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|Year : 2012 | Volume
| Issue : 5 | Page : 461-464
Paroxysmal occipital discharges suppressed by eye opening: Spectrum of clinical and imaging features at a tertiary care center in India
Bhavna Kaul, Garima Shukla, Vinay Goyal, Achal Srivastava, Madhuri Behari
Department of Neurology, All India Institute of Medical Sciences, New Delhi, India
|Date of Submission||16-Jun-2012|
|Date of Decision||01-Jul-2012|
|Date of Acceptance||19-Aug-2012|
|Date of Web Publication||03-Nov-2012|
Department of Neurology, Room No 2, 6th floor, Neurosciences Center, All India Institute of Medical Sciences, Ansari Nagar, New Delhi-110029
Source of Support: None, Conflict of Interest: None
Background: Paroxysmal occipital discharges (PODs) demonstrating the phenomena of fixation-off sensitivity have classically been described in childhood epilepsies with occipital paroxysms. Aim: We attempted to delineate the demographic, clinical and imaging characteristics of patients whose interictal electroencephalograms (EEGs) showed occipital discharges with fixation-off sensitivity at our center. Materials and Methods: During the period between 2003 and 2005, patients whose interictal EEGs showed PODs were included in the study. A detailed history, clinical examination and EEG findings along with imaging characteristics were analyzed. Results: Of the 9,104 interictal EEGs screened during the study period, 11 patients (6 females and 5 males) aged between 5 and 17 years were identified to have PODs with fixation-off sensitivity. Five had history of generalized tonic-clonic seizures. Three patients could be classified under Panayiotopoulos syndrome; the remaining 8 (72.2%) patients had symptomatic epilepsy. Conclusion: This study suggests that the phenomenon of fixation-off sensitivity is found not only in patients of idiopathic focal epilepsies, but also in a substantial number of patients of symptomatic epilepsy. The high proportion of symptomatic epilepsy with phenomenon of fixation-off sensitivity may be related to the referral pattern.
Keywords: Fixation-off sensitivity, occipital epilepsies, paroxysmal occipital discharges
|How to cite this article:|
Kaul B, Shukla G, Goyal V, Srivastava A, Behari M. Paroxysmal occipital discharges suppressed by eye opening: Spectrum of clinical and imaging features at a tertiary care center in India. Neurol India 2012;60:461-4
|How to cite this URL:|
Kaul B, Shukla G, Goyal V, Srivastava A, Behari M. Paroxysmal occipital discharges suppressed by eye opening: Spectrum of clinical and imaging features at a tertiary care center in India. Neurol India [serial online] 2012 [cited 2020 Jan 25];60:461-4. Available from: http://www.neurologyindia.com/text.asp?2012/60/5/461/103183
| » Introduction|| |
Paroxysmal occipital electroencephalographic (EEG) abnormalities, spikes, slow waves, sharp waves, are classically seen in idiopathic childhood epilepsies with occipital paroxysms (CEOP). Two distinct childhood epilepsy syndromes with CEOPs have been described: Panayiotopoulos type (early onset CEOP), which is common and benign and Gastaut type (late onset CEOP), which is rare and of uncertain prognosis. The term fixation-off sensitivity (FOS) was introduced by Panayiotopoulos to describe the forms of epilepsy, EEG changes, or both that are elicited by the elimination of central vision and fixation [total darkness, Ganzfeld stimulation, Frenzel glasses].  This phenomenon has been classically seen in the 2 childhood epilepsy syndromes mentioned above. This phenomenon also occurs in women of borderline intelligence with eyelid myoclonia, absence status epilepticus, and generalized tonic-clonic seizures. , The third group of patients in whom the phenomenon of FOS is observed are patients with idiopathic generalized epilepsy and photosensitivity. , FOS can also be seen in non-epileptic patients  We studied the clinical profile and the radiological features of consecutive patients who presented to our center with paroxysmal occipital discharges (PODs) demonstrating the phenomenon of fixation off sensitivity.
| » Materials and Methods|| |
Between January 2003 and December 2005, the interictal EEG records of all the patients recorded in the Electrophysiology Laboratory at our center were screened. A standard interictal EEG at our center consists of a 30-minute record including both awake and sleep states. Activation procedures are carried out in the form of photic stimulation and hyperventilation. Patients whose records showed PODs appearing on eye closure and suppressed by eye opening, the phenomenon of FOS, in the interictal EEGs were included for analysis. The EEGs were analyzed by 2 independent persons with experience in EEG reading and any discrepancy was resolved by discussion. During the second visit of the patient, (customarily 2 days following the EEG study, to collect the formal report), the history was reviewed for demographic features, duration since onset of seizures, number and frequency of seizures, semiology of seizure, history of migraine, febrile seizures or any other neurological illness, treatment history and detailed family history. Neurological examination was done for any focal neurological deficits. EEGs of patients were re-evaluated for any focal or generalized background abnormalities, focal spike, sharp wave or polyspike discharges over any region independent of occipital location, generalized (slow or >3 Hz spike and slow wave discharges) photo paroxysmal response or any other abnormality. Details of CT and MR imaging of all patients were recorded.
