs of salivation, facial twitching, chewing, growling, rapid turning…
This syndrome has been associated with hippocampal pathology. In human, similar syndrome is seen with
autoimmune limbic encephalitis and is associated with antibody against VGKC (voltage-gated potassium
channel complex). Similar pathology has been documented in cats and it is also suspected VGKC complex
antibody may play an important role in naturally occurring seizure disease in this species. Brain MRI showed
bilateral hippocampal T1 hypo- and isointensity and T2 hyperintensity.

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The term primary (or idiopathic) epilepsy implies a functional forebrain disorder causing recurrent epileptic
seizures with a normal interictal period and no identifiable toxic, metabolic or structural intracranial causes.
This type of epilepsy is considered less common in cats as compared to dogs. The diagnosis of primary
epilepsy is unfortunately a diagnosis of exclusion. There is to date no definitive diagnostic test to confirm this
diagnosis.
CHOOSING THE APPROPRIATE DIAGNOSTIC WORK-UP
Baseline blood work including a complete blood count, chemistry profile, thyroid profile, bile acids, blood
pressure as well as a urinalysis should be performed in all cats with seizures. These non-invasive tests may
help to diagnose metabolic causes of seizures and are useful in planning anesthesia for any potential
advanced imaging.
The typical evaluation of an animal with idiopathic epilepsy includes normal neurologic and physical
examinations, a history of seizures with normal behaviour, normal interictal periods and normal blood work.
Dog with idiopathic epilepsy typically begin to seizure between 1 and 5 years of age and, therefore, a dog
meeting these criteria is presumptively diagnosed with idiopathic epilepsy and advanced diagnostics are often
DISEASE MECHANISMS
(VITAMIN D AS ACRONYM)
(COMMON CAUSES IN
CATS ARE HIGHLIGHTED
IN BOLD)
SPECIFIC DISEASES
Vascular Ischemic stroke
Hypertension
Polycythemia
High-grade atrioventricular dysfunction
Inflammatory/
Infectious
Infectious encephalitis (Toxoplasma, Bacterial, FIP, Cryptococcus,
Blastomycosis, FIV, Aberrant parasitic migration, FeLV)
Meningo-encephalitis of unknown aetiology
(presumed immune-mediated)
Auto-immune limbic encephalitis
Trauma Head injury - may be chronic response to earlier trauma
Toxic Lead, organophoshate, ethylene glycol toxicities
Anomalous Hydrocephalus
Metabolic Hepatic encephalopathy, hypoglycaemia, hypocalcemia, hyperthyroidism,
renal (uraemic) encephalopathy
Idiopathic Primary epilepsy
Neoplastic Primary and metastatic brain tumour
Nutritional Thiamine deficiency
Degenerative Lysosomal storage disease

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not necessary. Because such typical guidelines are not available for the feline idiopathic epileptic, advanced
diagnostics are usually recommended for the seizuring cat, even when idiopathic epilepsy is suspected. Such
diagnostics include advanced imaging such as MRI or CT and potentially a CSF tap. A CSF tap is indicated if
the imaging is normal or the imaging is suggestive of intracranial disease and the cat is believed to have
normal intracranial pressure. If there is a large space occupying mass or there is evidence of brain herniation,
a CSF tap is contraindicated. Normal CSF is clear and colorless with less than 5 cells/µl of CSF and less than
27mg/dL protein (for a cisterna magna sample). Abnormalities on CSF are very sensitive to intracranial
disease, but often not specific. However, when evaluated in conjunction with the MRI/CT imaging, it can be a
helpful diagnostic tool. Cultures and infectious disease titers (Cryptococcus, toxoplasmosis and FIP) may
also be useful tests to be performed on CSF.
When finances are limited?
If the cat has no abnormal inter-ictal signs and no abnormalities on neurological examination, once
systemic/metabolic causes have been excluded, it is not unreasonable to start management (as below)
without having performed advanced imaging. However, the owners should be warned that intra-cranial
disease can not be excluded and clinical signs may progress.
In cases with evidence of intra-cranial disease where finances limit further investigation, managing the
seizures alone can maintain quality of life for a reasonable period of time in some cases (e.g. meningiomas
are the most common brain neoplasms in cats and are usually very slow growing). However owners should be
advised that the treatment is only palliative and clinical signs will progress. In this situation, euthanasia should
be considered once a good quality of life is no longer sustained.
MAINTENANCE THERAPY
The aim of any anti-epileptic treatment is to “control” the seizures by reducing their frequency, intensity and
severity with minimum side effects. Decision to start anti-epileptic treatment is still a subject of controversy.
Cats with a single seizure or isolated seizures separated by longs period of time do not require treatment.
Treatment is indicated when: The first seizure is life-threatening (status epilepticus or severe clusters),
multiple seizures are observed in a short period of time, seizures occur more than once a month and/or
owners objects to their frequency, the seizures are becoming more frequent or more severe, an underlying
progressive disorder has been identified as the cause of the seizures. The choice of anti-epileptic drug in a
particular species depends on the pharmacokinetic, efficacy, safety and cost of the treatment. Commonly
used anti-epileptics in cats are: phenobarbitone (3 mg/kg q12hrs orally), levetiracetam (20 mg/kg q8hrs
orally), zonizamide (5 to 10 mg/kg q24hrs orally) and pregabalin (2 to 4 mg/kg q8 to 12 hrs orally).
Phenobarbitone is the first choice of many clinicians for cats with seizures. In dogs, repeated phenobarbitone
administrations are known to alter estimated steady state serum concentration as a consequence of enzyme
induction. This results in the need to progressively increase oral dosage with time in order to maintain steady
state therapeutic level. This phenomenon of enzyme induction following repeat administration of

