Seizure Disorders: Diagnosis and Management

Margaret R. Wacker

Classification of Seizures

Seizures may occur in patients in the neurosurgical intensive care unit (NICU) as evidence of either a primary or secondary neurologic disease process. In addition, seizure thresholds may be lowered due to metabolic derangements or fever, as was the case in the case study. Seizures may also add to the injury to the brain, especially if they are recurrent, through the imposition of increased metabolic demand and/or hypoxia due to the suppression of respirations during the seizure episodes. Untreated or unrecognized status epilepticus can be fatal or cause permanent neurologic injury. Hence, efforts must be made to reduce the risk of seizures in the already neurologically compromised NICU patient.

Because many of the treatments for epilepsy are more effective for one or another seizure type, a brief review of types of seizures is necessary for choosing appropriate treatment. The International Classification of Epileptic Seizures (Table 23–1) is included here as a basis for the understanding of different types of seizures.¹ Generalized seizures, including those that have secondarily generalized, may affect respiration and thus be more dangerous to the patient, especially if they are recurrent.

Treatment of Seizures

Anticonvulsant medications should be selected by optimizing the drug for the type of seizures the patient has or for which the patient is at risk. For partial onset seizures, including those with secondary generalization, the preferred agents are carbamazepine and phenytoin. Alternative agents include valproate and many of the newer anticonvulsant agents. For absence seizures, first-choice agents are ethosuximide and valproate. Valproate is the first choice for atypical absence or atonic seizures. An alternative is lamotrigine for either absence or atypical absence/atonic seizures. Valproate is also the first choice for myoclonic seizures with the alternatives of lamotrigine, clonazepam, and clorazepate. For generalized tonic-clonic seizures, valproate, carbamazepine, and phenytoin are preferred agents, though newer antiepileptic drugs such as topiramate, lamotrigine, and zon-isamide may also be useful. In general, one agent should be chosen and increased to the maximum tolerated dose before beginning polypharmacy for the treatment of seizures.

Table 23–1 International Classification of Epileptic Seizures 1,2

Generalized seizures (bilaterally symmetrical and without local onset)
1. Tonic, clonic, or tonic-clonic (grand mal)
2. Absence (petit mal)
  1. Simple—loss of consciousness only
  2. Complex—with brief tonic, clonic, or automatic movements
3. Lennox-Gastaut syndrome
4. Juvenile myoclonic epilepsy
5. Infantile spasms (West’s syndrome)
6. Atonic (astatic, akinetic) seizures (sometimes with myoclonic jerks)
Partial, or focal, seizures (seizures beginning locally)
1. Simple (without loss of consciousness)
  1. Motor (tonic, clonic, tonic-clonic; Jacksonian; benign childhood epilepsy; epilepsia partialis continua)
  2. Somatosensory or special sensory (visual, auditory, olfactory, gustatory, vertiginous)
  3. Autonomic
  4. Psychic
2. Complex (with impaired consciousness)
  1. Beginning as simple partial seizures and progressing to impairment of consciousness
  2. With impairment of consciousness at outset
Special epileptic syndromes
1. Myoclonus and myoclonic seizures
2. Reflex epilepsy
3. Acquired aphasia with convulsive disorder
4. Febrile and other seizures of infancy and childhood
5. Hysterical seizures

In the setting of the NICU, the mode of administration of agents needs to be considered, because many patients are unable to take medications orally. Agents currently available in the United States for intravenous (IV) administration include lorazepam (Ativan), diazepam (Valium), phenytoin (Dilantin), fosphenytoin (Cerebyx), phenobarbital, and valproate (Depacon). In addition, diazepam is available for rectal administration.

Status Epilepticus

Status epilepticus is a special case of seizure activity without recovery of consciousness between seizures lasting for more than 30 minutes. There are ~100,000 cases per year in the United States.2,3 In half of the cases, it is the initial manifestation of a seizure disorder. The most commonly affected groups are young children and patients over 60 years of age. Status epilepticus can be either generalized or partial. Generalized status can be convulsive (tonic-clonic, tonic-clonic-tonic, or clonic), absence, secondary generalized, myoclonic, or atonic. Generalized convulsive status is the most frequent type of status epilepticus, of which 75% of cases are secondarily generalized. There are a variety of causes for status epilepticus, including febrile seizures; cerebrovascular accidents; infection, such as meningitis; idiopathic, epilepsy, or subtherapeutic anticonvulsants; electrolyte imbalance; drug intoxication, especially cocaine; alcohol withdrawal; traumatic brain injury; anoxia; and tumors.

