Clinical characteristics, seizure spread patterns and prognosis of seizures associated with a single small cerebral calcific CT lesion

Transcription

1 Seizure 1998; 7: Clinical characteristics, seizure spread patterns and prognosis of seizures associated with a single small cerebral calcific CT lesion J. M. K. MURTHY & V. SREENIVAS REDDY Department of Neurology, Nizams Institute of Medical Sciences, Hyderabad , India Correspondence to: Dr J. M. K. Murthy, Professor and Head, Department of Neurology, Nizam's Institute of Medical Sciences, Pnjagutta, Hyderabad , India Clinical characteristics of 97 patients with epilepsy associated with a small single cerebral calcific CT lesion (SSCCCTL), measuring 20 mm or less were analysed. The mean age was 20 years and 60% were in the first and second decades. Eighteen (18.5%) patients had a previous history of unprovoked seizures, with complex partial seizures (61%) being the most common type. Seizures could be localized to a single ILAE site in 73% of patients. None bad neurological deficit and electroencephalograph abnormalities were noted in 29% of patients. Fifty-one (53%) patients had breakthrough seizures and were more common with frontal location. By 7 years 71.5% (95% confidence intervals (CI) ) of patients achieved 3-year remission and 66% (CI ) had achieved 5-year remission. The clinical pattern of the seizures was clearly distinctive to allow it to be localized to the location of the lesion on computerized tomography (CT) scan in 25 (26%) patients and in another 31 (31%) patients nearer to the anatomical site of the lesion on the CT scan. There was discordance between clinical localization and CT location of the lesion in 15 patients. Nine of the l0 patients with occipital or parietooccipital location had focal tonic-clonic seizures with secondary generalization. Both patients with temporal location had motor seizures. The relevance of these findings to the seizure propagation was discussed. 4 Key words: small single cerebral calcific CT lesion, seizure spread. INTRODUCTION A single small cerebral calcific lesion measuring 20 mm or less, is one of the more common findings seen in CT brains of patients with epilepsy in the geographical areas where neurocysticercosis is endemic and forms one of the aetiological factors for symptomatic localization related epilepsy 1-6. This CT morphology represents the end stage in the natural history of parenchymal cysticercal cyst 5-9. There are no published reports on clinical characteristics and longterm prognosis of epilepsy associated with small single cerebral calcific CT lesions (SSCCCTL). The aim of the present study is to address this issue. MATERIAL AND METHODS The study material consisted of patients with a SSCC- CTL who had seizures as a presenting symptom. The SSCCCTL was defined as a single circular or oval calcific lesion measuring 20 mm or less without sur- rounding gliosis (Fig. 1). Patients were investigated for any other possible cause for epilepsy before they were included in the study. Information recorded from the case records included: date of first seizure, date of registration with the epilepsy clinic, date of index seizure, type of seizure I, localization of the seizure based on the seizure semiology II, electroencephalographic (EEG) abnormalities, family history of epilepsy, previous history of febrile convulsions and unprovoked seizures, neurological findings and treatment information prior to registration. The CT location of the lesion was also recorded. Follow-up information recorded included seizure recurrence and the possible factors and circumstances for recurrence, any change in medication and any new neurological or medical developments if any. The interval between discontinuation of antiepileptic drugs (AED) and relapse of seizures was also noted. All patients began monotherapy with unselected drugs at standard daily doses. Poor seizure control and/or relevant drug toxicity were required for dose / $12.00/0 ~ 1998 British Epilepsy Association

2 154 J.M.K. Murthy & V. Sreenivas Reddy Fig. 1: A single small calcific lesion. AGE DISTRIBUTION // >40 NO OF PATIENTS Fig. 2: Age distribution of patients with small single cerebral calcific CT lesion. adjustments or subsequent drug changes. Changes consisted of a switch to another monotherapy or addition of a second drug. Therapeutic drug monitoring was not routinely carried out. Remission was defined as a seizure-free period. Remission rates were calculated by actuarial analysis 12 with 95% confidence intervals (CI). The cumulative proportion of patients ever attaining a 3- or 5year remission was calculated from the index seizure as many patients were not on any AED medication before registration. The index seizure was defined as the seizure that caused the patient to register with the epilepsy clinic. Frequency of breakthrough seizures were also recorded in all patients. Break- through seizures were defined as seizures occurring after medication was prescribed but before attaining remission for those patients who were seizure free for a sufficient period 13. RESULTS Clinical f e a t u r e s There were 97 patients with SSCCCTL. Their mean age was 20 years (range years). The age distribution is shown in Fig. 2, with 58 (60%) patients in