| » Results|| |
During the study period a total of 9,104 interictal EEGs, including 3,558 EEGs in children under the age of 12 years, were screened. Fifty-six patients were referred with a tentative diagnosis of occipital lobe seizures. Eleven patients (6 females, 5 males) were identified to show PODs in the form of spike and wave discharges and sharp and slow wave discharges suppressed by eye opening [Figure 1] and [Figure 2]. Age of the patients ranged between 5 and 17 years and seizure duration ranged between three months and five years.Four patients had poorly controlled seizures, with daily episodes in two patients. Seizure frequency was variable in the remaining seven patients. Five patients presented with a history of only generalized tonic clonicseizures;three patients could be classified as Panayiotopoulos syndrome, with history of infrequent episodes of behavioral abnormalities, vomiting and impairment of consciousness. These 3 patients had normal cognitive functions. None of the 11 patients had migraine or family history of migraine or febrile seizures. One patient gave a history of controlled complex partial seizures (CPS) in paternal uncle. Two patients had a history of birth asphyxia and delayed developmental milestones.All patients had received carbamazepine, whereas four patients with poorly controlled seizures had also received phenytoin sodium and valproate and were on multiple antiepileptic drugs at the time of their visit to our center.One patient had left hemiparesis since perinatal period, one patient had mild mental retardation, and the rest did not have any neurologic deficits. Visual fields, tested by confrontation perimetry, were normal in all the patients.EEGs showed right hemispheric slowing in 2 patients and in the rest of the patients background activity was normal. EEGs in all the patients showed PODs with phenomenon of FOS. Of the 11 patients, 8 (72.72%) had symptomatic focal epilepsy [Table 1].
|Figure 1: Surface EEG recording showing spike and wave discharges brought on by eye closure, demonstrating the phenomenon of fixation-off sensitivity|
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|Table 1: Demographic, clinical and imaging characteristics of patients included in the study|
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| » Discussion|| |
There have been few studies in the past, none from the Asian region, describing the profile of patients with CEOP on EEG. Fois and colleagues, in their study of children with PODs, commented that they found few patients with idiopathic epilepsy syndromes.  In the study by Martinovic, of the 25 patients with FOS on EEG, 9 (36%) patients had symptomatic epilepsy.  Talwar and colleagues studied 30 patients with occipital-posterotemporal paroxysms and found 7 (23.3%) patients with partial seizures in whom an etiology could be identified.  In the study of 31 children with CEOP and phenomenon of FOS by Maher and colleagues, only 6 (19%) children with the characteristic EEG had CEOP and as many as 16%had a symptomatic epilepsy.  They concluded that the pattern of occipital discharges suppressed by eye opening with a normal background was not diagnostic of idiopathic childhood epilepsy syndromes and could well be secondary to symptomatic epilepsies, a finding confirmed by this study. In the study by Koutroumanidis and colleagues, of the 19 patients showing the phenomena of FOS, 3 patients had symptomatic epilepsy.  Libenson et al. studied 90 patients with occipital epileptiform discharges, though not specifically FOS, and found 56% of patients with symptomatic epilepsies.  They did not, however, exclude patients with generalized spike and wave discharges and slowing. They too concluded that idiopathic childhood epilepsies are rare in patients with occipital epileptiform discharges. The phenomenon of FOS in symptomatic occipital epilepsies has been hypothesized to be related to local hyperexcitability, either due to anatomic/physiologic substrates (cortical dysplasia, calcifications of celiac disease) or to cortical de-afferentiation.  Denervation of a cortical area may result in increased instability of the neuronal membrane resulting in spontaneous discharges. Central vision may be an inhibitory input for these discharges.
In this study we observed PODs and phenomenon of FOS not only in patients with idiopathic focal epilepsies but also in symptomatic epilepsies. However, there are some limitations in the interpretation of these results. The small patient number limits the generalizability of these findings. Moreover, ours is a tertiary care center offering a comprehensive epilepsy surgery program. There may have therefore been a referral bias in favor of poorly controlled/symptomatic epilepsies. These findings are, however, in keeping with previously published observations from western countries.
| » References|| |
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|3.||Koutroumanidis M, Tsatsou K, Sanders S, Michael M, Tan SV, Agathonikou A, et al. Fixation-off sensitivity in epilepsies other than the idiopathic epilepsies of childhood with occipital paroxysms: A 12-year clinical-video-EEG study. Epileptic Disord 2009;11:20-36. |
|4.||Panayiotopoulos CP. A clinical guide to epileptic syndromes and their treatment. London: Springer; 2007. |
|5.||Krakow K, Baxendale SA, Maguire EA, Krishnamoorthy ES, Lemieux L, Scott CA, et al. Fixation-off sensitivity as a model of continuous epileptiform discharges: Electroencephalographic, neuropsychological and functional MRI findings. Epilepsy Res 2000;42:1-6. |
|6.||Fois A, Malandrini F, Tomaccini D. Clinical findings in children with occipital paroxysmal discharges. Epilepsia1988;29:620-3. |
|7.||Martinovic Z. Clinical correlations of electroencephalographic occipital epileptiform paroxysms in children Seizure 2001;10:379-81. |
|8.||Talwar D, Rask CA, Torres F. Clinical manifestations in children with occipital spike-wave paroxysms. Epilepsia 1992;33:667-74. |
|9.||Maher J, Ronen GM, Ogunyemi AO, Goulden KJ. Occipital paroxysmal discharges suppressed by eye opening: Variability in clinical and seizure manifestations in childhood. Epilepsia 1995;36:52-7. |
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[Figure 1], [Figure 2]