Table 1.

Clinical features of all individuals with GABRG2 variants identified in this study.

	Patient 1	Patient 2	Patient 3	Patient 4	Patient 5	Patient 6	Patient 7	Patient 8
Variant	c.316G>A	c.316G>A	c.320T>C	c.844C>T	c.968G>A	c.968G>A	c.967C>T	c.1027 T>C
Origin	De novo	De novo	De novo	De novo	De novo	De novo	De novo	De novo
Protein change	p.A106T	p.A106T	p.I107T	p.P282S	p.R323Q	p.R323Q	p.R323W	p.F343L
Sex	Female	Male	Female	Female	Female	Female	Female	Female
Age at inclusion	7 years	9 years	3 years	10 years	4 years	3 2/12 years	9 years	6 years
Age at seizure onset	Day of life 1	3 months	1.5 months	1 year	10 months	1 year	11 months	1 year
Seizure type at onset	GTCS	Tonic	Tonic	Secondary generalized	FS, GTCS, myoclonic	FS, myoclonic	GTCS	Tonic
Seizure frequency at onset	Daily	Unknown	Daily	Unknown	Sporadic GTCS	Daily	Weekly	Daily
Further seizure types	Tonic, CPS	CPS, secondary generalized, atonic	Infantile spasms, tonic	Atypical absences	Myoclonic, absences, GTCS, CPS	Atonic, myoclonias during sleep, atypical absences, GTCS	Absences	None
AED responses	Seizure-free for 2 years on LEV	No clear response	No clear response	Slight improvement with LTG	No clear response	No clear response	VPA and TPM best combination	Some improvement on LEV
Seizure outcome	Seizure-free for 3 years (1 year seizure free off AED)	Remains intractable	Remains intractable	Remains intractable	Remains intractable	Remains intractable	Seizure-free for 3 years	Seizures Persist
EEG at onset	Normal	Normal	High voltage, slowing of background, sharp transients on the right side	Generalized and multifocal spikes	Normal	Generalized spikes, irregular spike-wave- complexes	Normal background, rare generalized spike waves	Excess diffuse beta and intermittent left temporal slowing.
Other EEG	No epileptiform activity seen	Diffuse xs beta, multifocal sharps	Background slowing, rare sharp transients right more than left	Generalized spike-wave nearly continuous	Generalized irregular spike wave	Generalized spikes, irregular spike-wave-complexes	Normal background frequencies, rare single generalized or hemispheric accentuated spike waves	poor organization, diffuse xs beta, frequent sharps maximal at the central vertex
Development	Severe global delay	Severe global delay	Severe global delay	Severe global delay	Severe global delay	Severe global delay	Severe global delay	Severe global delay
Language	Non-verbal	Non-verbal	Non-verbal	Non-verbal	Non-verbal	Non-verbal	Non-verbal	Non-verbal
Neurological exam	Hypotonia, nystagmus	Hypotonia, nystagmus, hyperkinetic movements with some choreoathetotic components	Hypotonia, nystagmus, hand stereotypies, choreoathetosis	Hypotonia, roving eye movements	Normal	Hypotonia, mild ataxia	Normal	Hypotonia, intermittent hand posturing
MRI findings	Delayed myelination	Volume loss	Normal	Normal	Normal	Normal	Normal	Falx hypoplasia

AED = antiepileptic drug; CPS = complex partial seizures; GTCS = generalized tonic-clonic seizures; FS = febrile seizures; LEV = levetiracetam; LTG = lamotrigine; TPM = topiramate; VPA = valproic acid; xs = excess.