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 Table of Contents  
ORIGINAL ARTICLE
Year : 2018  |  Volume : 5  |  Issue : 4  |  Page : 111-116

Value of computed tomography scan in evaluation of adult onset seizures in north-central Nigeria


1 Department of Radiology, University of Abuja Teaching Hospital, Abuja, Nigeria
2 Department of Radiology, Faculty of Clinical Sciences, University of Uyo, Uyo, Nigeria

Date of Web Publication20-Sep-2019

Correspondence Address:
Dr. Itanyi Ukamaka D.
Department of Radiology, University of Abuja Teaching Hospital, Abuja
Nigeria
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DOI: 10.4103/ssajm.ssajm_11_18

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  Abstract 


Background: Seizure is a sudden onset of paroxysmal event from abnormal excessive neuronal activity in the brain. Computed tomography (CT) is a veritable tool for evaluation of seizures in view of the relationship between the age of onset, clinical presentation, and radiologic findings. Aim: This article highlights common brain computed tomographic findings among patients with adult-onset seizures in Abuja, Nigeria. Methods: This was a retrospective study of the imaging records of 115 patients referred to the Radiology Department of University of Abuja Teaching Hospital for brain CT on account of adult-onset seizures from January 2014 to June 2017. Results: The mean age of the 115 adult patients studied was 41.2 ± 19.4 years with male-to-female ratio of 1.1:1. Sixty-five (56.5%) patients were less than 40 years whereas 50 patients (43.5%) were above 40 years. Majority (56.5%) of the patients had abnormalities in their cranial CT with 50 cases (43.5%) reported as normal. Patients with abnormal CT scan findings were older (49.9 ± 20.4 years) than those with normal CT scan (29.9 ± 9.9 years) with a higher incidence of abnormal CT findings in males (63.95%). Abnormal CT scan was seen in 21 (32.3%) of cases in <40-year age group increasing to 44 (88.0%) in >40-year age group. The most common structural abnormalities were brain atrophy (13.9%), intracranial tumors (12.2%), and brain infarction (10.4%). Conclusion: A single institutional study in Abuja, Nigeria, showed a high frequency of structural abnormalities on brain-computed tomograms of patients with adult-onset seizures with a significant increase with age.

Keywords: Brain abnormalities, computed tomography, seizures


How to cite this article:
D. IU, U. UF, J. O. A. Value of computed tomography scan in evaluation of adult onset seizures in north-central Nigeria. Sub-Saharan Afr J Med 2018;5:111-6

How to cite this URL:
D. IU, U. UF, J. O. A. Value of computed tomography scan in evaluation of adult onset seizures in north-central Nigeria. Sub-Saharan Afr J Med [serial online] 2018 [cited 2019 Oct 16];5:111-6. Available from: http://www.ssajm.org/text.asp?2018/5/4/111/267122




  Introduction Top


Seizure is a heterogeneous and paroxysmal event due to abnormal excessive or synchronous neuronal activity in the brain characterized by sudden recurrent episodes of sensory disturbance, convulsions, and loss of consciousness.[1],[2] In the general population, one out of 20 people suffer seizures in a lifetime but this may increase to one in 11 if one lives up to 80 years.[1] A study done by Osuntokun et al.[3] put the overall prevalence of seizures in the Nigerian community as 5.3/1000 whereas Bouh et al.[4] in Ivory coast showed that they represent 8% of admissions to the intensive care unit.

Seizures can be categorized based on presentation and etiology.[1] In terms of presentation, it could be generalized or partial seizures. A generalized seizure involves all areas of the brain, including both hemispheres, whereas a partial (focal) seizure involves only one area of the brain.[1] Partial seizure is said to be simple or complex depending on the absence or presence of unconsciousness, respectively. On the basis of etiology, seizures could be primary or secondary. It is primary when it is idiopathic but a secondary (symptomatic) seizure occurs when there is a recognizable cause like head injury, brain tumor, infection, stroke, congenital abnormality, degenerative disorders, or other space-occupying lesions.[1],[2] It is pertinent that the possible etiology of adult-onset seizures should be ascertained in view of the different treatment options.

Seizures can also be acute or chronic. Acute seizures are caused by a recent or current event like head trauma, acute stroke, and status epilepticus whereas chronic seizures are caused by a remote abnormality such as an old stroke.[1] A provoked seizure can also be precipitated by other factors such as electrolyte imbalance and drugs.

