The Massachusetts General Hospital Handbook of Neurology

Authors: Flaherty, Alice W.; Rost, Natalia S.

Title: Massachusetts General Hospital Handbook of Neurology, The, 2nd Edition

Copyright 2007 Lippincott Williams & Wilkins

> Table of Contents > Adult Neurology > Seizures

Seizures

A. Status epilepticus

A seizure that lasts for more than 30 minutes, or seizures that recur for more than 30 minutes without regaining consciousness in between. This is an emergency.

• 1. Initial assessment: ABCs (airway, breathing, cardiac), O₂ sats, coma exam (see Coma and Brain Death, p. 29), EKG, IV access, and draw labs. Coma exam can almost always be done before intubation and sedation.

• 2. Initial rx:

  • a. Thiamine, glucose: 100 mg IV, 50% dextrose 50 cc, naloxone.

  • b. Lorazepam (Ativan): 2 mg IV q2min 5, or diazepam (Valium) 5 mg IV q3min 4 while starting DPH load.

    • 1) Pediatric dosing: Diazepam 0.2 mg/kg IV at 1 mg/min, to max. of 10 mg. Or lorazepam 0.1 mg/kg IV under age 12, 0.07 mg/kg over age 12.

  • c. IV ACD: Avoid IV phenytoin if possible. Options:

    • 1) Fosphenytoin: see p. 162. Load 1000 mg PE (PE = phenytoin equivalent doses) IV/IM, at <150 mg/min. Cardiac monitor; check BP q min. Pediatric dose = 20 mg/kg IV at 0.5 mg/kg/min.

    • 2) Valproate: Load 1 g over 15-20 min (20 mg/kg). No immediate SEs to follow; check ammonia/LFTs in follow-up. Therapeutic level = 50-100.

• 3. Full assessment: H&P (see below), intubate if necessary, check labs, stat head CT. Consider lumbar puncture + Abx if pt. is febrile or has never seized before. Consider emergent EEG if pt. is comatose to rule out nonconvulsive status.

• 4. Second-line rx: Usually require intubation and arterial line (see p. 222) for BP monitoring.

  • a. Phenobarbital (Luminal): 20 mg/kg IV (100 mg/min) if still seizing after 40 min despite DPH and lorazepam.

  • b. Pentobarbital (Nembutal): 5 mg/kg IV load if still seizing after phenobarbital. Titrate dose (0.3-9 mg/kg/h) to obtain 3- to 15-sec periods of burst suppression on EEG.

  • c. Midazolam (Versed): 0.2 mg/kg IV loading dose as alternative to phenobarbital or pentobarbital. Titrate dose (0.1-0.4 mg/kg/h) to get burst on EEG.

  • d. Supportive care: Pressors if necessary. Cool pt. if febrile. Stop ACD drip once a day to see underlying EEG rhythm.

• 5. Special cases:

  • a. Partial status epilepticus: May be confused with tremor.

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  • b. Nonconvulsive status epilepticus: Usually there is some focal motor activity such as rhythmic blinking; rarely is there merely altered mental status. Nearly all pts. in nonconvulsive status are known epileptics. A test of 1-4 mg lorazepam IV/SL/PO should cause improvement (but may also improve catatonia).

  • c. Pyridoxine (B₆) deficiency: Consider giving pyridoxine 1 g IV or more if pt. is on isoniazid.

B. Seizure H&P

Aura, behavior during seizure, postictal period, h/o previous seizures or status epilepticus, drugs tried, nocturnal tongue biting or incontinence, febrile seizures as child, head injury, recent alcohol or other drugs, illness, sleep deprivation, relation to menstruation.

C. DDx of seizures

Syncope, myoclonus, tremor, pontine rigors, pseudoseizure, narcolepsy.

• 1. Nonepileptic seizures: See Table 27, p. 104.

D. Management of first seizure

• 1. Causes of new-onset seizures: Cerebral ischemia, bleed, trauma, mass, hydrocephalus, infection, toxin, metabolic, withdrawal (alcohol, benzodiazepine), overdose (cocaine, TCA, isoniazid), amyloid angiopathy, anoxia (usually does not respond to ACDs), idiopathic.

• 2. Tests: Consider head CT or MRI, LP, electrolytes (vigorous seizure alone can cause acidosis and hyperkalemia), Ca/Mg/Phos, CBC (vigorous seizure alone can cause WBC), screen urine and blood for toxins, EEG (best with sleep deprivation, photic stimulation, and hyperventilation), CXR to rule out lung primary tumor. Prolactin level elevation is unreliable evidence of a seizure.

• 3. Uncomplicated first seizure: Do LP if any suspicion of SAH or infection. If pt. is young, healthy, with normal exam and head CT, no need to admit. Get an outpt EEG and MRI + gadolinium, with thin cuts through hippocampus. Hold ACD unless seizure was prolonged. If workup negative, chance of recurrence is about 30%.

