European Journal of Cardiovascular Medicine

Seizure disorder is the commonest neurological disorder in India1. Epilepsy is characterized by recurrent unprovoked seizures. The incidence of epilepsy is 24–53 per 1, 00,000 people in developed countries. There are few studies in developing countries, none of which are prospective: they show rates from 49.3 to 190 per 1, 00, 000 populations. The etiology of seizures is different in India and other developing countries as compared to the developed world2. Although, generalized tonic–clonic seizures occur uniformly throughout the life, partial seizures are common in very young and elderly people.

Computed tomography (CT) scan plays a very important role in radiological assessment of patients presenting with seizures3. CT helps in detecting structural abnormalities of the brain (calcifications, hemorrhage, cyst, and tumors), ventricular pathologies, infections, infarctions and lesions with underlying calcification4. The sensitivity of CT scan for detecting intracranial structural disease in epileptics is approximately 30-40%. There is probably an increased sensitivity in focal seizures5. CT of brain in children shows abnormal findings in up to 58%, which include infective

lesions, focal and vascular lesions6. Inspite of availability of Magnetic Resonance Imaging (MRI), CT scan is still crucial in emergency situations because of its relative easy availability.

Aims and Objectives

The objectives of this study are:

1. To describe the CT scan findings in patients with focal seizures.
2. To correlate the CT scan findings with probable etiology in these patients.

Source of data:

The study was conducted at Sri Balaji Medical College, Tirupati. The study was conducted over a period of 18 months from January 2024 to December 2024. An informed consent was taken from individuals for their willingness to participate in the study.

Inclusion Criteria:

All patients with clinically diagnosed focal seizures who had abnormalities on CT scan of brain.

Exclusion Criteria:

Altered renal function test (Serum creatinine > 1.4 mg/dL).

Pregnancy

Method of collection of data:

This study was approved by the institutional review board and informed consent was taken from all the individuals prior to inclusion in the study. All the patients underwent CT brain (plain ± contrast study) with SIEMENS® SOMATOM Emotion® CT 16-slice scanner. Contrast enhancement was obtained using nonioniccontrast agent Iopromide 300, at a dose of 50 ml in adults and 1.5 ml/kg body weight in children.

Examination technique:-

CT of brain was performed from orbito-meatal line upto vertex at 5mm interval in axial planes parallel to orbito-metal line. Post study reconstruction in axial plane was done at 1.2 mm section. Multiplanar sagittal and coronal reconstruction using standard algorithm was done as and when required.

CT parameters used were:-

·         Standard brain ( axial scan):

·         Adults:

·         Slice thickness                   -    5 mm

·         kV                                      -    130

·         mAs                                   -    270

·         Effective dose [mSv]         -    3.84

Baseline data were collected from patients along with pertinent clinical history. Any previous studies, if available was requested and reviewed.

CT diagnosis was confirmed by one or more of the following:

·         Response to treatment on follow up CT scan.

·         CSF analysis. 

·         Surgery and histopathological findings.

·         MRI / MR spectroscopy.

·         Typical findings such as metastases in patients known to have primary malignancy elsewhere in the body.

Note: patients with 1. Parenchymal calcifications with no enhancement / edema, 2. Post traumatic complications 3. Vascular malformations and 4. Hydrocephalus did not require further evaluation.

CT findings, clinical diagnosis and final diagnosis were recorded in the proforma. Results were analyzed to evaluate causes for focal seizures.

A total of 151 patients were clinically diagnosed with focal seizures and referred for CT brain to department of Radiology. Of these, 86 patients had no abnormality on CT scan and they were given symptomatic treatment. 65 patients had abnormalities on the CT scan requiring further evaluation – they were included in our study.

