Epilepsy

Epilepsy is a chronic neurological disorder characterized by recurrent, unprovoked seizures resulting from abnormal excessive or synchronous neuronal activity in the brain. It is one of the most common neurological conditions in dogs and cats, with a prevalence estimated at 0.5-5.7% in dogs and 0.5-1% in cats. The condition is classified into three main categories: idiopathic (primary) epilepsy, structural (secondary) epilepsy, and reactive seizures (not true epilepsy but provoked by extracranial causes). Idiopathic epilepsy is defined by recurrent seizures with no underlying structural brain lesion or metabolic abnormality, and it is presumed to have a genetic basis in many breeds. Structural epilepsy arises from an identifiable intracranial pathology such as neoplasia, inflammatory disease, trauma, or vascular events. Reactive seizures are triggered by metabolic derangements (e.g., hypoglycemia, hepatic encephalopathy) or toxic exposures, and they are not considered epilepsy per se. The clinical manifestation of seizures can vary from focal (partial) to generalized, with or without loss of consciousness, and may be preceded by a prodromal phase or an aura. The diagnosis of epilepsy requires a thorough history, physical and neurological examination, and diagnostic testing to rule out other causes. Management typically involves antiepileptic drug therapy, with the goal of reducing seizure frequency and severity while minimizing adverse effects.

The etiology of epilepsy is diverse and depends on the classification. Idiopathic epilepsy is believed to have a genetic basis, with specific breeds showing a hereditary predisposition. In dogs, breeds such as the Beagle, Belgian Tervuren, Bernese Mountain Dog, Boxer, Cocker Spaniel, Collie, Dachshund, English Springer Spaniel, German Shepherd, Golden Retriever, Irish Setter, Labrador Retriever, Poodle, Saint Bernard, Shetland Sheepdog, and Siberian Husky have a higher incidence. In cats, idiopathic epilepsy is less common but has been reported in breeds like the Domestic Shorthair and Persian. Structural epilepsy results from intracranial causes including: primary brain tumors (e.g., meningioma, glioma, choroid plexus papilloma), metastatic neoplasia, inflammatory/infectious diseases (e.g., canine distemper virus, feline infectious peritonitis, toxoplasmosis, neosporosis, cryptococcosis, bacterial meningitis), traumatic brain injury, cerebrovascular accidents (ischemic or hemorrhagic stroke), congenital anomalies (e.g., hydrocephalus, lissencephaly), and degenerative diseases (e.g., storage diseases). Reactive seizures are caused by extracranial metabolic or toxic disturbances such as hypoglycemia (insulinoma, sepsis, hepatic insufficiency), hypocalcemia (eclampsia, hypoparathyroidism), hypernatremia or hyponatremia, hepatic encephalopathy, uremia, hyperlipidemia, and toxins (e.g., ethylene glycol, lead, organophosphates, strychnine, metaldehyde, chocolate, caffeine, and certain plants). Additionally, certain drugs can lower the seizure threshold, including fluoroquinolones, beta-lactam antibiotics, and theophylline.

Epilepsy is the most common chronic neurological disorder in dogs, with an estimated prevalence of 0.5-5.7%. It is less common in cats, with a prevalence of 0.5-1%. The condition can occur at any age, but idiopathic epilepsy typically manifests between 1 and 5 years of age, with a peak around 2-3 years. Structural epilepsy can occur at any age but is more common in older animals (over 6 years) due to the increased risk of neoplasia and cerebrovascular disease. Certain breeds are overrepresented for idiopathic epilepsy, including the Beagle, Belgian Tervuren, Bernese Mountain Dog, Boxer, Cocker Spaniel, Collie, Dachshund, English Springer Spaniel, German Shepherd, Golden Retriever, Irish Setter, Labrador Retriever, Poodle, Saint Bernard, Shetland Sheepdog, and Siberian Husky. In these breeds, a genetic basis is suspected, with modes of inheritance varying from autosomal recessive to polygenic. Sex predilection is not consistently reported, but some studies suggest a slight male predominance in certain breeds. Geographic variation may reflect breed popularity and genetic founder effects. In cats, idiopathic epilepsy is less common, and structural causes are more frequently identified. There is no clear seasonal pattern, but seizures may be triggered by stress, excitement, or changes in routine.