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phenobarbitone is negligible in cats. The elimination half-life is stable at around 34 to 43 hours and therefore
drug concentration of phenobarbitone are not expected to decrease in cats receiving long-term therapy
without changing the oral dosage. Monitoring of serum level is only justified shortly after the onset of
treatment (when steady state level is reached after 10 to 15 days) due to the differences in elimination kinetics
of phenobarbitone between population of cats or when drugs that might interfere with phenobarbitone’s
pharmacokinetic are added. Recommended therapeutic ranges have not been properly defined in cats but
are considered similar to the recommended one in dogs [20 to 35 ug/ml]. Cats should not be considered as
refractory to treatment until serum concentrations reach 35 ug/ml unless unacceptable side effects persist.
Side effects of phenobarbitone in cats include: sedation, ataxia, polyphagia, weight gain, neutropenia,
thrombocytopenia, coagulopathy, severe cutaneous eruptions and marked lymphadenopathy (idiosyncratic
delayed hypersensitivity). The author does not recommend the use of oral bromide in cats due to the high
incidence of side effect in this species and in particular clinical and radiographic signs similar to feline asthma
such as coughing and/or difficulty breathing.
EMERGENCY APPROACH TO STATUS EPILEPTICUS
The emergency approach to SE consists in sequentially stabilize and initiate drug therapy, institute
maintenance anti-epileptic treatment, treat recurrent seizures and look for an underlying cause.
Systemic stabilization
All cases of status epilepticus (SE; seizure activity lasting 5 minutes or more or multiple seizures without
recovery inbetween) or cluster seizures (2 or more seizures within 24 hours, between which the cat regains
consciousness) should be treated as “trauma” patients. While stopping the seizures is the ultimate aim, it is
essential to maintain a patent airway (place an endotracheal tube if concern occurs), support proper breathing
patterns and oxygenation (X Ref QRG 12 Administering oxygen therapy), provide circulatory support, and
maintain body temperature. All these measures are paramount since the combination of circulatory collapse,
organ hypoperfusion, and energy depletion that may occur due to SE can lead to severe, irreversible renal,
cardiac and hepatic organ failure.
Cessation of seizure activity
 Place IV catheter if possible
 Intravenous diazepam (DZP; 0.5 – 1.0 mg/kg) or midazolam (0.06 – 0.3 mg/kg) bolus as first line
emergency therapy. If intravenous access is not available, diazepam can be given rectally and
midazolam can be given intramuscularly at same dosage
 Obtain blood sample for emergency database (see below)
 If the bolus of DZP or midazolam is successful in ceasing seizure activity, but additional seizures
occur, two additional boluses of these drugs, or a continuous rate infusion (CRI) of DZP or midazolam
may be administered. A CRI of DZP at 0.5–2 mg/kg/hour or midazolam at 0.2 mg/kg/hour can be
provided; these drugs are administered diluted in 5% dextrose in water (D5W) in a volume

