Nonconvulsive status epilepticus

Nonconvulsive Status Epilepticus LORRAINE G. THIBODEAU, MD, PETER C. FERRERA, MD A 49qear-old man presentedwith dizzinessand altered behaviorassociated with a nonconvulsiveseizure. He had a long history of wellcontrolledtonic-clonicseizuresand daily episodesof 10-secondstaring spells. Despite normal neurological and laboratory examinations, an emergent electroencephalogramshowed changesconsistentwith nonconvulsivegeneralizedstatusepilepticus.(Am J EmergMed 1997;15:652653. Copyright© 1997 by W.B. SaundersCompany] Status epilepticus (SE) is defined as continuous or intermittent seizure activity that persists for greater than 30 minutes without a return to baseline function.l,2 Patients with nonconvulsive status epilepticus (NCSE) present with a change in their mental status associated with electroencephalographic evidence of seizure activity. NCSE is described as either primary generalized (absence SE) or partial (partial complex SE). 2,3Although the precise incidence of NCSE is unknown, as many as 25% of patients presenting in SE may have the nonconvulsive form. 4 We present the case of a 49-year-old man in absence status epilepticus (ASE) with a subtle clinical presentation.

CASE REPORT A 49-year-old man presented to the emergency department (ED) with a chief complaint of mild dizziness after a seizure. The patient had a history of infrequent generalized tonic-clonic seizures after childhood measles and daily 10-second staring spells. The patient's last tonic-clonic seizure was 8 years ago. He had been well until 2 hours before presentation, when he experienced a witnessed 1-hour episode of staring off into space with inability to respond to his wife. There was no incontinence or tonic-clonic movement. However, the patient complained of nonvertiginous dizziness, and his wife stated that he "seemed different" and was not acting himself. He denied tinnitus, visual changes, or headache, and review of systems and other past medical history was unremarkable. There were no changes in his medications, which consisted of valproic acid and a combination of primidone and phenobarbital. Physical examination in the ED showed a healthy-appearing man interacting appropriately. He had normal vital signs and an unremarkable general physical examination. The patient was alert, oriented, and able to follow complex commands. Ocular examination showed equally round and reactive pupils and no nystagmus. Cranial nerve function was intact. Sensor.c, motor, and cerebellar function examinations were normal. He had normal biceps and patellar deep tendon reflexes, and his toes were down going to noxious stimuli. The only remarkable physical finding was persistent rhythmic movements of both eyebrows, and his ability to From the Department of Emergency Medicine, Albany Medical Center, Albany, NY. Received July 11,1996, returned August 5, 1996; revision received August 16, 1996, accepted August 22, 1996. Address reprint requests to Dr Ferrera, Department of Emergency Medicine A-139, Albany Medical Center, Albany, NY 12208. Key Words: Absence status epilepticus, nonconvulsive status epilepticus, partial complex status epilepticus. Copyright © 1997 by W.B. Saunders Company 0735-6757/97/1507-000955.00/0

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perform calculations and short-term memory testing was decreased. Laboratory studies including complete blood cell count, electrolytes, blood urea nitrogen, creatinine, glucose, and calcium were normal. Anticonvulsant levels were within the therapeutic range (valproic acid 70.5 mg/dL, primidone 9.7 mg/dL, phenobarbital 6.4 mg/dL). After approximately 1 hour, the patient claimed to feel better, but his wife insisted that he was still not acting at his baseline. The Neurology Service was consulted and an emergent electroencephalogram (EEG) was performed 4 hours after the patient's arrival. EEG confirmed nonconvulsive generalized SE with 3/sec generalized spike and slow wave pattern. While undergoing continuous EEG monitoring, 1 mg doses of lorazepam were administered every 10 minutes until the seizure activity ceased. A total of 4 mg of lorazepam was required, and after 1 hour the patient's mental status improved markedly. The patient was then admitted to the neurological intensive care unit for observation without recurrence of his seizure activity. On discharge there was no change in his anticonvulsant regimen at the request of the patient and his wife.