The pathophysiology of epilepsy involves an imbalance between excitatory and inhibitory neurotransmission in the brain, leading to hypersynchronous neuronal firing. In idiopathic epilepsy, there is no structural abnormality, but functional changes in ion channels, neurotransmitter receptors, or synaptic transmission are implicated. Genetic mutations affecting voltage-gated sodium and potassium channels, GABA receptors, and other proteins have been identified in some forms of human epilepsy and are suspected in canine and feline epilepsy. The seizure focus, often in the temporal lobe or frontal cortex, generates abnormal electrical discharges that propagate to other brain regions. During a seizure, there is excessive release of excitatory neurotransmitters such as glutamate, leading to calcium influx and neuronal depolarization. Inhibitory mechanisms, primarily mediated by GABA, are overwhelmed. The seizure activity can be focal, remaining localized, or generalize to involve the entire cortex. Generalized seizures involve both hemispheres and are characterized by loss of consciousness and bilateral motor activity. The postictal phase is marked by transient neurological deficits due to neuronal exhaustion and metabolic disturbances. In structural epilepsy, the underlying lesion (e.g., tumor, inflammation, scar tissue) acts as a seizure focus by altering the local neuronal environment, causing abnormal excitability. Reactive seizures are caused by systemic metabolic derangements that alter the neuronal membrane potential or neurotransmitter balance, such as hypoglycemia reducing glucose supply to the brain, or hepatic encephalopathy leading to accumulation of neurotoxic substances like ammonia. The pathophysiology of epilepsy is complex and involves multiple pathways, including neuroinflammation, oxidative stress, and alterations in blood-brain barrier permeability.

Predisposing factors for epilepsy include genetic susceptibility, age, breed, and concurrent systemic diseases. Genetic factors are the most significant for idiopathic epilepsy, with certain breeds having a high heritability. Age is a critical factor: idiopathic epilepsy typically presents between 1 and 5 years, while structural epilepsy is more common in older animals. Breed-specific predispositions are well-documented, as listed in the epidemiology section. Concurrent systemic diseases, such as hepatic or renal insufficiency, can lower the seizure threshold and precipitate seizures. Metabolic disturbances, including hypoglycemia, hypocalcemia, and electrolyte imbalances, are predisposing factors for reactive seizures. Stress, excitement, and changes in routine can trigger seizures in epileptic animals. Environmental factors, such as exposure to toxins or certain medications, can also lower the seizure threshold. In cats, hyperthyroidism can predispose to seizures. Additionally, animals with a history of head trauma or central nervous system infections are at higher risk for developing structural epilepsy. Poor compliance with antiepileptic medication or abrupt discontinuation of therapy can precipitate seizure clusters or status epilepticus.

The clinical signs of epilepsy are primarily seizures, which can be classified as focal (partial) or generalized. Focal seizures involve a localized area of the brain and may manifest as motor signs (e.g., twitching of a limb or facial muscles), autonomic signs (e.g., salivation, pupil dilation), or behavioral signs (e.g., fly-biting, tail chasing, unexplained fear). Focal seizures can progress to generalized seizures (secondary generalization). Generalized seizures involve both hemispheres and are characterized by loss of consciousness, tonic-clonic muscle activity, and autonomic signs such as urination, defecation, and salivation. The seizure typically lasts 1-2 minutes, followed by a postictal phase of confusion, disorientation, blindness, or sleepiness that can last minutes to hours. Some animals may exhibit a prodromal phase (changes in behavior or mood) hours to days before a seizure, and an aura (the initial part of the seizure experienced by the animal) may be observed. In addition to seizures, animals with structural epilepsy may show interictal neurological deficits such as circling, head pressing, proprioceptive deficits, or behavioral changes, depending on the location of the lesion. Reactive seizures are typically generalized and may be accompanied by signs of the underlying metabolic or toxic cause, such as weakness, vomiting, or altered mentation. Status epilepticus, defined as continuous seizure activity lasting more than 5 minutes or two or more seizures without full recovery of consciousness, is a medical emergency and can lead to hyperthermia, hypoxia, and permanent brain damage.

