Simple partial status epilepticus in Chinese adults

Journal of Clinical Neuroscience (2005) 12(8), 902–904 0967-5868/$ - see front matter ª 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.jocn.2004.11.011

Clinical study

Simple partial status epilepticus in Chinese adults Andrew CF Hui FRCP, PY Tong BSSc BSSc, A Wong BSc BSc, TWH Leung MRCP, Patrick Kwan PhD, Lawrence KS Wong MD Department of Medicine and Therapeutics, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, Hong Kong, China

Summary Simple partial status epilepticus (SPSE) is uncommon compared with generalized tonic-clonic status epilepticus. We evaluated the clinical profile and predictors of poor outcome in a group of Chinese patients with this condition. We identified 32 patients above the age of 14 years with SPSE from a large urban hospital over an eleven-year period. Factors for poor outcome, defined as death or morbidity, were analyzed. The most common underlying causes were due to cerebrovascular disease (46.9%), CNS infection (15.6%), metabolic derangement (12.5%) and tumor (12.5%). At 30 days from the onset of seizures, 13(40.5%) patients had recovered fully and seven (21.9%) had died. Poor outcome was associated with the presence of an acute symptomatic injury. ª 2005 Elsevier Ltd. All rights reserved. Keywords: Epilepsy, status epilepticus, simple partial seizures, Chinese

INTRODUCTION Despite advances in diagnosis and management, generalized status epilepticus is associated with significant morbidity and mortality.1 Simple partial status epilepticus (SPSE) consists of persistent focal seizures without impairment of consciousness and with preserved neurovegetative regulation.2–6 The most common type is simple partial seizure involving the motor system with or without Jacksonian march.2–6 Other forms can also occur without motor manifestations but these are less common and include SPSE with language disturbance or with sensory, autonomic signs and symptoms. While most reports have focused on generalized tonicclonic status epilepticus, there are no formal population-based studies and there is limited clinical data on patients with the partial form, especially in Asian populations.7–12 The aim of this report was to investigate the clinical features, aetiology and outcome among patients who were admitted to an urban Chinese hospital with SPSE. METHODS Patients The study group consisted of patients over the age of 14 years who were diagnosed with simple partial status epilepticus (SPSE) at the Prince of Wales Hospital in Hong Kong, China (International Classification of Disease (ICD)-9 codes 345.40, 345.50, 345.70) This institution is the main regional public hospital and also tertiary referral centre for the New Territories East district. Cases were ascertained retrospectively from January 1993 to December 1999 and prospectively from January 2000 to December 2003. Patient identification was based on the records of the electro-diagnostic unit and the computerized admission and discharge records of the emergency and medical departments. The complete list was compiled by cross-referencing these multiple sources. Seizure type was classified according

Received 11 August 2004 Accepted 19 November 2004 Correspondence to: Andrew CF Hui FRCP, Department of Medicine and Therapeutics, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, Hong Kong, China. Tel.: +852 26323131/26323133; Fax: +852 26375396; E-mail: [email protected]

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to the recommendations from the International Classification of Epileptic Seizures, based on information from witnesses and medical staff.13 The following exclusion criteria applied: 1) Patients below the age of 15 years; 2) Patients with generalized tonic-clonic, absence or myoclonic status and 3) Patients who had complex partial status. The objective was to review the course of patients with status whose sole or main seizure type was simple partial.

Definitions The diagnosis of SPSE was based in part on Wieser’s operational definition and defined as clinical evidence of continuous seizure activity lasting 30 minutes or more without loss or severe alteration of consciousness. The charts were retrieved and relevant information from eligible patients was abstracted by a single neurologist using a standardized form. The following details were noted: patients’ name, age and sex; pre-morbid state and comorbidities, history of epilepsy and anti-epileptic drug use, seizure type, aetiology, results of laboratory and brain imaging, duration of hospital stay and outcome. The aetiology was recorded as being structural (such as stroke/tumor/trauma), metabolic or drug related. Evidence of low levels of anti-epileptic drugs (AED) was required in order to diagnose non-compliance with anticonvulsants as a cause. The primary cause was termed cryptogenic if there was insufficient clinical, laboratory or radiological to support a specific cause. Patients were initially treated according to established hospital recommendations for generalized convulsive SE, with intravenous diazepam or lorazepam followed by phenytoin loading of 15–20 mg/kg as first line anticonvulsive therapy.14 Secondline agents were not standardized. Delay in treatment was regarded as initiation of AEDs over 30 minutes after the onset of status, according to the medical records. Patients who were not controlled 60 minutes or more after starting treatment were defined as being in refractory SPSE. As a measure of functional status in survivors we used a simple three category score that had been previously used in patients following neurological insults: (a) normal - no neurological impairment; (b) mild impairment, i.e., some neurological abnormalities on examination such as mild hemiparesis but able to return to gainful employment; and (c) severe impairment, i.e., intellectual or neurological deficit precluding gainful employment.15 This was recorded in all