Treatment of status epilepticus is directed to stabilizing the patient by stopping seizure activity and addressing the underlying cause of the status epilepticus. Although status epilepticus is defined as seizures and interictal periods without return to baseline lasting for more than 30 minutes, any recurrent seizures without interval return to baseline should be treated aggressively. Historically, mortality from status epilepticus has been reported to be as high as 50%, although more recent data suggest it is on the order of 10 to 12%, to perhaps as high as 20%, of which only ~2% of deaths are directly attributable to the status epilepticus.^2,3 Morbidity and mortality may be due to central nervous system (CNS) injury caused by repetitive electrical discharges, systemic stress from the seizure (cardiac, respiratory, renal, or metabolic), or CNS damage from the insult that caused the status epilepticus.

Initial treatment should address the “ABCs” of airway, breathing, and circulation. This should include maintaining the airway with an oral airway or possibly intubation, the administration of supplemental oxygen, and cardiac and blood pressure monitoring. Once this has been accomplished, priorities must be to stop further seizure activity and to correct its cause.1–6 An IV of normal saline should be started as soon as possible, and both a benzodiazepine, such as lorazepam or diazepam, and phenytoin loading dose should be administered. The role of valproate is not yet defined for use in status epilepticus, although it is a potential additional anticonvulsant, which may be used. In general, except in the case of cocaine-induced seizures, a benzodiazepine alone should not be used; rather, it should be used in conjunction with a longer-acting anticonvulsant.

Concurrently, efforts should be started to identify and correct the underlying cause. This workup should include blood work consisting of electrolytes, glucose, magnesium, calcium, anticonvulsant level, and arterial blood gas. If there is any consideration of CNS infection, a lumbar puncture should be performed unless it is contraindicated. If the patient is hypoglycemic or if glucose cannot immediately be measured, 25 to 50 mL of Dextrose 50 (D50) should be given. Fifty to 100 mg of thiamine should be given immediately prior to the D50 in patients in whom thiamine deficiency might be present. Likewise, naloxone (Narcan 0.4 mg IV pump [IVP]) should be given in the case of patients who might have taken narcotics. An electronencelphalography (EEG) monitor is helpful if available. Paralytic agents will stop the visible manifestation of the seizures, but they do not stop the dangerous electrical activity in the brain that can lead to permanent neurologic damage. Thus they should be avoided in patients with status epilepticus, except for the use of short-acting agents for intubation. In some cases of prolonged seizure activity, paralytic agents may be helpful in reducing the lactic acidosis and rhabdomyolysis caused by the seizure activity. In these cases, continuous EEG monitoring is necessary to determine whether electrical seizures are continuing and possibly causing further damage to the brain. In addition, narcotics and phenothiazines should be avoided in status epilepticus because they lower the seizure threshold (Table 23–2).

Prophylaxis of Seizures

Evidence-based medicine guidelines are available for prophylaxis of seizures in the setting of both traumatic brain injury and brain tumors.7,8 In other disease processes, no clear evidence-based guidelines currently exist.

Table 23–2 Protocol for the Management of Status Epilepticus 1–3

1. Lorazepam (Ativan) 0.1 mg/kg IV up to 4 mg (average adult dose) at rate of <2 mg/minute
OR
Diazepam (Valium) 0.2 mg/kg (10 mg average adult dose) IV at 5 mg/minute
OR
Valproic acid 20 mg/kg diluted in water or vegetable oil administered rectally in pediatric patients with frequent seizures and no IV access

2. Phenytoin (Dilantin) or fosphenytoin (Cerebyx) load of 20 mg/kg IV at a maximal rate of 50 mg/minute. If phenytoin is used, cardiac monitoring should be performed and the rate slowed should arrhythmias occur.

3. If seizures continue, may give additional phenytoin up to a total of 30 mg/kg
OR
Phenobarbital IV up to a total load of 20 mg/kg. (Because phenobarbital may lower blood pressure and suppress respirations, these need to be monitored during its administration.)
OR
Paraldehyde 0.3–0.5 mg/kg in a 1% solution diluted 1:1 in vegetable oil administered rectally

4. If seizures continue, the patient should be intubated and general anesthesia instituted with pentobarbital to induce burst suppression. This should be started with a load of 15 mg/kg IV and continued at a rate of ~2.5 mg/kg/hour. Blood pressure should be closely monitored, and pressors may be needed to maintain an adequate blood pressure.
OR
Propofol can be used as an alternative to pentobarbital to induce burst suppression. A load of 40 mg is given and repeated to an induction dose of 2.0–2.5 mg/kg and maintenance of 0.1–0.2 mg/kg/minute. Similar to pentobarbital, blood pressure must be closely monitored, and pressors may be needed.
OR
Midazolam (Versed) 5–10 mg bolus at less than 4 mg/minute, followed by a 0.05–0.40 mg/kg/hour drip.
By this stage, continuous EEG monitoring should be used to titrate either pentobarbital or propofol to provide burst suppression. It should also be used to monitor the effect of treatment and should be instituted as early as is feasible in those patients with refractory status epilepticus who do not rapidly return to baseline function.

< div class='tao-gold-member'>

Only gold members can continue reading. Log In or Register to continue