The differential diagnoses for epilepsy include: 1) Reactive seizures due to metabolic causes: hypoglycemia (e.g., insulinoma, sepsis, hepatic insufficiency), hypocalcemia (eclampsia, hypoparathyroidism), hypernatremia or hyponatremia, hepatic encephalopathy, uremia, and hyperlipidemia. These are ruled out by serum biochemistry, urinalysis, and specific tests such as bile acids or insulin/glucose ratio. 2) Toxic seizures: exposure to ethylene glycol, lead, organophosphates, strychnine, metaldehyde, chocolate, caffeine, or certain plants. History of exposure and toxicology screens are helpful. 3) Structural epilepsy due to intracranial neoplasia: primary or metastatic brain tumors. MRI is the gold standard for diagnosis. 4) Inflammatory/infectious diseases: canine distemper virus, feline infectious peritonitis, toxoplasmosis, neosporosis, cryptococcosis, bacterial meningitis. CSF analysis and serology/PCR are diagnostic. 5) Cerebrovascular accidents: ischemic or hemorrhagic stroke. MRI and CSF analysis help differentiate. 6) Traumatic brain injury: history of trauma and imaging findings. 7) Congenital anomalies: hydrocephalus, lissencephaly. MRI is diagnostic. 8) Degenerative diseases: storage diseases, such as GM1 or GM2 gangliosidosis. Genetic testing and enzyme assays are available. 9) Idiopathic epilepsy: diagnosis of exclusion after ruling out all other causes. 10) Narcolepsy/cataplexy: episodic weakness or collapse without loss of consciousness, often triggered by excitement. 11) Vestibular disease: may cause head tilt, nystagmus, and ataxia, but not true seizures. 12) Syncope: transient loss of consciousness due to cardiac or respiratory causes, often associated with exercise or excitement. Cardiac evaluation (ECG, echocardiography) is necessary.

The diagnostic algorithm for epilepsy begins with a thorough history and physical and neurological examination. The history should include signalment, age of onset, seizure description (frequency, duration, type, triggers), response to previous treatments, and any exposure to toxins or trauma. The neurological examination helps localize the lesion to the forebrain (cerebrum) if interictal deficits are present. The next step is to rule out reactive seizures by performing baseline blood work: complete blood count (CBC), serum biochemistry profile (including glucose, calcium, electrolytes, liver enzymes, bile acids, and ammonia), and urinalysis. If metabolic or toxic causes are suspected, additional tests such as blood gas analysis, endocrine assays (e.g., insulin/glucose ratio, cortisol), and toxicology screens may be indicated. If the blood work is normal and the animal is between 1 and 5 years old with no interictal neurological deficits, a presumptive diagnosis of idiopathic epilepsy can be made, and antiepileptic therapy may be initiated. However, if the animal is older than 6 years, has interictal neurological deficits, or seizures are focal or refractory to treatment, advanced imaging (MRI) and cerebrospinal fluid (CSF) analysis are strongly recommended to rule out structural epilepsy. MRI is the imaging modality of choice for evaluating the brain, as it can detect neoplasia, inflammation, vascular events, and congenital anomalies. CSF analysis (cell count, protein, cytology, and possibly PCR for infectious agents) is essential for diagnosing inflammatory/infectious diseases. In some cases, electroencephalography (EEG) may be used to support the diagnosis of epilepsy and characterize seizure activity, but it is not widely available in veterinary practice. Genetic testing for known mutations (e.g., in breeds like the Lagotto Romagnolo for benign familial juvenile epilepsy) may be available. The diagnostic algorithm should be tailored to the individual case, considering the age, breed, and clinical presentation.

