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Warren W. Boling and André Olivier

Object. The goal of this study was to identify a reliable landmark for hand sensory function in the central area.

Methods. Hand sensory activation on positron emission tomography (PET) scans was analyzed in 27 patients. Each PET study was coregistered with the patient's magnetic resonance image and analyzed in two-dimensional and three-dimensional cortical surface reconstructions to define anatomicofunctional relationships.

Conclusions. The substratum of hand sensory function is a prominent fold of cortex elevating the floor of the central sulcus and connecting the pre- and postcentral gyri. Broca named this cortical fold the pli de passage moyen, and hand motor function has been localized to the precentral component of this structure. In this study the authors demonstrate that hand sensory function is highly correlated with the postcentral component of the pli de passage moyen, and that this structure is a reliable cortical landmark for identifying the aforementioned function.

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Warren Boling, David C. Reutens, and André Olivier

Object. The goal of this study was to establish a reliable method for identification of face and tongue sensory function in the lower central area.

Methods. All positron emission tomography (PET) clinical activation studies performed over a 3-year period at the Montreal Neurological Institute and Hospital were evaluated by coregistering the PET images with three-dimensional reconstructions of magnetic resonance images obtained in the same patients. In addition to stereotactic coordinates and measurements based on distance from the sylvian fissure, gyral and sulcal landmarks were analyzed to determine their reliability in localizing the sensory areas of the tongue and lower face.

The convolutional anatomy of the central area is an important guide to the identification of function. The sensory area of the tongue is recognized as a triangular region at the base of the postcentral gyrus; the sensory area of the lower face resides in the narrowed portion of the postcentral gyrus, immediately above the tongue area.

Conclusions. Cortical landmarks such as the substrata of tongue and face sensory impressions are more reliable guides than stereotactic coordinates or measurements for localizing function.

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Tracy Weimer, Warren Boling, David Pryputniewicz, and Adriana Palade

The authors report a case of status epilepticus secondary to limbic encephalitis that was successfully treated with temporal lobectomy. A 45-year-old woman presented in status epilepticus refractory to high-dose suppressive medical therapy. Magnetic resonance imaging of the brain showed T2- and FLAIR-weighted hyperintensities in the right temporal lobe, left and right frontal lobes, and pons. A lumbar puncture revealed normal findings. Continuous electroencephalography monitoring showed continued right temporal seizure activity. A paraneoplastic panel was positive for N-type voltage-gated calcium channels. Subsequent bronchial biopsy revealed small cell carcinoma of the lung. A right temporal lobectomy was performed due to refractory status, resulting in resolution of seizure activity and recovery of good neurological function. The authors describe their case and review the literature on surgical therapy for refractory status epilepticus and limbic encephalitis.

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Warren Boling, André Olivier, Richard G. Bittar, and David Reutens

Object

The object of this study was to identify a reliable surface landmark for the hand motor area and to demonstrate that it corresponds to a specific structural component of the precentral gyrus.

Methods

Positron emission tomography (PET) activation studies for hand motor function were reviewed in 12 patients in whom magnetic resonance imaging results were normal. Each patient performed a hand opening and closing task. Using a computer-assisted three-dimensional reconstruction of the surface of each hemisphere studied, the relationship of the hand motor area to cortical surface landmarks was evaluated.

Conclusions

The region of hand motor activation can be reliably identified on the surface of the brain by assessing anatomical relationships to nearby structures. After identification of the central sulcus, the superior and middle frontal gyrus can be seen to arise from the precentral gyrus at a perpendicular angle. A bend or genu in the precentral gyrus is constantly seen between the superior and middle frontal gyrus, which points posteriorly (posteriorly convex). The location of hand motor function, identified using PET activation studies, is within the central sulcus at the apex of this posteriorly pointing genu. The apex of the genu of the precentral gyrus leads to a deep cortical fold connecting the pre- and postcentral gyri and elevating the floor of the central sulcus. This deep fold was described by Paul Broca as the pli de passage fronto-pariétal moyen, and the precentral bank of the pli de passage represents the anatomical substratum of hand motor function. Observers blinded to the results of the activation studies were able to identify the hand motor area reliably after instruction in using these surface landmarks.

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Warren Boling, André Olivier, Richard G. Bittar, and David Reutens

Object. The object of this study was to identify a reliable surface landmark for the hand motor area and to demonstrate that it corresponds to a specific structural component of the precentral gyrus.

Methods. Positron emission tomography (PET) activation studies for hand motor function were reviewed in 12 patients in whom magnetic resonance imaging results were normal. Each patient performed a hand opening and closing task. Using a computer-assisted three-dimensional reconstruction of the surface of each hemisphere studied, the relationship of the hand motor area with cortical surface landmarks was evaluated.

