Optimizing the Detection of Subtle Insular Lesions on MRI When Insular Epilepsy Is Suspected

J. Blustajn; S. Krystal; D. Taussig; S. Ferrand-Sorbets; G. Dorfmüller; M. Fohlen

doi:10.3174/ajnr.A6143

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Fig 1.
3D-T1-weighted sequence with MPR processing showing the common gyral pattern of the insula: reference view to analyze the insula. A, T1WI oblique sagittal view, parallel to the base of the insula, anterior lobule. ASG indicates anterior short gyrus; MSG, middle short gyrus; PSG, posterior short gyrus. Posterior lobule: ALG indicates anterior long gyrus; PLG, posterior long gyrus, which appears classically shorter than the ALG. B, T1WI axial view shows the oblique cut plane parallel to the base of the insula. C, T1WI coronal view shows the oblique cut plane parallel to the base of the insula.
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Fig 2.
T1WI sagittal view representation of the peri-insular sulci. A, Superior peri-insular sulcus. B, Inferior peri-insular sulcus. C, Anterior peri-insular sulcus.
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Fig 3.
Patient 1. Isolated insular lesion. Oblique sagittal view parallel to the base of the insula. A, T1WI oblique sagittal view shows an unusual gyral pattern of the posterior lobule of the right insula, which shows 3 gyri (arrow). B, T1WI oblique sagittal view shows a normal gyral pattern of the contralateral insula. C, T2WI oblique sagittal view shows blurring of the most anterior long gyrus of the right insula (arrow). D, T2WI oblique sagittal view shows no blurring of the contralateral insula. E, T2WI oblique sagittal view with SEEG electrodes (ictal onset zone around electrode OP). OM, OP, IP, TP, and TS indicate the names of depth electrodes. F, FLAIR sagittal view of the right insula after an operation.
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Fig 4.
Patient 3. Insular lesion extending into the peri-insular sulcus. A, T1WI oblique sagittal view, parallel to the base of the insula, shows hypoplasia of the posterior insular lobule. B, T2WI coronal view perpendicular to the inferior peri-insular sulcus shows blurring of the posterior portion of the right inferior peri-insular sulcus (arrow). C, T2WI sagittal view shows the cut plane perpendicular to the posterior portion of the inferior peri-insular sulcus, used to obtain the coronal view in B. D, T2WI sagittal view with SEEG electrodes (ictal onset zone around OP, IP, TP, and TS, representing the depth electrodes). E, T2WI sagittal view after surgical resection of the posterior lobule of the insula and the superior temporal gyrus.

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Table 1:

Clinical data

Patient	Sex	Age at Seizure Onset (yr)	Neurologic Status before Surgery	Age at Last Surgery (yr)	Topography of Resective Surgery	Postsurgical Deficit	Pathology	FU Duration (yr)	Engel^{^a}
1	M	2.5	LH, Special education	13.0	Posterior Ins and posterior Op	0	FCD IIa	4.2	I
2	M	3.2	RH, MoMR	6.2	Anterior Ins and Op, + frontal Disc	Left facial paresis	FCD Ib	4.2	I
3	F	3.5	RH, Normal cognitive function	14.7	Posterior Ins and STG	0	Negative	2.4	I
4	F	0.8	RH, MoMR	3.0	Anterior Ins+ frontal Disc	0	FCD IIa	2.3	III
5	M	0.4	Left hemiparesis SMR, ASD	6.1	Anterior Ins+ frontal Disc	0	FCD IIa	0.9	I
6	F	2.0	LH, MiMR	7.6	Posterior Ins and parietal Op, temporal Op	0	FCD IIb	3.0	III
7	M	1.0	LH, MoMR, ASD	9.7	Anterior Ins and Inferior Frontal	0	FCD IIb	1.8	II

Note:—LH indicates left-handed; RH, right-handed; MiMR, mild mental retardation; MoMR, moderate mental retardation; SMR, severe mental retardation; ASD, autism spectrum disorder; Op, operculum; Ins, insula; STG, superior temporal gyrus; Disc, disconnection; FU, follow-up; yr, year.
↵a Engel Surgical Outcome Scale.

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Table 2:

Review of presurgical MRIs in patients with intractable insular epilepsy with no initial detection of insular lesions

Patient No.	Side	Insula		Peri-Insular Sulcus		Surrounding Structures
Patient No.	Side	Gyral Pattern	Blurring	Sulcal Form	Blurring	Gyral Pattern	Blurring
1	R	Supernumerary ALG	+	–	–	–	–
2	R	Poorly defined AL	+	Irregular anterior portion of SPS	Anterior SPS	–	Frontal opercula, orbitofrontal
3	R	Hypoplasia PL	−	–	Posterior IPS	Hypoplasia STG	STG, HG
4	R	Irregular AL	+	Irregular anterior portion of SPS	Anterior SPS	–	–
5	R	Irregular AL	+	–	APS	–	Frontal opercula, orbitofrontal
6	L	Thick PL	+	–	Posterior IPS	–	HG, temporal stem
7	L	Poorly defined AL	+	Poorly defined APS	APS	–	Pars orbitalis

Note:—ALG indicates the anterior long gyrus; R, right; L, left; SPS, superior peri-insular sulcus; PL, posterior lobule; IPS, inferior peri-insular sulcus; STG, superior temporal gyrus; HG, Heschl gyrus; AL, anterior lobule; APS, anterior peri-insular sulcus; –, normal; +, present; −, absent.