Liisa Metsähonkala

Combined use of non-invasive techniques for improved functional localization for a selected group of epilepsy surgery candidates.

Invasive cortical mapping is conventionally required for preoperative identification of epileptogenic and eloquent cortical regions before epilepsy surgery. The decision on the extent and exact location of the resection is always demanding and multimodal approach is desired for added certainty. The present study describes two non-invasive preoperative protocols, used in addition to the normal preoperative work-up for localization of the epileptogenic and sensorimotor cortical regions, in two young patients with epilepsy. Magnetoencephalography (MEG) was used to determine the primary somatosensory cortex (S1) and the ictal onset zones. Navigated transcranial magnetic stimulation (nTMS) was used to determine the location and the extent of the primary motor representation areas. The localization results from these non-invasive methods were used for guiding the subdural grid deployment and later compared with the results from electrical cortical stimulation (ECS) via subdural grids, and validated by surgery outcome. The results from MEG and nTMS localizations were consistent with the ECS results and provided improved spatial precision. Consistent results of our study suggest that these non-invasive methods can be added to the standard preoperative work-up and may even hold a potential to replace the ECS in a subgroup of patients with epilepsy who have the suspected epileptogenic zone near the sensorimotor cortex and seizures frequent enough for ictal MEG.

Interictal MEG reveals focal cortical dysplasias: special focus on patients with no visible MRI lesions.

PURPOSEnTo investigate the value of interictal magnetoencephalography (MEG) in localizing epileptogenic cortex in epilepsy surgery patients with focal cortical dysplasias (FCD), particularly in patients having no visible MRI lesions.nnnMETHODSnThirty-four patients with FCD and preoperative MEG were retrospectively evaluated. Interictal MEG spike source localizations in respect to the resected area were studied using postoperative MR imaging. The possible predictive value of MEG-findings in respect to the clinical outcome was evaluated. Results from intracranial recordings were also compared with the MEG localizations.nnnRESULTSnInterictal MEG spikes were observed in all but one patient. 17 of the 34 (50%) patients became seizure free (Engel class I). In patients with MEG dipole clusters (n=20) and Engel class I or II (n=15) 49% of the source clusters were removed on the average; the corresponding value in patients with Engel class III or IV (n=5) was 5.5% (p=0.02). Seven (54%) of the 13 patients with an MRI-negative lesion achieved Engel class I; the outcomes did not differ from patients having a visible MRI lesion (n=21; p=0.82). The concordance between MEG localizations and the invasive studies was good in nine of the 13 patients with no visible MRI lesionsnnnCONCLUSIONnMEG is particularly useful in finding small FCDs not visible on MRI. A more complete removal of MEG source cluster area is associated with better clinical outcome These features make it a valuable tool in pre-surgical evaluation of patients with intractable focal-type epilepsy and normal MRI.

Applicability of nTMS in locating the motor cortical representation areas in patients with epilepsy

BackgroundTranscranial magnetic stimulation (TMS) is increasingly used for non-invasive functional mapping in preoperative evaluation for brain surgery, and the reliability of navigated TMS (nTMS) motor representation maps has been studied in the healthy population and in brain tumor patients. The lesions behind intractable epilepsy differ from typical brain tumors, ranging from developmental cortical malformations to injuries early in development, and may influence the functional organization of the cortical areas. Moreover, the interictal cortical epileptic activity and antiepileptic medication may affect the nTMS motor threshold. The reliability of the nTMS motor representation localization in epilepsy patients has not been addressed.MethodsWe compared the nTMS motor cortical representation maps of hand and arm muscles with the results of invasive electrical cortical stimulation (ECS) in 13 patients with focal epilepsy. The nTMS maps were projected to the cortical surface segmented from preoperative magnetic resonance images (MRI), and the positions of the subdural electrodes were extracted from the postoperative low-dose computed tomography (CT) images registered with preoperative MRI.ResultsThe 3D distance between the average nTMS site and average ECS electrode location was 11u2009±u20094xa0mm for the hand and 16u2009±u20097xa0mm for arm muscle representation areas. In all patients the representation areas defined with nTMS and ECS were located on the same gyrus, also in patients with abundant interictal epileptic activity on the motor gyrus.ConclusionsnTMS can reliably locate the hand motor cortical representation area with the accuracy needed for pre-surgical evaluation in patients with epilepsy.

Force production and EMG activity of neck muscles in adolescent headache.

Purpose. This study compared the maximal force, EMG/force ratio and co-activation characteristics of the neck-shoulder muscles between 30 adolescents with migraine-type headache, 29 with tension-type headache, and 30 headache-free controls. Method. Force was measured with surface electromyography (EMG) from the cervical erector spinae (CES), the sternocleidomastoid (SCM) and trapezius muscles during the maximal isometric neck flexion, neck extension and shoulder flexion. Results. Girls with migraine-type headache had higher EMG/force ratios between the EMG of the left agonist SCM muscle and the corresponding maximal neck flexion (p = 0.030) and neck rotation force to the right side (p = 0.024) than the girls with tension-type headache. Migrainous girls had more co-activation of right antagonist CES muscle during maximal neck flexion force than the girls without headache (p = 0.015). Neck force production showed no significant differences between girls. Girls with tension-type headache displayed lower left shoulder flexion force than girls with migraine-type headache (p = 0.005) or with no headache (p = 0.005). In boys, no significant differences were observed. Conclusions. Girls with tension-type headache and migraine-type headache have differences in neuromuscular function in the neck-shoulder muscles. The data amplify our knowledge of the neck-shoulder muscle dysfunction in adolescent headache, and may encourage the use of specific rehabilitation methods in the management of different types of headache.

