Seizures can be either simple or complex, and partial or general. Simple seizures do not cause alteration of consciousness, whereas complex seizures do. Partial seizures affect only one localized region of the brain, whereas general seizures arise from several brain regions. Because her seizures do not cause loss of awareness they are simple. Because her symptoms are stereotyped, with focal findings (expressive language difficulty), they are partial. Partial seizures (either simple or complex) can secondarily generalize, which occurs when epileptiform activity spreads beyond the onset zone to include other regions in both hemispheres. Note that these traditional terms for seizure classification are being replaced with a new terminology, as described below in Berg et al.
The rising epigastric sensation is typically attributed to onset in the insular region, and the expressive language dysfunction suggests dominant inferior frontal origin. Thus a parsimonious explanation for the combination of these symptoms localizes onset to the insular/opercular area in the dominant hemisphere.
The non-invasive workup (seizure semiology, MRI, MEG) has narrowed down the seizure onset zone to the left insula, operculum, and/or mesial frontal region. Functional MRI and Wada testing can help lateralize language function and (especially with Wada) memory function, but neither are useful for localizing seizures. A repeat SPECT is unlikely to help. Either craniotomy for grid implant or stereo-EEG implant can help localize seizures. In this case, given the deep structures (insula, mesial frontal region) that need to be sampled, many centers would prefer stereo-EEG over grids and strips, but that choice is specific to the center’s experience.
This lesion is in the dominant supplementary motor area (SMA), a region on the medial aspect of the frontal lobe just anterior to primary motor territory. SMA syndrome consists of contralateral weakness (usually thought of more as difficulty initiating movements than actual weakness) that is usually temporary (days to weeks). In the dominant hemisphere, patients can also evidence temporary mutism. Permanent weakness could occur after primary motor damage. Sensory deficits typically occur after primary sensory region damage. Expressive and receptive aphasia can occur after damage to the language regions in the dominant inferior frontal and superior temporal regions. Verbal memory deficit can occur after dominant mesial temporal damage.
- Berg, A. T., Berkovic, S. F., Brodie, M. J., Buchhalter, J., Cross, J. H., van Emde Boas, W., et al. (2010). Revised terminology and concepts for organization of seizures and epilepsies: report of the ILAE Commission on Classification and Terminology, 2005-2009. Epilepsia, 51(4), 676–685.
- Isnard et al., “Clinical manifestations of insular lobe seizures: a stereo-encephalography study.” Epilepsia 45(9): 1079-1090, 2004.
- Cohen-Gadol et al., “Partial epilepsy presenting as episodic dyspnea: a specific network involved in limbic seizure propagation.” J Neurosurg 100(3): 565-576, 2004.
- Potgieser, A. R. E., de Jong, B. M., Wagemakers, M., Hoving, E. W., & Groen, R. J. M. (2014). Insights from the supplementary motor area syndrome in balancing movement initiation and inhibition. Frontiers in Human Neuroscience, 8, 960.
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