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patients who had survived and was limited to 30 days after the onset of SE. This was derived from the examination of patients during follow up, as a standard part of aftercare. Poor outcome was defined as death or grade c) at follow up. Analysis Data was analyzed using commercially available software (SPSS 9.0 for Windows, Chicago, IL). Continuous variables were compared using the two-tailed t-test or the Mann-Whitney test for non-normally distributed data while categorical variables were compared using chi-squared test or Fisher’s exact test as appropriate. Variables such as age, sex, the presence of an acute symptomatic injury, aetiology, duration of hospital stay, delay in treatment and the development of refractory seizures were analyzed to determine if they were associated with poor outcome. Statistical significance was set at the 0.05 level. RESULTS Thirty-two patients with partial SE were identified (17 men, 15 women) and the mean age was 50 years (range 14 to 80 years). Among this group of patients, 12 had a history of epilepsy and were already on anti-epileptic drug treatment. Three patients (9%) presented with aphasic SE, which were all confirmed by EEG, while the majority had focal motor (somatomotor) status (90.6%). There was a delay in instituting treatment in 18 cases (56.2%) while refractory SE developed in 17 (53.1%). SPSE occurred in the context of an acute symptomatic injury in 20 (62.5%) cases. The most common aetiology was cerebrovascular disease in 15 patients (46.9%), followed by CNS infection in five (15.6%). Other causes include metabolic derangement and tumour in four cases each (12.5%) while the cause was cryptogenic in another four patients (12.5%). EEG was available within 72 hours in 23 cases and among this group 7 (32%) showed focal or generalized slowing while 15 (68%) showed ictal and interictal sharp/spike waves. The mean duration of hospitalization was 21.1 € 19.5 days. Thirteen patients (40.5%) made a good recovery, 12 (37.5%) had a deterioration in functional ability compared with pre-morbid at thirty days after the onset of SE and seven (22%) had died; therefore poor outcome was encountered in 19 cases (59.5%). Details of the two groups are given in Table 1. The presence of an acute symptomatic injury causing simple partial status was associated with poor outcome (p < 0.01).

DISCUSSION In patients with persistent simple partial seizures, epileptic discharges remain confined to a limited brain region. The underlying pathophysiology is poorly understood but it may be related to the presence of focal well-defined lesions with sufficiently preserved surrounding neuronal inhibition to restrict the epileptogenic process. SPSE represents approximately a fifth of all types of status epilepticus and among these, simple partial motor convulsion are the most common form.2,3,16 One reason may be that other types such as aphasic or sensory SE present subtly, are more difficult to detect and are therefore under-diagnosed. Conventional scalp EEG may be normal or non-specific as only a small area of cortex may be involved. In contrast to patients with generalized convulsions in which a significant proportion are of unknown cause, the majority of patients from these series have a known aetiology, of which cerebrovascular disease was the most common cause.2,3 Our results are limited by a) the partly retrospective nature of the study as this may have lead to under-ascertainment of cases and b) the small sample size – additional causes for simple partial status and other factors associated with poor outcome may be identified if the sample population had been larger. As children were not included, syndromes associated with SPSE in this age group such as Rasmussen’s encephalitis, complex slow waves during sleep and Landau Kleffner syndrome were not represented. Despite these caveats, there are three interesting points to note. First is that refractory status occurred in over half the cases. In patients with different types of status epilepticus, those with focal motor seizures are more likely to be refractory to treatment that those with generalized or complex partial seizures.17 The second is the significant proportion of cases who were treated over 30 minutes after the onset of seizures. This may be due to the fact that simple partial seizures appear less urgent and medical staff are more accustomed to recognizing the dramatic presentation of generalized tonic-clonic attacks. One patient with simple partial motor seizure affecting one arm was initially misdiagnosed as having a tremor. A third feature is the shortterm mortality rate of 22%. It is conventionally thought that partial SE is associated with a low death rate but our series show that this may not be the case. Over half the patients had focal convulsions due to acute symptomatic event such as cerebral infarct, haemorrhage and CNS infection. It is recognised that the response rate and outcome is determined by the underlying cause; the majority of deaths are due to overwhelming medical complications.18–20 Precisely why certain aetiolo-

Table 1 Comparison between patients with good versus poor outcome following simple partial status epilepticus

N Age Gender (female) Acute Symptomatic Aetiologyb Stroke CNS infection Cryptogenic Metabolic Tumour Delay in Treatment Refractory status Total hospital stay a b

Good

Poor

p value

13 44.2 ± 22.1 6 (46.2) 4 Number (%) 5 (33.3) 3 (60.0) 3 (75.0) 1 (25.0) 1 (25.0) 7 (53.8) 5 (38.5) 13.2 ± 8.5 days

19 54.0 ± 16.0 9 (47.4) 16 Number (%) 10 (66.6) 2 (40.0) 1 (25.0) 3 (75.0) 3 (75.0) 11 (57.9) 12 (63.2) 27.6 ± 22.5 days

ns ns <0.01 ns ns ns ns ns ns ns ns

a

a a a a

Fisher’s Exact Test. Percentage of patients in each category.

ª 2005 Elsevier Ltd. All rights reserved.

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gies such as stroke and trauma are associated with better response than anoxic or CNS infection is uncertain. In light of the potential severity of this condition and the propensity for developing refractory status, further larger scale studies are needed to provide more insight into this condition.

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