Neck flexor muscle fatigue in adolescents with headache – An electromyographic study

Background: Muscular disorders of the neck region may be of importance for the etiology of tension‐type headache. However, in adolescents, there are no data on the association between neck muscle fatigue and headache.

Neck muscles cross‐sectional area in adolescents with and without headache – MRI study

Background: Cervical musculature may play an important role in the genesis of tension‐type headache. However, there are no reports on a possible association between the morphometrical features of the neck flexion and extension muscles and adolescence headache.

Characteristics of neck pain associated with adolescent headache

The objective of the study was to find out what kind of neck pain (NP) is associated with headache (HA) and with various headache variables: frequency, type, intensity, disturbance, and relief with analgesics. A population-based sample of 12-year-olds with and without HA (n = 304) was followed for 4 years. At the age of 16 years, NP was evaluated on the basis of self-reported symptoms and a thorough physical examination of the neck region. Both self-reported and measured NP were associated with HA variables. Co-occurrent NP was found in adolescents with migraine as often as in those with tension-type HA. Especially, muscle pain and intensive, frequent NP were associated with disturbing HA unresponsive to analgesics. The study indicates that concomitant NP should be considered in adolescent HA sufferers, and a thorough cervical and muscle evaluation is recommended when planning the treatment of HA.

Does Neck Pain Determine the Outcome of Adolescent Headache

The aim of the study was to examine the influence of concomitant neck pain (NP) on the outcome of headache (HA) frequency and HA type in adolescence. A population-based sample of 13-year-olds with or without HA (n = 228) was followed for 3 years. NP was evaluated at the beginning of the follow-up on the basis of recorded muscle tenderness and self-reported symptoms. During the 3 years of follow-up, changes in both HA type and frequency were common. NP interfering with daily activities at the age of 13 years predicted change from non-frequent (0-1/month) to monthly HA (>1/month), especially in boys (P = 0.03 boys, P = 0.06 girls). The use of physiotherapy predicted persistence of monthly HA in boys (P = 0.004). The changes in HA type were not predictable by NP. In conclusion, the risk of worsening HA in adolescence is more probable if the HA is associated with NP interfering with daily activities.

Adolescent Disc Degeneration - No Headache Association

The objective of the study was to determine whether adolescents with headache have more disc degeneration in the cervical spine than headache-free controls. This study is part of a population-based follow-up study of adolescents with and without headache. At the age of 17 years, adolescents with headache at least three times a month (N = 47) and adolescents with no headache (N = 22) participated in a magnetic resonance imaging (MRI) study of the cervical spine. Of the 47 headache sufferers, 17 also had weekly neck pain and 30 had neck pain less than once a month. MRI scans were interpreted independently by three neuroradiologists. Disc degeneration was found in 67% of participants, with no difference between adolescents with and without headache. Most of the degenerative changes were located in the lower cervical spine. In adolescence, mild degenerative changes of the cervical spine are surprisingly common but do not contribute to headache.

Cerebral glucose utilization measured with high resolution positron emission tomography in epileptic Finnish Spitz dogs and healthy dogs.

In human epileptic patients, changes in cerebral glucose utilization can be detected 2-deoxy-2-[(18) F] fluoro-D-glucose positron emission tomography (FDG-PET). The purpose of this prospective study was to determine whether epileptic dogs might show similar findings. Eleven Finnish Spitz dogs with focal idiopathic epilepsy and six healthy dogs were included. Dogs were examined using electroencephalography (EEG) and FDG-PET, with epileptic dogs being evaluated during the interictal period. Visual and semi-quantitative assessment methods of FDG-PET were compared and contrasted with EEG findings. Three independent observers, unaware of dog clinical status, detected FDG-PET uptake abnormalities in 9/11 epileptic (82%), and 4/8 healthy dogs (50%). Occipital cortex findings were significantly associated with epileptic status (P = 0.013). Epileptic dogs had significantly lower standardized uptake values (SUVs) in numerous cortical regions, the cerebellum, and the hippocampus compared to the control dogs. The lowest SUVs were found in the occipital lobe. White matter normalized and left-right asymmetry index values for all pairs of homologous regions did not differ between groups. Visual evaluation of the EEGs was less sensitive (36%) than FDG-PET. Both diagnostic tests were consensual and specific (100%) for occipital findings, but EEG had a lower sensitivity for detecting lateralized foci than FDG-PET. Findings supported the use of FDG-PET as a diagnostic test for dogs with suspected idiopathic epilepsy. Visual and semiquantitative analyses of FDG-PET scans provided complementary information. Findings also supported the theory that epileptogenesis may occur in multiple brain regions in Finnish Spitz dogs with idiopathic epilepsy.