3 Characteristics, spread patterns and prognosis of SSCCCTL 155 Table 1: Seizure type Simple partial 12 Complex partial 22 Complex partial with generalization 37 Generalized tonic-clonic seizures 26 Note: The majority of complex partial seizures began with motor symptoms. Table 2: Clinical localization of seizures by International League Against Epilepsy (ILAE) classification ILAE site Number (%) Primary motor cortex 51 (52.5) Supplementary motor cortex 7 Mesial temporal 4 (4.1) Parietal 3 Occipital 4 Cingulate 1 Frontopolar 1 Unlocalized 26 (26.8) the first and second decades. The male to female ratio was 1.7:1. Twenty-one patients (22%) presented with a single seizure, 25 (26%) had seizures in clusters at the time of presentation and 3 patients presented with status epilepticus. A previous history of unprovoked seizures was present in 18 (18.5%) patients and 10 (10%) of them had seizures in clusters. A history of seizure disorder in the family was present in 25 (26%) prebends and was present in first-degree relatives in 5. The most common type of seizure was complex partial seizures (61%) (Table 1). In 71 (73%) patients the clinical seizure pattern was sufficiently distinctive to allow it to be localized to a single ILAE site (Table 2). Table 3: Breakthrough seizures after starting antiepileptic drugs (AED) Number of seizures after AED l > 10 I. Number of seizures before AED I 1 > Clinical localization* Frontal (53) Posterior (7) I 2 1 Unlocalized (26) 8 I 2 * Reference 18. Table 4: Clinical location of the lesion in patients who had remote lesion on CT Clinical CT S number Age/sex localization localization 1 13/F Frontal Occipital 2 23/F Temporal Parietal 3 34/M Frontal Temporal 4 30/M Frontal Parieto-occipital 5 35/F Frontal Temporal 6 25/M Frontal Parieto-occipital? 14/F Frontal Occipital 8 20/M Temporal Parietal 9 8/F Frontal Parieto-occipital 10 I 0/M Temporal Parietal 11 48/F Frontal Occipital 12 15/M Frontal Occipital 13 29/M Parietal Occipital 14 50/M Frontal Occipital 15 20/M Frontal Parieto-occipital Note: Frontal means all the frontal lobe, including motor strip. EEG and neuroimaging findings Abnormalities in 28 (29%) patients were shown by EEG. Focal spike- or sharp-wave activity with or without secondary generalization was seen in 14 of these records, and of the remaining 14 patients focal slowing was seen in 12 and generalized slowing in two records. The location of the lesion on CT scan was on the fight side in 39 (40%) patients and on the left side in 58 (60%) patients. The parietal lobe was the site in 41 (42%) patients followed by the frontal lobe in 17 (18%) patients. Breakthrough seizures while receiving AED treatment Breakthrough seizures were seen in 51 (53%) patients. There was no correlation between the number of breakthrough seizures before complete control and the number of pretreatment seizures. Breakthrough seizures were more common in patients with clinical features suggestive of frontal-lobe origin (Table 3). Remission and relapses By 7 years, 71.5% (95% CI ) of patients had achieved a 3-year remission, and 66% (95% CI ) had achieved a 5-year remission. All four patients in whom seizure semiology was suggestive of temporal-lobe origin continued to have seizures. Antiepileptic drugs were withdrawn in 27 patients who had been seizure free for 2-5 years. Twentythree patients (85%) relapsed at an interval of 9-46 months. The mean duration of follow-up was 20.3 months (range months). The response to AED after relapse, however, was good, and these patients remained free of seizures for several months of further follow-up. Computerized tomography location of lesion and seizure localization The clinical pattern of seizures was clearly distinctive to allow it to be localized to the site of the lesion