Seizures are also categorized based on age of onset, and are thus categorized as childhood, juvenile, or adult (late)-onset seizures. Previous literature has shown an increasing incidence of abnormality with age in up to 3 to 41% of patients with first time seizure.[5] Seizures are usually a manifestation of an underlying pathology that requires thorough evaluation including a detailed medical history, physical examination, laboratory workup, and electroencephalographic and neuroimaging studies as dictated by clinical suspicion.[5] There is stigmatization of patients with seizures in a typical African setting hence the urgency in seeking medical advice even at the first episode.

A joint consensus statement from the American College of Emergency Physicians, the American Academy of Neurology, and others stated that immediate neuroimaging is indicated when a serious structural brain lesion is suspected in patients with partial-onset seizures as well as those who are older than 40 years.[1] Neuroimaging is also recommended for adults presenting with a first unprovoked seizure and for children with risk factors.[1] Neuroimaging along with computed tomography (CT) and magnetic resonance imaging (MRI) play a vital role in the management of adult-onset seizures because of the high possibility of detecting correctible abnormalities.[5] MRI is the imaging technique of choice in the investigation of patients with developmental disorders that constitute the most common underlying pathology in infants and young children with epilepsy.[6] It has the advantage of high soft tissue resolution, avoidance of harmful effect of ionizing radiation of tissues, and multiplanar capabilities. It is very sensitive in diagnosis of medial temporal sclerosis that is a common cause of epilepsy in adults. In neuroimaging armamentarium, CT is reserved for every adult after a first seizure, patients with increased risk of intracranial pathology like hemorrhages, infarctions, and lesions with associated calcification.[1],[7]

The International League against Epilepsy guidelines for neuroimaging studies suggest that a CT can be the diagnostic imaging of choice in patients with epilepsy if an MRI is not available.[6] CT has a greater advantage in acute emergency situations because of its speed of image acquisition and its ability to detect small foci of hemorrhage and calcifications. The relative availability and lower cost makes it the imaging modality of choice in a resource-constrained environment. CT is preferred in patients with ferromagnetic implants where MRI is contraindicated.

The diagnostic profile of patients with adult-onset seizures using CT has not been documented in north-central Nigeria and thus the need for this study. We sought to highlight the role of CT scan in the evaluation of patients with adult-onset seizures and to document the possible etiologic factors involved.


  Methods Top


Patients who were referred to the Radiology Department of University of Abuja Teaching Hospital for brain-computed tomographic scan on account of adult-onset seizures were recruited for this study. Their demographic data were extracted. Serial CT scan was done from the base of the skull to the vertex using 2–5-mm slice tissue thickness. Contrast examinations were additionally performed as indicated. CT images were evaluated by at least two radiologists with both agreeing on a diagnosis. Study period was from January 2014 to June 2017, and 115 patients were consecutively selected for this study.

Statistical methods

SAS software, version 9.3 (SAS Institute, Cary, NC, USA) was used for analysis. Graphical illustration was done with MS Excel. Numerical (mean, standard deviation, minimum, median, and maximum values for continuous variables; frequency and percentage for categorical variables) and graphical descriptors were used to summarize the data. Normality of the age variable was verified using Shapiro–Wilk test that revealed that the data was nonnormally distributed (P < 0.0001). Therefore, age differences between sexes and between normal and abnormal CT findings were compared with Mann–Whitney–Wilcoxon (MWW) two-sample test (nonparametric test), whereas differences in proportions of parameters were compared with either the Chi-square or the Fisher‘s exact test. In all statistical tests, significance level was set at an alpha level of 0.05.

Exclusion criteria included incomplete biodata, ambiguous diagnosis of seizures, previous history of head injury, and known intracranial neoplasm. Institutional consent was obtained from ethical and research committee.


