Sahel Medical Journal

ORIGINAL ARTICLE
Year
: 2015  |  Volume : 18  |  Issue : 2  |  Page : 78--82

Electroencephalographic findings in patients referred for electroencephalogram in a University Teaching Hospital in Northern Nigeria


Victor O Olisah1, Oluwatosin Adekeye1, Christopher I Okpataku1, Edwin E Eseigbe2,  
1 Department of Psychiatry, Ahmadu Bello University Teaching Hospital, Shika, Zaria, Kaduna State, Nigeria
2 Department of Paediatrics, Ahmadu Bello University Teaching Hospital, Shika, Zaria, Kaduna State, Nigeria

Correspondence Address:
Dr. Victor O Olisah
Department of Psychiatry, Ahmadu Bello University Teaching Hospital, Shika, Zaria, Kaduna State
Nigeria

Abstract

Background: Electroencephalogram (EEG) is a valuable investigation for the assessment of patients with seizures and some other neuropsychiatric disorders. The literature is scanty of reports describing its application and usefulness in Nigerian patients. In this study we analyzed the EEG records of a series of patients who were referred with various provisional diagnoses. Materials and Methods: EEG records of the entire 200 consecutive cases referred from various clinics within and outside a tertiary hospital in Northern Nigeria during a 1 year period were analyzed. Information on biodemographic data, clinical description of symptoms and provisional diagnosis made by referring physicians and the EEG diagnosis were obtained from the records. Results: Most of the attendees were aged between 10 years and 29 years (59.5%) and mostly males (63.5%). About 80% of the attendees had received a provisional diagnosis of seizure disorder (generalized and partial). The EEG diagnosis of seizure disorder accounted for 75%, normal EEG record accounted for 21% and organic brain disorder accounted for 4% of all EEG diagnosis. Generalized seizure disorder was the commonest seizure type by EEG diagnosis (50%). There was a significant association between the provisional diagnosis and EEG diagnosis (P < 0.05). Conclusion: Most of the patients referred for the EEG had their reports consistent with clinical suspicion. EEG was found to be a useful tool in the evaluation of seizures and organic brain disorder in our study.



How to cite this article:
Olisah VO, Adekeye O, Okpataku CI, Eseigbe EE. Electroencephalographic findings in patients referred for electroencephalogram in a University Teaching Hospital in Northern Nigeria.Sahel Med J 2015;18:78-82


How to cite this URL:
Olisah VO, Adekeye O, Okpataku CI, Eseigbe EE. Electroencephalographic findings in patients referred for electroencephalogram in a University Teaching Hospital in Northern Nigeria. Sahel Med J [serial online] 2015 [cited 2021 Dec 7 ];18:78-82
Available from: https://www.smjonline.org/text.asp?2015/18/2/78/160805


Full Text

 INTRODUCTION



An electroencephalogram (EEG) [1],[2],[3],[4] is a record of the electrical activity of the brain using an electronic device. A single interictal EEG often helps to classify epilepsy [5],[6],[7] and can provide support for a diagnosis of epilepsy when the clinical features are highly suggestive. However, EEG is rarely, if ever, the sole determinant of this diagnosis. [8] EEG can help to predict the risk of recurrence after a first seizure [9] and the risk of relapse after drug withdrawal. [10] It may also be recommended in other conditions such as headaches, head injuries, fainting spells, organic brain disorders [11] and psychiatric disorders. [11],[12],[13],[14],[15]

Several studies have shown that the commonest reason for EEG referral is to diagnose epilepsy. [11],[16],[17] A study in Kano, Northern Nigeria found that 92% of patients referred for EEG came with a clinical suspicion of seizure disorder. [16]

The EEG has a relatively low sensitivity in epilepsy. [7] In healthy adults with no declared history of seizures, the incidence of epileptiform discharge in routine EEG was 0.5%. [18] It is crucially important to recognize that normal phenomena, artifacts, and nonspecific abnormalities, occurring in about 20% of the general population, are open to misinterpretation and may yield false positive results. [19] This is especially true where EEG results are interpreted by technicians or physicians without adequate training.

