Generalized seizures, with or without twitching, occur in the advanced stages of many other illnesses, such as hypertensive encephalopathy, the posterior reversible encephalopathy syndrome from various drugs (PRES, as discussed in Chap. 33), sepsis—especially gram-negative septicemia with shock—and hepatic coma. Usually, seizures in these circumstances can be traced to an associated metabolic abnormality and are revealed by appropriate studies of the blood. Seizures are a central feature of the eclamptic syndrome as discussed in a separate section below.
In most cases of seizures caused by metabolic and withdrawal states, treatment with antiepileptic drugs is not necessary as long as the underlying disturbance is rectified. Indeed, antiepileptic drugs are usually ineffective in halting the seizures if the metabolic disorder persists.
Medications and Other Drugs as Causes of Seizures
In addition to the withdrawal states, a large number of medications are themselves capable of causing seizures, usually when toxic blood levels are attained. The antibiotic imipenem and excessive doses of other penicillin congeners as well as linezolid may be responsible, particularly if renal failure leads to drug accumulation. Cefepime, a fourth-generation cephalosporin, widely used for the treatment of gram-negative sepsis, can result in status epilepticus, if given in excessive dosage (Dixit et al). Renal dysfunction, preexisting brain lesions and previous epilepsy have been emphasized as features associated with antibiotic-induced seizures in a review by Sutter and colleagues (2015), and they emphasize that the evidence for associations between seizures and specific antibiotics are often based on limited evidence.
The tricyclic antidepressants, bupropion, and lithium may cause seizures, particularly in the presence of a structural brain lesion. Lidocaine and aminophylline are known to induce an unheralded single convulsion if administered too quickly or in excessive doses. The use of the analgesic tramadol has also been associated with seizures. Curiously, the anesthetic propofol, which is discussed further on as a potent anticonvulsant in the treatment of status epilepticus, has caused marked myoclonic phenomena in some patients and, rarely, seizures. These may occur during induction or emergence from anesthesia or as a delayed effect (Walder et al).
The list of medications that at one time or another have been associated with a convulsion is long and, if no other explanation for a single seizure is evident, the physician is advised to look up in standard references the side effects of the drugs being administered to the patient. In a few of our otherwise healthy adult patients, extreme sleep deprivation coupled with ingestion of large doses of antibiotics or adrenergic medications or other remedies that are used indiscriminately for the symptomatic relief of colds has been the only plausible explanation for a single or doublet seizure.
Furthermore, many illicit drugs of several varieties may cause seizures. Among the most prominent are cocaine, high-potency synthetic cannabinoids, abuse of amphetamines, phencyclidine, psilocibin, lysergic acid and related compounds. Some of these cause convulsions through an intermediate of extreme hypertension of vasculopathy but others seem to have a direct neurotoxic effect.
Global Arrest of Circulation
Cardiac arrest, suffocation or respiratory failure, carbon monoxide poisoning, or other causes of hypoxic encephalopathy tend to induce diffuse myoclonic jerking and generalized seizures as cardiac function resumes. The myoclonic-convulsive phase of this condition may last only a few hours or days, in association with coma, stupor, and confusion; or it may persist indefinitely as an intention myoclonus state (Lance-Adams syndrome). These movements are to be distinguished from the convulsive movements of syncope discussed earlier in the chapter and in Chap. 17.