4 156 J.M.K. Murthy & V. Sreenivas Reddy Table 5: CT scan location of the lesion in patients and clinical localization of the seizure---a comparison Clinical seizure CT location of the lesion location F P T O FP PO OT FT i. Limited to the site of lesion I 2. Nearer to the site of lesion Remote from site of lesion Unlocalized F, frontal; P, parietal; T, temporal; O, occipital; FP, frontoparietal: PO, parieto-occipital; OT, occipitotemporal; FT, frontotemporal. on the CT scan in 25 (26%) patients. In 31 (32%) patients the location of the CT lesion was nearer to the location of the anatomical site to which seizure semiology could be localized. In these 31 patients the location of the lesion was in the parietal lobe nearer to the motor strip and all of them had tonic--clonic seizures. In another 15 (15%) patients the location of the lesion on the CT scan was remote from the anatomical localization of seizures by clinical features. In the remaining 26 (27%) patients the seizure was unlocalized (Table 4). In 18 of them the lesion was located on CT in the frontal lobe or in the parietal lobe nearer to the motor strip. In the remaining eight patients the lesion was located in the occipital lobe. Of the 10 patients with occipital or parieto-occipital location 9 had focal tonic-clonic seizures with secondary generalization. Three patients with parietal location had clinical features suggestive of temporallobe epilepsy. Both of the patients with temporal location had focal tonic--clonic seizures with secondary generalization (Table 5). DISCUSSION A parenchymal cysticercal cyst in the brain passes through four stages in its natural evolution 7. The stages are vesicular, colloid, granulonodular and calcific. The majority of patients with parenchymal lesions become symptomatic during granulonodular and calcific stages 8"9. Seizure is the common mode of presentation during the calcific stage. Seizures associated with SSCCCTL can be of any type and neurological examination is often normal 14. This study showed that remission rates are similar to any remote symptomatic epilepsy 15. Other important clinical characteristics seen in these patients included a high incidence of breakthrough seizures before remission and a high rate of relapse following the withdrawal of antiepileptic medication. The size of the lesion in these patients was very small measuring between 5 and 20 mm, more often less than 10 mm. This is likely to allow precise localization of the seizure phenomenon by the onset and spread. Clinical features form the basis of localization in the ILAE classification 11. How- ever, in clinical practice, it is not always possible to localize to one anatomical site epilepsies which are localization related. In the National General Practice Study of Epilepsy only 24% of localization-related epilepsies could be clinically localized to a single ILAE proposed site of origin 16. Whereas seizure semiology often allows localization of seizures to one larger cerebral region Discordance between clinical localization based on seizure semiology and location of the lesion on neuroimaging is not an uncommon feature in patients with symptomatic localization-related epilepsies 16' t8 Of the 41 patients with parietal location of the lesion only three had a sensory onset. In 31 patients the lesion was nearer to the motor strip and in seven localization was not possible to one anatomical site. This discordance between clinical localization and location of the lesion on neuroimaging probably reflects the spread of seizure discharges. Earlier clinical studies stress that patients with seizures originating in the occipital lobe can present with confusing complex ictal patterns that can lead to localization errors ~9, 20. Ajmone-Marsan and Ralston 2 I stated that 'discharges arising from the visual region may possess the greater potentiality for complexity of seizure formation'. They predicted that seizures originating in the occipital lobe could spread anteriorly by several different pathways, above and below the sylvian fissure and medially or laterally. The clinical seizure manifestations would reflect these various spreads. A variable seizure spread pattern was demonstrated in patients with occipital-lobe epilepsy by intracranial recordings by Williamson et a122. An occipitotemporal spread was demonstrated in those patients who had automatisms typical of temporal-lobe seizures and suprasylvian spread was demonstrated in those patients who presented with tonic or clonic motor manifestations, or both. Studies on temporal and spatial characteristics of intracerebral seizure propagation during temporal-lobe epilepsy suggest that frontal regions are more frequently invaded 23. In the current study, frontal lesions demonstrated on imaging presented with generalized seizures, a feature well known to be associated more commonly with frontal than extrafrontal lesions 18, 24.

