Intracranial EEG analysis in tumor-related epilepsy: Evidence of distant epileptic abnormalities

OBJECTIVE

In patients with tumor-related epilepsy (TRE), surgery traditionally focuses on tumor resection; but identification and removal of associated epileptogenic zone may improve seizure outcome. Here, we study spatial relationship of tumor and seizure onset and early spread zone (SOSz). We also perform quantitative analysis of interictal epileptiform activities in patients with both TRE and non-lesional epilepsy in order to better understand the electrophysiological basis of epileptogenesis.

METHODS

Twenty-five patients (11 with TRE and 14 with non-lesional epilepsy) underwent staged surgery using intracranial electrodes. Tumors were outlined on MRI and images were coregistered with post-implantation CT images. For each electrode, distance to the nearest tumor margin was measured. Electrodes were categorized based on distance from tumor and involvement in seizure. Quantitative EEG analysis studying frequency, amplitude, power, duration and slope of interictal spikes was performed.

RESULTS

At least part of the SOSz was located beyond 1.5 cm from the tumor margin in 10/11 patients. Interictally, spike frequency and power were higher in the SOSz and spikes near tumor were smaller and less sharp. Interestingly, peritumoral electrodes had the highest spike frequencies and sharpest spikes, indicating greatest degree of epileptic synchrony. A complete resection of the SOSz resulted in excellent seizure outcome.

CONCLUSIONS

Seizure onset and early spread often involves brain areas distant from the tumor.

SIGNIFICANCE

Utilization of epilepsy surgery approach for TRE may provide better seizure outcome and study of the intracranial EEG may provide insight into pathophysiology of TRE.

Peripheral WBC count and serum prolactin level in various seizure types and nonepileptic events

PURPOSE

To analyze effects of different types of seizures and nonepileptic events as well as effects of seizure duration and lapse between the time of seizure and blood collection on serum prolactin level and peripheral white blood cell (WBC) count.

METHODS

We prospectively collected blood samples from all patients admitted to our Epilepsy Monitoring Unit at baseline and after an event. Blood samples were analyzed, and serum prolactin level and WBC count were determined. Statistical analyses were performed to evaluate the relation of each type of seizure, its duration, and time lapse between a seizure and collection of blood sample to the serum prolactin level and peripheral WBC count.

RESULTS

Serum prolactin level increases above twice the level at baseline after a complex partial seizure or a generalized seizure. Peripheral WBC count is elevated above the upper limit of normal in about one third of cases after a generalized seizure. In generalized seizures, the length of a seizure is positively associated, whereas the lapse time between the seizure onset and blood draw is negatively correlated with the increase in WBC count. Thus the longer the seizure and quicker the blood draw, the higher the WBC count.

CONCLUSIONS

We conclude that complex partial or generalized seizures are associated with an increase in serum prolactin level. Peripheral WBC count increases significantly after a generalized seizure and is probably transient in nature.

Volumetric MRI, pathological, and neuropsychological progression in hippocampal sclerosis

OBJECTIVE

To examine the relationships between age at onset and duration of seizure disorder with severity of hippocampal sclerosis (HS) and cognitive functioning in patients with HS and unilateral temporal lobe epilepsy.

METHODS

Twenty-six subjects had left temporal lobe seizure onset; 20 had right temporal onset. Measures were age at seizure onset, duration of seizure disorder divided by age (seizure duration), history of febrile convulsion (FC), ratio of the smaller hippocampal volume to the larger (HF) as determined by volumetric MRI, and pathologic HS grade.

RESULTS

Results showed that pathologic HS grade and HF were positively related to seizure duration, and negatively related to seizure onset. When subjects were divided into onset prior to age 10 versus later, subjects with earlier onset had higher mean pathologic HS grade and smaller (more asymmetric) mean HF. When subjects were divided into seizure duration <0.5 (i.e., less than half current lifetime) vs greater, subjects with seizure duration > or =0.5 had higher mean pathologic HS grade and lower mean HF. There was also evidence for earlier age at seizure onset and longer seizure duration being associated with worse performance on neuropsychological measures. FC was not related to either seizure duration or age at seizure onset, but patients with a history of FC showed higher pathologic HS grade and lower HF. A history of FC was not related to cognitive functioning.

CONCLUSIONS

Unilateral HS patients with earlier seizure onset and longer duration of epilepsy have more severe HS and greater hippocampal volume asymmetry. This suggests that HS may be a progressive disorder with risk for cognitive dysfunction.

