Role of Electroencephalography in Presurgical Evaluation of Temporal Lobe Epilepsy

Table 1

Clinical details of the illustrative cases.

Case	Figure	Age/sex/age at seizure onset	Seizure type	Interictal EEG (VEEG)	Ictal EEG (VEEG)	MRI brain	Neuropsychology	FDG-PET/; SPECT	Surgical procedure/; histopathology	Outcome (Engel score)	Comments
1	4	30/M/16	CPS with epigastric aura; Febrile seizures in childhood	Right anterior temporal IEDS,; moderate right temporal theta-delta; Right temporal TIRDA	Type I rhythm over right temporal/temporal-polar regions	Right MTS	Mild nonverbal dysfunction	None	Right TLY; Severe HS with a small area of cortical dysplasia in temporal neocortex	Grade I	Typical MTLE; Type I IEDs; Focal slowing; Type 1 ictal rhythm.; Associated cortical dysplasia with MTS [2, 3]
2	5, 6	60/M/41	CPS	Right temporal IEDS; Occasional right temporal theta	Type II ictal rhythm	Cavernous hemangioma in the right temporal neocortex	Normal	None	Limited corticectomy	Grade I	Late-onset epilepsy; Oligospikes; Type 2 ictal pattern
3	7, 8, 9, 10	27/F/16	CPS with unclear aura	Rare right anterior temporal IEDs; Mild right temporal theta	Right temporal type I ictal rhythm; Subdurals covering right temporal and the lesion; Spikes (often periodical) and slowing over temporal pole, HC, and PHC areas; Electrographic seizures over PHC area; Clinical seizures: ictal onset over anterior mesial temporal structures with rapid posterior temporal lesion area with a faster frequency	Right posterior temporal enhancing lesion (fusiform gyrus); Normal mesial temporal structures	Mild nonverbal dysfunction	PET—mild hypometabolism right mesial temporal structures	TLY with lesionectomy; DNET; Mild neuronal loss and abnormal neurons in the HC	Grade I	Oligospikes; Spikes and seizures are not always congruent; Dual pathology occurs.; Importance of dealing with both pathologies to achieve better seizure outcome [4, 5]
4	11	20/M/18	CPS	Occasional mild right temporal slowing; No spikes	Initially, no clear changes. Late right temporal theta delta lateralization	Right posterior temporal enhancing lesion (fusiform gyrus)	Very mild nonverbal dysfunction	SPECT (<4 seconds)—no areas of increased perfusion other than lesion	Lesionectomy; Pilocytic astrocytoma	Grade I	Late lateralization in temporal lobe epilepsy [6]
5	12, 13, 14	32/M/16	CPS, no clear aura; Febrile seizures in childhood	Essentially normal	Scalp: right temporal type I rhythm with onset of clinical semiology; Subdurals with bitemporal lines: left temporal ictal onset spreading to right temporal at onset of clinical semiology without involving the left neocortical temporal areas.	Severe left MTS	Moderate verbal dysfunction	None	Selective AH; Severe HS	Grade I	Seizure pattern spread and surface expression need inferior and lateral temporal cortex involvement for surface expression; Wasted hippocampal syndrome; Ictal SPECT of limited use here as seizures remained subclinical when localised to the left temporal lobe; In this case, interictal PET might be valuable if it shows left mesial temporal hypometabolism and normal right temporal metabolism
6	15	38/F/13	CPS	Bitemporal theta; Bilateral anterior temporal IEDS; (Right > left (70 : 30))	Left temporal type 2 rhythm; No right temporal seizure onset (16 seizures)	severe left MTS and subtle right HC signal changes	Moderately severe verbal and mild nonverbal dysfunction	PET—left temporal hypometabolism	Left temporal polar selective AH	Grade I	Bitemporal IEDs in TLE,; seizure onset zone, neuropsychology, MRI, and PET help ascertain degree of laterality and predict outcome
7	16	42/F/32	CPS with left upper limb paraesthesia at onset, hypersalivation, and hypomotor	Left temporal theta-delta; Left temporal-frontal IEDS	Type 1 left temporal rhythm after few seconds of attenuation	Left MTS, subtle signal changes in right HC	Moderate verbal > mild nonverbal dysfunction	PET—left mesial temporal and left insular hypometabolism	Medical management	None	EEG alone does not distinguish temporal from temporal plus epilepsies

CPS: complex partial seizures, IEDS: interictal epileptiform discharge, MTS: mesial temporal sclerosis, HC: hippocampus, PHC: parahippocampus, HS: hippocampal sclerosis, TLY: temporal lobectomy, AH: Amygdalo-hippocampectomy.