5 Characteristics, spread patterns and prognosis of SSCCCTL 157 REFERENCES I. Wadia, R.S., Makhale, C.N., Kelkar, A.B. and Grant, K.B. Focal epilepsy in India with special reference to lesions showing ring or disc like enhancement on contrast CT. Journal of Neurology, Neurosurge~. and Psychiat O, 1987; 50: Mishra, S., Verma, R., Lekhra, O.P. and Mishra, N.K. CT observations in partial seizures. Neurology India 1994; 42: Sotelo, J., Guerrero, V. and Rubin, F. Neurocysticercosis: a new classification based on active and inactive forms. Archives of Internal Medicine 1985; 145: Murthy, J.M.K. and Ravi, Y. The syndromic classification of International League Against Epilepsy: A hospital based study from South India. In: Progress h~ Neurology (Eds J.S. Chopra and I.M.S. Sawhney). New Delhi. Churchill Livingstone 1995: pp Del Brutto, O.H., Wadia, N.H., Dumas, M., Cruz, M., Tseng, S.W.V. and Schantz, P.M. Proposal of diagnostic criteria for human cysticercosis and neurocysticercosis. Journal of Neurological Science 1996; 142: de Bittencourt, P.R.M., Adamolekum, B., Bharucha, N. et al Epilepsy in the tropics: II Clinical presentations, pathophysiology, immunologic diagnosis, economics and therapy. (ILAE commission report). Epilepsia 1996; 37: Escobar, A. The pathology of neurocysticercosis. In: Cysticercosis of the Central Nervous System (Eds E. Palcios, I. Rodriguez-Carabajal and J. Taveras. Springfield, 1L, Charles C. Thomas, 1983: Locke, G.E., Byrd, S.E., Zant, J.D., Biggers, S.L. and Kramer, L.D. Seizures and cerebral cysticercosis in the United States. Epilepsia 1986; 27: Kramer, L.D., Locke, G.E., Byrd, S.E. and Daryabagi, J. Cerebral cysticercosis; Documentation of natural history with CT. Radiology 1989; 171: Commission on classification and terminology of the International League Against Epilepsy: Proposal for revised clinical and electroencephalographic classification of epileptic seizures. Epilepsia 1981; 22: Commission on Classification and Terminology of the International League Against Epilepsy. Proposal for revised classification of epilepsies and epileptic syndromes. Epilepsia 1989; 30: Kaplan, E.L. and Meier, P. Nonparametric estimation from incomplete observations. Journal of the American Statistical Association 1958; 53: I. 13. Camfield, C., Camfield, P., Gordon, K. and Dooley, J. Does the number of seizures before treatment influence ease of control or remission of childhood epilepsy? Not if the number is 10 or less. Neurology 1996; 46: Del Brutto, O.H., Santibanez, R., Noba, C.A., Aguirre, R. and. Diaz, F. Epilepsy due to neurocysticercosis: Analysis of 203 patients. Neurology 1992; 42: Cockerell, O.C., Anthony, L.J., Josemir, W.S., Hart, Y.M. and Shorvon, S.D. Remission of epilepsy results from the National General Practice Study of Epilepsy. Lancet 1995; 346: Manford, M., Hart, Y.M., Sander, J.W.A.S. and Shorvon, S.D. The National General Practice Study of Epilepsy: the syndrumic classification of the International League Against Epilepsy applied to epileptics in general population. Archives of Neurology 1992; 40: Loiseau, P., Duche, B. and Loiseau, J. Classification of epilepsies and epileptic syndromes in two different samples of patients. Epilepsia 1991 ; 32: Manford, M., Hart, Y.M., Sander, J.W.A.S. and Shorvon, S.D. National General Practice Study of Epilepsy (NGPSE): Partial seizures in a general population. Neurology 1992; 42: Russell, W.R. and Whitty, C.W.M. Studies in traumatic epilepsy 3--Visual fits. Journal of Neurology, Neurosurgery and Psychiatry 1955; 18: Takeda, A., Bancaud, J., Talairach, J. et al. Concerning epileptic attacks of occipital origin. Electroencephalography and Clinical Neurophysiology 1970; 28: Ajmone-Marsan, C. and Ralston, B.L. The Epileptic Seizure. Its Functional Morphology and Diagnostic Significance. Springfield, IL, Charles C. Thomas, Williamson, P.D., Thadani, V.M,, Darcey, T.M., Spencer, D.D., Spencer, S.S. and Mattson, R.H. Occipital lobe epilepsy: clinical characteristics, seizure spread patterns, and results of surgery. Annals of Neurology 1992; 31: Adam, C., Hilaiare, J.M.S. and Richer, F. Temporal and spatial characteristics of intracerebral seizure propagation: predictive value in surgery for temporal lobe epilepsy. Epilepsia 1994; 35: Ketz, E. Brain tumors and epilepsy. In: Handbook of Neurology vol 16 (Eds P. Vinken and G.W. Bruyn), Amsterdam, Elsevier, 1974: pp