In animals with epilepsy, routine laboratory findings are typically unremarkable if the epilepsy is idiopathic. However, during or immediately after a seizure, there may be transient changes such as lactic acidosis, hyperglycemia, and increased creatine kinase (CK) due to muscle activity. These changes are non-specific and resolve within hours. In reactive seizures, laboratory abnormalities reflect the underlying cause: hypoglycemia (glucose < 60 mg/dL), hypocalcemia (ionized calcium < 1.0 mmol/L), hypernatremia or hyponatremia, elevated liver enzymes and bile acids in hepatic encephalopathy, elevated BUN and creatinine in uremia, and hyperlipidemia. In structural epilepsy, CBC may show leukocytosis or left shift if there is an inflammatory process. Serum biochemistry may reveal elevated liver enzymes if the lesion is metastatic or if there is secondary hepatic involvement. CSF analysis is crucial: in inflammatory diseases, there may be increased protein and nucleated cell count (pleocytosis) with a predominance of lymphocytes, neutrophils, or eosinophils depending on the etiology. In neoplasia, CSF may be normal or show mild protein elevation. Specific biomarkers such as S100B and neuron-specific enolase have been investigated but are not routinely used. Genetic testing for specific mutations (e.g., in the EPM2A gene in Lafora disease) may be available for certain breeds. In cats, testing for feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) may be indicated if infectious causes are suspected.

Imaging plays a critical role in the diagnostic workup of epilepsy, particularly to rule out structural causes. Magnetic resonance imaging (MRI) is the gold standard for brain imaging in veterinary medicine. In idiopathic epilepsy, MRI is typically normal. In structural epilepsy, MRI findings depend on the underlying lesion: brain tumors appear as space-occupying masses with contrast enhancement, often with surrounding edema; inflammatory diseases may show diffuse or multifocal T2-hyperintense lesions with variable contrast enhancement; cerebrovascular accidents appear as focal areas of restricted diffusion on diffusion-weighted imaging (DWI) in acute ischemic stroke, or as hemorrhagic lesions with signal characteristics depending on the age of the hemorrhage; congenital anomalies such as hydrocephalus show ventricular dilation. Computed tomography (CT) is less sensitive than MRI for detecting soft tissue lesions but may be useful for detecting calcified lesions, bone involvement, or acute hemorrhage. CT is also more readily available and may be used when MRI is not feasible. Radiography of the skull is rarely helpful but may be used to detect fractures or osteomyelitis. Ultrasonography is not useful for brain imaging in adult animals due to the skull, but in neonates with open fontanelles, it can be used to assess hydrocephalus. Advanced imaging should be performed before CSF collection to avoid iatrogenic changes. In cases of suspected reactive seizures, imaging of other organs (e.g., abdominal ultrasound for insulinoma, thoracic radiographs for metastatic disease) may be indicated.

Cytology and histopathology are primarily used in the diagnosis of structural epilepsy when a mass lesion or inflammatory process is identified. Fine-needle aspiration (FNA) of a brain mass is rarely performed due to the risk of hemorrhage and the difficulty of accessing intracranial lesions. However, if a mass is accessible (e.g., via a burr hole), cytology may reveal neoplastic cells (e.g., meningioma, glioma) or inflammatory cells. CSF analysis is a form of cytology that is routinely performed: normal CSF has a low nucleated cell count (< 5 cells/µL) and protein concentration (< 25 mg/dL in dogs, < 20 mg/dL in cats). In inflammatory diseases, there is pleocytosis with a predominance of lymphocytes (viral, rickettsial), neutrophils (bacterial, fungal), or eosinophils (protozoal, parasitic). Neoplastic cells may be seen in CSF in cases of lymphoma, choroid plexus tumors, or metastatic carcinoma. Histopathology is obtained via biopsy or at necropsy. In idiopathic epilepsy, the brain is histologically normal. In structural epilepsy, histopathology reveals the specific lesion: e.g., meningioma shows whorls of meningothelial cells; glioma shows neoplastic glial cells; inflammatory diseases show perivascular cuffing with lymphocytes, microglial nodules, and sometimes intranuclear or intracytoplasmic inclusion bodies (e.g., canine distemper virus). Special stains (e.g., immunohistochemistry for CD3, CD20, GFAP) can help differentiate cell types. In storage diseases, histopathology shows vacuolation of neurons due to accumulation of metabolic products.

