Table.

Clinical characteristics of patients with GABA_AR antibodies in serum and CSF samples

	Sex, age in years	Presentation and main symptoms	CSF	MRI	EEG e in CSF	History of autoimmunity or cancer	Treatment	Outcome	Sample: subunit target (a1/β3 titres)
Patients with high titres of serum GABAAR anti bodies and with antibodies detectable in CSF
1 (index patient 1)	F, 16	Memory, cognitive, and affective problems for several months. Developed headache and 9 days later tonic-clonic seizures progressing to status epilepticus	23 WBC/µL; protein 60 mg/dL	Multifocal increased T2/FLAIR signal with cortical-subcortical involvement	Generalised slowing, bilateral temporal seizures. Generalised periodic discharges	Hodgkin’s lymphoma 10 months before onset of encephalitis	Anticonvulsants: LEV, TPM, MDZ, barbiturate coma. Immunosuppressants: MTP, IVIG, PEX, RTX, CPH	Progressive neurological recovery after 12 weeks in hospital. At 15-month follow-up she had returned to school with mild cognitive deficit that is improving	Serum: α1, β3 (>1/1280) CSF: α1 (>1/320)
2 (index patient 2)	M, 51	Behavioural change, depression, psychosis, and mutism for several weeks. Developed partial clonic seizures and epilepsia partialis progressing in 48 h to status epilepticus	Normal WBC and protein concentration; OCB-positive	Multifocal increased T2/FLAIR signal with extensive cortical- subcortical involvement	Right temporal ictal activity, secondary generalisation. Generalised periodic discharges	Idiopathic thrombocytopenic purpura; TPO and thyroglobulin antibodies	Anticonvulsants: LEV, DZP, LCM, PHT, MDZ, PPF, barbiturate coma. Immunosuppressants: MTP, IVIG, PEX, CPH, RTX.	After 10 weeks, status epilepticus persisted and the patient died of sepsis	Serum: α1, β3 (1/1280) CSF: α1 (1/320)
3	M, 28	Subacute presentation of behavioural and cognitive deficits followed 5 days later by complex partial seizures and status epilepticus	Normal WBC and protein concentration	Bilateral mesiotemporal high T2/FLAIR signal	Ictal activity	TPO antibodies	Anticonvulsants: PPF, MDZ, LEV, PHT, TPM, CLB, barbiturate coma. Immunosuppressants: MTP with PDN taper.	After 8 weeks in the intensive care unit he gradually returned to baseline function. At last follow-up (18 months) he was seizure free and back to work	Serum: α1, β3 (1/640) CSF: α1, β3 (1/160)
4	M, 3	Acute development of confusion, lethargy, dystonic tongue movements, chorea of limbs and trunk, opsoclonus, ataxia, evolving in 24 h to complex partial seizures and status epilepticus	154 WBC/µL; protein 59 mg/dL	Multifocal high T2/ FLAIR signal in brainstem and cerebellum with involvement of basal ganglia and hippocampi	Generalised slowing and bioccipital ictal activity	GABABR antibodies in serum and CSF	Anticonvulsants: multiple, barbiturate coma. Decompressive posterior craniectomy due to cerebral oedema. Immunosuppressants: MTP, IVIG	After 4 weeks, status epilepticus persisted and the patient died of sepsis	Serum: NA CSF: α1, β3 (1/320)
5	M, 4	Progressive right hemiparesis; 2 months later, partial seizures progressing to status epilepticus	Increased WBC and protein concentration	Abnormal FLAIR changes suggesting encephalitis	Generalised slowing and ictal activity	No	Anticonvulsants: LEV. Immunosuppressants: No	Substantial recovery but, 2·5 years after symptom onset, still requires antiepileptics to prevent seizures.	Serum: α1 (1/320) CSF: α1/β3 (1/40)
6	M, 63	Subacute memory problems, gustatory and olfactory hallucinations, facial cramps, psychomotor agitation, tinnitus	75 WBC/µL; increased protein concentration; OCB-positive	Right temporal cortex high T2/ FLAIR signal	Frontotemporal ictal activity	GABABR, GAD65, TPO and thyroglobulin antibodies	Anticonvulsants: VPA, LEV, barbiturate. Immunosuppressants: PDN	Full recovery. 7 years later: diplopia and hemiataxia that spontaneously resolved (positive GAD65 but negative GABAAR and GABABR antibodies)	Serum: NA CSF: α1/β3 (1/20)
Patients with low titres of serum GABAAR antibodies and without antibodies detectable in CSF