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corresponding to the maintenance requirements (50 ml/kg/day), to maintain a seizure-free state. An
infusion pump or syringe driver must be used for accuracy. Careful monitoring of heart rate, blood
pressure and respiratory rates as well as diligent nursing care is needed while cats are being treated
with diazepam or midazolam CRIs due to their cardiorespiratory depressant effects. Once seizure-
free for approximately 6 hours, the infusion should be slowly tapered, by 25% every 6 hours, to avoid
potential withdrawal-induced seizure activity, while carefully monitoring for additional seizure activity.
 Concerns regarding aqueous solubility, formation of deposits and adsorption onto polyvinyl chloride
tubing have been raised with DZP. Compatibility should be checked before combining DZP with any
other medication or intravenous fluid as formation of precipitates is common (e.g. with calcium-
containing fluids). Never administer if a precipitate forms. Use of midazolam in lieu of DZP
circumvents many of these concerns; however this is far more expensive. If DZP is used the
administration set should be protected from light by covering with a bag or bandaging, and changed
every 2 hours.
 If diazepam is unsuccessful in ceasing seizure activity, other options include phenobarbital and
propofol. Phenobarbital can be used as an initial IV bolus dose of 3 mg/kg but it must be stressed
that the effect is not immediate, but rather can take 15-25 minutes, so overdosing needs to be
avoided, and its use needs to be considered early on in a patient presenting in status epilepticus or
with cluster seizures. Using phenobarbital as an emergency drug is useful when phenobarbital is the
chosen maintenance drug. Phenobarbital can also be used as an intravenous loading dose of 18
mg/kg. However, it is recommended to administer smaller boluses (2-4 mg/kg) to avoid excessive
sedation, repeating every 20-30 minutes, to effect but not exceeding 18 mg/kg over 24 hours. Note
that recovery from phenobarbitone or propofol sedation/anaesthesia may include paddling
movements of the limbs, which should not be confused with recurrent seizure activity. Differentiation
between the two can be achieved by turning the cat in a different recumbency. Motor activity caused
by propofol will be expected to stop while an epileptic seizure cannot be stopped.
 A CRI of propofol can be considered if the above fails to control the seizures. Propofol is very
successful in quickly ceasing seizure activity when diazepam has failed to achieve this, and an initial
bolus of 1-4 mg/kg can be used to effect followed by a constant rate infusion of 0.1–0.4 mg/kg/min
titrated to effect. Once seizure-free for approximately 6 hours, the infusion should be slowly tapered,
by 25% every 6 hours, to avoid potential withdrawal-induced seizure activity. In addition to causing
apnoea, propofol is also a cardiovascular depressant so, this too requires careful monitoring.
Propofol is a phenol and thus capable of causing oxidative injury to RBC of the cat resulting in Heinz
body formation and possible haemolytic anaemia, although this is rarely clinically significant following
seizure management.
 All of the above drugs, though useful emergency drugs, cause sedation of varying degrees, which is
undesirable. Intravenous levetiracetam is a viable alternative, not causing sedation and having no
known side effects in cats. Levetiracetam is administered in 20 mg/kg intravenous boluses. Its
intraveinous use may be effective for 8 hours, at which time it can be repeated if necessary. It is not a
veterinary licensed drug and is expensive so is unlikely to be on the shelf in most veterinary clinics.

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However, it may be possible to obtain on prescription from a chemist or local hospital if urgent need
arises.
Once the seizures stop, institution of a maintenance antiepileptic treatment (phenobarbitone 3 mg/kg orally or
intramuscular (if oral intake is not possible due to excessive sedation) q12hr) is critical to prevent seizure
recurrence. In a cat already receiving phenobarbitone, oral phenobarbitone dosage can be increased by 25 to
30% if serum level is low and re-checked 10-15 days later and/or a 2nd or 3rd anti-epileptic drug be started:
levetiracetam (20 mg/kg orally q8hr), zonizamide (5 to 10 mg/kg orally q24hr) and pregabalin (2 to 4 mg/kg
orally q8 to 12 hr).
Identify and treat underlying condition
Alongside initial management of the seizures, investigations should begin for treatable underlying causes, with
investigations initially including an emergency database (PCV, total solids, blood glucose and electrolytes)
and blood pressure assessment. Hypoglycaemia should be treated if this is severe (<3.0 mmol/l) and has
resulted in seizure. Medical history should be reviewed, including potential toxin exposure and possibility of
trauma. Further investigations such as advanced imaging of the brain (CT/MRI) and CSF analysis are only
considered when SE is controlled and the cat is systemically stable.