In our study of 65 patients, 30 patients were in the age group 0-20 years (46.1%). This was followed by 17 patients in the age group 21-40 years (26.1%), nine patients in the age groups 40-60 years and 9 patients were > 60 years (13.8%) 

Table1. Age distribution of Patients

Table 2.Gender distribution of Patients

Table 3.Types of seizures

Table 4. Lobe involvement

Table 5. Number of lesions

Table 6.Side of brain involved

Table 7. Location of lesion

Table 8:- Diagnosis

Patients presenting with focal seizures can have wide range of CT abnormalities depending upon the etiology. CT can reliably identify and localize the abnormalities so that further management can be planned accordingly. The aim of the study is to document the various abnormalities on CT scan and to study the causes of focal seizures.  151 patients who were clinically diagnosed with focal seizures were referred for CT brain to Department of Radiology. Of these 151 patients, 86 patients having no abnormality on CT did not require further imaging and they were treated symptomatically. A total of 65 (43.3%) patients with abnormalities on the CT scan were evaluated.

Our results are in agreement with data reported from other studies. In a study evaluating CT abnormality in 84 patients with focal seizures, abnormal findings were observed in 40 (47.65%) patients6. Another similar study in 26 patients reported abnormal finding in 13 (50 %) patients1. There is however, wide variability in incidence of abnormal CT findings in patients with focal seizures, with few studies reporting a lower incidence of about 35% 7, while other studies reported a higher incidence of abnormal findings of up to 64%62, 63.In our study, the incidence of focal seizures was maximum in age group between 1 to 20 years (n = 30cases; 46.1%). We also observed that incidence of focal seizures decreases with advancing age. Our results are in agreement with Singh A et al, who in their study of 446 patients with focal seizures found that about 47 % (n = 210)were in age group of 1 to 20 years. Additionally, they also reported a reduction in incidence of focal seizures with advancing age8.

In our study, incidence of focal seizures was higher among males (n = 37; 56.9%). Our results are in agreement with findings reported by Kafle DR et al who in their study of 70 patients with focal seizures also found a similar male predominance (n = 40; 57.1 %)9.

In our study, we observed that solitary lesions (n = 41; 63 %) are more common than multiple lesions. However in a study done by Garg R K et al in 101 patients, showed  that nearly half of the patients had  solitary lesions (n = 49; 48.5 %)10.Of 65 patients in our study, frontal lobe was the commonest location (n = 37; 43%) for the lesions. Similar finding was seen in study done by Pandey J et al, who observed that more than 31% were seen in the frontal lobe In our study, supratentorial lesions (n = 60; 93.7 %) were seen in more patients. Our results are in agreement with Jindal N et al. who in a study of 80 patients found 61(76.2%) patients with supratentorial lesions11.

In our study, diagnosis was confirmed by response to treatment / follow up CT scan in 36 patients, MRI in 10 patients, CSF analysis in 9 patients and histopathology in 5 patients.  In our study, we observed neurocysticercosis (NCC) to be the most common (n = 24; 36.9%) cause for focal seizures, followed by tuberculoma (n = 11; 17.3%). These two conditions accounted for more than half of all the cases. Other causes were parenchymal calcifications (n = 9), tumors (n = 9), infarct (n = 3), cystic lesions (n = 3), post trauma complications (chronic SDH and gliosis) (n = 2), vascular malformations (n = 2), hydrocephalus (n = 1) and cerebral abscess (n=1). Our results are in agreement with Yashodhara P et al who in a study of 40 cases found 24 (60%) had NCC, followed by tuberculoma 8(20%), neoplasms 5 (12.5%), and calcified granuloma, arachnoid cyst and brain abscess were found in one patient each (2.5%)

Neurocysticercosis (NCC)

Among patients with NCC, 16 had ring enhancing lesions with central scolex and moderate perilesional edema (colloidal vesicular stage), some patients with multiple lesions showed NCC of various stages (from vesicular stage to calcifiedstage). Del Brutto et al stated that ring enhancing lesion with scolex is the absolute diagnostic criterion for (NCC)12. This was seen in most of our cases.

In our study, NCC was the primary cause for focal seizures in 24 patients  (36.9 %).Our results are in agreement with Chandy M J et al who in a study of 30 patients and Garg R K et al who in a study of 151 patients, found NCC to be the most common etiology10.