7	M, 2	Subacute onset partial seizures; 4 months later, choreathetoid movements and status epilepticus.	Normal WBC and protein concentration	Cortical atrophy	Generalised slowing and right parietal ictal activity	No	Anticonvulsants: CBZ, VPA, MDZ, LEV, ketogenic diet, barbiturate coma. Immunosuppressants: MTP with PDN taper	Partial response, cognitive and motor skills improved. At last follow-up (2 years), partial seizures persist	Serum: β3 (1/160) CSF: negative
8	M, 41	Subacute onset generalised seizures with fever, epilepsia partialis continua, aphasia. 2 years later, status epilepticus	Normal WBC and protein concentration	Multifocal cortical- subcortical high T2/FLAIR signal in both hemispheres	Bifrontal ictal activity	GAD65 antibodies	Anticonvulsants: VPA, OXC, LEV. Immunosuppressants: MTP with PDN taper	Partial response at initial presentation. Status epilepticus responded to anticonvulsants	Serum: α1 (1/160) CSF: NA
9	F, 15	Reduced verbal output and seizures	8 WBC/µL; normal protein concentration	Bilateral fronto- temporal increased T2/FLAIR signal, leptomeningeal enhancement	Multifocal ictal activity	GAD65 antibodies	NA	NA	Serum: α1, β3 (1/160) CSF: NA
10	F, 32	Multifocal refractory seizures	Normal WBC and protein concentration	Normal	Bilateral temporal ictal activity and multifocal interictal epileptiform discharges	Type 1 diabetes mellitus, Hashimoto’s thyroiditis. GAD65, TPO and thyroglobulin antibodies	Anticonvulsants: OXC, CBZ, LCM, LEV, ZNS, TPM, CLB, PHT, LTG. Immunosuppressants: IVIG, PDN, ciclosporin	After 7 years she still has uncontrolled seizures	Serum: α1/β3 (1/40) CSF: NA
11	F, 74	Subacute onset of lethargy and alternating changes in level of consciousness. Suspected temporal lobe seizures	Normal WBC and protein concentration	Normal	NA	Previous history of ovarian cancer	NA	NA	Serum: α1/β3 (1/40) CSF: NA
12	F, 16	Behavioural changes, insomnia, orofacial dyskinesia, decreased level of consciousness, brief seizure, dysautonomia	17 WBC/µL; normal protein concentration	Left temporal cortical-subcortical high T2/FLAIR signal	Generalised Slowing	NMDAR antibodies in serum and CSF samples	Anticonvulsants: VPA Immunosuppressants: MTP, IVIG, PEX, RTX	Full recovery, gradual improvement over many months	Serum: α1/β3 (1/20) CSF: negative
13	M, 19	stiff-person syndrome since age 14 years	Normal WBC; protein 85 mg/dL	Not done	Not done	Type 1 diabetes mellitus. GAD65 antibodies	Clonazepam, baclofen. Immunosuppressants: No	Marked improvement. At last follow-up (16 years) he is independent for all daily life activities	Serum: α1/β3 (1/40) CSF: NA
14	M, 12	stiff-person syndrome since age 5 years; brief episodes of seizures	NA	Hippocampal high T2/FLAIR signal	Right temporal seizures, bifrontal sharp waves	GAD65 antibodies	Anticonvulsants: LEV. Immunosuppressants: IVIG, RTX	Partial improvement of stiff-person symptoms, free of seizures	Serum: α1/β3 (1/20) CSF: NA
15	M, 21	stiff-person syndrome since age 16 years	Normal WBC and protein concentration	Normal	Normal	Antinuclear antibodies; anti-endomysial immunoglobulin A	Anticonvulsants: CBZ, OXC. Immunosuppressants: IVIG	Partial improvement	Serum: α1/β3 (1/20) CSF: NA
16	M, 46	Stiff -limb syndrome	Not done	Not done	Not done	No	Baclofen Immunosuppressants: No	Substantial improvement	Serum: α1/β3 (1/20) CSF: NA
17	F, 34	Opsoclonus-myoclonus syndrome	NA	Normal	Not done	No	NA	NA	Serum: α1/β3 (1/40) CSF: NA
18	M, 65	Opsoclonus-myoclonus syndrome	Normal WBC and protein concentration	Normal	Not done	Antinuclear antibodies	Immunosuppressants: MTP	No response, died few months after onset	Serum: α1/β3 (1/20) CSF: negative

CBZ=carbamazepine. CLB=clobazam. CPH=cyclophosphamide. DZP=diazepam. F=female. GABAR=gamma-aminobutyric acid receptor. GAD65=glutamic acid decarboxylase 65. IVIG=intravenous immunoglobulin. LCM=lacosamide. LEV=levetiracetam. LTG=lamotrigine. M=male. MDZ=midazolam. MTP=intravenous methylprednisolone. NA=not available. NMDAR=N-methyl-D-aspartate receptor. OCB=oligoclonal bands. OXC=oxcarbazepine. PDN=oral prednisone. PEX=plasma exchange. PHT=phenytoin. PPF=propofol. RTX=rituximab. TPM=topiramate. TPO=thyroid peroxidase. VPA=valproate. WBC=white blood cell count. ZNS=zonisamide.