The epidemiology of epilepsy in Nigeria did not differ much from other African countries. Osuntokun et al. reported a prevalence rate of 5.3/1000 among the inhabitants of a rural community, with the highest age-specific prevalence ratio occurring below the age of 20 years. [20] Most African studies reported a slight male excess. [21],[16] Simple partial seizures are less frequent than complex partial seizures in most series reported among Nigerian patients. [22],[23],[24] Generalized tonic-clonic (GTC) seizures constitute the largest subgroup of generalized epilepsies in Nigerian children. [16],[22],[24] It accounted for between 25% and 65% of the generalized epilepsies in several series published in Nigeria. [23],[24] Though, community based studies showed a higher prevalence of partial seizures over generalized, the latter is more prevalent in hospital admissions data. [16],[21]

Not much has been published on the use of EEG in routine clinical practice in Nigeria. Again, there is no operational guideline in Nigeria for making EEG requests and not many physicians are aware of the usefulness and limitations of EEG in the evaluation of neurological, medical, and psychiatric disorders. In this study, we analyzed the EEG records of a series of patients who were referred with various provisional diagnoses. Our objectives are to determine the various EEG diagnoses in our environment and assess the correlation between EEG diagnosis and clinical diagnosis. We also set out to observe the various sources of referrals for EEG.

 Materials and Methods



This is a descriptive, retrospective study of EEG records of the entire 200 consecutive attendees referred for EEG at a University Teaching Hospital in Northern Nigeria during the period between July 2012 and June 2013.

Information on biodemographic data, source of referral, clinical description of symptoms, provisional diagnosis made by referring physicians and the EEG diagnosis were obtained from the records. The Ethics and Research Committee of the University Teaching Hospital approved the study protocol.

Electroencephalogram requests are attended to daily at the unit by the EEG technician using a 32 channel phoenix digital EEG machine. The records along with technical reports are submitted to consultant psychiatrists' with special training in the techniques and interpretation of EEG for interpretation and diagnosis.

The data obtained was analyzed using the Statistical Package for Social Sciences (SPSS) version 17 (SPSS Inc., 2008). Percentages and charts were generated for relevant data, while the Chi-square test was used to test the significance of associations for categorical variables. All test of significance was carried out at 5% level of probability.

 RESULTS



Electroencephalogram records of the first 200 consecutive attendees referred for EEG at a University Teaching Hospital were studied. The biodemographic characteristics are shown in [Table 1]. Most of the participants were aged between 10 years and 29 years (59.5%) and mostly males 63.5%.{Table 1}

The sources of referral of attendees for EEG are shown in [Table 2]. The highest referral came from the general outpatient clinic (GOPC) 52%, followed by the department of psychiatry (28%).{Table 2}

The provisional diagnosis made by referring physicians is shown in [Figure 1]. A provisional diagnosis of seizure disorder (general, simple, and complex partial) was made among 79.5% of attendees and psychotic disorder was made in 10% of attendees. Organic brain disorder was the provisional diagnosis of 2.5% of attendees and 8% had other diagnosis.{Figure 1}

The EEG diagnosis based on the interpretation of the EEG records is shown in [Figure 2]. The majority (75%) were diagnosed with a seizure disorder. This was followed by attendees who had a normal EEG diagnosis constituting about 21% and organic brain disease accounting for 4%.{Figure 2}

Of all attendees with EEG diagnosis of seizure disorder, 50% had features of generalized seizure disorder, 7.1% had partial seizure disorder with secondary generalization, 35.7% had complex partial seizure disorder, and 7.2% had simple partial seizure disorder.

The congruency between provisional diagnosis made by referring physicians and the EEG diagnosis is illustrated in [Figure 3]. The bar chart indicates a strong association (X (1, N = 200) =195.945, P = 0.000) between provisional diagnosis and EEG diagnosis.{Figure 3}

 DISCUSSION



This study found that majority of the attendees for EEG is aged below 30 years and mostly males. This is not surprising since the commonest clinical indication for EEG is epilepsy and many studies have shown that the highest age-specific prevalence ratio occur below the age of 20 years. [16],[20] Most African studies have also reported a slight male excess. [16],[21] In most parts of Africa, males more readily come to the hospital for socioeconomic reasons and hence predominate in the hospital populations. This pattern holds true for Nigerians with epilepsy.

The sources of referral of attendees for EEG in this study showed that the highest referral came from the GOPC (52%) followed by the department of psychiatry (28%). The GOPC is the first point of call for all patients coming into the hospital except those on emergency. Patients are assessed, investigated and managed by specialist physicians in family medicine. Only patients requiring more specialized care are referred to the relevant specialist clinics. Since majority of patients pass through the GOPC and considering the specialized care at the clinic, it is expected that many referrals for investigations will come from that clinic. The department of psychiatry has the next highest number of EEG referrals in the study. This is likely due to several reasons. Firstly, the EEG unit of the hospital resides in the department of psychiatry and there is a lot of awareness about its usefulness. Secondly, a high proportion of patients with epilepsy especially those with complex partial seizures and other seizure types with prominent behavioral symptoms are referred to and managed in the department of psychiatry. Thirdly, a significant number of EEG request is to rule-out organic basis for psychosis and conversion seizures. The department also manages childhood conditions such as mental retardation and other childhood developmental disorders majority of which are associated with seizures.