In our current study of 24 patients with NCC, 14 (58.4%) showed single lesion and 10(41.6%) had multiple lesions. This was seen in other studies. In a study of 109 patients by Gauchan E et al13, 89 (81.6%) patients had single lesion and in a study of 51 patients by Bhattacharjee S et al 37 (71.1%) showed a single lesion14.

Tuberculoma

In our study, eleven patients (17%) were diagnosed as tuberculoma. The lesions were ill defined isodense or hypodense areas, showing irregular ring enhancement with surrounding edema. Welchman JM described CT appearance of 14 cases of tuberculoma as mass lesion which is isodense with the brain substance surrounded by intense ring on contrast enhancement.

Diagnosis of tuberculoma was based on CT appearances along with one or more supporting evidences such as meningeal enhancement, past history of TB, CSF analysis, chest X-ray and MRI.Out of eleven patients, four patients with neck stiffness showed leptomeningeal enhancement, four patients had past history of TB, five patients had elevated protein in CSF analysis and 2 patients were diagnosed by MRI (hypointense signal intensity on T2 weighted images and MRS showed increased lipid peak).Of 11 patients with tuberculoma, 4 patients showed leptomeningeal enhancement. Zhang SR et al in a study which included 14 cases of intracerebral tuberculoma, 9 cases had leptomeningeal enhancement 15.

In our study of 11 tuberculoma cases, 7 had solitary lesion and 4 had more than one lesions. In 8 of the patients the lesion / largest lesion measured 20 mm or more. All lesions showed irregular enhancement with extensive perilesional edema. Rajshekar et al showed that out of 31 ring enhancing lesions, 25 were cysticerci, and 6 tuberculomas all cysticercus granulomas were less than 20 mm in size in comparison to tuberculomas which were greater than 20 mm. Moreover, 5 out of 6 tuberculomas were irregular in outline 16.

In our study, all patients with tubercular lesions resolved following ATT. Our findings are similar to findings reported by Tandon PN et al who in a study of 50 patients with intracranial tuberculomas treated with ATT, found that most of the small and medium sized lesions had resolved completely.Zhang SR et al reported that majority of tuberculomas could decrease in size or get completely resolved with adequate antituberculous treatment15. Vengsarkar US et al opined that the advent of CT has greatly influenced the diagnosis and management of intracranial tuberculomas.

Parenchymal calcifications

In our study, nine patients (13.8 %) had parenchymal calcifications. The lesions were hyperdense with no surrounding edema or contrast enhancement.  Our results are in agreement with Bajaj S et al who in a study of 170 patients, found calcification in 18 (16.9%) patients17.

Primary tumors

There were three patients (4.6%) with tumors. All patients underwent subsequent MRI. All patients underwent surgery and the final diagnosis was pilocytic astrocytoma in two patients and medulloblastoma in the third. Of the two patients with pilocytic astrocytoma, one was located in midline in the posterior fossa and the other was suprasellar in location. Both patients had cystic masses with enhancing mural nodule.

The patient with medulloblastoma had a large, well defined, mass lesion in midline posterior fossa. The mass was heteogenous with multiple small cystic components. The lesion showed heterogeneous enhancement.  Minford AM et al, in a study of 82 patients with focal seizures, found that two patients (2.4%) had primary tumours. They concluded that a computed tomogram is indicated in every child with focal seizures18.

Metastasis

There were six patients (9.2%) with metastatic lesions. Our results are in agreement with Lavizzari SG et al who in a study of 193 cases, found 19 patients (9.8 %) with metastases19. Age of the patients in our study ranged from 40 to 65 years. Primary lesion was carcinoma breast in three patients, carcinoma lung in two and renal cell carcinoma in one. The lesions were hypodense with extensive vasogenic edema causing mass effect on surrounding structures. The lesions showed homogenous, heterogeneous or irregular ring enhancement.

Infarcts

In our study, three (4.6%) patients had infarcts. Of these, two patients had MCA territory infarcts. Third patient had venous infract in left fronto-parietal region with hemorrhagic transformation. Singh A et al in a study of 446 cases with focal seizures, found 29 (6.5%) cases with infarcts8 and Singh P et al in a study of 44 cases with focal seizures, found 6 (13.4 %) cases with infarcts21.

