What investigations should be done in a first-time seizure in an elderly patient?

Investigations for First-Time Seizure in Elderly Patients

All elderly patients presenting with a first-time seizure require emergent head CT scanning in the emergency department, along with serum glucose and sodium levels. Age over 40 years is itself an indication for emergent neuroimaging due to the high risk of structural lesions such as stroke and tumor in this population 1.

Essential Laboratory Tests

Obtain these tests immediately for all elderly patients:

• Serum glucose - hypoglycemia is a common reversible cause that must be identified urgently 1, 2, 3
• Serum sodium - hyponatremia is frequently associated with seizures in elderly patients 1, 2, 3
• Pregnancy test - for women of childbearing age only (less relevant in most elderly patients) 1

Neuroimaging - Critical in Elderly Patients

Head CT scan should be performed in the emergency department for elderly patients with first-time seizure 1. The evidence strongly supports this approach because:

• 23% of patients with new-onset seizures have acute stroke or tumor on CT 1
• 22% of patients with normal neurologic examination still have abnormal CT findings 1
• Age over 40 years is specifically listed as an indication for emergent ED neuroimaging 1
• MRI is preferred over CT when available for detailed evaluation, except when acute intracranial bleeding is suspected 2, 4

The elderly population has substantially higher rates of structural brain lesions (tumors, strokes, subdural hematomas) compared to younger patients, making imaging findings directly impact management and mortality 1.

Additional Testing Based on Clinical Context

Consider expanded metabolic panel if:

• History of renal insufficiency - check calcium, magnesium, phosphate 1, 2
• Malnutrition or diuretic use - check calcium, magnesium, phosphate 1, 2
• Suspected alcohol-related seizure - check magnesium levels 2, 3

Lumbar puncture is indicated when:

• Patient is immunocompromised - perform after head CT 1
• Fever is present - suggests CNS infection 1
• Signs of meningeal irritation exist 2

Toxicology screening:

• Consider drug of abuse screen, though routine use lacks strong evidence 1
• More relevant if clinical suspicion exists for substance use 2, 3

Critical Pitfalls to Avoid

Do not defer neuroimaging in elderly patients. While guidelines allow outpatient neuroimaging for young, healthy patients who return to baseline, elderly patients have much higher rates of serious structural lesions requiring immediate intervention 1. The 23% rate of stroke or tumor found on CT in new-onset seizures makes delayed imaging potentially dangerous in this age group 1.

Do not perform extensive electrolyte panels routinely. Only glucose and sodium have sufficient evidence for routine testing 1, 2. Calcium, magnesium, and phosphate should be reserved for patients with specific risk factors (renal disease, malnutrition, diuretics) 1, 2.

Do not perform lumbar puncture on alert, afebrile, immunocompetent patients - there is no evidence supporting this, and it delays more important investigations 1.

Electroencephalography

EEG is recommended for all patients with first-time seizure to assess recurrence risk and guide treatment decisions, though timing can be non-emergent 4, 5. Emergent EEG should be considered if persistent altered consciousness or nonconvulsive status epilepticus is suspected 3.

Risk Stratification for Elderly Patients

The elderly population requires more aggressive investigation because:

• Seizures are typically symptomatic rather than idiopathic 6, 5
• Structural lesions (stroke, tumor, subdural hematoma) are common 1, 4
• Metabolic derangements from polypharmacy and comorbidities are frequent 7, 6
• Consequences of missed diagnoses carry higher morbidity and mortality 6, 5