Conclusions. The region of hand motor activation can be reliably identified on the surface of the brain by assessing anatomical relationships to nearby structures. After identification of the central sulcus, the superior and middle frontal gyrus can be seen to arise from the precentral gyrus at a perpendicular angle. A bend or genu in the precentral gyrus is constantly seen between the superior and middle frontal gyrus, which points posteriorly (posteriorly convex). The location of hand motor function, identified using PET activation studies, is within the central sulcus at the apex of this posteriorly pointing genu. The apex of the genu of the precentral gyrus leads to a deep cortical fold connecting the pre- and postcentral gyri and elevating the floor of the central sulcus. This deep fold was described by Paul Broca as the pli de passage fronto-pariétal moyen, and the precentral bank of the pli de passage represents the anatomical substratum of hand motor function. Observers blinded to the results of the activation studies were able to identify the hand motor area reliably after instruction in using these surface landmarks.

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Donald W. Gross, Isabelle Merlet, Warren Boling, and Jean Gotman

Object. When considering resection of epileptic generators near the central sulcus, it is essential to define the spatial relationship between the epileptic generator and the primary sensorimotor hand area. In this study, the authors assessed the accuracy of dipole modeling of electroencephalographic spikes and median nerve somatosensory evoked potentials (SSEPs) in defining this relationship preoperatively and noninvasively.

Methods. Epileptic spikes and SSEPs in patients with focal central area epilepsy were represented by dipole models coregistered onto global magnetic resonance images. In patients who underwent surgery, spike dipoles were also compared with findings of electrocorticography (ECoG) and with the resection area. To improve the accuracy of the dipole models, anatomical landmarks of the hand area were used to assess the error in SSEP dipole location, and this error measure was used to correct the location of spike dipoles.

Five patients with central epilepsy were studied, three of whom underwent ECoG-guided surgical resections. The location of SSEP dipoles correlated well with anatomical landmarks of the primary sensory hand area. The relative position of the spike and SSEP dipoles correlated well with the patients' ictal symptoms, ECoG findings, and the location of the epileptic focus (as defined by the resection cavity in patients who became seizure free postoperatively). Corrected spike dipoles were located even closer to the resection cavity.

Conclusions. The calculation of the relative location of spike and SSEP dipoles is a simple noninvasive method of determining the relationship between the primary hand area and an epileptic focus in the central area. The spatial resolution of this technique can be further improved using easily identifiable anatomical landmarks.

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Warren Boling, Frederick Andermann, David Reutens, François Dubeau, Laetitia Caporicci, and André Olivier

Object. The goal of this study was to evaluate the efficacy of surgery for temporal lobe epilepsy (TLE) in older (≥ 50 years of age) patients.

Methods. The authors conducted a review of all patients 50 years of age or older with TLE surgically treated at the Montreal Neurological Institute and Hospital since 1981 by one surgeon (A.O.). Only patients without a mass lesion were included. Outcome parameters were compared with those of younger individuals with TLE, who were stratified by age at operation.

In patients aged 50 years and older, the onset of complex partial seizures occurred 5 to 53 years (mean 35 years) prior to the time of surgery. Postoperatively, over a mean follow-up period of 64 months, 15 patients (83%) obtained a meaningful improvement, becoming either free from seizures or only experiencing a rare seizure. Most surgery outcomes were similar in both older and younger individuals, except for a trend to more freedom from seizures and increased likelihood of returning to work or usual activities in the younger patients. Note that a patient's long-standing seizure disorder did not negatively affect their ability to achieve freedom from seizures following surgery.

Conclusions. Surgery for TLE appears to be effective for older individuals, comparing favorably with results in younger age groups, and carries a small risk of postoperative complications.

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Warren Boling, Michael Parsons, Michal Kraszpulski, Carrie Cantrell, and Aina Puce

Object

The pli de passage moyen (PPM) is an omega-shaped cortical landmark bulging into the central sulcus. There has been considerable interest in the PPM given that hand motor and sensory tasks have been found on functional magnetic resonance (fMR) imaging to activate the structure. Note, however, that the cortical function subserved by the PPM is not completely understood. Finger and thumb function are somatotopically organized over the central area and encompass a larger cortical surface than the anatomical PPM. Therefore, a sensory or motor hand area within the PPM would be redundant with the somatotopically organized digit function in the primary sensorimotor cortex. In this study the authors aimed to clarify the function subserved by the PPM and further evaluate hand area function in the primary sensorimotor cortex.

Methods

To further elucidate the function subserved by the PPM, patients underwent cortical stimulation in the region of the PPM as well as fMR imaging–demonstrated activation of the hand area. Two separate analytical methods were used to correlate hand area functional imaging with whole-hand sensory and motor responses induced by cortical stimulation.