DISCUSSION Convulsive status epilepticus (CSE) is a common and easily recognizable problem encountered in the ED. However, patients presenting with NCSE pose a diagnostic challenge because the clinical findings may be extremely subtle. The actual incidence of NCSE is unknown because many cases may go undetected and attributed to other causes of altered mental status.1 All age groups are affected by NCSE. 1,z,5 In a small number of cases, NCSE is the initial manifestation of a previously undiagnosed seizure disorder. 1,5,6However, most patients who present with absence SE (ASE) or partial complex SE (PCSE) have a known seizure disorderY Predisposing factors leading to the development of NCSE include changes in the dosing of an anticonvulsant regimen, benzodiazepine withdrawal, metabolic disturbances (eg, hypocalcemia), and generalized tonic-clonic seizures. 3,8 There are two general classifications for NCSE: ASE and PCSE. ASE has also been referred to as primary generalized nonconvulsive SE or petit-mal SE. ASE usually begins abruptly, whereas PCSE tends to be more gradual and with a focal sourceJ Patients may appear normal to the examining physician, but family members or friends may claim that the patient is not behaving normally. 1,3,4 Patients in NCSE may even be able to complete complex tasks, but often will have evidence of cognitive and speech deficits, v3~5,6 Psychiatric disturbances such as hallucinations or frank psychosis have also been reported. 1 Complete unresponsiveness is rarely seen in cases of ASE, but is more often seen with PCSE. 1 Automatisms, abnormal facial movements, and persistent blinking or twitching may be the only clues to diagnosis. TM ASE was originally thought to be much more common than PCSE, but the true incidence of PCSE has probably been grossly underestimated because of its variable clinical expression and the necessity of EEG confirmation, and also

THIBODEAU AND FERRERA • NONCONVULSIVE STATUS EPILEPTICUS

because focal ictal discharges may rapidly become generalized.3,7 Symptoms may last for hours to days, with cases of up to 2 months reported.l,5 ASE usually terminates abruptly, either spontaneously or after the administration of a benzodiazepine. PCSE is normally followed by a postictal phase. 1 However, differentiation of ASE from PCSE based on clinical grounds, EEG findings, and response to treatment may not always be possible. 5-7 The differential diagnosis is broad, and without the use of electroencephalography, the symptoms of NCSE may be confused with migraine, transient ischemic attacks, transient global amnesia, and psychiatric disorders. 1,3,5 Therefore, patients who present with subtle mental status changes, especially those with prior seizure disorders, should have the diagnosis of NCSE included in the differential diagnosis. An EEG should be performed if the facility has the capability. EEG findings with ASE classically shows a bilaterally synchronous 3/sec spike and wave pattern, as was evident in our patient. 1,3,9 However, Granner and Lee 1° have shown that there is a heterogeneous morphology to the EEG pattern in patients with NCSE, with an atypical spike and wave pattern (ie, less than 3/sec spikes) being the most common finding. In addition, the EEG pattern in NCSE can be further classified as generalized, focal, or secondarily generalized following a focal pattern.l° Management of the patient with NCSE includes the determination of the underlying etiology of the episode. Infection, metabolic derangements, subtherapeutic anticonvulsant levels, and other factors should be excluded. Ideally, an EEG should be performed before initiation of treatment. 3 NCSE is highly responsive initially to the administration of benzodiazepenes, such as lorazepam and diazepam, but these agents are not effective for long-term control. 1,3,4,6,7,I0 For long-term treatment, ethosuximide and valproic acid may be used to manage absence seizure, whereas carbamazepine, phenytoin, phenobarbital, primidone, and valproic acid are useful for control of partial seizures. 1,3 Although CSE is clearly associated with significant neurological morbidity and occasionally mortality, the neurological prognosis of NCSE appears to be good. 1,8 ASE apparently does not have serious neurological sequelae. 11 PCSE, however, may be associated with memory and behavioral changes. 3,11,12 Nevertheless, patients who have

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sustained prolonged periods of PCSE have made full neurological recovery.3

CONCLUSION NCSE is an uncommon neurological emergency that must be considered in the differential diagnosis of any patient presenting with altered mental status, especially in those with known seizure disorders. Neurological and behavioral findings may be extremely subtle, and the diagnosis may go unrecognized. Emergent EEG is necessary to confirm the diagnosis of NCSE. Initial treatment is with benzodiazepines, but other anticonvulsant agents are needed for long-term control. The prognosis of NCSE is thought to be good, but some patients may experience long-term memory behavioral deficits with PCSE. Further studies are needed to correlate outcome of these patients with neuropsychiatric testing.

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