Are Sub‐Saharan epileptic people less photosensitive? A Senegalese study of photoparoxysmal response in a reference epilepsy centre^*

Abstract

The photoparoxysmal response (PPR) is defined as the occurrence of generalized spike, spike-wave or polyspike-wave discharges consistently elicited by intermittent photic stimulation (IPS). PPR is not well studied in Sub-Saharan African people. We prospectively studied the epidemiological, clinical, and EEG characteristics of PPR among consecutive patients recorded at the clinical neurophysiology unit of Fann University Hospital (Dakar, Senegal). Methods. Among 6,808 EEG recordings including 3,065 pathological EEGs, we collected 56 EEGs with PPR (0.8% of all recorded EEGs and 1.8% of anormal EEGs), from 31 women and 25 men (sex ratio: 0.8). The mean age was 13.3 years (range: 8 months to 59 years). Results. The peak of photosensitivity was found in the range of 6 to 10 years. Of the PPR cases, 12 had clinical manifestations during IPS. Generalized epilepsy was diagnosed in 23 (41%) patients and 18 (32%) had focal epilepsies. The most epileptogenic stimulation frequencies were between 12 and 24 Hz (range: 1-28 Hz). PPR were mainly triggered during eye closure (64%), and 41 patients (73% of PPR cases) were classified as Type 4 (Waltz classification). Conclusions. Our results confirm lower rates of photosensitivity in African Sub-Saharan people compared with others. Although the current data do not support a role of short-term ambient light levels, subject to consistent data from larger cohorts, it may be interesting to study the probable epigenetic-mediated protective role of sunshine against photosensitivity.

Visually sensitive seizures: An updated review by the Epilepsy Foundation

“…Studies of ethnic origin and photosensitivity have not been conclusive, but several studies suggest a lower prevalence in Black Sub-Saharan Africans compared with their White counterparts. 113 Prevalence PPR studies documented the highest values in adolescents. 125 A very recent study evaluating PPR prevalence based on a scored database of 10,671 EEG studies confirmed this prevalence.…”

“…123 Black Africans are less likely than Caucasians to have visually sensitive seizures. 113 The prognosis of visually sensitive seizures is fair but not great, with a 14%-37% probability of remission. Photosensitivity results from both genetic and environmental factors, but genetics are especially important.…”

“…106 Many types of seizures can be provoked by visual stimuli, including most commonly tonic-clonic seizures in about 80% 9 and the remainder with lower prevalence, including absence seizures, 107 tonic seizures, focal seizures from the temporal lobe, 108 myoclonic absence seizures in patients with Dravet syndrome, 109 myoclonic seizures, 110 and idiopathic photosensitive occipital lobe epilepsy (IPOE). [111][112][113][114] Photic-induced myoclonic seizures may be underrepresented in epidemiological studies, since some people seek medical attention only after having a tonicclonic seizure. IPOE 111,112 is on a continuum between focal and generalized seizures and may present with photosensitive absence, myoclonic or tonic-clonic seizures.…”

“…In Great Britain, the annual incidence of first seizures precipitated by videogames has been estimated at 1.5 per 100,000 among those 7‐ to 19‐year‐olds 123 . Black Africans are less likely than Caucasians to have visually sensitive seizures 113 . The prognosis of visually sensitive seizures is fair but not great, with a 14%‐37% probability of remission.…”

“…It used to be said 10 that Europeans commonly had their first seizure in front of a TV, although this is unlikely to still be the case now that digital screens have replaced cathode ray tubes that refreshed at 50 Hz. Studies of ethnic origin and photosensitivity have not been conclusive, but several studies suggest a lower prevalence in Black Sub‐Saharan Africans compared with their White counterparts 113 …”