Review article Epileptic Disord 2014; 16 (4): 385-94

Non-convulsive status epilepticus in the elderly Shuli Cheng Western Health - Neurology, Victoria, Australia Received April 2, 2014; Accepted September 23, 2014

ABSTRACT – Altered mental state is a very common presentation in the elderly admitted to the emergency department. It has been determined that about 16% of patients aged 60 or older with confusion of unknown origin have non-convulsive status epilepticus. The diagnosis of non-convulsive status epilepticus is difficult in the elderly because possible aetiologies of confusion may present with the same clinical picture. Non-convulsive status epilepticus in the elderly carries major morbidity and mortality, attributable primarily to aetiology, and treatment is complex, involving treatment of the aetiology and concomitant medical illnesses, whilst balancing the side effects and drug interactions of antiepileptic drugs. Key words: non-convulsive status epilepticus, elderly, mental state, EEG, etiology

Non-convulsive status epilepticus (NCSE)

doi:10.1684/epd.2014.0709

Definition and criteria for NCSE

Correspondence: Shuli Cheng Western Health - Neurology, Gordon street Footscray Footscray, Victoria 3011, Australia

Epileptic Disord, Vol. 16, No. 4, December 2014

Non-convulsive status epilepticus is a term that covers a range of disparate conditions, denoting prolonged electrographic seizure activity (set arbitrarily at 30 minutes) with resultant non-convulsive clinical symptoms (Walker et al., 2005). The electrographic seizure activity is divided into clear-cut and equivocal criteria (table 1). There continues to be difficulties and controversies (equivocal criteria; description number 5 in table 1) with regards to determining EEG abnormal periodic discharges as epiphenomena in severely injured brains or as harmful epileptiform discharges that could lead to additional brain injury. One theory is that periodicity is a surrogate

marker for severe cerebral injury and does not cause further brain injury. Another hypothesis is that periodic discharges and seizures in the acutely-injured brain lead to secondary neuronal injury via excessive metabolic demand, excitotoxicity, or other mechanisms (Claassen, 2009). Chong and Hirsch (2005) proposed an ictal-interictal injury continuum (figure 1) to put into context the likelihood of neuronal injury for each type of discharge in a given clinical setting in order to guide management (Chong and Hirsch, 2005). A working definition used in some studies is the Young’s criteria in adults (table 2) (Young et al., 1996). Chong and Hirsch (2005) discussed two caveats of Young’s criteria. Firstly, the criteria were intended to be specific to seizures and not necessarily for the purpose of accurate diagnosis. Therefore, a pattern that does not fulfil these criteria

385

S. Cheng

The Ictal-Interictal-Injury Continuum High

GCSE

Potential for 2° Neuronal Injury

NCSE

NCS

SIRPIDs

PLEDS-Plus

EPC

Low

GPEDs

5B

TW

PLEDs proper

Ictal

Interictal

Figure 1. The ictal- interictal-injury continuum plot demonstrating various clinico-electrographic diagnoses. The potential for secondary neuronal injury (shown on the y-axis) should be a more important indicator of whether treatment should be aggressive. If clinical correlate is present with any of the patterns, it would be considered ictal by definition, though this does not necessarily suggest an appreciable increase in the likelihood of neuronal injury (Chong and Hirsch, 2005). EPC: epilepsia partialis continua; GCSE: generalized convulsive status epilepticus; GPEDs: generalized periodic epileptiform discharges; NCS: non-convulsive seizures; NCSE: non-convulsive status epilepticus; PLEDs: periodic lateralized epileptiform discharges; S-B: suppression burst; SIRPIDs: stimulus induced rhythmic, periodic, or ictal discharges; TW: triphasic waves.

could still be ictal, but cannot be proven based on the EEG pattern alone. Secondly, regarding number 4 of the secondary criteria (“significant improvement in clinical state or baseline EEG after antiepileptic drugs”), Chong and Hirsch (2005) cited the example of triphasic waves as non-ictal period patterns which are often eradicated with a bolus of benzodiazepines, thus qualifying as a seizure based on Young’s criteria. Therefore, more stringent criteria are required in the case of the appearance of previously absent EEG patterns alone to suggest a seizure (table 3) (Chong and Hirsch, 2005). This appears to be a stricter set of criteria, to be used in clinical practice and research. There is a need to validate both the Young’s and the modified Young’s criteria. The Young’s and modified Young’s working criteria appear to encompass all the criteria (clear-cut and equivocal) presented in table 1. With the secondary criteria (table 3), it is difficult to provide a consensus on the type and dose of “rapidly acting antiepileptic drugs (AEDs)” used,

386

whether patients should have an immediate or delayed response, and to what degree an improvement is considered “significant”. Epidemiology The epidemiological data of NCSE is fraught with methodological problems. Attempts to estimate have yielded an overall population incidence of NSCE between 5.6-18.3/100,000/year (from direct epidemiological studies) and 32-85/100,000/year (extrapolation from non-epidemiologically based data) (Walker et al., 2005). Classification The classification of NCSE can be subdivided by age, and further subdivided according to the forms of NCSE observed in epileptic encephalopathies, cerebral development, aetiology and syndrome (Sutter and

Epileptic Disord, Vol. 16, No. 4, December 2014

Non-convulsive status epilepticus in the elderly

Table 1. Criteria for electrographic seizure activity (Walker et al., 2005). Criteria

Descriptions

Clear-cut criteria

1. Frequent or continuous focal electrographic seizures, with ictal patterns that wax and wane with change in amplitude, frequency, and/or spatial distribution. 2. Frequent or continuous generalized spike wave discharges in patients without a prior history of epileptic encephalopathy or epilepsy syndrome. 3. Frequent or continuous generalized spike-wave discharges, which show significant changes in intensity or frequency (usually a faster frequency) when compared to baseline EEG in patients with an epileptic encephalopathy or epilepsy syndrome. 4. Periodic lateralised epileptiform discharges (PLEDs) or bilateral periodic epileptiform discharges (BiPEDs) occurring in patients in coma in the aftermath of a generalized tonic-clonic status epilepticus (subtle status epilepticus).

Equivocal

5. Frequent or continuous EEG abnormalities (spikes, sharp waves, rhythmic slow activity, PLEDs, BiPEDs, generalized periodic epileptiform discharges [GPEDs], triphasic waves) in patients whose EEG showed no previous similar abnormalities, in the context of acute cerebral damage (e.g. anoxic brain damage, infection, trauma). 6. Frequent or continuous generalized EEG abnormalities in patients with epileptic encephalopathies in whom similar interictal EEG patterns are observed, but in whom clinical symptoms are suggestive of NCSE.

Table 2. Young’s criteria for non-convulsive seizures. NCSE is defined as any pattern lasting for at least 10 seconds, with at least one primary criteria 1-3 and one or more secondary criteria. Criteria

EEG features

Primary criteria

Repetitive generalized or focal spikes, sharp waves, spike-wave or sharp-and-slow wave complexes at >3/sec._Repetitive generalized or focal spikes, sharp waves, spike-and-wave or sharp-and-slow wave complexes at

Non-convulsive status epilepticus in the elderly.

Altered mental state is a very common presentation in the elderly admitted to the emergency department. It has been determined that about 16% of patie...
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