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EEG follow-up for epilepsy showed intermittent interictal discharges and photic responses elicited by intermittent photic stimulation at 1 Hz, 17 Hz, and 21.5 Hz, with typical driving at 9 and 15 Hz. Molecular testing identified a heteroplasmic m.3243A>G mutation (66%). The study highlights distinct PPR patterns across frequencies and discusses mechanisms linking mitochondrial dysfunction to seizure susceptibility.",{"@graph":69,"@context":122},[70,84,105],{"@type":71,"itemListElement":72},"BreadcrumbList",[73,77,79,82],{"item":74,"name":75,"@type":76,"position":8},"https://docshare.wps.com","Home","ListItem",{"item":78,"name":9,"@type":76,"position":14},"https://docshare.wps.com/document/",{"item":80,"name":35,"@type":76,"position":81},"https://docshare.wps.com/document/healthcare/",3,{"item":83,"name":65,"@type":76,"position":19},"https://docshare.wps.com/document/low-frequency-photoparoxysmal-responses-in-a-patient-with-melas/458518/",{"url":83,"name":65,"@type":85,"image":86,"author":91,"headline":65,"publisher":94,"fileFormat":97,"inLanguage":63,"description":67,"dateModified":98,"datePublished":99,"encodingFormat":97,"isAccessibleForFree":100,"interactionStatistic":101},"DigitalDocument",{"url":87,"@type":88,"width":89,"height":90},"https://docshare.wps.com/thumbnails/low-frequency-photoparoxysmal-responses-in-a-patient-with-melas/458518.png","ImageObject",300,407,{"name":92,"@type":93},"Cart","Person",{"url":74,"name":95,"@type":96},"DocShare","Organization","application/pdf","2026-11-07","2026-09-30",true,{"@type":102,"interactionType":103,"userInteractionCount":14},"InteractionCounter",{"@type":104},"ViewAction",{"@type":106,"mainEntity":107},"FAQPage",[108,114,118],{"name":109,"@type":110,"acceptedAnswer":111},"What is low-frequency photoparoxysmal response (PPR) and how is it defined?","Question",{"text":112,"@type":113},"Low-frequency PPR is PPR elicited by intermittent photic stimulation at less than 5 Hz. It is an epileptiform EEG phenomenon provoked by photic stimulation and may range from posteriorly dominant to generalized discharges.","Answer",{"name":115,"@type":110,"acceptedAnswer":116},"Which intermittent photic stimulation frequencies produced PPR in this MELAS patient?",{"text":117,"@type":113},"PPR and epileptiform responses were elicited at 1 Hz, 17 Hz, and 21.5 Hz, while typical photic driving responses were observed during intermittent photic stimulation at 9 Hz and 15 Hz.",{"name":119,"@type":110,"acceptedAnswer":120},"What genetic mutation was found in the patient?",{"text":121,"@type":113},"Molecular testing showed a heteroplasmic m.3243A>G mutation (66%) in the patient’s mitochondrial DNA extracted from peripheral blood leukocytes.","https://schema.org",{"og:url":83,"og:type":124,"og:title":65,"og:site_name":95,"og:description":67},"article",{"robots":126,"canonical":83},"index,follow",{"doc_id":128,"site_id":62},458518,1790753567,{"code":4,"msg":5,"data":131},{"doc_id":128,"user_id":132,"nickname":92,"user_avatar":133,"doc_module":4,"category_id":34,"category_name":35,"doc_title":65,"doc_description":67,"doc_content":134,"file_id":135,"file_url":136,"file_type":137,"file_size":138,"view_count":14,"is_deleted":4,"is_public":8,"is_downloadable":8,"audit_status":8,"page_count":81,"language":139,"language_code":63,"site_id":62,"html_lang":63,"table_of_contents":140,"faqs":141,"seo_title":142,"seo_description":67,"update_tm":129,"read_time":39,"preview_page_count":4},18829141979164,"https://eur-avatar.wpscdn.com/davatar_6f874abed73319feea01a86fa6f0fab8","Rev. Neurol. 2025; 80(12): 40724 [https://doi.org/10.31083/RN40724](https://doi.org/10.31083/RN40724)  \nCase Report  \nLow-Frequency Photoparoxysmal Responses in a Patient With MELAS  \nYung-Hsiu Lu 1 , Dau-Ming Niu 1 ,2, Wei-Sheng Lin 1 ,3 , *  \n1Department of Pediatrics, Taipei Veterans General Hospital, 11217 Taipei, Taiwan, ROC  \n2Institute of Clinical Medicine, National Yang Ming Chiao Tung University, 112304 Taipei, Taiwan, ROC  \n3 School of Medicine, National Yang Ming Chiao Tung University, 112304 Taipei, Taiwan, ROC  \n*[Correspondence:](Correspondence: wshenq@yahoo.com.tw)[ wshenq@yahoo.com.tw](Correspondence: wshenq@yahoo.com.tw) (Wei-Sheng Lin) Academic Editor: Jaume Sastre-Garriga  \nSubmitted: 10 May 2025 Revised: 14 August 2025 Accepted: 2 September 2025 Published: 25 December 2025  \nRespuestas Fotoparoxísticas de Baja Frecuencia en un Paciente con MELAS  \nA 16-year-old female received an electroencephalography (EEG) as a follow-up examination for her epilepsy. She has been diagnosed with mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS) at the age of 13, when she had suffered from recurrent stroke-like episodes involving right and left posterior quadrants of the cerebrum respectively during a 2-month period. Molecular testing revealed heteroplasmic (66%) m.3243A>G mutation in her mitochondrial genome extracted from peripheral blood leukocytes. The CARE checklist associated with this article can be found in the Supplementary Material.  \nShe has been treated with levetiracetam, Coenzyme Q10, carnitine, and arginine. Overt seizure occurred infrequently (~1/year) in the subsequent course. Routine EEG atthe last follow-up showed occasional interictal epileptiform discharges, which were similar to the findings in her previous EEG. Besides, epileptiform responses were elicited by intermittent photic stimulation (IPS) at 1 Hz (Fig. 1a), 17 Hz, and 21.5 Hz (Fig. 1c), while typical photic driving responses were seen during IPS 9 and 15 Hz (Fig. 1b) .  \nPhotoparoxysmal response (PPR), a well-established marker of photosensitivity, is defined as an epileptiform electroencephalographic phenomenon provoked by IPS, which could be limited to IPS train or self-sustained [1] . PPR comprises a continuum, ranging from posteriorly dominant to generalized discharges. Low-frequency PPR, defined as PPR elicited at \u003C5 Hz IPS, has been observed in several clinical entities belonging to the progressive myoclonus epilepsies category, including neuronal ceroid lipofuscinosis type 2 (CLN2), myoclonic epilepsy with ragged red fibers (MERRF), and Lafora disease. In addition, it has also been reported in adults with MELAS and CreutzfeldtJakob disease [2] . As a relatively uncommon electrophysiological phenomenon, low-frequency PPR may serve asa diagnostic clue in conjunction with the clinical contexts [3,4] .  \nThe standard method for determining EEG photosensitivity is IPS across different frequency ranges. The  \nfrequency-response curve and its underlying brain dynamics are apparently nonlinear [5], with a lower threshold for PPRs at both low and high-frequency IPS. The rarity of low-frequency PPR suggests that a more constrained electrophysiological milieu might be required for its generation. Indeed, past EEG in this patient already showed PPRs during conventional but not low-frequency IPS. Furthermore, our patient exhibited different patterns of PPRs to highfrequency (21.5 Hz) versus low-frequency (1 Hz) IPS. The former took the form of short-lasting (~1 second) 4–5 Hz bilateral asymmetric spike-wave discharges (Fig. 1c), which were more akin to her usual interictal epileptiform activities. In contrast, the low-frequency PPRs exhibited oneto-one correspondence and time-locked to visual flashes (Fig. 1a), which might suggest the possibility of giant visual evoked potential (VEP) . Nonetheless, the spike-and-wave morphology and the negative polarity of the main component ofthe discharges may help distinguish ","cbCaikWhFTc5X3FC","https://ap.wps.com/l/cbCaikWhFTc5X3FC","pdf",944932,"English","# Case Report\n## Patient history and genetic finding\n## EEG photosensitivity and photic stimulation findings\n## Definition and clinical significance of low-frequency PPR\n## Mechanistic discussion and patient education\n## Mitochondrial dysfunction and seizure susceptibility","[{\"question\":\"What is low-frequency photoparoxysmal response (PPR) and how is it defined?\",\"answer\":\"Low-frequency PPR is PPR elicited by intermittent photic stimulation at less than 5 Hz. It is an epileptiform EEG phenomenon provoked by photic stimulation and may range from posteriorly dominant to generalized discharges.\"},{\"question\":\"Which intermittent photic stimulation frequencies produced PPR in this MELAS patient?\",\"answer\":\"PPR and epileptiform responses were elicited at 1 Hz, 17 Hz, and 21.5 Hz, while typical photic driving responses were observed during intermittent photic stimulation at 9 Hz and 15 Hz.\"},{\"question\":\"What genetic mutation was found in the patient?\",\"answer\":\"Molecular testing showed a heteroplasmic m.3243A\\u003eG mutation (66%) in the patient’s mitochondrial DNA extracted from peripheral blood leukocytes.\"}]","Low-Frequency Photoparoxysmal Responses in a Patient With MELAS | PDF"]