The study found that the commonest reason for EEG referral is to diagnose or rule-out epilepsy as 79.5% of attendees were referred with a provisional diagnosis of seizure disorder. The next most important reason for EEG referral among attendees is to diagnose or rule-out organic basis for psychosis as 10% of EEG attendees are referred with provisional diagnosis of psychotic disorder. Another important reason for EEG referral is to help diagnose organic brain disorder (delirium, dementia, brain tumors, encephalopathies, etc.). This is in keeping with studies showing that the most frequent reasons for an EEG referrals is to help diagnose/classify epilepsy and less frequently to exclude a general medical condition, such as delirium as a cause of or a contributing factor to the presenting symptoms. [11],[16],[17]

The EEG diagnosis based on the interpretation of the EEG records showed that 75% of attendees received EEG diagnosis of seizure disorder. This implies that the EEG is a very important investigation in the evaluation and management of patients with seizure disorders. Organic brain disorder accounted for 4% of EEG diagnosis. This covers conditions suspected to be delirium, dementia, space occupying lesions in the brain, cerebral palsy, and other encephalopathies. It was interesting to find that 21% of EEG diagnosis was normal. Some of them must have been true negatives and others false negative. The implication of this finding is that EEG is an important test in the evaluation of patients with seizure disorders but may not be very reliable. Studies have shown that EEG has relatively low sensitivity even in seizure disorders. [7] Clinicians must continue to rely a great deal on clinical presentation. The study by Owolabi et al. found that 92% of patients referred for EEG was for seizure disorder but only about 58% had abnormal EEG findings. [16] This finding is in keeping with some other studies. [8],[9],[10],[11],[17]

The study showed that generalized seizure disorder was the commonest type of seizure disorder among attendees accounting for 50% of all EEG diagnosis of seizure disorders. This is in keeping with other studies that found that generalized seizure disorder is the most prevalent seizure type in hospital based studies as oppose to community based studies where complex partial seizure was found to be the most prevalent seizure type. [16],[21] A possible reason for this is because of the severe nature of the clinical presentation of generalized seizure disorder, more patients are likely to present to the hospital. Another reason is that studies have found generalized seizure disorder to be the commonest type in children [22],[24] and they accounted for a significant proportion of EEG attendees in this study.

The study found a congruency between provisional diagnosis made by referring physicians and the EEG diagnosis. There was a strong association between provisional diagnosis and EEG diagnosis especially for seizure disorder. This implies that EEG is a useful investigation in the evaluation of seizure disorders. The EEG was also found useful in the screening for an organic basis for psychosis and other organic brain disorders.

Even though no guideline is in use for EEG referrals in Nigeria, the congruency found in this study between EEG diagnosis and provisional diagnosis is an indication that regardless of the sources of referrals, the physicians are fairly aware of the usefulness of EEG in the evaluation and management of seizure disorders and some other neuropsychiatric disorders. However, the authors acknowledge that EEG services are limited in Nigeria and the available ones are probably under-utilized. For instance in Kaduna State, Northern Nigeria, there are only three hospitals where EEG can be done, two federal government owned and a private owned. These EEG units are staffed by nurse technicians and physicians who have undergone limited EEG training in the techniques and interpretation of EEG. Therefore there is considerable potential for misinterpretation of results.

There is need to put in place a guideline that will help increase awareness of the usefulness and the appropriate utilization of EEG services in Nigeria for the benefit of our patients.

Overall, this analysis of the first 200 consecutive attendees to the EEG unit of a University Teaching Hospital in Northern Nigeria did not differ significantly from the findings in other parts of the country; it highlighted the pattern of use and the usefulness of EEG services within the hospital.

The small number of patient EEG records used in this study may limit the strength of statistical analysis, making it difficult to generalize results. Another limitation of this study is its retrospective study design. Some of the EEG records had incomplete information about clinical signs, symptoms and provisional diagnosis made by referring physicians. Hence, there is a need for a further prospective study on the subject.

 ACKNOWLEDGMENT



We are grateful to the Psychiatric nurses/Technicians at the EEG Unit of the Department of Psychiatry, Ahmadu Bello University Teaching Hospital, Zaria for their help in data collection.

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