Vascular malformations

Vascular malformations were seen in two (3.0 %) patients - one patient had arterio-venous malformation in left parietal lobe and the other had developmental venous anomaly in left frontal lobe. Seollo-lavizzaribalmer C in a study carried out on 112 patients, found vascular abnormality in one patient (1.12%) 22 and Chee MW et al in a study of 80 patients found arteriovenous malformation (AVM) in three patients (3.75%) 23.

Abscess

Cerebral abscess was seen in one patient. The lesion appeared as a large hypodense lesion and showed peripheral ring enhancement with surrounding edema. On MRI the lesion was hypointense on T1and hyperintense on T2WI with restricteddiffusion. MRS showed increased lactate peak. In a study Rodriguez et al observed that incidence of brain abscess in patients with seizure was 3.24%24.

Post traumatic focal seizures

Two patients (3.0 %) had post traumatic focal seizures due to subdural hematoma and gliotic changes in one patient each. Hirani M in a study of 50 patients found 4 patients (4 %) had post traumatic seizures25.Vidwan S in a study of 23 patients with focal seizures found gliotic changes in one patient.

Cystic lesions

Three patients (4.6%) had cystic lesions which included epidermoid cyst, arachnoid and colloid cyst. Patel P J in a study of 115 patients found 11.3 % having specific abnormality, such as infarction and cystic lesions (arachnoid and porencephalic cysts) 26.

Hydrocephalus

One patient (1.5 %) had hydrocephalus. All ventricles (bilateral lateral, third and fourth) were dilated. No mass lesion was detected. Our results are in agreement with Kramer et al, Baheti et al and Singh P et al who in their study observed hydrocephalus in 1 (2.1%)76,1 (2.1%) 1 and 2 (4.54 %)74patients of focal seizures respectively.

Causes of focal seizures in developed vs developing countries

In our study, NCC has higher prevalence than tuberculoma (37% vs 17%). Similar findings have been reported elsewhere in India. Singh S et al in their evaluation of 44 cases with focal seizures, observed NCC in 7 patients (15.91%) patients and tuberculoma in 4 patients (9.1%) 27. Our results are different compared with few other studies. A study conducted in Western Rajasthan by Bahethi R et al reported cerebral atrophy as a cause for focal seizures in 23% of patients, followed by intraparenchymal calcifications (11%). They had a significantly lower proportion of patients with infectious causes such as NCC or tuberculoma1. Possible reasons for this difference could be cultural and socioeconomic differences between these regions, including eating habits.

Role of CT in focal seizures

Few studies have reported the importance of CT and MRI in focal seizures. International League against Epilepsy guidelines for neuroimaging studies recommend CT in patients with seizures, whenever magnetic resonance imaging is not available. It also recommends that patients who have intractable seizures have an MRI study if a CT is normal7. This suggests the role of CT as an initial investigation for evaluation of focal seizures.

Few studies have shown no significant difference in incidence of abnormal CT and MRI findings in patients with focal seizures (27.8 % vs 30.5 %). The authors concluded that sensitivity of CT was similar to MRI

In our study of 151 patients with focal seizures, CT scan was normal in 86 patients – they didn’t required any further imaging and were offered symptomology treatment. 65 patients had abnormalities on CT scan. Only 10 patients out of a total of 151 patients with focal seizures needed further imaging with MRI. This shows that CT scan is a reliable modality in evaluation of focal seizures.

NCC and tuberculoma were the commonest cause for focal seizures. CT helped in identifying the various stages of NCC. CT also helped in differentiating NCC from tuberculoma. Other etiological factors included parenchymal calcifications, metastasis, tumors, vascular malformations, abscess and infarcts.CECT helps in screening patients with focal seizures in order to identify patients with structural abnormalities. Majority of patients have classical findings on CT and undergo prompt treatment. A minority of patients may require further evaluation such as MRI, and CSF analysis.Given its easy availability and affordability, CT is the primary investigation in evaluation of focal seizures.

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