46. Epileptiform statuses - causes, diagnostic, management

What are epileptic seizures characterised by?

General tonic-clonic convulsions and focal seizures with loss of consciousness.

Tonic phase: stiff limbs; clonic phase: limp limbs, usually tonic followed by clonic

What are the different presentations of epileptic seizures according to frequency?

1. Isolated seizure (self-limiting, most common)

2. Cluster seizures (more than 1 seizure in a 24-hour period)

3. Status epilepticus (continuous seizure activity lasting more than 5 minutes)

How can seizures be classified according to location?

1. Focal

2. Generalised

How can seizures be classified according to their clinical signs?

1. Tonic

2. Tonic-clonic

3. Clonic

4. Myoclonic

5. Atonic

6. Absence

What is status epilepticus?

Continuous seizure activity lasting more than 5-10 minutes (generalised tonic-clonic), longer than 20-30 minutes (focal) or multiple seizures without clinical or electroencephalographic normalisation between seizures. It is a life-threatening emergency

What are the two phases of status epilepticus?

Compensatory and decompensatory

What happens during the compensatory phase of status epilepticus (first 30 minutes)?

The brain tries to compensate for oxygen and glucose demands by increasing brain blood flow, causing elevation in body temperature, bronchial secretions, and salivation. This can further develop into lactic acidosis, hypoglycaemia, and electrolyte imbalances

What happens during the decompensatory phase of status epilepticus (after 30 minutes)?

Cerebral regulatory mechanisms fail, leading to cerebral oedema, neuronal cell death, cardiac arrhythmias, and pulmonary hypertension. After 60 minutes, increased intracranial pressure, multiple organ failure, and death can occur

How is epilepsy classified?

1. Primary (idiopathic, inherited)

2. Secondary (due to a progressive underlying cause; trauma, neoplasia, meningoencephalitis)

What are some intracranial causes of secondary epilepsy?

1. Inflammatory meningoencephalitis

2. Viral infections (distemper, FIV, FeLV)

3. Metabolic disorders (storage disease)

4. Brain tumours/neoplasia

5. Vascular accidents (clot or bleed)

6. Idiopathic causes

7. Hydrocephalus

8. Traumatic accidents

What are some extracranial causes of secondary epilepsy?

1. Hepatic encephalopathy (hepatic failure, portosystemic shunt)

2. Toxins (plants, lead, mycotoxins, pyrethroids, organophosphates, carbamate, rat bait, strychnine, chocolate/caffeine, ethylene glycol)

3. Metabolic disorders (hypoglycaemia, hypocalcaemia, ischaemia, B1 (thiamine) deficiency)

What are the stages of a seizure?

Prodrome/aura, ictus, and post-ictal stage

What are some signs of the prodrome stage?

Abnormal behaviour such as restlessness, nervousness, whining, shaking, or salivating

What happens during the ictus stage?

The seizure itself, lasting from a few seconds to several minutes.

It can involve mild changes or complete loss of consciousness and body function.

Tonic-clonic convulsions may occur: the animal falls over, loses consciousness, extends limbs (tonic phase), followed by paddling (clonic phase), hypersalivation, blindness, ataxia, disorientation, circling, urination/defecation, and dilated pupils

What are some signs of the post-ictal stage?

Disorientation, ataxia, restlessness, blindness, and deafness

What information is important to gather in the history for diagnosing seizures?

Frequency, duration, clinical status between seizures, present and past medical history, postural deficits, exposure to toxins, and a description of the seizure type and frequency. Seizures commonly occur when the patient is resting or sleeping

What is the purpose of a neurological examination in diagnosing seizures?

To target tests at the cerebral cortex and identify alterations in mental status, blindness, lack of menace response, and proprioceptive deficits (knuckling)

What laboratory tests are used in diagnosing seizures?

1. Complete haematology (PCV)

2. Biochemistry (glucose, BUN, creatinine, acid-base status, electrolytes including calcium)

3. Urinalysis

4. Bile acid test (to assess for portosystemic shunt)

5. CSF examination (cytology, culture)

6. Imaging (X-ray, CT, MRI)

What medications are used to manage epilepsy?

1. Thiamine (in juvenile form to help protect brain development)

2. Diazepam (for emergency/rarely occurring seizures, IV or per rectum)

3. Phenobarbital (for recurring seizures)

4. Bromide (only in dogs, not for acute)

5. Propofol (to control external manifestations but not stop seizure activity itself)

6. Levetiracetam

Which drugs can be used for monotherapy?

1. Diazepam

2. Phenobarbital

3. Levetiracetam

What is the dose of diazepam?

0.5-1 (max. 2) mg/kg

What is the dose of phenobarbital?

5 (max 8) mg/kg

How long can propofol be used, and at what dose?

Use for 6-8 hours to calm the brain. 1-5 mg/kg, CRI: 0.2-0.4 mg/kg/min

What is the dose of levetiracetam?

60 mg/kg

What medication is used for long-term management of epilepsy that is not hepatotoxic?

Keppra (levetiracetam), which can be used in patients with portosystemic shunts

What can look like a seizure, but is not?

Spasms

What is the difference between spasms and seizures?

Spasms: pure muscle involvement

Seizures: depolarisation of neurons, which acts on muscles

What is the difference between epileptic seizures and epileptiform seizures?

Epileptic: Benign form of epilepsy. Shorter. Usually follow a pattern (e.g. every 5 days)

Epileptiform: aetiology influenced by organs or systems other than the brain. Longer and more severe. Often can’t determine prodromal/aura stage.

Which part of the brain is mainly affected with lesions/tumours?

Midbrain

What is a common differential diagnosis for seizures?

Toxins