Lennox Gastaut Syndrome – A strategic shift in diagnosis over time?

Background: Lennox Gastaut Syndrome (LGS) is an epilepsy syndrome presenting in childhood, classically characterised by a triad of cognitive or developmental impairment, multiple seizure types and EEG features of slow-spike waves (SWW), with or without paroxysmal fast activity (PFA) in sleep. There is increasing scientific opinion in favour of a less rigid approach to LGS diagnosis and this clinical audit attempts to shed light on how the LGS diagnostic criteria used may have changed over time, in a large tertiary paediatric neurology unit (Great Ormond Street Hospital (GOSH), London, UK).

Methods: Electronic patient records were reviewed for patients with a diagnosis of LGS made at GOSH within two time periods, 2014-2017 and 2018-2021. Patient demographics, aetiology, clinical features, EEG features, investigation results and medications were reviewed. Findings were compared against the International League Against Epilepsy (ILAE) Diagnostic Manual criteria for LGS diagnosis (the classical triad plus PFA in sleep). Existing GOSH data regarding total number of new epilepsy referrals to GOSH and ICD10 codes (including all epilepsy and epilepsy syndromes) per year were also used to review LGS diagnoses as proportions of new epilepsy referrals and total number of epilepsy diagnoses.

Results: 5 LGS diagnoses were made in 2014-2017 compared to 40 diagnoses made in 2018-2021. There was a steep increase in the number of LGS diagnoses and LGS diagnoses as a proportion of total epilepsy diagnoses in the last 4 years, coinciding with the licensing of cannabidiol for management of LGS in the UK in 2018. There was a much less marked increase in LGS diagnoses as a proportion of epilepsy referrals from 2018 (and an as yet unexplained high proportion in 2014). The 2014-17 cohort fit a more classical LGS diagnostic criteria of the triad plus presence of PFA on sleep EEG (100% in 2014-17 vs 68% in 2018-21), with a more classical preceding history of infantile spasms (80% in 2014-17 vs 23% in 2018-21). Common seizure types were similar in both groups and a male preponderance was also noted in both groups. Cannabidiol use in LGS patients has also increased over time, all prescribed after 2018.

Conclusions: Despite the limitations of the small numbers of patients in each group, the results of this clinical audit are in keeping with changing clinical trends in favour of a broader LGS diagnostic criteria. The combination of this less rigid diagnostic criteria, the steep increase in diagnosis seen from 2018 onwards (coinciding with UK cannabidiol licencing for LGS in 2018) and the fact that most of the LGS patients in both groups are currently prescribed cannabidiol, may reflect a strategic shift in attitude towards LGS diagnosis or an increase in referrals for LGS, possibly to help facilitate access to novel treatments.