  Results Top


A total number of 115 patients were studied and subjected to analysis. The proportions of male and female participants in the study were about the same with a male-to-female ratio of 1.1:1 [Table 1].There were 65 (56.5%) patients who were less than 40 years whereas 50 (43.5%) who were 40 years and older [Figure 1]. On the average, the male patients were older than the female patients; the mean age for females was 35.5 ± 16.2 years whereas the mean age for males was 46.3 ± 20.6 years [Table 1]. There was also a significant difference between the ages of patients who had normal and abnormal CT findings; on the average, patients with abnormal CT scan were older (49.9 ± 20.4 years) than those with normal CT scan (29.9 ± 9.9 years) [Table 1]. Females had 48.2% abnormal CT scan and males had 63.9% abnormal CT scan as seen in [Table 2]. The difference was not statistically significant (P = 0.0883). Abnormal CT scan was seen in 21 (32.3%) of cases in the <40-year age group whereas in the age group 40 years and older it was 44 (88.0%). The difference was statistically significant (P < 0.001). It was therefore observed that the older age group has higher tendency of CT abnormalities than the younger age group [Table 3]. Eighty-six patients (75% of the study population) did not have their seizure type specified. Out of the 115 patients, only 29 (men = 20, 69.0%; women = 9, 31.0%) had seizure types specified. Focal seizure was seen in 12 (41.4%) of the patients with specified seizure type whereas generalized seizure was seen in 17 (58.6%). Generally, 50 cases (43.5%) of the patients showed normal CT scan results whereas 65 cases (56.5%) showed abnormal CT scan results. Considering those with specified seizure type, nine cases (31.0%) of the patients showed normal CT scan results whereas 20 cases (69.0%) had abnormal CT findings [Table 4]. CT scan was abnormal in 66.7% of patients with focal seizure and 70.6% of patients with generalized seizure. The difference was not statistically significant (P = 0.568) [Table 4].
Table 1 Baseline characteristics for age and sex

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Figure 1 Distribution of participants by age group (original image).

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Table 2 Distribution of patients according to sex and CT scan findings

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Table 3 Distribution of patients according to age and findings in CT scan

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Table 4 Association between type of seizure and findings in CT scan

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Analysis of CT scan results showed that brain atrophy [Figure 2] was the most common abnormality seen (13.9%), followed by brain tumors [Figure 3] that was seen in 12.2% of the study population, and infarctions which constituted 10.4% of the cases [Table 5]. In patients <40 years, atrophic changes were the most common abnormal CT findings (8.7%), whereas in patients who were ≥40 years, tumors and infarctions (10.4% each) were the most common CT abnormalities seen [Table 6].
Figure 2 Axial contrast-enhanced image at the level of the lateral ventricles showing marked prominence of the cerebral sulci with dilatation of the lateral ventricle and periventricular blaire; features connoting cerebral atrophy in a patient with seizure disorder (original image).

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Figure 3 Axial contrast-enhanced image at the level of the anterior horn of the lateral ventricles showing an avidly enhancing dural-based mass extending medially into the right frontal lobe; features connoting meningioma in a patient with seizure disorder (original image).

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Table 5 Findings on CT scan among patients with abnormal CT scan results

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Table 6 CT scan findings by age among patients with abnormal CT scan results

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  Discussion Top


The three most common structural abnormalities found on brain-computed tomographic images of patients with adult-onset seizures in this study were brain atrophy (13.9%), intracranial tumor (12.2%), and brain infarction (10.4%). This is comparable to a study by Sinha et al.[8] However, a study in Western Nepal contrasted our study as neurocysticercosis (36.85%) was the most common abnormality detected on CT scan.[9] In general, structural abnormalities on brain CT were seen in 56.5% of our studied population. The closest to our study in terms of sample size and frequency of abnormality is the study by Rogel-Ortiz.[10] He prospectively studied 130 adult patients with adult-onset seizures and found structural brain lesions in 51% of the patients. Russo and Goldstein[11] also had similar observation wherein 46.7% of their studied population had structural brain abnormalities despite the fact that their study was limited to single episode seizure.

Epidemiologically, structural lesions in seizure disorder are likely to be different depending on the age at presentation.[12] In our study, abnormal CT scan was seen in 32.3% of patients below 40 years but as high as 88% of patients who were 40 years and above. This observed difference is statistically significant (P < 0.001). Another study showed specific intracranial lesions in 60.1% in patients less than 40 years whereas 62.3% of those older than 40 years had intracranial lesions diagnosed on CT.[9] The high incidence of abnormal CT findings with increasing age reported in most studies is because majority of the implicating brain lesions causing the seizures are age related.

