Causes of Convulsions in Adults
Convulsions in adults result from a broad spectrum of etiologies that can be systematically categorized into provoked (acute symptomatic) and unprovoked causes, with the most common being antiepileptic drug noncompliance, alcohol-related seizures, stroke, CNS infections, metabolic derangements, and structural brain lesions.
Classification Framework
Seizures are fundamentally divided into two categories 1, 2:
- Provoked seizures (acute symptomatic): Occur at the time of or within 7 days of an acute neurologic, systemic, metabolic, or toxic insult
- Unprovoked seizures: Occur without acute precipitating factors, including remote symptomatic seizures from insults occurring more than 7 days prior
Most Common Etiologies in Clinical Practice
The predominant causes identified in emergency department presentations include 3:
- Antiepileptic drug noncompliance - the single most common cause in patients with known epilepsy
- New-onset seizures without prior history
- Alcohol-related seizures (including withdrawal and chronic use effects)
Metabolic and Electrolyte Causes
Electrolyte Abnormalities
Critical metabolic triggers that can precipitate seizures include 1, 2, 4:
- Hyponatremia - one of the most significant electrolyte triggers
- Hypocalcemia - can trigger seizures at any age, even without prior seizure history
- Hypomagnesemia - particularly in patients with renal failure or chronic alcoholism
- Hypernatremia - less common but important cause
- Hypercalcemia - can precipitate seizures
Glucose Abnormalities
Both extremes of glucose metabolism can cause seizures 1, 2, 4:
- Hypoglycemia - frequently missed on history and physical examination alone
- Hyperglycemia - particularly in diabetic emergencies
Other Metabolic Causes
Critical pitfall: History and physical examination predict most metabolic abnormalities, but occasional cases of hypoglycemia and hyponatremia are missed without laboratory testing 3, 2. Therefore, all first-time seizure patients require complete metabolic panel evaluation 2.
Structural/Neurological Causes
Cerebrovascular Disease
Stroke represents a major cause with age-dependent incidence 3, 2, 4:
- Acute stroke - common in adults, especially elderly
- Remote stroke (>7 days prior) - causes unprovoked seizures
- Intracranial hemorrhage including subdural hematomas 3, 2
- Vascular malformations 3, 2
Mass Lesions
Traumatic Causes
- Acute traumatic brain injury - causes immediate seizures 2, 4
- Remote traumatic brain injury - causes unprovoked seizures 2
Developmental Abnormalities
- Malformations of cortical development 2
Key clinical correlation: Focal neurologic examination findings have 97% correlation with symptomatic (structural) seizures 2, 4. CT scan identified focal lesions in 34% of all seizure patients, with 17% occurring even in those with normal neurologic examinations 3.
Infectious Causes
CNS Infections
Life-threatening infectious etiologies requiring urgent intervention include 1, 2, 4:
- Meningitis (bacterial or cryptococcal) - especially in immunocompromised patients
- Viral encephalitis (particularly herpes simplex) - critical diagnosis requiring immediate treatment
- CNS toxoplasmosis - in HIV/AIDS patients
- Cryptococcal meningitis - in immunocompromised hosts
- HIV encephalopathy 2
Critical warning: Fever in seizure patients warrants strong consideration of CNS infection 2, 4. In one study, 5 of 9 febrile patients had CNS infections 3. Immunocompromised patients have significantly higher rates of infectious etiologies 2.
Toxic and Drug-Related Causes
Illicit Substances
- Cocaine - causes seizures in approximately 10% of cocaine-related medical admissions, with 70% being single generalized seizures 2, 4
- Other illicit drugs 2
Medication-Induced Seizures
Prescribed medications that lower seizure threshold include 1, 2:
- Tramadol - even at therapeutic doses
- Tricyclic antidepressants 2, 4
- Antihistamines 2, 4
- Theophylline 2, 4
- SSRIs (particularly vilazodone) - can cause breakthrough seizures in controlled epilepsy 1
Withdrawal Syndromes
- Alcohol withdrawal - should be a diagnosis of exclusion in first-time presentations 1. However, this remains a common cause overall 3, 5
Important caveat: Alcohol withdrawal seizures require elimination of other symptomatic causes before diagnosis, as this should not be a default diagnosis 1, 2.
Idiopathic/Genetic Causes
- Idiopathic epilepsy - seizures without identifiable structural or metabolic cause, representing 24-27% of cases in some series 3, 2
- Genetic epilepsy syndromes 2
Special Population Considerations
HIV/AIDS Patients
New-onset seizures require consideration of 2:
- CNS toxoplasmosis
- Primary CNS lymphoma
- Cryptococcal meningitis
- HIV encephalopathy
In one study, 8 HIV patients with seizures had 5 with treatable infections, including 2 with positive lumbar puncture results despite being afebrile without meningeal signs 3.
Patients with Genetic Syndromes
- 22q11.2 deletion syndrome - 4-fold increased epilepsy risk due to hypocalcemia and hypomagnesemia 1
Diagnostic Approach Priorities
All first-seizure patients require 2:
- Complete blood count
- Comprehensive metabolic panel (including glucose, sodium, calcium, magnesium, renal function)
- Toxicology screen when appropriate
- CT scan to identify structural lesions
Approximately 8% of seizure patients have correctable metabolic abnormalities 2, and in 3 cases from one series, metabolic abnormalities (hypoglycemia, hyponatremia, hypocalcemia) were not predicted by history and physical examination 3.
Epidemiological Context
In a study of adult medical admissions, acute symptomatic seizures accounted for 5.2% of admissions, with the following distribution 5:
- Infections: 36.2%
- Stroke: 29.8%
- Metabolic: 12.8%
- Toxic: 10.6%
- Other causes: 10.6%
Notably, infectious causes predominated in patients under 50 years, while stroke was more common in those 50 years and above 5.