Spared somatomotor and cognitive functions in a patient with a large porencephalic cyst revealed by fMRI

To date functional magnetic resonance imaging (fMRI) has not been extensively used in presurgical evaluation of patients with intractable epilepsy. Patient S.P. presented with left frontal originating seizures, secondary to a large porencephalic cyst that encompassed much of his occipital and temporal cortex and a substantial portion of ipsilateral parietal cortex. Nevertheless, S.P. did not demonstrate any gross impairments of praxis or speech. Scalp electroencephalogram (EEG) telemetry revealed reduced background activity in the left hemisphere, an absence of identifiable normal sleep states, and confirmed the left frontal origin of his seizures with a prolonged postictal state, suggesting that the remaining cortex in S.P.'s left hemisphere did not function normally despite his apparently normal appearance. Dichotic listening results also suggested that S.P. had an atypical language representation suggestive of either bilateral or right hemisphere speech representation. Surgical intervention to remove the remaining left hemisphere cortex was a serious consideration for treatment of S.P.'s seizures. We used fMRI to evaluate whether or not the remaining cortex in S.P.'s left hemisphere supported any cognitive or motor functions. Even though the volume of cerebral cortex was severely reduced and displaced in the left hemisphere, fMRI revealed significant activation in this remaining tissue in response to motor, somatosensory, and word generation tasks. In other words, we were able to demonstrate using fMRI that the remaining tissue in S.P.'s left hemisphere continued to support some motor and cognitive functions. The possible implications of these findings in terms of functional reorganisation are discussed briefly.