The treatment of epilepsy aims to reduce seizure frequency and severity while minimizing adverse effects. The decision to initiate antiepileptic drug (AED) therapy is based on the frequency and severity of seizures. Generally, therapy is recommended if the animal has more than one seizure per month, cluster seizures, status epilepticus, or severe seizures that impair quality of life. The first-line AED for dogs is phenobarbital, with a starting dose of 2.5-5 mg/kg PO q12h. The dose is titrated to achieve a therapeutic serum concentration of 25-40 µg/mL (dogs) and 20-30 µg/mL (cats). Phenobarbital is effective in 60-80% of dogs. Potassium bromide is often used as an add-on or alternative, with a loading dose of 400-600 mg/kg PO divided over 2-5 days, followed by a maintenance dose of 30-40 mg/kg PO q24h. Therapeutic serum concentration for bromide is 1-3 mg/mL. In cats, phenobarbital is also the first choice, but bromide is less commonly used due to a higher risk of bronchial irritation. Levetiracetam is a newer AED with fewer adverse effects, starting at 20 mg/kg PO q8h, and can be used as an add-on. Zonisamide is another option, starting at 5-10 mg/kg PO q12h. For emergency management of status epilepticus or cluster seizures, diazepam (0.5-1 mg/kg IV) or midazolam (0.2-0.3 mg/kg IV) is used, followed by a continuous rate infusion (CRI) of diazepam (0.1-0.5 mg/kg/hour) or levetiracetam (2-5 mg/kg/hour). If seizures are refractory, propofol (1-2 mg/kg IV bolus, then CRI at 0.1-0.4 mg/kg/min) or pentobarbital (3-15 mg/kg IV slow, then CRI) may be used. In addition to AEDs, treatment of the underlying cause is essential for structural or reactive epilepsy. For example, surgical resection of a brain tumor, antimicrobial therapy for infectious meningitis, or correction of metabolic derangements. Supportive care includes maintaining hydration, nutrition, and preventing self-trauma during seizures. Dietary therapy, such as a ketogenic diet, has been shown to be beneficial in some refractory cases, particularly in dogs. Regular monitoring of serum drug concentrations, liver function, and complete blood count is necessary to adjust dosages and detect adverse effects.

The prognosis for epilepsy depends on the underlying cause and response to therapy. For idiopathic epilepsy, the prognosis is generally good to fair, with 60-80% of dogs achieving good seizure control with phenobarbital or bromide. However, some animals may be refractory to treatment, and the condition is typically lifelong, requiring chronic medication. The median survival time for dogs with idiopathic epilepsy is approximately 5-7 years after diagnosis, but many live a normal lifespan with adequate control. Poor prognostic indicators include early age of onset (< 1 year), high seizure frequency at diagnosis, cluster seizures, status epilepticus, and poor response to initial therapy. Structural epilepsy has a more guarded prognosis, depending on the nature of the lesion. For example, meningiomas in dogs have a median survival time of 6-12 months with surgery and radiation therapy, while inflammatory diseases may respond well to immunosuppressive therapy. Reactive seizures have a variable prognosis depending on the underlying cause; if the metabolic or toxic cause is corrected, the seizures may resolve. However, if the cause is irreversible (e.g., cirrhosis), the prognosis is poor. In cats, the prognosis for idiopathic epilepsy is generally good, but structural causes are more common and carry a worse prognosis. Overall, the goal of treatment is to improve quality of life, and many animals can live comfortably with epilepsy.