Results

A relationship of the anatomical PPM with cortical stimulation responses as well as hand fMR imaging activation was observed.

Conclusions

A strong relationship was identified between the PPM, whole-hand sensory and motor stimulation responses, and fMR imaging hand activation. Whole-hand motor and whole-hand sensory cortical regions were identified in the primary sensorimotor cortex. It was localized to the PPM and exists in addition to the somatotopically organized finger and thumb sensory and motor areas.

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Aviva Abosch, Neda Bernasconi, Warren Boling, Marilyn Jones-Gotman, Nicole Poulin, François Dubeau, Frederick Andermann, and André Olivier

Object. Selective amygdalohippocampectomy (SelAH) is used in the treatment of mesial temporal lobe epilepsy (MTLE). The goal of this study was to determine factors predictive of poor postoperative seizure control (Engel Class III or IV) following SelAH.

Methods. A retrospective study was conducted of 27 patients with poor seizure control postoperatively (Engel III/IV group), in comparison with 27 patients who were free from seizures after surgery (Engel I/II group). The results of electroencephalography, magnetic resonance (MR) imaging, and pathological studies were reviewed, and volumetric MR image analysis was used to compare the extent of the mesial structures that had been resected.

In 56% of patients in the Engel III/IV group, significant bitemporal abnormalities were displayed on preoperative EEG studies, compared with 24% of patients in the Engel I/II group (p < 0.05). An analysis of preoperative MR images disclosed five patients (19%) in the Engel III/IV group and no patient in the Engel I/II group with normal hippocampal volumes bilaterally. Thirteen patients in the Engel III/IV group subsequently underwent either extension of the SelAH (six cases) or a corticoamygdalohippocampectomy (seven patients). Three patients from the former and one patient from the latter subgroup subsequently became seizure free (four patients total [34%]). The remaining nine patients did not improve, despite the fact that they had undergone near-total resection of mesial structures.

Conclusions. The majority of patients receiving suboptimal seizure control following SelAH did not meet the criteria for unilateral MTLE, based on EEG, MR imaging, and/or histopathological studies. These patients were therefore unlikely to benefit from additional resection of mesial structures. With the benefits of modern imaging, and by strict adherence to selection criteria, SelAH can be predicted to yield excellent postoperative seizure control for nearly all patients with unilateral MTLE. There remains a subpopulation, however, that meets the criteria for MTLE, but does not become free from seizure following SelAH.

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Jason G. Mandell, Kenneth L. Hill, Dan T. D. Nguyen, Kevin W. Moser, Robert E. Harbaugh, James McInerney, Brian Kaaya Nsubuga, John K. Mugamba, Derek Johnson, Benjamin C. Warf, Warren Boling, Andrew G. Webb, and Steven J. Schiff

OBJECT

The incidence of temporal lobe epilepsy (TLE) due to mesial temporal sclerosis (MTS) can be high in developing countries. Current diagnosis of MTS relies on structural MRI, which is generally unavailable in developing world settings. Given widespread effects on temporal lobe structure beyond hippocampal atrophy in TLE, the authors propose that CT volumetric analysis can be used in patient selection to help predict outcomes following resection.

METHODS

Ten pediatric patients received preoperative CT scans and temporal resections at the CURE Children's Hospital of Uganda. Engel classification of seizure control was determined 12 months postoperatively. Temporal lobe volumes were measured from CT and from normative MR images using the Cavalieri method. Whole brain and fluid volumes were measured using particle filter segmentation. Linear discrimination analysis (LDA) was used to classify seizure outcome by temporal lobe volumes and normalized brain volume.

RESULTS

Epilepsy patients showed normal to small brain volumes and small temporal lobes bilaterally. A multivariate measure of the volume of each temporal lobe separated patients who were seizure free (Engel Class IA) from those with incomplete seizure control (Engel Class IB/IIB) with LDA (p < 0.01). Temporal lobe volumes also separate normal subjects, patients with Engel Class IA outcomes, and patients with Class IB/IIB outcomes (p < 0.01). Additionally, the authors demonstrated that age-normalized whole brain volume, in combination with temporal lobe volumes, may further improve outcome prediction (p < 0.01).

CONCLUSIONS

This study shows strong evidence that temporal lobe and brain volume can be predictive of seizure outcome following temporal lobe resection, and that volumetric CT analysis of the temporal lobe may be feasible in lieu of structural MRI when the latter is unavailable. Furthermore, since the authors' methods are modality independent, these findings suggest that temporal lobe and normative brain volumes may further be useful in the selection of patients for temporal lobe resection when structural MRI is available.