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SUMMARY Introduction. The seizure propagation phenomenon by inducing remote symptoms brings several difficulties in finding the seizure onset and delineating the epileptic network which should be taken into consideration in epilepsy surgery. By demonstrating a difficult (MRI negative) epilepsy surgery case explored with invasive presurgical evaluation we highlight the importance to recognise the secondary sensory area and to explore the the parieto-opercular-insular-medial frontal network in certain cases. A further conclusion is the consideration of the redistributory role of the insula as a special structure in the cerebral connectome, having a role in epileptic network organisation. Aims. To support the role of the insula in the organisation of an opercular – medial frontal epileptic network and to confirm Penfield’s the “second somatic sensory leg area” by way of a case report. We try to give an up to date exploration of our patient’s remote epileptic seizures by way of a connectome. Methods. The epileptic disorder was studied with intensive video EEG monitoring and two times 3T MRI. Interictal FDG (fluorodeoxyglucose) PET was also undertaken. Beside the scalp EEG and computerized frequency analysis, the evaluation was performed by invasive EEG with 2 grids and 2 strips and an insular deep electrode in addition. Electrical cortical stimulation and cortical mapping were also undertaken. Results. The video-EEG study revealed the complex seizure semiology. The left sided global somatosesensory aura in the leg, followed supplementary motor area manifestations represented a remote seizure. The seizure onset zone and the symptomatogenic zone were localised by the invasive electrophysiology. With the insular deep electrode we succeeded to explore the propagation of ictal activity to the insula and later to frontal medial surface. The PET, the negative 3T MRI results and the postprocessing morphometry confirmed the lesional origin and localised the epileptogenic area to the second somato-sensory field where a dysgenesis was located. Conclusions. By preoperative invasive video-EEG evaluation, the second somato-sensory leg area was delineated as the seizure onset zone. The resection of this area by IIb type cortical dysgenesis, resulted in a complete relief of the seizures. The invasive video-EEG revealed the peculiar role of the insula in the propagation of the epileptic seizure from the second sensory leg area to the ipsilateral fronto-medial supplemetary motor area. Our results, confirm, that the insula has a relay or node function on the parietal opercular-fronto-medial epileptic network. The connectome of the insula is a further additive of the scale-free features of the remote epileptic networks.

The cortico-cortical connections of area 7b (or PF) in the parietal lobe of the monkey have been studied with the method of axoplasmic transport of horseradish peroxidase or with the method of axonal terminal degeneration. Area 7b is reciprocally and precisely connected with area 5, the second somatic sensory area (SII), area 23 of the cingulate cortex, the retroinsular area (Ri), the granular insular area (Ig), and with the cortex in the walls of the superior temporal sulcus.

Summary Single injections of tritiated amino acids into the first somatic sensory area (SI) of the rat neocortex result in axoplasmically transported labeling of the stratum griseum intermediale and stratum griseum profundum of the ipsilateral superior colliculus. The terminal labeling in these layers takes the form of multiple, column-like patches. The SI projection is somatotopically organized with the face and head representations projecting to an extensive anterolateral part of the colliculus and the limb representations projecting to a restricted posterolateral part. Injections of horseradish peroxidase into the superior colliculus result in retrograde labeling of corticotectal cells in the superficial part of layer VB of SI and of the second somatic sensory area (SII).

The second somatic sensory area (S II) was originally described on the basis of evoked potential mapping studies (1, 64, 65). This type of physiological study and the more detailed microelectrode mapping studies that followed have provided important data concerning the functional organization of this region of the cerebral cortex. Unfortunately these physiological data have not been correlated with connectional or cytoarchitectonic data. The need for such correlative information is suggested by studies such as that of Carreras and Anderson (7), whose division of the anterior ectosylvian gyrus in the cat into functional areas on the basis of the vascular pattern of the cortex is still widely quoted.

The study here reported was carried out more than 35 years ago, when the method of electrical stimulation of nerve fibers in the exposed spiral osseous lamina, first applied to the cat by Woolsey and Walzl (43, 44) was employed to define topological relations between the cochlea and the cortical auditory field in the monkey [Walzl and Woolsey (33); Woolsey and Walzl (45)]. Only a general diagram of the results has ever been published [Woolsey and Fairman (42); Walzl (32); Woolsey (37); Davis (11); Woolsey (41)]. The present account fully reports the data collected and undertakes to relate the findings to more detailed results now available on the cat [Woolsey (41); Reale and Imig (29)] and to other auditory studies on primates [Ades and Felder (1); McCulloch et al. (23); Licklider and Kryter (22); Pribram et al. (28); Kennedy (20); Woolsey (41); Neff (25); Bailey et al. (4); Brugge and Merzenich (7); Merzenich and Brugge (24); Imig et al. (19)]

Summary A detailed microelectrode mapping study of the second somatic sensory area (SII) in cats anesthetized with either sodium pentobarbital or nitrous oxide disclosed that: (1) The orientation of the body representation in SII is reversed in a mediolateral direction from the way it has been portrayed in the past. The limbs are directed laterally, not medially in the anterior ectosylvian gyrus. (2) Units in the somatotopically organized mechanoreceptive portion of SII do not commonly have bilateral receptive fields. This result is unaltered by the lightness or depth of anesthesia in the subject. It is suggested that the lack of bilateral representation in cat SII when compared with the predominance of bilaterally in monkey SII may represent a valid species difference. (3) The somatotopic organization of projections to the hand and digit areas of cat SII does not follow the body topography. Rather, the projections form strips or chains of receptive fields which are oriented near the transverse plane. Neighboring strips in the hand projection area may not be at all similar in their receptive field makeup. It is suggested that these strips are related to the receptive field pattern encountered as the dorsal rootlets enter the central nervous system.

Averaged cortical responses to labyrinthine stimulation induced by sudden cessation of single rotations were studied using a Mnemotron Computer of Average Transients. Following rotation there appeared in cats with the eyelids closed diffuse, slow, sometimes multiphasic responses. They were probably due to excitation of the diffuse thalamic system. In human subjects similar responses could be obtained either diffusely or prevalent or exclusively from the preoccipital and/or parastriate area. The responses observed in posterior parts of the cerebral hemisphere following cessation of rotation appeared also, if the animals were flaxedilized, or the second somatic sensory area was ablated in both hemispheres. Bilateral labyrinthectomy abolished these responses. While the observation of the ocular reactions to labyrinthine stimulation permits one to ascertain the excitability of the vestibulo-ocular reflex arc only, the recording of the cortical responses to rotation may perhaps be developed into a clinical too...