Follow-up for epileptic animals is essential to monitor response to therapy, adjust drug dosages, and detect adverse effects. After initiating AED therapy, serum drug concentrations should be measured after 2-4 weeks to ensure therapeutic levels. Phenobarbital levels should be checked again at 3-6 months and then every 6-12 months. Bromide levels should be monitored similarly. Liver function (ALT, ALP, bile acids) and CBC should be evaluated every 6-12 months for animals on phenobarbital, as it can cause hepatotoxicity and bone marrow suppression. For animals on bromide, serum chloride and electrolyte levels should be monitored, as bromide can cause hyperchloremia. Owners should keep a seizure diary to record the date, time, duration, and type of seizures, as well as any potential triggers. If seizures are not controlled, the AED dose may be increased, or an additional AED may be added. If adverse effects are observed, the dose may be reduced or the drug changed. In cases of status epilepticus or cluster seizures, hospitalization and intensive monitoring are required. Long-term follow-up should include regular neurological examinations to assess for progression of any underlying disease. For animals with structural epilepsy, repeat imaging (MRI) may be indicated if neurological status deteriorates. For animals with reactive seizures, monitoring of the underlying metabolic condition is necessary. The goal of follow-up is to achieve the best possible seizure control with the fewest adverse effects, and to maintain a good quality of life.

Pearls: 1) Always rule out reactive causes before diagnosing idiopathic epilepsy; a simple blood glucose test can be life-saving. 2) In young dogs (1-5 years) with normal interictal neurological examination and normal blood work, a presumptive diagnosis of idiopathic epilepsy is reasonable, and AED therapy can be initiated without advanced imaging. 3) Phenobarbital is the first-line AED in dogs and cats; it is inexpensive and effective. 4) When using potassium bromide, a loading dose is necessary to achieve therapeutic levels quickly; maintenance dosing alone takes weeks to reach steady state. 5) Levetiracetam is a safe add-on with minimal drug interactions and is well tolerated. 6) For status epilepticus, administer diazepam or midazolam IV immediately, and have a plan for a CRI if seizures persist. 7) Always check serum phenobarbital levels if seizures are not controlled; non-compliance is a common cause of breakthrough seizures. 8) In cats, avoid bromide due to the risk of bronchial irritation; phenobarbital is preferred. 9) Consider a ketogenic diet for refractory epilepsy in dogs. 10) Educate owners about the importance of consistent medication administration and the risks of abrupt discontinuation. Pitfalls: 1) Failing to perform a thorough neurological examination may miss interictal deficits that indicate structural disease. 2) Starting AED therapy without a definitive diagnosis may mask signs of an underlying progressive disease. 3) Using diazepam alone for long-term management is ineffective and can lead to tolerance. 4) Overdosing phenobarbital can cause severe sedation, ataxia, and hepatotoxicity; always titrate based on serum levels. 5) Abruptly discontinuing AEDs can precipitate status epilepticus. 6) Ignoring the possibility of reactive seizures in older animals with metabolic disease. 7) Not monitoring liver function in animals on chronic phenobarbital therapy. 8) Assuming that a single seizure is epilepsy; a single seizure may be a reactive event and does not require lifelong therapy. 9) Failing to consider drug interactions, such as phenobarbital inducing hepatic enzymes and affecting other medications. 10) Not providing clear instructions to owners on how to manage a seizure at home, including when to seek emergency care.

