Neurology
Question 295 of 300
A 19 year old woman is brought to the Emergency Department following a seizure. What is the most common metabolic cause of seizure activity?
Answer:
Seizure activity secondary to metabolic derangements is most commonly caused by hypoglycemia. The only treatment required in this situation may be intravenous (IV) glucose. Prolonged seizure activity may also cause hypoglycemia so that the cause and effect relationship may sometimes be reversed, and further therapy may be required.Epilepsy
Neurology
Last Updated: 17th March 2023
A seizure is the transient occurrence of signs or symptoms due to abnormal excessive or synchronous neuronal activity in the brain. Seizures can manifest as a disturbance of consciousness, behaviour, cognition, emotion, motor function, or sensation. There are two main types of seizures:
- Focal seizures — originate in networks limited to one hemisphere, and may be localised or more widely distributed. Focal seizures are divided into those with retained awareness or impaired awareness.
- Generalised seizures — originate in bilaterally distributed networks, and can include cortical and subcortical structures (but not necessarily the whole cortex). Generalised seizures are divided into motor and non-motor (absence) seizures.
An isolated seizure can be caused by toxic, metabolic, structural, and infectious factors and should not be confused with epilepsy. Epilepsy is a neurological disorder in which a person experiences recurring seizures.
Causes
A cause of epilepsy is only identified in about one third of people with the disorder. Causes of epilepsy include:
- Structural — abnormalities visible on structural neuroimaging, for example stroke, trauma, or malformation of cortical development.
- Genetic — epilepsy resulting from a known or presumed genetic mutation (not necessarily inherited) in which seizures are a core symptom of the disorder, for example Dravet syndrome.
- Infectious — epilepsy results from a known infection in which seizures are a core symptom of the disorder (rather than seizures due to acute infection such as meningitis). Examples include tuberculosis, cerebral malaria, HIV, and congenital infection such as Zika virus.
- Metabolic — epilepsy results from a known or presumed metabolic disorder in which seizures are a core symptom of the disorder (which may occur as a result of a genetic defect). Examples include porphyria, aminoacidopathies, or pyridoxine deficiency.
- Immune — epilepsy that results directly from an immune disorder (where there is evidence of auto-immune mediated central nervous system inflammation) in which seizures are a core symptom of the disorder. Examples include anti-NMDA receptor encephalitis and anti-LG11 encephalitis.
Complications
Complications of epilepsy include:
- Sudden unexpected death in epilepsy (SUDEP), in which a person with epilepsy dies suddenly without an identifiable cause. It is the most common cause of epilepsy-related death in young adults with uncontrolled epilepsy (rare in children). A significant risk factor is nocturnal seizures. The risk of SUDEP is reduced in people with optimized seizure control.
- Injuries — any seizure involving loss of awareness can cause trauma. Drowning, road accidents, and falls have all been associated with generalised tonic-clonic seizures. In pregnancy, abdominal trauma can cause ruptured fetal membranes and premature labour, although the risk is low.
- Depression and anxiety disorders are more common in adults and some children with epilepsy, particularly in people with poor seizure control, compared with the general population.
- Absence from school or work — occurs more commonly in people with epilepsy.
Assessment of person presenting with first seizure
- History
- Any risk factors suggesting a predisposition for epilepsy.
- Clinical features suggesting other causes of seizures, or an alternative diagnosis to epilepsy.
- What happened before, during and after the attack (from the patient and an eyewitness). This should include:
- Any subjective symptoms at the start of the seizure (aura) — suggestive of focal epilepsy; these may provide information on where the seizure might arise.
- Any potential triggers, for example sleep deprivation, stress, light sensitivity, or alcohol use.
- Specific features of the seizure, for example:
- Short-lived (less than 1 minute), abrupt, generalised muscle stiffening (may cause a fall) with rapid recovery — suggestive of tonic seizure.
- Generalised stiffening and subsequent rhythmic jerking of the limbs, urinary incontinence, tongue biting —suggestive of a generalised tonic-clonic seizure.
- Behavioural arrest — indicative of absence seizure.
- Sudden onset of loss of muscle tone — suggestive of atonic seizure.
- Brief, 'shock-like' involuntary single or multiple jerks —suggestive of myoclonic seizure.
- Residual symptoms after the attack (post-ictal phenomena), such as drowsiness, headaches, amnesia, or confusion (usually occur only after generalised tonic and/or clonic seizures).
- Examination
- Cardiac, neurological, and mental state, and a developmental assessment if appropriate.
- Examination of the oral mucosa to identify lateral tongue bites.
- Identification of any injuries sustained during the seizure.
- Investigations
- Bloods such as full blood count, urea and electrolytes, liver function tests, glucose, and calcium.
- A 12-lead electrocardiogram (ECG).
- A pregnancy test should be performed in patients of childbearing age.
- Offer brain neuroimaging tests if an underlying structural cause is suspected.
Differential diagnosis
Conditions which may present with similar features to epilepsy include:
- Vasovagal syncope.
- Cardiac arrhythmias.
- Panic attacks with hyperventilation.
- Non-epileptic attack disorders (psychogenic non-epileptic seizures, dissociative seizures, or pseudoseizures).
- Transient ischaemic attack.
- Migraine.
- Medication, alcohol, or drug intoxication or withdrawal.
- Sleep disorders.
- Movement disorders.
- Hypoglycaemia and metabolic disorders.
- Transient global amnesia.
- Delirium or dementia — altered awareness may be mistaken for seizure activity.
In children, differential diagnoses also include:
- Febrile convulsions.
- Breath-holding attacks.
- Night terrors.
- Stereotyped/ritualistic behaviour — especially in those with a learning disability.
Management of first seizure
- A patient presenting with a first seizure may be discharged home, accompanied by a responsible adult, if they have normal neurological and cardiovascular examination and the ECG and bloods are normal.
- Urgently refer all people suspected of having a first epileptic seizure to a specialist with training and expertise in epilepsy, to confirm the diagnosis.
- Do not routinely start anti-epileptic medication.
- Essential information on how to recognise a seizure, first aid, and the importance of reporting further attacks should be provided to the person, and their family/carer/parent as appropriate.
- Advise the person to stop driving while waiting to see the specialist for confirmation of the diagnosis, to avoid potentially dangerous work or leisure activities (for example working with heavy machinery or at heights, or swimming), and to be mindful of safety in the home (for example showering rather than taking baths), and at school.
- Advise the person about lifestyle factors that may lower the seizure threshold and make recurrence more likely, for example sleep deprivation and the use of alcohol and social drugs.
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
