Chapter 31-17: Seizures

TEXTBOOK PRESENTATION

Generalized seizures classically present with tonic-clonic activity, loss of consciousness and postural tone, incontinence, and a prolonged postictal period of lethargy. The purpose of this review is to focus on features that help distinguish seizures from syncope.

DISEASE HIGHLIGHTS

1. 3% of the US population suffers a seizure in their lifetime

2. Seizures are the cause of transient loss of consciousness (that may mimic syncope) in 1–7% of patients.

3. Etiology of seizure and prevalence in patients over age 60

   1. Idiopathic, 35%

   2. Ischemic, 49%

   3. CNS tumor, 11% (about 1/3 primary, 2/3 metastatic)

   4. CNS trauma, 3%

   5. CNS infection, 2%

   6. Metabolic disturbances

      1. Hypoglycemia and hyperglycemia (marked)

      2. Hypoxia

      3. Hyponatremia

      4. Hypocalcemia

      5. Uremia

   7. Medications

      1. Numerous medications have been implicated.

      2. Some commonly used medications that cause seizures (albeit rarely) include cyclosporine, fentanyl, meperidine, lidocaine, phenothiazines, quinolones, theophylline, tricyclic antidepressants, and bupropion.

   8. Illicit drugs ie, MDMA (Ecstasy), cocaine

   9. Withdrawal states (ie, alcohol, baclofen, benzodiazepines, and opioids)

EVIDENCE-BASED DIAGNOSIS

1. FP: Tongue laceration, head turning, and unusual posturing are the most specific clinical features and substantially increase the likelihood of seizure (specificity, 97%, LR+, 12–15) (see Table 31-7).

2. Most patients with generalized seizures have postictal confusion. The absence of a postictal period makes generalized seizures unlikely (sensitivity, 94%, LR−, 0.09).

3. Certain symptoms are unusual in patients with seizures and their presence reduces the likelihood of seizure.

   1. Diaphoresis preceding spell, LR 0.17

   2. Chest pain preceding spell, LR 0.15

   3. Palpitations, LR 0.12

   4. Dyspnea prior to spell, LR 0.08

   5. CAD, LR 0.08

   6. Syncope with prolonged standing, LR 0.05

4. Convulsive syncope

   1. Limb jerking is not specific for seizures.

   2. 15–90% of patients with syncope not related to seizures experience limb jerking, a phenomenon referred to as convulsive syncope. Limb jerking due to syncope is associated with myoclonic jerks, which should be distinguished from tonic-clonic activity.

      1. Myoclonic jerks tend to be arrhythmic and asymmetric, whereas the opposite is true of tonic-clonic activity.

      2. Myoclonic jerks tend to be briefer (average of 6.6 seconds) than tonic-clonic activity seen in seizures (≈ 1 minute)

      3. Myoclonic jerks never precede collapse, whereas tonic-clonic activity may precede collapse.

   3. Finally, unlike generalized seizures, which are usually associated with a significant postictal period, convulsive syncope is not associated with a significant postictal period (< 1 minute).

   4. Patients who appear to have refractory “seizure disorders” and nonspecific abnormalities on electroencephalogram (EEG) should undergo a cardiac evaluation to rule out convulsive syncope with myoclonic jerks.

5. A point score to distinguish seizures from syncope has been developed (Table 31-8). Point scores of ≥ 1 suggest seizures (sensitivity, 94%; specificity, 94%; LR+, 16; LR−, 0.06).

6. Evaluation

   1. EEG

      1. Indicated in the evaluation of patients with possible seizures

      2. Sensitivity is low between episodes (35–50%), but increases with sleep deprivation

      3. Specificity 98%

   2. Neuroimaging

      1. 37% of adults with new-onset seizures have structural lesions (eg, tumors, strokes) as do 15% of those without focal neurologic findings.

      2. Indicated in all adults with new-onset seizures.

      3. In acute cases, ...