The following drug protocols are based on Plumb's Veterinary Drug Handbook and current veterinary guidelines. For dogs and cats with epilepsy, the following medications are commonly used: 1) Phenobarbital: Dogs: initial dose 2.5-5 mg/kg PO q12h; titrate to maintain serum concentration 25-40 µg/mL. Cats: 1.5-2.5 mg/kg PO q12h; therapeutic range 20-30 µg/mL. Adverse effects: sedation, ataxia, polyphagia, polydipsia, hepatotoxicity. Monitor liver enzymes and serum levels. 2) Potassium bromide: Dogs: loading dose 400-600 mg/kg PO divided over 2-5 days, then maintenance 30-40 mg/kg PO q24h. Therapeutic range 1-3 mg/mL. Cats: not recommended due to bronchial irritation. Adverse effects: sedation, vomiting, pancreatitis. Monitor serum levels and chloride. 3) Levetiracetam: Dogs and cats: 20 mg/kg PO q8h; can be increased to 60 mg/kg q8h if needed. Adverse effects: sedation, ataxia. No therapeutic monitoring required. 4) Zonisamide: Dogs: 5-10 mg/kg PO q12h; cats: 5-10 mg/kg PO q24h. Adverse effects: sedation, anorexia, hepatotoxicity. Monitor liver enzymes. 5) Diazepam: For emergency seizure control: 0.5-1 mg/kg IV (dogs and cats); can be repeated up to 3 times. For status epilepticus, administer as CRI at 0.1-0.5 mg/kg/hour. Adverse effects: respiratory depression, hypotension. 6) Midazolam: 0.2-0.3 mg/kg IV or IM; can be used as CRI at 0.1-0.3 mg/kg/hour. 7) Propofol: For refractory status epilepticus: 1-2 mg/kg IV bolus, then CRI at 0.1-0.4 mg/kg/min. Adverse effects: respiratory depression, hypotension. 8) Pentobarbital: 3-15 mg/kg IV slow, then CRI at 0.5-2 mg/kg/hour. Requires intensive monitoring. 9) For reactive seizures due to hypoglycemia: administer 50% dextrose (1-2 mL/kg IV diluted 1:1 with saline) and treat underlying cause. 10) For hepatic encephalopathy: lactulose (0.5-1 mL/kg PO q8h) and antibiotics (e.g., metronidazole 7.5 mg/kg PO q12h) to reduce ammonia production. Always adjust dosages for renal or hepatic impairment, and monitor for drug interactions. For example, phenobarbital induces hepatic enzymes, which may increase the metabolism of other drugs. Use caution when combining AEDs, as additive sedation may occur.

The management of epilepsy in dogs and cats has been the subject of numerous studies and consensus guidelines. The American College of Veterinary Internal Medicine (ACVIM) published consensus statements on the diagnosis and treatment of epilepsy in dogs and cats in 2015 and 2016, respectively. These guidelines recommend a stepwise approach to diagnosis, including ruling out reactive and structural causes, and emphasize the importance of AED therapy for animals with recurrent seizures. Key clinical trials have evaluated the efficacy of phenobarbital, bromide, levetiracetam, and zonisamide. A landmark study by Podell et al. (1995) demonstrated that phenobarbital is effective in controlling seizures in 60-80% of dogs. A study by Boothe et al. (2012) compared phenobarbital and bromide and found no significant difference in efficacy, but phenobarbital had a faster onset of action. Levetiracetam has been shown to be effective as an add-on therapy in dogs with refractory epilepsy, with a study by Volk et al. (2008) reporting a 50% reduction in seizure frequency in 50% of dogs. Zonisamide has also been evaluated, with a study by Dewey et al. (2004) showing similar efficacy to phenobarbital. For status epilepticus, a study by Platt et al. (2002) demonstrated that diazepam CRI is effective in controlling seizures in dogs. Recent research has focused on the use of ketogenic diets, with a study by Patterson et al. (2005) showing a significant reduction in seizure frequency in dogs fed a medium-chain triglyceride diet. Genetic studies have identified mutations associated with epilepsy in certain breeds, such as the Lagotto Romagnolo and the Belgian Shepherd, which may lead to targeted therapies in the future. Overall, the evidence supports a multimodal approach to epilepsy management, including AED therapy, dietary modification, and treatment of underlying causes when identified.