Left Temporal Lobectomy Using Functional MRI in a Math Genius: A Case Report
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.279704
Source of Support: None, Conflict of Interest: None
Keywords: Cognition, functional MRI, mesial temporal sclerosis, Wada testingKey Messages: Left-sided Anterior temporal lobectomy (ATL) makes a patient at risk for language and verbal memory deficits. The functional magnetic resonance imaging helps to predict the localization of these functions and can make safe ATL possible.
Left temporal lobe epilepsy (TLE) may be associated with verbal memory, calculations, and language deficits. Anterior temporal lobectomy with amygdalohippocampectomy (ATL) is a highly effective treatment for alleviating epilepsy in these patients;, however, it can be associated with verbal and cognitive deficits in 30–50% of the patients. Selective amygdalohippocampectomy (SAH), and even minimally invasive treatments such as radiofrequency thermoablation, laser ablation of the hippocampus cannot prevent these deficits since they essentially resect or destroy hippocampus. Many patients undergo responsive neurostimulation (RNS) or deep brain stimulation (DBS) of the anterior nucleus of the thalamus, but these are palliative treatments and are associated with lower rates of seizure freedom compared to ATL. The Wada test is considered a gold standard to delineate the memory and language areas, but this test is invasive, carries risk, is costly, and is not available everywhere. In such a situation, functional magnetic resonance imaging (fMRI) has been recommended for localization and lateralization of patient's memory and language. Nevertheless, the reliability of the fMRI to clear a mathematics genius with left TLE for ATL is not known. Indeed, a robust examples of successful fMRI use in delineating cognitive abilities are yet undescribed.
We here present a patient with left TLE who had amazing calculation skills for spoken language. He could identify the day of the week of any time in history simply by knowing its date. This patient underwent successful ATL with the preservation of all his cognitive abilities, even in the immediate postoperative period only on the guidance of fMRI and neuropsychological assessment.
Our patient was a right-handed 23-year-old man, a student, with amazing ability to identify the day of the week of any given date in history in 1–2 s. He had drug-refractory epilepsy since eight years of age and difficulty remembering new things since the previous year. The seizures occurred 3–4 times/month, with an aura of uneasiness, fearfulness, and automatisms with the left hand, followed by tonic contractions of the right upper and lower limb and generalization. He was on levetiracetam, oxcarbazepine, and clobazam in adequate doses without relief from seizures. The MRI was suggestive of left hippocampal sclerosis, video electroencephalogram (VEEG) showed T3 spikes, and subtraction ictal single-photon emission computed tomography showed left temporal localization [Figure 1]. The neuropsychological assessment showed impaired verbal memory of immediate, delayed and learning ability, and immediate and delayed visual memory. He had intact visuoconstructive ability and normal focused and sustained attention, and intact long-term percent recall (93%).
fMRI task details
The fMRI study was carried out using a 32-channel head coil on a 3.0T MR Scanner (Ingenia 3.0T TX, M/s. Philips). The language and semantic verbal memory tasks were incorporated into a block design with four cycles of activity alternating with the baseline.
During the word generation (WGT) and syntax reading tasks (SRT), the case was instructed to read simple semantic Hindi words and sentences. For the semantic memory task (SMT), the instruction was to remember the correct synonym or antonym of the noun among the four options represented by an LED screen. During the semantic-syntactic and comprehension task (SSCT), the subject was asked to correct the syntax of the jumbled sentences. The entire paradigm was generated using SuperLab software (Cedrus, Inc., San Pedro, CA, USA), and the visual cues were presented using an MR- compatible LED screen.
FMRI data analysis
The fMRI data were analyzed by the statistical parametric mapping (SPM) software (Wellcome Trust, London, UK; version SPM 12) using MATLAB (version: 126.96.36.1995 (R2011), Math- Works, Inc., Natick, MA, USA). The BOLD whole-brain series were corrected for motion. Data were transformed using linear warps into a standard anatomical space during normalization processing. Finally, data were spatially smoothed (6 Hz) before post-processing. Brain activation patterns were overlaid onto the normalized 3D T1-weighted and render images. The coordinates of the local maxima of the threshold (P value uncorrected: 0.001) SPM map was converted from MNI frame to standard Talairach coordinates using Ginger ALE, and subsequently, an automated procedure (Talairach Client) was performed to assign an anatomic label to these coordinates by searching for the label associated with the nearest gray matter coordinate.
His fMRI for word production tasks showed blood oxygen level-dependent (BOLD) signal from the bilateral inferior frontal gyrus, for comprehension showed the bilateral temporal lobe (right > left) and for semantic memory showed the right temporal lobe and left superior temporal lobe activation [Figure 1].
The patient underwent ATL considering anatomo-electro-clinical concordance and shifting of verbal and cognitive functions to the right side. He had an uneventful postoperative course. The patient had complete preservation of his cognitive ability even in the immediate post operative period, as shown in Video 1. The histopathology report was suggestive of mesial temporal sclerosis. At 15 months follow-up, he had no seizures with improvement of his learning abilities.
Our patient had concordance between clinical semiology, VEEG, and imaging, guiding to the left TLE localization. He had unique arithmetic skills even with impairment of verbal memory shown on neuropsychological assessment. This was due to preserved language areas in bilateral superior temporal gyrus and inferior frontal gyrus and calculation in the parietal lobe. Left ATL carried inherent risks for his amazing abilities. Since the Wada test is invasive, does not allow for localization of cognitive functions, and is not available in out country, we did fMRI along with neuropsychological assessment to localize the functions. The fMRI showed comprehension and verbal memory representation in bilateral temporal lobes with right > left. Even the motor speech area was also more in the right inferior frontal gyrus. This gave us the confidence to proceed with left ATL surgery.
There is increasing evidence of fMRI comparability to the gold standard Wada test for language studies, and as a predictor of postoperative verbal memory decline after left temporal lobectomy. fMRI can be combined with intraoperative neuronavigation and cortical stimulation to determine language mapping; however, we could not do it because our patient did not give the consent for awake surgery.
Mathematic skills involve the comprehension of written or spoken language, number processing, and calculation, retrieving arithmetic facts, and producing the result in writing or speaking. Calculation skills per se involve bilateral (left > right) horizontal intraparietal sulcus, prefrontal, and cingulate cortex. These skills for reading input has shown to be preserved in temporal lobe atrophy, but one can have his calculation skills in jeopardy for spoken input in left TLE.
Being able to identify the day of the week based on a date (date, month, and year) involves multiple calculations and remembering some numbers. Its formula is (year code + month code + century code + date number – leap year code) mod 7. One has to remember the codes mentioned above and quickly do calculations to answer it. Our patient did these calculations within 1–2 seconds. This he could do even with a left TLE.
This case is good evidence of an effective use of noninvasive investigations to perform a safe ATL in left TLE in a right-handed executive person. Complex calculation skills, semantic verbal memory, comprehension, and motor speech were preserved in this case using fMRI and neuropsychological assessment.
Functional MRI is an effective method to guide ATL in left TLE.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
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Conflicts of interest
There are no conflicts of interest.