[15O]-water PET and intraoperative brain mapping: a comparison in the localization of eloquent cortex

[15O]-water PET was performed on 12 patients with structural lesions for localization of the motor (n = 5), language (receptive and expressive; n = 6), and visual cortex (n = 1). All these patients underwent interactive image-guided surgery using an infrared digitizer and intraoperative electrical stimulation mapping for motor, sensory, language, and visual cortex location. MRI-PET coregistration was performed using a surface matching approach that integrated functional information with interactive image guidance during the surgical procedure. An awake craniotomy with motor and sensory intraoperative stimulation was performed using a registered bipolar electrode that was tracked on real-time during the surgical procedure. Intraoperative functional findings were displayed and saved on the registered MRI images. The sites of functional PET activation during the performance of motor, visual and language tasks were then compared to the results of intraoperative cortical stimulation in 11 patients and visual evoked potentials in one. The results of the PET activation studies were concordant with the findings of intraoperative stimulation in all cases. During resection of the structural lesions, intraoperative stimulation was continued in the subcortical pathways, and five patients had positive responses on areas not identified by the functional PET. Furthermore, 3 patients showed transitory changes in function (speech arrest 1, naming difficulty 1, and motor weakness 1) that were reversible after changing the dissection technique or a brain retractor. [15O]-water PET was reliable in identifying the motor, visual, and language cortex. Language-related rCBF increases were highly distributive, although only part of these activations were subjected to intraoperative stimulation. We conclude that [15O]-water PET can be used for preoperative noninvasive identification of functional cortex and may be useful in neurosurgical preplanning. Intraoperative mapping still remains the main means to avoid neurological damage as it can be performed during the entire surgical procedure to avoid damage to cortex, pathways, and damage secondary to ischemia or edema (brain retraction).

Specificity of volumetric magnetic resonance imaging in detecting hippocampal sclerosis

BACKGROUND

Magnetic resonance imaging (MRI)-based volumetric measurements of the hippocampal formation are useful in detecting unilateral hippocampal sclerosis (HS) in patients with temporal lobe epilepsy. In this pathologic entity, volumetric MRI analysis shows the epileptogenic structure to be atrophic when compared with the normal, nonepileptogenic side. Some authors have suggested that the radiological features of atrophy of medial temporal lobe structures are common in patients with complex partial seizures, but also are seen frequently in other seizure types and can occur even in patients without epilepsy.

OBJECTIVE

To determine if seizures originating in extrahippocampal sites cause gliosis, cell loss, and atrophy of medial temporal lobe structures (i.e., HS).

METHODS

We studied 110 patients with chronic epilepsy using volumetric MRI measurements of the hippocampal formation. Seventeen patients had pathologically proven HS, 27 patients had seizures due to extratemporal structural lesions, 15 patients had seizures caused by extrahippocampal temporal lobe lesions, 29 patients had primary generalized epilepsy, and 22 patients had secondary generalized epilepsy.

RESULTS

All 17 patients with HS showed significantly reduced absolute hippocampal formation volumes of greater than 2 SDs below the mean of the control groups. The preoperative hippocampal formation volume measurements correlated well with the severity of HS on pathological examination. Hippocampal volumes were within the normal range in all patients with primary generalized epilepsy, secondary generalized epilepsy, extratemporal structural lesions, and extrahippocampal temporal lobe lesions.

CONCLUSIONS

Seizures originating at extrahippocampal sites do not cause gliosis, cell loss, or atrophy of medial temporal structures. Significant reduction in hippocampal volumes is a specific marker for HS.

Verbal learning subtypes in traumatic brain injury: a replication

Traumatic brain injury (TBI) has been associated with memory impairments, but the severity and qualitative aspects of such impairment do not appear homogeneous across patients. This study sought to replicate an earlier investigation that found distinct verbal learning subtypes in TBI using the California Verbal Learning Test (CVLT). CVLT data from 88 acute rehabilitation inpatients with mild, moderate, and severe traumatic brain injuries were analyzed with multiple cluster analytic techniques. Cluster analyses yielded five learning subtypes, three of which appeared similar to the subtypes previously identified as Active, Disorganized, and Passive subtypes, and two that appeared similar to the Deficient subgroup. Traumatic brain injury appears to be characterized by heterogeneous, but fairly reliable, verbal learning subtypes that can be detected early postinjury.

Effect of soft contact lenses on experimental Pseudomonas and Candida keratitis

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