• 4. Hospital admission: Consider admitting pts with nonresolving change in their neuro exam, elderly pts with first seizure (for more rapid tumor workup), and alcoholics with active withdrawal.

• 5. Acute seizure rx:

  • a. Benzodiazepines: For alcohol withdrawal seizures or if pt seizes repeatedly. Lorazepam 2-4 mg IV/IM or diazepam 5-10 mg IV. Use only lorazepam in liver failure. Lorazepam has a slower onset but lasts longer (1 h vs. 20 min) because it is less fat soluble. This is the opposite time course of its sedative effects.

  • b. DPH: Not for alcohol withdrawal seizures. Do not need to load it IV if pt not seizing.

    • 1) Oral: 300 mg PO q3h 3; then 300 mg qhs. Warn pt. of SEs: double vision, vertigo, fatigue.

    • 2) 1g DPH over 45 min on cardiac monitor; if pt. is in status epilepticus, give it in 20 min. Painful.

  • c. Transition to chronic drugs: Consider immediately starting a switch to another agent if you think it would be a better long-term choice.

E. Seizure classification by clinical type

• 1. Generalized:

  • a. Tonic-clonic ( grand mal ): LOC with bilateral jerking, often preceded by aura. Often tongue biting or incontinence, postictal confusion.

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    A focal onset or Todd's (transient focal postictal) paralysis suggests the seizure is secondarily generalized from a partial seizure.

  • b. Atonic ( drop attacks ).

  • c. Absence ( petit mal ): Usually in children; see p. 150.

  • d. Myoclonic epilepsy: Usually in children; see p. 149.

• 2. Partial (focal, local): May become secondarily generalized.

  • a. Simple (no impairment of consciousness): May be motor, sensory, or ANS, depending on site of focus.

  • b. Complex (impairment of consciousness): Often preceded by psychosensory aura. Seizure has confusion automatisms. Often from mesial temporal or frontal lesion.

F. Management of chronic seizures

• 1. Causes of chronic seizure disorder (epilepsy):

  • a. Underlying defect: Structural damage, genetic, metabolic.

  • b. Precipitants of seizure: Fever; low ACDs, Ca, Na, or blood sugar; sleep deprivation; or the acute causes listed above.

• 2. Typical seizure, known epilepsy: Pts. can leave emergency room as soon as they are back to baseline. They do not need a head CT unless they have head injury and nonresolving change in their neuro exam.

• 3. Rx of seizure disorder:

  Table 31. Choice of anticonvulsant by type and comorbid condition.

  Indication Try AVOID Seizure Type Partial or secondary Levetiracetam,   generalized carbamazepine > valproate   Primary generalized Valproate, carbamazepine Ethosuximide Absence Ethosuximide, valproate DPH Myoclonic Valproic acid, clonazepam DPH, carbamazepine Centrotemporal DPH, phenobarbtal   Other Factors Young woman Lamotrigine, carbamazepine DPH Depression Lamotrigine DPH, phenobarbital HIV Valproate, lamotrigine DPH, phenobarbital Labile, impulsive Valproate, carbamazepine   Liver disease Levetiracetam, lamotrigine   Overweight Topiramate, oxcarbazepine DPH, phenobarbital Pain Valproate, carbamazepine, gabapentin DPH, phenobarbital

  • a. ACD choice: Lower doses of two agents are sometimes more tolerated than high doses of one agent. For dosing, side effects, and mechanisms, see Anticonvulsants, p. 161.

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  • b. Avoid precipitants: Alcohol, sleep deprivation. Oral contraceptives may help perimenstrual seizures.

  • c. Avoid driving: Laws vary; it is typically illegal for pt to drive for 6 mo after a seizure.

  • d. In pregnancy: see p. 97.

  • e. Discontinuing ACDs: Typically considered if pt has not had a seizure in 2 years. May want to check EEG; chance of recurrence is higher if EEG is abnormal. See also p. 161, for taper regimens.

  • f. Epilepsy surgery: To treat poorly controlled, disabling seizures after more than a year of failed aggressive medical management.

G. Seizure prophylaxis

Pts. should sometimes be on ACDs even if they have never seized, e.g., in:

• 1. Brain tumor: see p. 120. Usually not necessary, unless there is danger of herniation or it is a melanoma.

• 2. Post head injury: See Trauma, p. 119.

• 3. Intracranial hemorrhage: Q.v. p. 61. All pts. with spontaneous subarachnoid hemorrhage should get an ACD; subdural and parenchymal bleeds are controversial; probably do not need prophylaxis.

• 4. Routine craniotomy: Consider 2 wk of ACD.

H. Proconvulsant drugs

The following may lower seizure thresholds in some pts.: some Abx (amphotericin B, -lactams, fluconazole, isoniazid, metronidazole, praziquantel, zidovudine), anticholinergics, antihistamines, glucocorticoids, lithium, naloxone, narcotics (especially meperidine), neuroleptics, oxytocin, all stimulants, TCAs, x-ray contrast agents.