In the index study, the order of occurrence of intracranial CT lesions were brain atrophy, encephalomalacia, and tumors in those less than 40 years, whereas in those above 40 years, tumors, infarction, and atrophy are the common findings. These concur with the observation of earlier researchers.[2],[13],[14],[15],[16]

Some intracranial tumors are known to be seizures-associated tumors such as gangliogliomas, dysembryo-plastic neuroepithelial tumors, pleomorphic xanthoastrocytomas, low-grade gliomas (oligodendrogliomas and astrocytomas), low-grade mixed glial tumors, and mixed glial-glioneuronal tumors.[5],[12] Histological evaluation of the tumors was however not done in our study. The proportions of male and female participants in the study were 53.0% and 47.0%, respectively, with the male patients being older than the female patients. It is possible that the earlier onset of adult-onset seizures among females may have been the consequences of previous events of hypertension, diabetes, preeclampsia, eclampsia, and cardiogenic and thrombotic conditions on the female brains encountered in previous pregnancies.[12]

Among the 29 (25.2%) cases of clinically specified seizures type in this study, focal seizure was seen in 12 (41.4%) whereas generalized seizure was seen in 17 (58.6%) cases. This is in agreement with other studies with similar high frequency of adult-onset generalized seizures.[7],[17] In our study, CT structural abnormalities were more in generalized seizures (70.6%) compared to 66.7% of patients with focal seizure. The difference was not statistically significant (P = 0.568). On the other hand, 75% of the studied population did not have their seizure type specified and this was worse with females (69%). This calls for more dedication on the part of the clinicians in history taking to achieve better seizure taxonomy, even if this information has to be extracted from a relation accompanying the patient to the hospital.

Normal brain CT scans were shown in 43.5% (n = 50) of our studied population. Out of this number, 88% (n = 44) were below 40 leaving 12% (n = 6) for patients above 40. It was observed by earlier authors that normal brain CT is seen in seizures caused by medical conditions like drug reaction, high fever, acute infectious diseases, dehydration, and acute metabolic disturbance.[18] These conditions cannot be diagnosed on CT, and they may be responsible for the observed normalcy in the index study. Also, CT is inferior to MRI in resolving and delineating the five epileptogenic unique anatomic substrates of focal seizures, namely hippocampal sclerosis, cortical dysplasia, intracranial neoplasm, vascular abnormalities (arteriovenous and cavernous malformations), gliosis, and other miscellaneous abnormalities.[19],[20],[21] In addition, CT alone may miss ischemic and other evolving lesions causing acute symptomatic seizures.[7] In view of these observations, the scenarios of normalcy as outlined in our study is of concern to us as it calls to question the utility of CT in evaluating seizures among patients less than 40 years of age. This is a major limitation of this study. The advocacy therefore is that patients with seizure disorder having normal brain CT findings should be made to benefit from MRI that has better soft tissue resolution.Another limitation may be that the age of onset may not necessarily coincide with the age of presentation at the clinic, as some patients may have been diagnosed a long time before presentation to the clinic. Some may have also had unrecognized seizures a long time before referral to the clinic. The above two scenarios translate to adventitiously ascribing childhood and juvenile-onset seizures to adult-onset seizures. It is also worthy to note that the observed structural abnormalities in this study may be coexistent conditions that have preceded, accompanied, or followed the diagnosis of seizures.[22]

Good clinical acumen is also mandatory to exclude pseudoseizures like transient alteration in consciousness, syncope, psychogenic nonepileptic seizures, and sleep-related phenomena.

The significance of this study is that it has highlighted treatable symptomatic seizures that were caused by infections, vascular lesions, and intracranial space-occupying lesions like tumors, hemorrhages, and encephalomalacia. It also further highlighted the utility of CT in the evaluation of such patients when MRI is not available as seen in many hospitals in Nigeria.


  Conclusion Top


In a single institutional study in Abuja, north-central Nigeria, the frequency of structural abnormalities on brain-computed tomograms of seizure patients is as high as 56.5%. More of these abnormalities are seen in male patients above 40 years and among patients with generalized seizures. The three most common noted structural abnormalities are brain atrophy, intracranial tumors, and brain infarctions. Majority of these structural abnormalities are amenable to treatment thus enhancing the role of CT in the management of patients with seizure disorders, particularly when MRI is not available.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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    Figures

  [Figure 1], [Figure 2], [Figure 3]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]



 

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